Reducing Impacts of Hatchery Steelhead Programs. Robert B. Lindsay Ken R. Kenaston R. Kirk Schroeder

Transcription

1 Reducing Impacts of Hatchery Steelhead Programs Robert B. Lindsay Ken R. Kenaston R. Kirk Schroeder Oregon Department of Fish and Wildlife 2501 S.W. First Street P.O. Box 59 Portland, Oregon January 2001 Final report for project F-120-R funded in part by the Sport Fish and Wildlife Restoration Program administered by the U.S. Fish and Wildlife Service, October 1988 to September 1996.

2 CONTENTS EXECUTIVE SUMMARY...1 Designation of Wild Fish Populations...1 Stray Hatchery Steelhead in Oregon Coastal Rivers...1 Overlap of Hatchery and Wild Spawners...2 Use of Local Brood Stock in Hatchery Programs...2 Reducing Interbreeding of Hatchery with Wild Fish...3 Acclimation...3 Sterilization...3 INTRODUCTION...5 DESIGNATION OF WILD FISH POPULATIONS...6 STRAY HATCHERY STEELHEAD IN OREGON COASTAL RIVERS...6 Methods...7 Results...11 Degree of Straying...11 Origin of Strays...11 Discussion...18 OVERLAP OF HATCHERY AND WILD SPAWNERS...20 Trask River Mid-Coast Streams Siuslaw River Methods...23 Results...25 Necanicum River Methods...31 Results...31 Conclusions...34 USE OF LOCAL BROOD STOCK IN HATCHERY PROGRAMS...34 Methods...34 Collecting Brood Stock and Rearing Juveniles...35 Returning Adults...40 Results and Discussion...41 i

3 REDUCING INTERBREEDING OF HATCHERY WITH WILD FISH...47 Acclimation...47 Methods...48 Release of Juvenile Steelhead:...48 Recovery of Returning Adult Steelhead:...51 Results...53 Homing Within the Siuslaw Basin:...53 Survival:...56 Straying to Alsea River:...57 Discussion...58 Homing Within the Siuslaw Basin :...58 Survival:...61 Straying into the Alsea River:...62 Conclusions...63 Implementation Considerations...63 Residual Juveniles:...63 Recycled Adults:...65 Sterilization of Hatchery Steelhead...68 Methods...69 Results and Discussion...70 ACKNOWLEDGMENTS...75 REFERENCES...76 APPENDIX...86 Trap Efficiencies at Weir Sites in the Siuslaw basin, ii

4 EXECUTIVE SUMMARY A study was conducted from 1988 to 1996 to provide managers with information needed to reduce the risk of winter steelhead hatchery programs on genetic characteristics of wild steelhead consistent with the Oregon Department of Fish and Wildlife's Wild Fish Management Policy. We conducted work in five subject areas. First, we helped identify geographic boundaries of coastal wild steelhead populations. Secondly, we defined the magnitude of hatchery straying and the origin of these strays in coastal populations. Third, we determined the percentage of hatchery fish that spawned with wild fish in selected coastal rivers and looked at methods managers could use to monitor this percentage. Fourth, we compared the performance of returns from local brood stock with that from transplanted brood stock that had been used for hatchery programs in the past. Finally, we evaluated the use of an acclimation period to attract returning hatchery adults to a collection site and the use of sterilization to prevent hatchery fish from interbreeding with wild fish. Designation of Wild Fish Populations The transfer of steelhead stocks among basins is one hatchery practice that could reduce survival of wild fish because of interbreeding between locally adapted, native populations and transplanted stocks. The primary purpose for delineating stock boundaries was to formally identify these native populations so that steelhead management programs, especially hatchery programs, could be designed to minimize genetic risks to wild populations. Based in part on our initial listing of steelhead stocks in 1988, the Oregon Department of Fish and Wildlife delineated stock boundaries for steelhead as well as other species in Oregon. In general, each of the major basins in Oregon and, in some cases, subbasins within major basins were designated as separate stocks. Stray Hatchery Steelhead in Oregon Coastal Rivers Oregon s Wild Fish Management Policy established guidelines for the percentage of hatchery fish allowed in wild spawning populations. Hatchery fish in a stream may be composed of returns from smolts released into that stream as well as strays from releases into other streams. Options for reducing the number of hatchery fish in a river basin depend, in part, on knowing how much of the hatchery component of a run is composed of stray hatchery fish. This study examined origin and straying of hatchery winter steelhead among 16 river basins on the Oregon coast. Straying levels of hatchery steelhead exceeded the 10% Wild Fish Management Policy standard for genetically dissimilar hatchery fish in natural spawning populations in 10 of 16 Oregon coastal rivers surveyed. Stray hatchery steelhead averaged 11% (range 4 26%) of samples in rivers where hatchery steelhead were released and 22% (range 9 43%) in rivers where no hatchery fish were released. The two predominant factors that contributed to straying were releases of stocks transplanted from their natal 1

5 basin and releases into adjacent basins. Releases of transplanted stocks into adjacent basins accounted for 41% of the strays and releases of transplanted stocks into nonadjacent basins accounted for 29% of strays. Local stocks of steelhead released into adjacent basins accounted for 16% of the strays. Strategies to reduce straying may include using local brood stocks, rearing and releasing fish within their natal basins, reducing numbers of hatchery fish released, and eliminating some hatchery releases. Overlap of Hatchery and Wild Spawners Although fishery data were used to measure the degree and origin of hatchery straying, we wanted to know if fishery data could also be used as a tool to estimate the actual proportion of hatchery fish in wild spawning populations. We also wanted to know if hatchery and wild fish overlapped in time and in space during spawning. Work was conducted in the Trask River near Tillamook, Oregon in 1989, in three short coastal streams along the central Oregon coast in 1990, in the Siuslaw River from 1991 through 1993, and in the Necanicum River in The hatchery and wild composition of the recreational harvest of winter steelhead in the sport fishery reflected the composition on spawning areas and appeared adequate to determine compliance with the Wild Fish Management Policy. In all basins surveyed there was considerable overlap in spawn timing between hatchery and wild steelhead although wild fish tended to spawn later and over a longer period than hatchery fish. Use of Local Brood Stock in Hatchery Programs The use of locally adapted native stocks in hatchery programs assumes that these stocks are best suited for survival in natural environments and that their use in hatcheries will reduce genetic risks from interbreeding with wild stocks. The Wild Fish Management Policy recognized that genetic risk to wild populations is reduced when hatchery brood stocks are developed from native stocks and some wild fish are incorporated into hatcheries. With this portion of the study, we provided managers with a comparison of performance between hatchery releases into the Siuslaw River of a local stock (Siuslaw) and that of a transplanted stock (Alsea). Relative survival from smolt-to-adult was not significantly different between Siuslaw and Alsea smolts released into the Siuslaw River in 1991, 1993, and In addition, overall contribution to the recreational fishery in the Siuslaw River was not significantly different between the two stocks. In all three years Siuslaw stock adults tended to migrate later than Alsea stock adults. The later migration timing shifted recreational harvest of Siuslaw fish into March compared with Alsea stock. Straying of adults into the Alsea River was significantly (P < 0.01) reduced by using Siuslaw stock. Lower stray rates of the locally adapted Siuslaw stock and higher stray rates of Alsea stock into the Alsea River suggest a hereditary component in the homing behavior of steelhead. 2

6 Reducing Interbreeding of Hatchery with Wild Fish We investigated two strategies for reducing interbreeding of hatchery with wild steelhead on spawning grounds. We evaluated the use of an acclimation period prior to release to direct returning adults to a specific location where they could be captured and removed from the spawning population. We also evaluated sterilization of hatchery fish as a method for producing fish that would not spawn with wild fish, but would contribute to recreational fisheries. Acclimation We evaluated pre-release acclimation of hatchery winter in Whittaker Creek, a tributary of the Siuslaw River. The objective was to reduce the number of hatchery fish in wild steelhead spawning areas while providing hatchery steelhead for recreational fisheries. We found no difference in homing rate or in survival between hatchery steelhead acclimated for 30 d and those trucked from the hatchery and released directly. The mean proportion of adult steelhead accounted for in Whittaker Creek from releases was 92% and 97% for direct and acclimated groups, respectively. In contrast, 15% of adults from hatchery smolts released at four traditional sites in the main-stem Siuslaw River were accounted for in Whittaker Creek. Spatial distribution of catch in recreational fisheries was similar for direct and acclimated groups and occurred nearer Whittaker Creek than catch from traditional releases. The study shows that acclimation of juveniles is not necessary to achieve a high rate of homing of adult hatchery steelhead to a release site. Direct tributary releases in conjunction with an adult collection facility can be used as a management strategy to contain hatchery fish within the release basin while providing recreational harvest. Further, acclimation of steelhead smolts in the Siuslaw basin did not reduce straying of these fish into the Alsea River upon return as adults. Sterilization Hormone-sterilization of hatchery steelhead was examined as a way of preventing interbreeding between wild and hatchery fish on spawning grounds. The objective was to determine if sterilized hatchery steelhead would return at a rate high enough to provide fisheries benefits while reducing interactions between hatchery and wild fish. The study was conducted in the South Santiam River, a major tributary in the Willamette River basin. Summer steelhead were used because few wild summer steelhead occur in the South Santiam River. We followed procedures developed for rainbow trout to sterilize groups of steelhead in each of 3 years. 3

7 The mean smolt-to-adult return rate for three years of releases combined was 2.1% for control groups and 0.5% for sterile groups, a four fold reduction in survival. Treatment groups returned at an older age than control groups. Fish returning from sterilized groups were mostly male, developed secondary sexual characteristics, and produced viable sperm. The hormone-sterilization of hatchery steelhead, by the methods we used, is not an option for reducing interactions between hatchery and wild fish. 4

8 INTRODUCTION The persistence of hatchery programs and of productive natural populations of anadromous fish may depend, in part, on the ability of fish managers to conserve genetic resources. Native stocks have adapted to diverse natural habitats which improves survival over a wide range of conditions. The capacity of steelhead to persist when faced with environmental change is, in part, a function of their evolutionary history. The combined evolutionary histories of many wild stocks of steelhead determine the genetic capacity of the species to cope with environmental change. Genetic resources can be lost inadvertently by fish managers through harvest regulations, hatchery programs and practices, and other traditional management activities that tend to focus on the short term (Kapuscinski and Jacobson 1987). Because fish stocks removed from their natural habitat change genetically when reared in hatcheries (Hershberger 1980; Allendorf et al. 1987), the only way to conserve genetic resources of steelhead, given present technology, is by maintaining wild stocks (Hershberger 1980). The Oregon Department of Fish and Wildlife's (ODFW) Wild Fish Management Policy (ODFW 1992) was adopted out of recognition of the importance of genetic resources to the long-term health of fish species in Oregon. People influence the genetic diversity of wild fish by altering habitats, by harvesting fish, and by stocking hatchery fish. Habitat issues are being addressed by a multitude of restoration plans as well as through ODFW s Habitat Division. Catch and release regulations for wild steelhead throughout much of Oregon has reduced harvest. The goal of our steelhead study was to provide information that would help decrease the risk of detrimental effects of hatchery programs on the genetic characteristics of wild steelhead. We assumed that hatchery fish would continue to be an important part of Oregon s steelhead management program. We provided information in several subject areas so managers could develop strategies to reduce genetic risk to wild steelhead populations. First, we helped identify geographic boundaries of wild steelhead populations so managers could identify streams where hatchery stocks were incompatible with wild native stocks. Secondly, we defined the magnitude of hatchery straying and the origin of these strays in coastal populations because strays constituted genetically dissimilar fish and, consequently, were restricted under the Wild Fish Management Policy. Third, we determined the percentage of hatchery fish that spawned with wild fish in selected coastal rivers and looked at methods managers could use to monitor this percentage. These data could be used to determine the status of hatchery programs relative to guidelines in the Wild Fish Management Policy. Fourth, where transplanted stocks had been used in the past, we compared the performance of hatchery adults that originated from local wild brood stock with that of hatchery adults originating from transplanted hatchery brood stock. Although the use of local brood stocks in hatcheries would reduce the risk of genetic impacts on wild fish, managers needed to know how the change to local brood stocks might impact sport fisheries. Finally, we investigated two strategies for reducing interbreeding of hatchery with wild steelhead on spawning grounds. We evaluated the use of an acclimation period prior to release to direct returning adults to a collection site 5

9 where they could be removed from the spawning population. We also evaluated sterilization as a method for producing hatchery fish that would not spawn with wild fish, but would contribute to recreational fisheries. DESIGNATION OF WILD FISH POPULATIONS Wild populations of steelhead have adapted to physical and biological conditions present within the basins in which they spawn and rear. Conservation of genetic resources requires that variation within populations and variation among populations be maintained. Although within population variation appears to be far greater than among population variation in rainbow trout in the Columbia River drainage (Krueger et al. 1981), Parkinson (1984) found significant biochemical differentiation between steelhead populations in adjacent streams in British Columbia. Patterns of allelic variation in the Columbia River (Schreck et al. 1986) and the coast (McIntyre 1976) suggest that steelhead stocks geographically close tend to be more similar than stocks geographically distant. Some exchange between populations surely exists and is an important attribute of the species (Thorpe et al. 1981). Meffe (1986) points out that Variance among naturally isolated populations, however subtle, should be preserved and exploited through continued isolation wherever possible. Parkinson (1984) and Schreck et al. (1986) suggest that as many separate stocks be maintained as possible. The transfer of steelhead stocks among basins is one hatchery practice that could reduce survival of wild fish because of interbreeding between locally-adapted, native populations and less-adapted, transplanted stocks. The primary purpose for delineating stock boundaries was to formally identify these native populations so that steelhead management programs, especially hatchery programs, could be designed to minimize genetic risks to wild populations. Our initial list of steelhead stocks in 1988 (Lindsay et al. 1988) was revised prior to inclusion in a list of wild steelhead populations in a 1992 report on the status of wild fish in Oregon. In general, each of the major basins in Oregon and in some cases subbasins within major basins were designated as separate steelhead stocks. Later reports refined this listing (Kostow 1995) and identified management strategies for some steelhead populations (ODFW 1994). STRAY HATCHERY STEELHEAD IN OREGON COASTAL RIVERS Homing to a natal site is characteristic of salmonids, but mature fish that migrate to and spawn in a stream other than their natal one are considered strays (Quinn 1993). Straying is a natural component of salmonid behavior that enables fish to colonize new habitat (Milner and Bailey 1989) and to avoid locally unfavorable conditions (Leider 1989). However, straying of hatchery fish concerns fish managers because of potential negative impacts on wild populations of interbreeding with hatchery fish (Allendorf and Ryman 1987; Leider et al. 1990; Hindar et al. 1991). 6

10 Studies of salmonids have examined specific mechanisms affecting homing such as release time (Hansen and Jonsson 1991; Unwin and Quinn 1993), release location (Lister et al. 1981; Johnson et al. 1990; Solazzi et al. 1991), or age of returning adults (Quinn and Fresh 1984; Quinn et al. 1991; Labelle 1992). A few studies have examined straying of salmon in large geographic areas (Labelle 1992; Unwin and Quinn 1993; Pascual and Quinn 1994). Studies of steelhead have focused on straying at small geographic scales (Shapovalov and Taft 1954; Leider 1989). We are aware of just one study on straying of steelhead over a large geographic area (Lirette and Hooton 1988). Because hatchery fish are released in certain locations for specific purposes (e.g., fishery harvest), strays from other hatchery releases may create management problems if they stray in large numbers. Large numbers of hatchery strays could inflate the abundance of hatchery fish in a river, which could increase the interaction of hatchery and wild fish and prevent fish managers from meeting management objectives for individual basins. These concerns led Oregon to adopt a Wild Fish Management Policy to reduce the potential impacts of hatchery fish on wild fish (ODFW 1992). Oregon s Wild Fish Management Policy sets guidelines for the percentage of hatchery fish allowed in the wild spawning population. Options for reducing the number of hatchery fish in a river basin depend in part on knowing the number and origin of strays that occur with natural spawners. Kenaston (1989) reported that hatchery steelhead composed 28% of the catch of steelhead in Oregon streams where no hatchery steelhead were released. However, these data were based on voluntary collections of scales and were predominantly from two coastal streams. Our study expanded on that work and examined the degree and origin of straying of hatchery winter steelhead among several major river basins on the Oregon coast. More detailed discussion of our study is in Schroeder et al. (In Press). Methods In our study hatchery steelhead were considered strays if they returned to a river basin other than where they were released. Several studies have demonstrated that hatchery steelhead tend to return to specific release sites within a river basin (Wagner 1969; Cramer 1981; Slaney et al. 1993; see also Acclimation in this report). The degree and origin of strays from hatchery steelhead releases were studied in several major river basins along the Oregon coast, a distance of about 300 mi (Figure 1). Hatchery winter steelhead were differentially marked with clips of fins or maxillary bones for three brood years at steelhead hatcheries on the Oregon coast, and were released as smolts in (Table 1). We grouped the releases into two groups: local stocks and transplanted stocks. Local stocks were steelhead released into their natal basin, and included groups reared within the natal basin and those reared outside the natal basin. Transplanted stocks were steelhead taken from their natal basin and released into another basin. Some releases of transplanted stocks were reared within the basin where they were released, but most were reared outside the release basin. Because the number of distinct clip combinations is limited, some overlap existed in the clips (Table 1). However, in most cases duplicate clips were released in geographically 7

11 Necanicum PACIFIC OCEAN Nehalem Tillamook Bay Nestucca Salmon Siletz Yaquina Alsea Yachats Tenmile Cape Siuslaw Wilson Trask Drift N Umpqua Tenmile Smith 0 25 MILES 50 Coos Coquille Cape Blanco Sixes Elk Rogue Chetco Winchuck Figure 1. Western Oregon coastal rivers showing where winter steelhead were sampled or where juvenile hatchery steelhead were released. 8

12 distant areas of the coast. Some hatcheries that released steelhead into several basins were unable to differentially clip all their releases because they were unable to rear separate groups of steelhead from the time of clipping in the fall to release in the spring. Release groups returned as adults in the through the run years. Data were collected on stray hatchery fish in 12 streams by using trap catches and creel surveys. Seven of these streams were stocked with hatchery steelhead (Nestucca, Siletz, Yaquina, Alsea, Siuslaw, Coquille, and Chetco rivers), and five streams received no hatchery fish (Trask, Elk, Sixes, and Winchuck rivers, and Drift Creek) (Figure 1). In addition, we used data reported by anglers to examine the percentage of stray hatchery fish in four streams (Necanicum, Nehalem, Umpqua, and Rogue rivers) when 20 or more reports were received for a specific stream in a given year. These data were from an ODFW program where anglers voluntarily collected scales and clip information from the steelhead they caught in Oregon rivers. We calculated degree of straying within a surveyed basin as the percentage of the total sample of winter steelhead (hatchery and wild) that was of stray hatchery origin. We could not calculate a true stray rate (percentage of a release group that strayed) because we could not account for all adult returns of a given release. The hatchery portion of the return to a basin was divided into a homing component (those from releases into that basin) and a straying component (those from releases into other basins). In catch-and-release fisheries, the catch of wild fish was determined from angler interviews during creel surveys. In most cases, we used scales to age fish and to assign them to a release group. Where no scales were available, we used fish length to estimate age. Steelhead with clips that could not be assigned to a particular release were classed as "unknown strays". Unmarked hatchery steelhead, as determined by scale analysis, were also included in the "unknown stray" category for most rivers. However, we sampled a large number of unmarked hatchery steelhead in two southern Oregon rivers (Chetco and Winchuck) in years when all Oregon releases were marked. We assumed these fish were from unmarked releases of steelhead from northern California hatcheries. Previous studies documented that hatchery summer steelhead from northern California hatcheries strayed to the Rogue River, a southern Oregon river (Everest 1973; Satterthwaite 1988). California hatcheries also released some clipped winter steelhead during this study, which we recovered in Oregon rivers. The degree of straying was estimated by using all data where steelhead could be classified as either wild, local hatchery, or stray hatchery fish. In contrast, the origin of strays was determined only from hatchery steelhead that could be assigned with reasonable assurance to a particular release group. Voluntary information from anglers was included in estimates of the degree of straying from years or rivers where wild steelhead could be kept. However, where catch and release regulations were in effect for wild steelhead, we used voluntary information from anglers only to examine origin of strays because we lacked information on the wild component of the run. 9

13 Table 1. Clips and numbers of winter steelhead smolts released from hatcheries on the Oregon coast, Clip abbreviations are: Ad = adipose; Rp = right pectoral; Lp = left pectoral; Rv = right ventral; Lv = left ventral; Rm = right maxillary; Lm = left maxillary Release 1991 Release 1992 Release Number (thousands) Number (thou- Number (thousands) Hatchery (Stock) a Release location Fin clip Fin clip sands) Fin clip Local stocks reared and released in natal basin Nehalem (NH) Nehalem Rv, Lv 157 Ad, AdRv, 154 Lp, AdRv, 160 AdLv AdLv Cedar Creek (TR) Nestucca Ad 130 Ad 130 Alsea (AL) Alsea AdRm, AdLm 116 AdRp, AdLp 120 AdRp, AdLp 120 Rock Creek (SU) b S. Umpqua RvLm 19 AdRv, LvLm 70 Bandon (CQ) c Coquille AdRv 116 Lp, RvRm 184 RvLm, RvRm 120 Cole Rivers (RO) d Rogue Ad, AdRp, 150 Ad, AdRv, 150 Ad, AdLvRm, 150 AdLp AdLv AdLvLm Cole Rivers (AP) d Applegate Ad, AdRvRm, AdRvLm 150 Ad, AdRpRm, AdRpLm 150 Ad, AdRvRm, AdRvLm 150 Local stocks reared outside and released in natal basin Nehalem (NC) Necanicum Rv 2 Alsea (SI) Siuslaw LpLm 35 Alsea (CO) Coos AdLv 120 Alsea (CQ) Coquille LvLm 25 Bandon (CO) c Coos Ad 10 Rm 10 Elk River (CT) Chetco Lv 52 AdLm 42 AdLm, AdRm 50 Transplanted stocks reared in release basin Rock Creek (AL) b S. Umpqua AdLv 46 LvRm 35 Transplanted stocks reared outside release basin Nehalem (NH) Necanicum Lv 40 Ad 40 Lp 40 Cedar Creek (TR) Tillamook e Ad 25 Ad 25 Wilson e Ad 120 Ad 120 Kilchis e Ad 40 Ad 40 Miami e Ad 10 Ad 10 Alsea (AL) Salmon Lp 37 Rp 35 Lv 35 Siletz Lp 108 Rp 100 Lv 100 Yaquina Lp 30 Rp 30 Lv 20 Siuslaw Lp 178 RpRm, 127 RpRm RpLm, 166 RpLm, LpRm LpLm, LpRm Smith Lp 65 Rp 65 Lv 65 Coos Lp 40 Rp 65 Tenmile Lp 30 Alsea (CO) Tenmile Rv 30 AdLv 25 Alsea (CQ) Coos LvLm 79 RvRm 54 a Stock abbreviations are: AG = Applegate (Rogue basin); AL = Alsea; CO = Coos; CQ = Coquille; CT = Chetco; NC = Necanicum; NH = Nehalem; RO = Rogue; SI = Siuslaw; SU = South Umpqua; TR = Three Rivers (Nestucca basin). b North Umpqua basin. c Coquille basin. d Rogue basin. e Rivers entering Tillamook Bay. 10

14 Results Degree of Straying In Oregon coastal rivers where hatchery steelhead were released, the incidence of stray hatchery fish ranged from 4 to 26% of the total sample (Table 2). The highest incidence of straying was in the Alsea River, where over 25% of the total catch was composed of stray hatchery fish (Table 2). Stray hatchery steelhead composed an average 22% of the composition of winter steelhead in five streams where no hatchery fish were released (Table 2). The percentage of stray hatchery fish exceeded 10% in four of the five streams. Drift Creek (a tributary of the Alsea River) and Trask River (a tributary of Tillamook Bay) had the highest incidences of straying (Table 2). Most of the stray hatchery fish in these two streams were from large outsystem hatchery releases made in nearby rivers. The Winchuck River also had a high degree of straying, but most of these strays originated from releases of local stocks either into the Chetco River or into northern California basins. Stray steelhead in two Vancouver Island streams where no hatchery fish were released accounted for 3% and 41% of the total catch (Billings 1987, cited in Lirette and Hooton 1988). Stray hatchery steelhead increased the occurrence of hatchery steelhead in rivers where hatchery fish were released by an average of 5%. The additive percentage of straying and homing hatchery steelhead in 11 coastal rivers where hatchery fish were released composed a mean of 58% (range 26 87%) of the total sample. Lirette and Hooton (1988) reported that stray hatchery steelhead in accounted for an average 14% (range 0 44%) of the total hatchery catch in 9 Vancouver Island basins. Origin of Strays Generally, most of the stray hatchery steelhead in the surveyed streams were from nearby releases (Table 3). Of the known strays in 16 streams, releases from adjacent streams (defined as the nearest basin receiving hatchery fish north and south of the mouth of the subject stream) accounted for 57% of the strays (Figure 2), and composed the majority of strays in 10 of the 16 sampled streams. Alsea stock steelhead transplanted into the Siuslaw River and straying to the Alsea basin accounted for 50% of the fish that strayed to an adjacent basin. If Siuslaw strays to the Alsea basin are excluded, releases into adjacent basins accounted for 38% of all strays (Figure 2). The median distance between adjacent basins was 23 mi, whereas the median distance that steelhead strayed from their release basin was 34 mi (range mi). Strays from hatchery releases in northern California rivers were most frequent, reported in 11 of the 16 Oregon streams we surveyed (Table 3). Of the hatchery releases in Oregon basins, strays from Umpqua River releases were most frequent, reported in 8 of 16 streams (Table 3). Eighty-nine percent of these strays were from releases of Alsea stock steelhead into the Umpqua basin. 11

15 Table 2. Number of wild, homing hatchery, and straying hatchery winter steelhead recovered in Oregon coastal rivers, run years. Data are from creel surveys, traps, and voluntary angler reports. Angler reports were used only where wild steelhead could be kept. Origin Streams Sampled Homing Straying Percent (years) Wild hatchery hatchery strays Streams with hatchery releases Necanicum (1) Nehalem (1) Nestucca (3) Siletz (3) Yaquina (3) Alsea (3) Siuslaw (3) Umpqua (3) Coquille (3) Rogue (1) Chetco (3) Streams without hatchery releases Trask (3) Drift a (3) Elk (1) Sixes (1) Winchuck (3) a Tributary of Alsea River that enters Alsea Bay. We examined the north-south pattern of straying in eight rivers that were surveyed with creel census or traps. Strays in rivers north of the Siuslaw and in the Chetco River were predominantly from releases made to the south (Figure 3). The majority of strays in the Siuslaw and Coquille rivers were from releases made to the north (Figure 3). Alsea River releases or Alsea outsystem releases accounted for most of the northern releases that strayed into the Siuslaw River (Table 3). Hatchery steelhead reared at Alsea Hatchery (Alsea and Coos stocks) and released in the Coos basin accounted for most of the strays from northern releases in the Coquille River (Table 3). Strays in the Winchuck River were equally from releases made north and south of the river (Figure 3), and were primarily from the Chetco River and northern 12

16 Table 3. Number and origin of hatchery winter steelhead in Oregon coastal rivers with and without hatchery releases, run years (except Elk and Sixes, run year only). Homing hatchery returns are highlighted. Sampled streams and release groups are listed by proximity north to south from top left. Release group Streams Cedar Cr. Alsea Alsea Unknown sampled Necanicum Nehalem Hatchery a transplant b local Siuslaw c Umpqua Tenmile Coos d Coquille Rogue Chetco California strays Streams with hatchery releases Necanicum Nehalem Nestucca Siletz Yaquina Alsea e Siuslaw Umpqua Coquille 20 f Rogue Chetco Streams without hatchery releases Trask Drift Elk Sixes 4 4 Winchuck a Released into Nestucca River and into Tillamook Bay rivers. b Includes hatchery steelhead released into Salmon, Siletz, Yaquina, Smith, and Coos rivers. Does not include releases into the Siuslaw River. c Released from Alsea Hatchery into the Siuslaw. d Includes some fish that may have been released into nearby Tenmile Creek. e Two steelhead released from hatcheries in the lower Columbia River were also recovered in the Alsea River. f Probably from releases into the nearby Coos River.

17 60 50 with Siuslaw strays to Alsea without Siuslaw strays to Alsea Percent of strays Number of basins from the release basin Figure 2. Frequency distribution of stray hatchery steelhead in Oregon coastal basins by the proximity to the release basin, run years. Graph shows data with and without transplanted Alsea Hatchery releases into the Siuslaw River that strayed back to the Alsea basin. California releases (Table 3). We did not include the Trask River in this analysis because we could not determine if steelhead from Cedar Creek Hatchery strayed from releases in nearby Tillamook Bay streams or from Nestucca River releases. We examined the straying pattern of hatchery steelhead to the north and south of Cape Blanco (Figure 1), which was used by NMFS as the geographic delineation between two Evolutionarily Significant Units (ESU; Waples 1991) of coastal steelhead (Busby et al. 1996). The ocean migration of Oregon coastal steelhead from rivers north of Cape Blanco is believed to be north into the Gulf of Alaska, while those from rivers south of Cape Blanco are believed to migrate offshore in the general vicinity of southern Oregon and northern California (Everest 1973; Pearcy et al. 1990; Pearcy 1992). For example, Pearcy et al. (1990) reported that marked juvenile steelhead from south of Cape Blanco were rarely recovered north of there. However, data on steelhead recoveries in the ocean are based on few recoveries of juveniles or adults in limited areas. Information reported by Burgner et al. (1992) suggested that at least some steelhead tagged in the Gulf of Alaska returned to rivers south of Cape Blanco, although these steelhead might not have originated from the stream to which they returned. 14

18 100% North South 80% 60% Percent 40% 20% 0% Nestucca Siletz Yaquina Alsea-Drift Siuslaw Coquille Chetco Winchuck Figure 3. Percentage of stray hatchery winter steelhead in eight Oregon coastal rivers that strayed to the north or south of where they were released, run years. Steelhead from releases south of Cape Blanco (Rogue, Chetco, California) were observed in all coastal rivers south of the Nestucca where we had recovery data (Table 3). About 15% of all strays sampled within an ESU were from the neighboring ESU. These recoveries suggest some steelhead overshoot their release basin and enter a basin in the neighboring ESU to spawn, or ocean migration patterns are more variable than has been hypothesized and that some south coast steelhead migrate north in the ocean and stray as they return south on their spawning migration, and vice versa. Strays from releases transplanted outside their natal basin accounted for 70% of all stray hatchery fish reported in Oregon coastal rivers. Local stocks reared and released in their natal basins accounted for 18% of all strays and local stocks reared outside their natal basins accounted for 12% of all strays. In addition, we compared the incidence of strays from different release groups (reared within and outside of release rivers). Use of a local brood stock (Siuslaw and Umpqua) appeared to reduce the incidence of strays in the home or rearing basin, and in other basins (Table 4). Interestingly, the return to the Alsea basin of Alsea steelhead reared and released in the Umpqua suggests some imprinting at the egg development stage or a genetic component for homing. By contrast, few Umpqua steelhead strayed into the Alsea, indicating straying of Umpqua fish to the Alsea is an uncommon occurrence. For other local stocks, strays from steelhead reared within the natal basin were slightly lower than strays from steelhead reared outside their home streams (Table 5). 15

19 Table 4. Percentage of the stray hatchery steelhead recovered in Oregon coastal rivers from releases of local and transplanted brood stocks into the Siuslaw and Umpqua rivers. Numbers of recoveries were adjusted to account for unequal release numbers. Siuslaw River a Umpqua River b Siuslaw stock Alsea stock Umpqua stock Alsea stock Percent strays in Alsea River 1 6 <1 4 Other rivers c 0 1 (1) 1 (1) 10 d (7) a Reared in Alsea basin. b Reared in Umpqua basin. Alsea stock eggs were incubated at Alsea Hatchery and transferred as eyed eggs. c Number of basins is in parentheses. d Mean percentage. Table 5. Percentage of the stray hatchery steelhead recovered in Oregon coastal rivers that could be attributed to various release strategies or use of stocks. Includes only data for which we could attribute recoveries to specific release groups. Stock Rearing basin Percentage of all strays in Release location Rearing basin Other basins a Local brood stock releases Alsea Alsea Alsea (6) N. F. Nehalem N. F. Nehalem N. F. Nehalem (6) Coquille Coquille Coquille -- 6 (3) Coos Alsea Coos 4 14 (4) Chetco Elk Chetco 0 20 (5) Transplanted stock release Alsea Alsea Transplanted b (4) a Average for basins where strays were found; number of basins shown in parentheses. b Alsea stock releases in Salmon, Siletz, Yaquina, Siuslaw, Smith, and Coos rivers. Steelhead transplanted from Alsea Hatchery were particularly apt to stray, accounting for 84% of the known stray hatchery fish in the Alsea River, and composed the highest percentage of strays in other rivers compared to other releases (Table 5). Almost 70% of these strays were from releases into the Siuslaw River. In a 1980s 16

20 marking study of transplanted releases from Alsea Hatchery, Kenaston and MacHugh (1985b and 1986) also showed a high incidence of adults straying back to the Alsea River from fish transplanted to the Siuslaw River (Table 6). The release of Alsea steelhead in the Alsea accounted for 39% of strays in the Siuslaw compared to 25% for Alsea outsystem releases. By contrast, in-stream releases of Alsea fish accounted for just 2% of strays in Drift Creek (despite nearby releases in the lower river), and 25% and 57% of the strays were from outsystem and Siuslaw releases, respectively. Table 6. Percentage of the total return to the Alsea River of transplanted Alsea stock winter steelhead that were from differentially marked releases into five coastal basins brood years (data from Kenaston and MacHugh 1985b,1986). Data were from creel surveys and returns to Alsea Hatchery and were adjusted to account for unequal release numbers. Brood Release river year Siletz Yaquina Siuslaw Smith Tenmile Creek Returns to the Alsea River from transplanted releases of Alsea stock accounted for 25 34% of the total hatchery return to the river in our study, compared to returns of 8 19% in the 1980s marking experiment. The increased proportion of these strays in our study is likely because of increases in transplanted releases (72 and 24% for Siuslaw and other rivers, respectively) and decreases in the local releases (10%). In the Hoh River, Washington, hatchery steelhead straying back to the rearing river accounted for 34 41% of the total hatchery return (Hiss et al. 1986, cited in Lirette and Hooton 1988). Steelhead from transplanted releases of Alsea stock also composed about 75% of the known strays in the Nestucca River (Table 3). These fish could have come from releases either into the Salmon River (the nearest geographic release) or into the Siletz River, another nearby river that had three times the number of hatchery steelhead released as Salmon River. However, the estimate of strays in the Nestucca is likely underestimated because transplanted releases from Cedar Creek Hatchery were not differentially marked from releases into the Nestucca basin. Therefore, we could not determine the degree of straying into the Nestucca River from Tillamook Bay releases. Transplanted releases of Alsea stock steelhead (including Siuslaw releases) accounted for 20% of the strays in the Coquille and may have been from releases into the nearby Coos River (Table 3). Although most of the hatchery steelhead in the Trask River were likely from Cedar Creek releases transplanted into nearby Tillamook Bay streams, some Nehalem River steelhead were also observed in the Trask (Table 3). 17

21 Discussion Stray hatchery fish create difficulties in attempts to manage rivers for naturally producing populations. Under Oregon's Wild Fish Management Policy, only 10% of the naturally spawning population may be composed of genetically dissimilar fish (ODFW 1992). Stray hatchery steelhead composed 10% or more of the total catch in 10 of 16 Oregon coastal rivers. The genetic integrity of locally-adapted populations can decrease with rates of migration (and gene flow) from stray hatchery fish as low as 5 10% (Emlen 1991; Felsenstein 1997), especially when selection pressures maintaining local adaptations are lower than the rate of gene flow between populations (Felsenstein 1997). NMFS has used an interim straying guideline of less than 5% of the naturally spawning populations to limit the proportion of stray, non-native hatchery fish (NMFS 1996). We documented high percentages of stray hatchery steelhead in several coastal rivers, including rivers with a hatchery that supplies large numbers of fish for release in other basins (Alsea River) and rivers where no hatchery releases are made (e.g., Trask and Winchuck rivers and Drift Creek). Strays in the Trask River and Drift Creek were predominantly from releases of transplanted stocks. Strays in the Winchuck River were mainly from releases in nearby Chetco River or from unmarked hatchery fish believed to be from northern California. Genetic effects of stray fish on a local population depend on the gene flow between the two groups, not just the physical migration of fish (Felsenstein 1997). Some fish exhibit exploratory behavior and may ascend nonnatal rivers before returning to their natal stream to spawn (Ricker 1972; Leider et al. 1985; Labelle 1992). Data in this study were collected by several techniques including trapping and surveys of fisheries and tributary streams. Although steelhead captured in this study could have been exhibiting exploratory behavior, the stray fish caught in the surveyed rivers had left the ocean and entered a basin other than the one where they were released. In addition, winter steelhead are generally close to spawning when they ascend freshwater and some data in this study were from traps and foot surveys in streams where steelhead were spawning. Although some information in this study is from surveys of fisheries, other facets of our winter steelhead research indicated that the composition of hatchery and wild steelhead in fisheries was similar to that measured on spawning grounds (see OVERLAP OF HATCHERY AND WILD SPAWNERS). We believe the proportions of stray hatchery steelhead we measured in the total catch of rivers is a good measure of the interbreeding potential between the nonnative hatchery fish and the naturally produced fish in those rivers. Stray hatchery fish can potentially affect wild populations through reduction in fitness of the wild populations by spreading deleterious alleles, through elimination of genetic differences between hatchery and wild populations, and through demographic effects such as harvest in mixed fisheries and competition (Nelson and Soulé 1987; Hindar et al. 1991; Busack and Currens 1995; Fresh 1997; Reisenbichler 1997). 18

22 Large numbers or proportions of stray hatchery fish in a river could create several problems for fish managers. Most hatchery steelhead programs have been developed to provide recreational fisheries by releasing smolts in specific locations. If large numbers of returning adults enter rivers other than the one where they were released it can cause problems with management programs designed to provide harvest on hatchery fish while increasing escapement of wild fish. For example, large numbers of hatchery steelhead returning to the river where they were reared rather than where they were released would likely decrease the percentage of hatchery fish caught by anglers and increase the escapement of hatchery fish to spawning grounds. Conversely, lower returns of hatchery fish to their release site could reduce the probability of catching hatchery fish and could cause underestimates of hatchery returns to that basin, perhaps leading to increases in the releases of hatchery fish. In addition, hatchery strays can negate management efforts to minimize the influence of hatchery fish on a wild spawning population (such as isolating returning hatchery fish through directed releases at specific sites, development and release of local brood stocks, and genetic maintenance of hatchery stocks). Hatchery strays would likely spread throughout a river rather than return to a specific location. In addition to genetic risks to naturally produced steelhead in the basin, large numbers of strays to the rearing hatchery also pose a genetic risk to the hatchery brood stock, if efforts are being made to maintain local hatchery stocks. If stray hatchery fish can not be physically differentiated from local hatchery fish, they could be incorporated into the local hatchery stock. In our study, the two predominant factors that contributed to straying in Oregon coastal basins were releases in nearby basins and releases of transplanted stocks. Another factor contributing to straying was steelhead returning to their rearing basin instead of their release basin. Few hatchery steelhead strayed to their natal basin or to a basin where they had been incubated, although these types of releases were limited. In general, the percentage of strays within a basin that was from a particular type of release (e.g., local or transplanted stocks) varied considerably and was influenced by geographic proximity to that release. Several rivers we surveyed did not have large numbers of stray hatchery steelhead, therefore reducing the overall impact of hatchery fish on wild steelhead populations in these rivers requires reducing the influence of locally released hatchery fish rather than solving a "straying problem". In other rivers, stray hatchery fish did represent a large proportion of the total population in streams with and without hatchery releases. Because our data do not implicate a particular release strategy as the cause of straying in Oregon coastal rivers, all steelhead releases should be evaluated for modifications that could reduce straying. Possible solutions to reducing the number of stray hatchery fish in problem streams include use of local brood stock, direct stream releases in tributaries to increase homing, rearing and release within natal basins, reduction in hatchery releases, or a combination of these strategies. As demonstrated elsewhere in this report, homing of winter steelhead to release sites in tributary streams was highly accurate (see Acclimation). In addition, we found that use of a local brood stock reduced the amount of straying to the rearing or home basin and to other basins. 19

23 Work with additional experimental releases, indicated returns from a local brood stock (Siuslaw) strayed to the rearing hatchery (Alsea) at a lower rate than did returns from a transplanted stock (Alsea) (see USE OF LOCAL BROOD STOCK IN HATCHERY PROGRAMS). Lirette and Hooton (1988) also noted that a local stock of steelhead strayed at a lower rate than a transplanted stock. Hatchery fish that have been reared in a location distant from the release basin may home better to the release basin than fish reared in a nearby basin (Lirette and Hooton 1988; Quinn 1993). However, Labelle (1992) reported that certain stocks of coho salmon were more susceptible to straying when exposed to foreign water sources during rearing. OVERLAP OF HATCHERY AND WILD SPAWNERS Because fishery data were used, in part, to measure the degree of hatchery straying and the origin of strays, we wanted to know if fishery data reflected the actual proportion of hatchery fish in natural spawning populations. We also wanted to know if hatchery and wild fish overlapped in time and in space during spawning. The Wild Fish Management Policy (ODFW 1992) established specific criteria for the percentage of hatchery fish allowed in a naturally spawning population. Up to 50% of the natural spawning population can be hatchery-reared if native brood stock is used and wild fish are incorporated annually into the brood stock. The use of transplanted hatchery fish lowers the percentage to 10% or less. Work was conducted in the Trask River near Tillamook, Oregon in 1989, in three short coastal streams along the central Oregon coast in 1990, in the Siuslaw River from 1991 through 1993, and in the Necanicum River in Trask River 1989 Scales from adult steelhead in the Trask River were used to estimate the proportion of hatchery strays in the Trask and to compare the proportion of hatchery fish on the spawning grounds with that in the fishery. Differences in growth patterns on scales between hatchery and wild steelhead are distinctive enough to accurately separate hatchery from wild fish (Peterson 1978; Kenaston and MacHugh 1985a). No hatchery steelhead are released into the Trask River. We used fish collected at weirs and by electrofishing to represent the spawning population of steelhead in the Trask River. A weir was installed in Edwards Creek, a tributary of South Fork Trask River 21 miles above tidewater, on 1 February and fished through 26 May. In addition, steelhead were collected from 8 January to 13 May at a weir located in the East Fork Trask River at Trask Hatchery Pond (about 21 miles above tidewater). We also spent 4 days in late March and April electrofishing from a drift boat on a 2-mile section of North Fork Trask River starting at RM 26. A Coffelt GPP 5.0 electrofisher (generator and output control box) was used to capture fish. 20

24 Scale samples were taken from captured fish and the fish were sexed and measured to the nearest 0.5 inch. Fish were given an opercle punch prior to release to identify recaptures. Scale collections from the winter steelhead fishery were obtained from a creel survey and through a volunteer scale program (Kenaston and MacHugh 1983). The creel area in the Trask was divided into five sections to examine differences in the proportion of strays from lower to upper areas. In addition to taking scales, we recorded the sex of steelhead and measured them to the nearest 0.5 inch. We separated hatchery from wild steelhead with scale analysis by assuming that only hatchery steelhead migrate as age 1 smolts (Lindsay et al. 1989). We caught 40 adult steelhead in Edwards Creek of which 35 had readable scales. Of these, five (14%) were hatchery fish. All hatchery fish were males and were caught in March (Figure 4). Wild steelhead were caught from mid February through late May (Figure 4). The weir on the East Fork Trask River caught 73 adult steelhead of which 63 had readable scales. Of these 15 (24%) were hatchery fish. Both hatchery and wild fish were caught throughout the trapping period (Figure 4). We captured nine adult steelhead in four days of electrofishing the North Fork Trask River. Of the eight readable scales, six were wild and two were hatchery fish. The proportion of hatchery strays estimated from the Trask fishery was similar to that estimated on the spawning grounds (Table 7). Based on the creel data, lower river areas tended to have a higher proportion of stray hatchery fish than upper river areas (Table 8). In addition, Trask Hatchery trap on Gold Creek, a tributary of lower Trask near RM 10, caught 50 steelhead in January 1989 of which 94% were hatchery strays. These fish were not included in the estimate of the overall proportion of hatchery fish that spawn in the Trask. Mid-Coast Streams 1990 A two-person crew was used from January through April 1990 to capture adult steelhead in Cape Creek, Tenmile Creek and the Yachats River, three streams on the central Oregon coast managed for wild steelhead. No hatchery steelhead smolts have been released into Cape and Tenmile Creek. Hatchery steelhead smolts were last released into the Yachats River in Adult steelhead were captured with backpack and boat electrofishers, seines, and dip nets in spawning areas. Scales were collected and interpreted for hatchery or wild origin. Numbered Floy tags were put on steelhead before they were released to avoid counting fish twice. A creel survey was also conducted to compare hatchery-wild composition in the fishery with that in spawning areas. 21

25 14 Number Wild Hatchery East Fork Trask River Edwards Creek January February March April May Month Figure 4. Overlap of spawn timing of hatchery and wild steelhead in the East Fork Trask River and in Edwards Creek, Table 7. A comparison of the percentage of hatchery winter steelhead in spawning areas in the Trask River with the percentage estimated from catch in the fishery, run year. Hatchery steelhead are not released into the Trask River. Steelhead sampled in Measure Fishery a Spawning areas b Percent hatchery strays % confidence limits Sample size a Includes wild and hatchery fish sampled in a creel survey and in the volunteer scale program b Based on fish caught in Edwards Creek trap, at East Fork Trask River Dam, and by electrofishing in North Fork Trask River. 22

26 Table 8. Percentage of hatchery fish in the catch of hatchery and wild winter steelhead sampled with a creel survey in sections of the Trask River, run year. Hatchery steelhead smolts are not released into the Trask River. Measure Lower (RM 4 9) Trask River Middle (RM 9 13) Upper (RM 13 18) N. Fork Trask S. Fork Trask Percent hatchery strays % confidence limits a 0 35 a Sample size a Confidence limits were estimated to be from 0% (lower limit) to the maximum percentage that would give a 95% chance of obtaining a sample size N with no hatchery strays (upper limit) (personal communication 3 November 1989 with Mary Buckman, Oregon Department of Fish and Wildlife, Corvallis). The proportion of hatchery steelhead in the sample was greatest early in the season and lowest at the end of the season (Table 9). The average proportions of hatchery steelhead in spawning areas were in good agreement with proportions in the fishery, although sample sizes from the fishery were small (Table 9). Methods Siuslaw River Adult hatchery winter steelhead that returned to the Siuslaw River in through originated primarily from annual releases into the Siuslaw of about 150,000 smolts from Alsea Hatchery (Alsea River stock) on the North Fork Alsea River. Because Alsea fish are a transplanted stock in the Siuslaw, the Wild Fish Management Policy required that hatchery fish compose no more than 10% of the naturally spawning population. We captured adult steelhead in spawning tributaries with traps and with dipnets to determine the proportions of hatchery and wild fish on spawning grounds. Hatchery fish were identified either by fin marks or by growth patterns on scales depending on the year (all hatchery fish released on the Oregon coast were externally marked beginning with the 1990 release). We captured adult steelhead with weirs on four Siuslaw River tributaries each year (Table 10). In an additional trap was installed at Siuslaw Falls (RM 100) on the main stem and fished from 28 December 1990 to 10 May We captured steelhead in other tributaries primarily by using foot surveys and a 23

27 Table 9. Adult steelhead captured on spawning grounds and sampled in fisheries in Cape and Tenmile creeks and the Yachats River, Captured on spawning grounds in Stream, origin Jan Feb Mar Apr Total Fishery Cape Creek: Hatchery Wild % Hatchery Tenmile Creek: Hatchery Wild % Hatchery Yachats River: Hatchery Wild % Hatchery two-person crew with dipnets (Table 10). In we surveyed 41 tributaries for steelhead. The number of tributaries surveyed was reduced in and mainly to those where surveys indicated steelhead abundance was highest. Adult sampling with weirs and dipnets was generally conducted throughout the run period, from December through April. For each fish collected, we recorded fork length, sex, and fin clip, removed a scale sample, and tagged the fish with a Floy tag before releasing them. The percentage of hatchery fish spawning in tributary streams was estimated in two ways. First, we simply calculated the percentage of hatchery fish in the combined catches in all tributaries. This tended to give more weight to tributaries where more fish were captured. Second, we used each tributary where both wild and hatchery fish were captured as an independent estimate of the percentage of hatchery fish in the run. The mean of these estimates for all tributaries sampled gave another estimate of the percentage hatchery fish in the run. We present estimates based on both methods because potential biases in each cannot be determined with the data collected. Although the weighted method may reflect differences in population abundance among tributaries, it could just as likely reflect differences in sampling efficiency between methods and among tributaries. Calculation of mean values, on the other hand, gives as much weight to tributaries 24

28 where few fish spawn as to those where many more spawn and may not represent the overall population in the basin. Considerably more effort would be needed in sampling spawning grounds to reduce these biases in a basin the size of the Siuslaw. We used a creel survey (Lindsay et al. 1994) of anglers fishing the Siuslaw River to estimate the proportion of hatchery fish in the catch. A creel person checked anglers 5 days per week including weekends and recorded marks, collected scale samples, recorded sex, and measured length on each fish checked. A catch and release regulation for wild fish was adopted on the Siuslaw River beginning in January 1992 where only fin marked hatchery fish could be legally kept by anglers. Unmarked fish (wild) had to be released. Estimates of the proportion of wild fish in the catch beginning in 1992 was based on asking anglers how many wild fish they had caught and released that day. We compared composition in spawning areas with those in the sport catch to determine if fishery data reflected spawning composition in the Siuslaw River. Results Forty-one tributary streams were sampled in the Siuslaw basin in (Lindsay et al. 1991). A total of 371 steelhead was captured in 18 of these streams (Table 10). Wild steelhead were found in only nine streams. The date of first spawning of wild steelhead in individual tributaries ranged from 16 January to 9 April (Table 10). We captured eight pairs of steelhead on redds during tributary surveys in Three of the eight pairs contained a mix of hatchery and wild fish (Table 11). In , 33 steelhead that were passed above weirs were later recaptured at the weirs as kelts on their downstream migration (Table 12). In general, males stayed upstream longer than females. Both males and females stayed upstream longer in a large tributary, West Fork Indian Creek, than they did in two small ones, Fish and Turner creeks. In Turner Creek we recaptured 10 hatchery steelhead on redds after they had been tagged at the weir and passed upstream. Males were recaptured on redds an average of 7.3 days (n = 6) after tagging and females 1.8 days (n = 4) after tagging. We captured 363 steelhead in nine streams in the Siuslaw basin in (Table 13). Wild steelhead were found in eight of the streams surveyed. The date of first spawning of wild fish in these tributaries ranged from 6 January to 10 March. We captured 301 steelhead in streams sampled in (Table 14). The date wild steelhead first spawned ranged from 28 December to 19 March in the tributaries surveyed. 25

29 Table 10. Overlap of hatchery and wild winter steelhead in tributary spawning areas in the Siuslaw River basin, Sampling began 16 Jan Creek a Number of weeks Number captured surveyed Hatchery Wild Date of first wild spawning Hatchery fish after first wild spawning Cleveland Deadwood Mar 2 (67%) Elk Fish b Jan 55 (81%) Green Greenleaf Feb 9 (53%) Hula Indian trib Mar 0 Indian W.F. b Jan 31 (25%) Meadow Nelson Pataha San Antone Jan 22 (79%) Thompson Turner b Jan 45 (85%) Waite Apr 0 Walker Whittaker b Jan 12 (60%) a Only includes streams where steelhead were captured. Twenty-three other streams were surveyed but no steelhead were captured. b Weirs installed on these streams in Table 11. Date of capture of eight pairs of steelhead on redds in tributaries of the Siuslaw River, Hatchery male x wild female Wild male x hatchery female Hatchery male x hatchery female Wild male x wild female 29 Jan 30 Jan 11 Feb 1 Apr 17 Jan Feb Feb Mar -- 26

30 Table 12. Mean number of days between upstream passage of steelhead above weirs on three tributaries in the Siuslaw River basin and their later recapture as kelts at these weirs, Tributary Hatchery Wild Stream Male Female Male Female length (mi) n Mean n Mean n Mean n Mean Turner Creek Fish Creek WF Indian Creek Table 13. Overlap of hatchery and wild winter steelhead in spawning areas in the Siuslaw River basin, Fish caught at weirs include downstream migrating adults (kelts) seined immediately above the weirs. Creek Date first Date first observed Number captured surveyed (weeks) Hatchery Wild Hatchery Wild Percent hatchery Fish Dec 31 (11) Feb 6 Feb Greenleaf a Dec 10 (20) Dec 19 Jan 6 b Indian: Upper Jan 18 ( 5) Mar 10 Mar West Fork a Dec 13 (27) Jan 17 Jan San Antone Dec 27 ( 9) Mar 5 Jan 7 c Thompson Dec 30 (10) Feb 5 Mar Turner a Dec 4 (17) Jan 29 Jan Waite Dec 27 (10) Jan 15 Jan Whittaker a Dec 16 (21) Jan 6 Jan a Weirs installed on these streams. b No fish caught between Dec 19 and Jan 6. c Dead fish that appeared to be wild. 27

31 Table 14. Overlap of hatchery and wild winter steelhead in spawning areas in the Siuslaw River basin, Fish caught at weirs include downstream migrating adults (kelts) seined immediately above the weirs. Creek Date first Date first observed Number captured surveyed (weeks) Hatchery Wild Hatchery Wild Percent hatchery Green 29 Jan ( 5) 29 Jan 4 Mar Fish 29 Dec ( 9) 28 Jan 8 Mar Greenleaf a 23 Dec (25) 28 Dec 28 Dec Indian: Upper 11 Jan ( 7) -- 9 Feb West Fork a 7 Jan (23) 11 Jan 10 Feb North Fork 11 Jan ( 6) 3 Feb San Antone 22 Dec (10) 25 Jan 25 Jan Thompson 28 Dec (11) 23 Feb 23 Feb Turner a 18 Dec (14) 26 Jan 19 Mar Waite 31 Dec (11) 24 Jan Whittaker a 17 Dec (25) 22 Dec 29 Dec Pataha 12 Jan ( 8) 26 Jan 26 Jan Walker 27 Jan ( 3) 27 Jan Pat 10 Mar ( 3) 10 Mar Esmond 15 Jan ( 4) Deadwood b 13 Jan ( 6) -- 2 Feb Herman 30 Dec ( 4) Elk 30 Dec ( 6) Velvet 30 Dec ( 1) Cleveland 5 Jan ( 1) Taylor 11 Jan ( 1) Gibson 30 Dec ( 3) Meadow 24 Mar ( 1) Hula 2 Mar ( 2) Nelson 19 Jan ( 3) Barber 15 Mar ( 2) Chickahominy 12 Jan ( 4) 18 Feb Unnamed c Apr ( 1) a Weirs installed on these streams. b Includes Misery, Panther, W.F. Deadwood and S.F. Bear creeks. c Upstream of Whittaker Creek. 28

32 The percentage of hatchery fish spawning in Siuslaw tributary streams over three years ranged from 43% to 69%, depending on the method used to calculate the percentage (Table 15). The percentage of hatchery fish in the sport fishery ranged from 57% to 72%. In and , the percentage of hatchery fish in the fishery was within the range of the two methods used to estimate the percentage on spawning grounds (Table 15). This appeared to be true even though wild fish had to be released and hatchery fish could be kept in the sport fishery under catch and release regulations adopted in January In the fishery estimate was only slightly higher than the highest estimate on the spawning grounds (72% versus 67%, respectively). Table 15. Percentage of hatchery steelhead in spawning areas based on two methods of estimation and in the sport fishery, Siuslaw River, , , run years. A catch and release regulation for wild steelhead was adopted on January 1, Sample size is in parentheses. Method of estimation Percentage hatchery fish in all tributaries combined 62 (371) 43 (364) 61 (301) Mean percentage hatchery fish in tributaries where both wild and hatchery fish were captured 67 (7) 65 (9) 69 (9) Percentage hatchery fish in the sport fishery 72 (65) 57 a (565) 67 (407) a Estimate may be low because we assumed all unmarked fish released were wild even though hatchery adults that spent three summers in the ocean would not have been marked. Logically, catch and release regulations should result in fewer hatchery fish on spawning areas because some would be removed in the fishery. Four hypotheses would explain the similarity between the percentage of hatchery fish estimated on spawning grounds and that in the angler catch: (1) wild fish released are caught more than once by anglers thereby inflating the number of wild fish in the fishery; (2) anglers exaggerate the number of wild fish caught and released when interviewed by creel technicians thereby inflating the number of wild fish; (3) wild fish die after being caught and released at the same rate as hatchery fish that are caught and kept by anglers, and; (4) sampling methods on the spawning grounds are not sensitive enough to detect a change in the percentage hatchery fish caused by catch and release regulations. 29

33 Although all these hypotheses are probably true to some extent, we suspect the most likely hypothesis to explain the similarity in fishery and spawning ground estimates is number 4. Figure 5 shows that catch and release regulations, even at high exploitation rates, make only small changes in the proportion of hatchery fish on the spawning grounds when the percentage of hatchery fish in the run is high. In the Siuslaw River the percentage of hatchery fish in the run was nearly 70%. A 35% exploitation rate under catch and release regulations for wild fish would result in only a 14% decrease in the percentage hatchery fish on the spawning grounds (i.e. a decrease from 70% to 60% hatchery fish). We doubt our spawning survey and trapping methods were sensitive enough to detect this small of a decrease Decrease in Percentage of Hatchery Fish % Hatchery Fish 50% Hatchery Fish 70% Hatchery Fish Exploitation Rate Figure 5. Hypothetical decrease in the proportion of hatchery fish on spawning grounds under catch-and-release regulations for wild fish when the percentage of hatchery fish in the run prior to the fishery is 30%, 50%, and 70%. Necanicum River 1996 The study in the Necanicum River was done to determine the spatial and temporal distribution of hatchery and wild fish spawning in the basin. No creel survey was conducted. Annual releases of hatchery fish in the Necanicum have averaged about 40,000 smolts. The hatchery stock used is from the North Fork Nehalem River and are reared at Nehalem Fish Hatchery. 30

34 Methods Sampling began on 3 January and continued until 30 April. Twelve tributaries were sampled along with eight sections of the main-stem Necanicum River (Table 16). Each section was sampled every 7 10 days with the smaller, less productive, tributaries sampled less frequently. All of the tributaries were approximately 4 10 meters wide, and the main-stem portions were meters wide. A two-person crew conducted the surveys by walking sections of each stream and locating steelhead with the aid of polarized sunglasses. When a fish was observed, one crew member would enter the stream above the fish while the other person remained downstream. With the use of a 30-in. diameter nylon-mesh dip net, the upstream person would force the fish downstream where the fish was then intercepted by the person downstream. Gill nets were also used to capture fish when surveying large sections and during high water conditions. When fish were observed, the gill net was stretched across the stream below the fish. The fish were then forced downstream into the net where they became entangled. Fish were identified as hatchery or wild by the presence or absence of fin clips. Scale samples were collected and fork lengths were measured. Sex and spawning condition (bright, ripe, or spawned out) was also recorded. All fish captured were marked by putting a hole in the opercle with a paper punch to identify recaptures. The fish were then released back into the stream. Redd counts were also recorded during surveys. Redds were marked with flagging in January and February. Redds were marked with painted rocks in March and April. Results Three hundred and eighty six steelhead were observed during the study period and of those, 210 (54%) were captured (Table 16). Our ability to see steelhead was greater in tributaries than in main-stem sections. The ratio of fish observed per redd counted was 1.38 fish per redd in tributary streams and 0.49 fish per redd in main-stem sections. Capture success was also greater in tributary streams (59%) than in mainstem sections (46%). The main stem was only sampled in March and April due to high water in January and February. The percentage of wild and hatchery steelhead differed between tributaries and main-stem sections. In tributaries 20% of the fish captured were wild and 80% were hatchery. In the main stem, 77% were wild and 23% were hatchery. For the entire 31

35 Table 16. Winter steelhead in survey sections of the Necanicum River basin, January April, Survey section Captured (seen) Wild Hatchery Redds Recaptured Necanicum River: Hwy 26 bridge S. Fk. Necanicum S. Fk. Necanicum Lindsley Cr. 4 (16) Lindsley Cr. ODOT station 7 (20) ODOTstation N. Fk. Necanicum 16 (34) N. Fk. Necanicum L. Humbug Cr. 12 (18) L. Humbug Hwy 5 bridge 7 (16) Hwy 53 bridge Hwy 26 bridge 0 ( 0) Upper Necanicum R. 15 (29) Beerman Cr. 14 (24) Klootchie Cr. 15 (22) Mail Cr. 29 (44) S. Fk. Necanicum: Mouth Brandis Cr. 0 ( 0) Brandis Cr Trib A 4 (16) Trib A barrier 4 (13) Trib A 5 (18) Trib B 11 (14) N. FK. Necanicum 14 (18) Little Humbug Cr. 23 (37) Warner Cr. 1 ( 1) Bergsvik Cr. 7 (14) Joe Cr. 5 ( 9) Grindy Cr. 17 (23)

36 basin, 37% were wild fish and 63% were hatchery fish. Basin-wide estimates of the percentage of wild and hatchery fish are likely biased toward tributaries because of the longer sampling period, greater visibility, and higher capture rates than in main-stem sections. Most hatchery steelhead entered spawning areas in January and February with a noticeable break in spawn timing between wild and hatchery fish during the second week of March (Figure 6). Increased spawning activity of wild fish began in mid-march and continued through April (Figure 6). Hatchery fish were captured in 14 of the 16 weeks sampled and wild fish were captured in 15 of the 16 weeks sampled. Hatchery steelhead were found through the end of April in low numbers and wild steelhead were found as early as sampling began in January hatchery wild Number January February March April Figure 6. Hatchery and wild winter steelhead captured each week in all survey sections combined in the Necanicum River basin, January April, Tributaries most commonly used by spawning steelhead were Little Humbug, Mail, Klootchie, Beerman, and Grindy creeks (Table 16). Suitable spawning areas were found throughout the main stem. The best area was in a 3.7 mi section between the confluence of the South Fork Necanicum (RM 12.8) and the confluence of Little Humbug Creek (RM 16.6). Redd superimposition was especially high in the section from the Oregon Department of Transportation yard (RM 14.7) to the North Fork Necanicum (RM 15.2). Fish spawning in the main stem repeatedly used the best spawning areas, which lead to high rates of redd superimposition. Many of the painted rocks used to mark redds were buried or displaced by newly spawning fish. 33

37 Conclusions The hatchery and wild composition of the catch of winter steelhead in sport fisheries reflects the composition on spawning areas and is adequate to determine compliance with Wild Fish Management Policy, especially where management is far from the criteria specified in the policy. In all basins, there was considerable overlap in spawn timing between hatchery and wild steelhead although wild fish tended to spawn later and over a longer time period than hatchery fish. USE OF LOCAL BROOD STOCK IN HATCHERY PROGRAMS The use of locally-adapted native stocks in hatchery programs recognizes that these stocks are best suited for survival in natural environments and that their use in hatcheries will reduce genetic risks from interbreeding with wild stocks. Native populations of wild steelhead have evolved life history strategies (MacLean and Evans 1981), body form (Ihssen et al. 1981), and physiology (Ihssen et al. 1981; Schreck et al. 1986) that increases survival in their environment. The Wild Fish Management Policy (ODFW 1992) recognizes that genetic risk to wild populations is decreased when hatchery brood stocks are developed from native stocks and some wild fish are incorporated into hatcheries. With this portion of the study, we provide managers with a comparison of performance between hatchery releases of a local stock with that of a transplanted stock. The performances compared were relative return rate and contribution to fisheries. An unexpected difference in straying was also observed. Methods The study was conducted in the Siuslaw River, a large river on the central Oregon coast (Figure 7). Lake Creek, a major tributary of approximately the same size as the main stem, flows into the Siuslaw River 7 mi above tidewater at RM 29 (Figure 7). Winter steelhead primarily spawn in tributaries of the Siuslaw River below Esmond Creek (RM 57) and in several tributaries of Lake Creek. Spawning generally occurs from January through May. A popular recreational fishery for steelhead occurs in the main-stem Siuslaw River from the head of tide (RM 22) upstream to Whittaker Creek (RM 46) and in Lake Creek from its mouth to Greenleaf Creek (RM 14). We released two stocks of hatchery winter steelhead into the Siuslaw River in 1991, 1993, and One stock originated from wild adults collected in the Siuslaw River (i.e. local stock). The other stock originated from a highly domesticated hatchery stock in the Alsea River collected at Alsea River Hatchery (i.e. transplanted stock). We considered adult steelhead in the Siuslaw as a wild fish if it had not been reared as a juvenile in a hatchery, regardless of its parentage. Scale patterns and clips of fins or 34

38 Pacific Ocean NF Siuslaw Thompson Siuslaw WF Indian Green River Deadwood Turner Lake Waite Whittaker Greenleaf San Antone Meadow Triangle Lake Nelson Wolf Fish Pataha Wildcat Esmond Siuslaw River Figure 7. Map of the Siuslaw River showing trap sites ( ) for winter steelhead. Not all traps were operated each year. maxillary bones were used to distinguish hatchery from wild steelhead. Alsea stock winter steelhead have traditionally been used for the hatchery program in the Siuslaw basin with about 175,000 released annually between 1982 and Collecting Brood Stock and Rearing Juveniles We used several types of weirs and traps on tributaries to collect wild Siuslaw River winter steelhead for brood stock where past data indicted wild steelhead spawned. Schroeder (1996) describes types and construction methods of weirs used in the Siuslaw basin as well as other techniques used to collect adult salmon and steelhead. Four tributaries were trapped in each of 3 run years, , , (Table 17). In 1990 we also tried angling and electrofishing to collect brood stock; however, these methods were eliminated because of high mortality or low 35

39 catch (Table 18). Our goal was to obtain enough brood stock to provide an annual release group of 30,000 smolts of local origin. A group of 30,000 Alsea stock smolts from Alsea Hatchery was used as a control group each year. Table 17. Wild steelhead trapped for brood stock in tributaries of the Siuslaw River, , , and run years. Insufficient wild brood stock was collected in Creek Date trap installed Date trap removed Days Wild fish fished Kept Released Dead Esmond 7 Feb 2 May West Fork Indian 2 Mar 18 May Greenleaf 14 Mar 2 May Whittaker 23 Mar 3 May West Fork Indian 13 Dec 18 Jun a 27 b 0 Greenleaf 10 Dec 29 Apr Turner 4 Dec 27 Apr Whittaker 16 Dec 13 May b West Fork Indian 7 Jan 15 Jun 147 c Greenleaf 23 Dec 14 Jun Turner 18 Dec 21 Jan d Whittaker 17 Dec 9 Jun a One fish kept but not spawned. Released into Lake Creek. b One fish mistakenly transported to Carter Lake along with hatchery fish. c Does not include 12 days when the weir was washed out. d Washed out and not replaced. 36

40 Table 18. Mortality by capture method of wild winter steelhead captured for brood stock in the Siuslaw River, Method Number held Pre-spawning mortality Post spawning mortality Trap Electrofishing Sport angling 9 6 a 0 a One additional female close to death was released. Steelhead captured in the Siuslaw River basin were transported to earthen ponds on private property and held in 6-in diameter x 40-in long PVC tubes suspended from a floating wooden frame (Figure 8). Parents for 1991 and 1993 releases were held in a pond located on Johnson Creek, a tributary of Lake Creek at about RM 6. For the 1994 release, the holding pond was located on a small fork of Swamp Creek, which flows into Triangle Lake (RM 19), at the headwaters of Lake Creek. Fish were held until their origin (wild or hatchery) could be verified with scales. Fish verified as originating from a hatchery were released. Wild fish were checked weekly until they were mature enough to spawn. Steelhead captured early in the season took longer to mature than those captured later in the season (Figure 9). Figure 8. Steelhead held in tubes suspended from a floating wooden frame. 37

41 60 50 Maturation time (d) February March April May Capture date Figure 9. Maturation times for steelhead collected from main-stem areas (open triangles, n = 14) and tributaries (solid squares, n = 69) in the Siuslaw basin, Wild steelhead adults were live-spawned at the holding pond in 1990 and 1992 and kill-spawned in In 1990 luteinizing hormone (Fitzpatrick et al. 1984) was injected into the body cavity of six female and one male steelhead to induce or speed maturation. Two of the six females showed no response and were released unspawned 14 days later. The remaining four females matured and were spawned 3 days later. The only injected male matured and was spawned 6 days later. Hormones were not used in other years. Gametes were collected in individual containers, put on ice, and transported about 1.5 hours to a disease isolation laboratory in Corvallis, Oregon for fertilization. Gametes were crossed at the laboratory in a 2 x 2 spawning matrix whenever possible to increase the effective population size. The eggs from each female were split into two lots and the sperm of each male was split into two lots. Sperm from male 1 was used to fertilize one of the egg lots from female 1 and from female 2. Sperm from male 2 was used to fertilize the other egg lots from female 1 and from female 2. Each mating in the spawning matrix was incubated separately in 0.5 gallon plastic containers (Figure 10). Each container had its own water supply line and the effluent from each jar went directly into a drain and holding tank where it was treated with chlorine. The fish were held at the laboratory until they received disease clearance from pathologists (Table 19). Fish were then transferred to Alsea Hatchery in 1990 and 1992 as fry, and in 1993 as eyed eggs. Once there, they were reared to smolts in 38

42 separate ponds as part of the normal Alsea Hatchery production. The control group of Alsea stock was collected, incubated, and reared to smolts at Alsea Hatchery as part of the hatchery's standard production. Figure 10. Incubation jars used for isolating each mating. Table 19. Spawning and incubation of wild Siuslaw winter steelhead at the Corvallis laboratory prior to transfer to Alsea Hatchery for rearing to smolt. Run year Number spawned Eggs taken Mortality to Transfer Eyedeggs Time of transfer Number Life stage Date ,387 17% 53% 42,600 Fry Aug ,800 29% 61% a 36,701 Fry Apr 24 May ,600 13% 13% 38,986 Eyed eggs Feb 22 Mar 29 a About 25,000 hatched fry died at the laboratory when a tractor broke a water main. Siuslaw and Alsea smolts were released into the Siuslaw River in early April in the same proportions at each release site (Table 20). Smolts were released in 1991 into the main-stem Siuslaw River at several locations from the mouth of Whittaker Creek to below the confluence with Lake Creek. Releases in 1993 and 1994 were made into Lake Creek at several locations between Indian Creek (RM 2.5) and Greenleaf Creek (RM 14.5). 39

43 Table 20. Siuslaw and Alsea stocks of winter steelhead smolts released into the Siuslaw River in 1991, 1993, and % confidence limits are in parentheses. Stock Fin clip Date released Number Fork length (cm) at release 1991 Siuslaw LPLM 25 Mar 35, (+0.8) Alsea LPRM 25 Mar 48, (+0.7) 1993 Siuslaw ADRM 31 Mar 32, (+0.9) Alsea ADLM 31 Mar 42, (+0.6) 1994 Siuslaw ADRM 30 Mar 33, (+2.3) Alsea ADLM 30 Mar 36, (+2.2) Returning Adults Adults returning from the three years of releases were sampled with traps located on four tributaries of the Siuslaw River in , on 10 tributaries in , and on 12 tributaries in and (Figure 7 and Table 21). In addition, statistically designed creel surveys (Lindsay et al. 1994) were used to estimate harvest in the recreational fishery in the Siuslaw River each year beginning in (Table 21). Fish straying into the Alsea River were sampled each year with creel surveys (not statistically designed to estimate harvest) and with the trap at Alsea Hatchery on the North Fork Alsea River (Table 21). We did not sample 3-salt (i.e. those that spent three summers in the ocean) adult returns in from the 1994 release. We used combined trap and sport catch data in the Siuslaw and Alsea rivers to compare relative survival and straying back to the Alsea River between Siuslaw and Alsea stocks. We used estimated harvest by month and by area from the statistical creel to compare catch and catch distribution of the two stocks in the Siuslaw recreational fishery. Catch distribution was limited to 2-salt adults from the 1993 and 1994 releases because the study ended before 3-salts from the 1994 release returned. In addition, catch distribution was not estimated for the 1991 release because the statistical creel started the year after 2-salt adults returned and too few adults were 40

44 checked in the non-statistical creel. A one-way repeated analysis of variance was used to test for significant differences in survival, recreational harvest, and straying of adults returning from 1991, 1993, and 1994 releases. We used P < 0.05 as the measure of statistical significance. Table 21. Adult returns from 1991, 1993 and 1994 releases of Siuslaw and Alsea stocks of winter steelhead smolts into the main-stem Siuslaw. Numbers have been adjusted to a standard 30,000 smolt release. Siuslaw River Alsea River Fishery a Tributaries b Fishery Hatchery Stock 2-salt 3-salt 2-salt 3-salt 2-salt 3-salt 2-salt 3-salt 1991 Siuslaw c 3 Alsea Siuslaw Alsea Siuslaw Alsea a A statistical creel survey was used to estimate total catch beginning in ; therefore, 2-salt catch from the 1991 release is not expanded. b Numbers expanded for trap efficiency beginning with 3-salt returns from the 1991 release (APPENDIX ). c Alsea Hatchery closed their trap on March 25, 1993 and may have missed some of the later-migrating Siuslaw stock (2-salt). Results and Discussion Relative survival from smolt-to-adult was not significantly different between the Siuslaw and Alsea smolts released into the Siuslaw River in 1991, 1993 and 1994 (Table 22). In addition, overall contribution to the recreational fishery in the Siuslaw 41

45 River was not significantly different between the two stocks. Although not statistically different, estimated catch of Siuslaw stock in the Siuslaw River sport fishery was higher than that of Alsea stock in 2 of the 3 years sampled (Table 23). Table 22. Relative survival (percentage) of Siuslaw and Alsea stocks based on trap catch and angler harvest in the Siuslaw and Alsea rivers. Release year Siuslaw Alsea Table 23. Recreational harvest of Siuslaw and Alsea stocks of winter steelhead in the Siuslaw River adjusted to a 30,000 smolt release. Release year Siuslaw Alsea a a Includes only 2-salt harvest. The spatial distribution of recreational catch through the winter from 1993 and 1994 releases was also similar for both stocks (Table 24). Siuslaw and Alsea groups were caught primarily in Lake Creek where they were released as smolts (Table 24). Siuslaw stock adults tended to migrate later than Alsea adults (Figure 11). The later migration timing shifted recreational harvest of Siuslaw fish into March compared with Alsea stock (Tables 25 and 26). This was especially true of the 1990 brood released in About 80% of the sport catch in and 45% of the catch in of both groups occurred in January and February (Table 25). The difference between years in the percentage caught in these two months likely reflected differences in river conditions, which influenced catch timing. 42

46 Table 24. Distribution (percentage) of sport catch by river section of Siuslaw and Alsea stocks of 2-salt winter steelhead in the Siuslaw River, December through March, 1993 and 1994 releases. Smolts were released into Lake Creek. Stock Lower Siuslaw a Upper Siuslaw Lake Creek 1993 release Siuslaw Alsea release Siuslaw Alsea a Extends from tidewater upstream to the confluence with Lake Creek. Table 25. Distribution (percentage) of sport catch by month of Siuslaw and Alsea stocks of 2-salt winter steelhead in the Siuslaw River, 1993 and 1994 releases. Stock December January February March 1993 release Siuslaw Alsea release Siuslaw Alsea

47 Percentage Percentage Percentage Jan 1-15 Feb 1-15 Mar 1-15 Apr 1-15 May 1-15 Two-Week Time Period Siuslaw Alsea Figure 11. Migration timing of Siuslaw and Alsea stocks of adult hatchery winter steelhead (2-salts only) into traps located on tributaries of the Siuslaw River from smolt releases in 1991, 1993, and

48 Table 26. The percentage of the sport catch that occurred in March of Siuslaw and Alsea stocks of adult hatchery steelhead, 1991, 1993, and 1994 releases. Release year, ocean age at return Siuslaw Alsea 1991: 2-salt 25 a 3 3-salt : 2-salt salt : 2-salt salt a No statistical creel survey was conducted. The later migration timing of Siuslaw stock was related to the time eggs were collected from their parents. In all three years over 60% of the eggs from Siuslaw brood stock were taken after March 1, but only an average of 8% of the eggs of Alsea brood stock were taken after that date (Table 27). The egg take for the 1991 release was the latest of all three years with all of the eggs taken after March 1 and 83% taken after April 1. No eggs were taken after April 1 for 1993 or 1994 releases of Siuslaw stock. This probably explains the late migration timing of adults returning from the 1991 release compared to other years. Several authors have found that migration timing is a heritable trait in anadromous salmonids (MacHugh 1981; Lane et al. 1990; Gharrett and Smoker 1993). Table 27. The percentage of eggs taken from Siuslaw and Alsea brood stocks after March 1, 1991, 1993, and 1994 releases. Siuslaw brood stock were wild fish collected in the Siuslaw River; Alsea stock were hatchery fish collected in the Alsea River. Release year Siuslaw Alsea a b a No eggs were taken after March 10. b Eighty three percent of the eggs were taken after April 1. 45

49 Alsea River steelhead reared at Alsea Hatchery and released as smolts into the Siuslaw River have strayed at a high rate as adults back to the Alsea River rather than returning to the Siuslaw River (Kenaston and MacHugh 1986; see also STRAY HATCHERY STEELHEAD IN OREGON COASTAL RIVERS). However, straying of adults into the Alsea River was significantly (P < 0.01) reduced by using Siuslaw stock. Straying was reduced by more than 50% in all three years of comparison, although both stocks were reared as juveniles at Alsea Hatchery and trucked to the Siuslaw River for release (Table 28). Within the Siuslaw, however, both stocks homed to their release site as smolts (see Table 24). Increased homing to the Siuslaw contributed to higher catch of Siuslaw stock than Alsea stock in two of the years sampled. In the other year (1991 release), many of the Siuslaw stock adults returned after the fishery closed the end of March. Table 28. Percentage of the total catch of Siuslaw and Alsea stocks of winter steelhead in traps and in fisheries straying into the Alsea River. Release year Siuslaw Alsea a a Alsea Hatchery closed their trap on March 25, 1993 and may have missed some of the later-migrating Siuslaw stock (2-salt). Lower stray rates of the locally-adapted Siuslaw stock and higher stray rates of Alsea stock into the Alsea River suggest a hereditary component in homing behavior of steelhead. However, the incubation history of the two stocks also differed. Siuslaw stock were incubated in well water at a laboratory in Corvallis pending disease clearance before being transferred to Alsea Hatchery for rearing to smolt. Alsea stock were incubated and reared entirely at Alsea Hatchery. Siuslaw stock were held for different lengths of time in Corvallis and transferred to Alsea Hatchery at different developmental stages in each of three years. We transferred fed fry to the hatchery in early August in 1990, and in late April to mid May in We transferred eyed eggs from late February through March in Returns of Siuslaw stock from each of these years strayed less into Alsea River than Alsea stock regardless of how long Siuslaw fish were held at the Corvallis laboratory. This suggests heredity was a component of homing behavior although we cannot rule out differences in imprinting that may have occurred prior to the eyed-egg stage. Evidence from other studies suggest a genetic component in homing for chinook (McIsaac and Quinn 1988) and pink salmon (Bams 1976). 46

50 REDUCING INTERBREEDING OF HATCHERY WITH WILD FISH We evaluated two potential management strategies that could reduce interbreeding of hatchery with wild fish. Acclimating hatchery juveniles at release sites prior to release to improve homing has been suggested as a strategy for segregating returning adults from wild fish (ODFW 1994, Kapuscinski 1997; Reisenbichler 1997; Brannon et al. 1998; Bugert 1998). Sterilizing hatchery fish to prevent spawning with wild fish was another strategy discussed early in the development of the Wild Fish Management Policy. Acclimation We defined acclimation as the short-term rearing (usually 2 6 weeks) of juvenile salmonids at a release site immediately prior to the fish's release. Fish are acclimated by holding them in natural or constructed ponds that use water from the home stream. Acclimation of hatchery fish has been used throughout the Pacific Northwest (Fast et al. 1991; Cuenco et al. 1993; Whitesel et al. 1994) as a management technique to increase survival and to improve the accuracy of homing (Kapuscinski 1997; Reisenbichler 1997; Brannon et al. 1998; Bugert 1998). Although several studies have evaluated the use of acclimation to increase survival (Johnson et al. 1990; Fast et al. 1991; Savitz et al. 1993; Whitesel et al. 1994), only one has evaluated its use to improve homing (Savitz et al. 1993). Acclimation may increase survival by reducing stress associated with transportation of hatchery juveniles to release sites (Ayles et al. 1976; Johnson et al. 1990). Transporting juvenile salmonids causes stress in smolts (Barton et al. 1980; Specker and Schreck 1980; Matthews et al. 1986), that may reduce survival if fish are released directly into natural environments. Elevated stress levels return to normal several days to one week after transportation (Strange et al. 1978; Barton et al. 1980; Specker and Schreck 1980). Acclimation may also increase the accuracy of homing by conditioning fish to a specific release site (Bugert 1998). Although homing in salmon is not completely understood, it is thought to be an olfactory response to specific chemical characteristics of natal streams (Cooper et al. 1976; Hasler and Scholz 1983). Olfactory imprinting by juvenile fish appears to occur primarily at the time of smolt transformation and migration (Everest 1973; Hasler and Scholz 1983; Morin and Døving 1992; Dittman et al. 1996). However, some salmon and steelhead undergo smolt transformation in areas of a watershed that are distant from the streams where they hatched or reared, yet return to their natal streams as adults (Murray and Rosenau 1989; Scrivener et al. 1994). This indicates the presence of a genetic component to homing (Bams 1976; McIsaac and Quinn 1988) or that some imprinting occurs before the smolt transformation. Oregon developed a Wild Fish Management Policy in 1992 that acknowledged the value of wild fish populations and set protection of genetic resources as a priority in management (ODFW 1992). The interbreeding of hatchery and wild fish poses risks to 47

51 conserving and utilizing the genetic resources of wild populations. Standards were developed in the Wild Fish Management Policy governing the allowable proportion of hatchery fish spawning with wild fish. Acclimation of hatchery steelhead has been proposed, among other strategies, as a way to manipulate the return distribution of hatchery steelhead. We conducted an experiment in the Siuslaw River to test the use of acclimation in attracting adult steelhead to a collection site to reduce the number of hatchery fish in wild steelhead spawning areas. A subset of this information appears in Kenaston et al. (In Press). We chose the Siuslaw River for the experiment for two reasons. First, it had a large allocation of hatchery steelhead smolts, which enabled us to release multiple groups, each large enough to evaluate adult returns. Secondly, research done in the mid 1980 s (Kenaston and MacHugh 1985a; Kenaston and MacHugh 1985b; Kenaston and MacHugh 1986) showed that a large proportion of the Alsea stock hatchery smolts released into the Siuslaw River to supplement the steelhead fishery, returned as adults to the Alsea River, where the hatchery is located, rather than to the Siuslaw River. Acclimation may help reduce straying of returning adults into the Alsea River. Methods Release of Juvenile Steelhead: We used Alsea River winter steelhead reared at Alsea Hatchery for this study. At the time we conducted the study, hatchery steelhead from Alsea Hatchery were being used to provide recreational fisheries in the Siuslaw River as well as several other Oregon coastal rivers. Since then, a Siuslaw River brood stock has been developed for hatchery programs in the Siuslaw River (see USE OF LOCAL BROOD STOCK IN HATCHERY PROGRAMS). We excised a pectoral fin and a maxillary bone in different combinations to identify fish in each group. Fish were marked in mid-november at Alsea Hatchery. Fork lengths were measured on samples from each group just prior to release. Pathologists examined the groups prior to transport and cleared them for release. Juvenile hatchery steelhead were transported in hatchery liberation trucks about 2 h from Alsea Hatchery to the Siuslaw River in late winter and early spring (Table 29). We began work on acclimation in We erected a portable, 12 ft x 50 ft x 5 ft raceway (Modutank model AB 0313 Aqua Breeder, Figure 12) at the Konnie Memorial Access (RM 2) on the banks of Lake Creek. About 400 gal/min of water was diverted from a small, high gradient tributary into the raceway. This site was only used in 1991 and subsequently moved because the tributary supplying water was too small (approximately 3 ft 3 /s) to attract returning adult steelhead and Lake Creek was too large (approximately 2,000 ft 3 /s in winter) to effectively trap returning steelhead. 48

52 In 1992 we erected the raceway on Whittaker Creek about 100 yards upstream from its confluence with the Siuslaw River. Two diesel engines pumped 460 gal/min of water into the raceway. Whittaker Creek has a mean winter flow of approximately 40 ft 3 /s, a basin size of approximately 11 mi 2, and contributes about 8% of the main-stem Siuslaw flow in April when hatchery juvenile steelhead were released. Table 29. Experimental groups of Alsea Hatchery winter steelhead smolts released to evaluate acclimation in a portable raceway in the Siuslaw basin. Mark abbreviations: RP = right pectoral fin, LP= left pectoral fin, RM = right maxillary bone, LM = left maxillary bone. Release year, group Days acclimated Date released Number released Mean length (SE) at release (cm) Mark 1991 a : Direct 0 Mar 25 29, (0.5) RPRM Acclimated 26 Mar 24 26, (0.2) RPLM 1992: Direct 0 Apr 1 29, (0.1) RPRM Acclimated 32 Mar 31 29, (0.2) RPLM Main-stem 0 Apr 1 46, (0.1) LPRM 1993: Direct b 0 Mar 31 29, (0.4) RPRM Acclimated 33 Mar 29 29, (0.4) RPLM Main-stem 0 Apr 1 45, (0.4) LPLM 1994: Direct 0 Mar 30 30, (0.1) RPRM Acclimated 33 Mar 29 29, (0.2) RPLM Main-stem 0 Mar 30 40, (0.1) LPLM Letz c 0 Mar 28 25, (0.2) LPRM a Releases into Lake Creek. All other years were released into Whittaker Creek. b About 7,100 steelhead smolts from the direct group were mistakenly released into the main-stem Siuslaw River near the mouth of Whittaker Creek. c Alsea stock reared from eyed eggs to smolts at a pond on Letz Creek (RM 105) in the Siuslaw basin, then released into Whittaker Creek. An additional 2,836 fish were released without a distinctive LPRM mark. Acclimated groups were held for about 30 d prior to release. A net was placed over the raceway to prevent bird predation. In the 3 years of study at Whittaker Creek, loading in the raceway initially ranged from 7.7 to 9.6 lbs of fish/gal/min and at release ranged from 10.3 to 11.6 lbs of fish/gal/min. Fish that died during the acclimation period were removed and subtracted from the number initially put into the raceway. In

53 and 1994 the fish were hand fed every 1.5 h each day from 0800 to 1800 hours, 7 d/week. Fish in 1993 were fed double rations every other day on the same schedule as in 1992 and There was no significant difference (P = 0.85) in mean length among acclimated, direct, and main-stem groups at release (Table 29). On the day of release, a fish retention screen was removed and steelhead were allowed to migrate out of the raceway through a 6 in diameter discharge pipe directly into Lake Creek or Whittaker Creek. Those not immediately leaving were forced out of the raceway with a seine. Direct groups were released into Lake Creek or Whittaker Creek 1 d or 2 d after acclimated fish were released from the raceway. The Lake Creek direct group was released into Lake Creek via the portable raceway. Whittaker Creek direct groups were released into the same Whittaker Creek pool as acclimated groups. Most acclimated and direct fish volitionally left the release pool within 1 d. Any fish remaining after 1 d were forced out of the pool with a seine. In 1993 about 25% of the direct group was mistakenly released into the main-stem Siuslaw River 20 yards above the mouth of Whittaker Creek rather than into Whittaker Creek. Figure 12. Portable raceway on the banks of Whittaker Creek used to acclimate winter steelhead. 50