WHITE STURGEON MITIGATION AND RESTORATION IN THE COLUMBIA AND SNAKE RIVERS UPSTREAM FROM BONNEVILLE DAM. ANNUAL PROGRESS REPORT

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1 WHITE STURGEON MITIGATION AND RESTORATION IN THE COLUMBIA AND SNAKE RIVERS UPSTREAM FROM BONNEVILLE DAM. ANNUAL PROGRESS REPORT APRIL MARCH 2006 Edited by: Thomas A. Rien Oregon Department of Fish and Wildlife In Cooperation With: Washington Department of Fish and Wildlife U.S. Geological Survey Columbia River Inter-Tribal Fish Commission Montana State University Prepared For: U.S. Department of Energy Bonneville Power Administration Environment, Fish and Wildlife P.O. Box 3621 Portland, OR Project Number Contract Number August 2007

2 CONTENTS Page EXECUTIVE SUMMARY by Thomas A. Rien REPORT A. Evaluate the success of developing and implementing a management plan for enhancing production of white sturgeon in reservoirs between Bonneville and McNary dams. by Colin G. Chapman and Michele Hughes REPORT B. Evaluate the success of developing and implementing a management plan to enhance production of white sturgeon in reservoirs between Bonneville and McNary dams by Olaf P. Langness, Dennis R. Gilliland, Brad J. Cady, and Brad W. James REPORT C. Describe reproduction and early life history characteristics of white sturgeon populations in the Columbia River between Bonneville and Priest Rapids dams. Define habitat requirements for spawning and rearing white sturgeon and quantify the extent of habitat available in the Columbia River between Bonneville and Priest Rapids dams by Michael J. Parsley and Pete Kofoot REPORT D. Evaluate the success of developing and implementing a management plan for enhancing production of white sturgeon in reservoirs between Bonneville and McNary dams. by Blaine L. Parker REPORT E. Determine spawning interval of white sturgeon in the Columbia River. by Molly A. H. Webb

3 EXECUTIVE SUMMARY We report on our progress from April 2005 through March 2006 on determining the effects of mitigative measures on productivity of white sturgeon populations in the Columbia River downstream from McNary Dam, and on determining the status and habitat requirements of white sturgeon populations in the Columbia and Snake rivers upstream from McNary Dam. The study is a cooperative effort by the Oregon Department of Fish and Wildlife (ODFW; Report A), Washington Department of Fish and Wildlife (WDFW; Report B), U.S. Geological Survey (USGS), Columbia River Inter-Tribal Fish Commission (CRITFC; Report C), and Montana State University (MSU; Report D). This is a multi-year study with many objectives requiring more than one year to complete; therefore, findings from a given year may be part of more significant findings yet to be reported. Highlights of results of our work are: Report A The total population of white sturgeon ( 54 cm FL) in The Dalles Reservoir in 2005 was estimated at 102,757 fish. The previous estimate completed in 2002 was 104,349 fish. The 2005 stock assessment indicated a 4% increase in sub-legal sized fish, an 81% reduction in legal-sized fish, and a 55% reduction in over-legal sized fish from 2002 levels. The size distribution of white sturgeon in The Dalles Reservoir was estimated to be: 98.1% <110 cm FL, 1.1% cm FL, and 0.8% >137 cm FL. The overall recapture rate of PIT-tagged sturgeon was 3.1%. Catch per effort for all reservoir sections and weeks combined was 8.02 white sturgeon per setline-day. Catch was distributed throughout the reservoir, with no significant difference in mean CPUE between reservoir sections (ANOVA, F= 1.1, P= 0.42). Of the 347 sturgeon that were marked and recaptured during sampling periods 1-4, 310 (or 89%) were recovered within 10 Km of the original marking location. Fish captured in 2005 had a mean relative weight of 105.4, which was not significantly different than the past two stock assessments in The Dalles (1997 & 2002). We estimated the age of 177 white sturgeon captured from The Dalles Reservoir during the 2005 stock assessment. Age estimates ranged from 5-40 years, with a median age of 11 years. Sturgeon captured and aged during the 2005 stock assessment were estimated to be significantly older (two-way ANOVA, F= 9.5, P<0.001) than sturgeon (of similar sizes) captured and aged during the 2002 stock assessment. The estimated ages from 2005 may reflect an unintentional bias towards older age estimates due to our awareness that past estimates tended to underestimate the age of individual fish (Rien and Beamesderfer 1994). 3

4 Data collected from actual recaptured fish in The Dalles Reservoir reveal a different pattern of annual growth than was predicted from the 2005 age estimates and the derived von Bertalanffy growth function. Small fish (41-60 cm FL) appear to grow at nearly twice the rate predicted from the von Bertalanffy growth function. Additionally, beginning at approximately 100 cm FL, sturgeon in The Dalles Reservoir appear to experience an increase in annual growth rate. This increasing growth rate continues until approximately 140 cm FL, at which size their annual growth rate declines once again. The von Bertalanffy growth function (and therefore the annual growth increments predicted from the von Bertalanffy growth function) assumes a decreasing growth rate throughout the life of the fish. Report B The 2005 white sturgeon harvest (recreational, commercial, and subsistence) in Management Zone 6 was 3,158 fish. This is the lowest total harvest since 1991, and is reflective of the guideline reductions ( ) in all three pools, and a low recreational harvest in all three pools this year. Recreational retention seasons were closed on June 11 in Bonneville Reservoir, June 25 in The Dalles Reservoir, and July 11 in John Day Reservoir. Compliance with the Sturgeon Management Task Force (SMTF) annual harvest guidelines has been addressed through in-season management actions. Harvest in Bonneville Reservoir during the past five seasons ( ) has averaged 97% of the recreational guideline and 69% of the commercial guideline. Harvest in The Dalles Reservoir for the same period averaged 112% of the recreational guideline and 102% of the commercial guideline. Harvest in John Day Reservoir averaged 84% of the recreational guideline and 80% of the commercial guideline. With two exceptions (2000 and 2003) harvest per angler trip in Bonneville Reservoir has decreased each year since Harvest per angler trip in The Dalles Reservoir trended downward since 2001 (the highest since 1995) to the lowest since Harvest per angler trip in John Day Reservoir is also the lowest since The handle of oversize white sturgeon in the John Day recreational fishery has increased since 1995, averaging 10.2% of white sturgeon handled during The handle of oversize white sturgeon in the John Day Reservoir recreational fishery is nearly three times greater than that for Bonneville and The Dalles reservoirs. Report C River discharge and water temperatures that occurred during April through July 2005 provided conditions suitable for spawning by white sturgeon downstream from Bonneville, The Dalles, John Day, and McNary dams. Optimal spawning temperatures in the four tailraces occurred for 3-4 weeks and coincided with the peak of the river hydrograph. However, the peak of the hydrograph occurred in mid May and discharges dropped quickly 4

5 and water temperature rose during June, which is reflected in the monthly and annual indices of suitable spawning habitat. Indices of available spawning habitat for the month of June 2005 were less than one-half of the average of the period from Bottom-trawl sampling in the Bonneville Reservoir revealed the presence of young-of-theyear (YOY) white sturgeon but the proportion of positive tows was quite low at Report D During 6 December 2005 through 21 January 2006 Tribal fishers set 1,059 overnight gillnet sets. This effort captured a total of 3,357 white sturgeons (including recaptures). They marked 3,034 white sturgeon by removing the 11th left lateral scute, and they applied PIT tags to 1,634 of these fish. White sturgeon captured in these efforts were cm FL (mean 78.0 cm). This is a 19.0 cm decrease from the mean in Catch per net was higher in than , 3.17 fish per set compared to About 95% of the catch of white sturgeon was less than 48 inches TL (minimum legal size). We observed a four-fold increase in the numbers of cm FL fish from to We observed a slight increase in the proportion of sublegals (<48 inches TL) from to , and an approximate 50% decline in the numbers of legal-sized (48-60 inches) and over-legal sized fish (>60 inches TL) during the same time period. Proportions of sublegals, legals, and over-legals in %, 7.6%, and 3.3% respectively, and in the proportions were 95.1%, 3.3 %, and 1.6% respectively. Report E Montana State University researchers collected gonadal biopsies from adult white sturgeon below Bonneville Dam. The objective of this research is to describe the maturation cycle in wild white sturgeon. White sturgeon were caught by sport-fishers. Gonadal tissue was collected by biopsy, and the gonad samples were processed histologically. A total of 535 adult white sturgeon have been marked with spaghetti tags, scute marks, and PIT tags below Bonneville Dam since 2000 (n=183 in 2000, n=90 in 2001, n=67 in 2002, n=101 in 2003, n=57 in 2004, n=37 in 2005). Gonadal biopsies have been collected from 400 of these fish. In 2005, a total of 49 fish were caught, 12 of which were tagged in previous years and 37 of which were "new" fish to the study. A total of 46 gonad samples were collected for histological analysis. Of these, 29 were collected from females and 13 were collected from males. 5

6 The reproductive structure of the oversize white sturgeon population below Bonneville Dam was determined using the data. Of the females (n=266), 61% were previtellogenic (Stages 1 and 2), 27% were vitellogenic (Stages 3 and 4), 5% were postvitellogenic or ripe (Stage 5), 5% were postovulatory (Stage 7), and 2% were atretic (Stage 8). Of the males (n=134), 58% were non-reproductive (Stage 2), 13% were midspermatogenic (Stage 3 and 4), 24% were spermiating (Stage 5), and 5% were postspermiation (Stage 6). 6

7 WHITE STURGEON MITIGATION AND RESTORATION IN THE COLUMBIA AND SNAKE RIVERS UPSTREAM FROM BONNEVILLE DAM ANNUAL PROGRESS REPORT APRIL MARCH 2006 Report A Evaluate the success of developing and implementing a management plan for enhancing production of white sturgeon in reservoirs between Bonneville and McNary dams This report includes: 1) An update of abundance, life history parameters, and population dynamics of white sturgeon in The Dalles Reservoir, 2) a summary of annual recruitment of young-of-year white sturgeon in Columbia and Snake River reservoirs, and 3) results of white sturgeon transplant supplementation in The Dalles and John Day reservoirs. Prepared By: Colin G. Chapman and Michele Hughes Weaver Oregon Department of Fish and Wildlife Southeast Evelyn Street Clackamas, OR February 2007

8 TABLE OF CONTENTS ABSTRACT... 9 INTRODUCTION METHODS STOCK ASSESSMENT TRAWL AND HAUL SUPPLEMENTATION YOUNG-OF-YEAR INDEXING RESULTS STOCK ASSESSMENT TRAWL AND HAUL SUPPLEMENTATION YOUNG-OF-YEAR INDEXING DISCUSSION STOCK ASSESSMENT TRAWL AND HAUL SUPPLEMENTATION YOUNG-OF-YEAR INDEXING PLANS FOR NEXT YEAR ACKNOWLEDGMENTS REFERENCES APPENDIX

9 ABSTRACT This report summarizes data collected from April 2005 through March 2006 and provides: 1) an update of abundance, life history parameters, and population dynamics for white sturgeon Acipenser transmontanus in The Dalles Reservoir, 2) a review of annual transplant supplementation of juvenile white sturgeon from the Columbia River below Bonneville Dam to John Day Reservoir, and 3) an evaluation of annual recruitment of young-of-year white sturgeon in three Columbia River and two Snake River reservoirs. Sampling to estimate the abundance of white sturgeon in The Dalles Reservoir was coordinated with staff from the Oregon Department of Fish and Wildlife (ODFW), the Columbia River Inter-Tribal Fish Commission (CRITFC), and the Washington Department of Fish and Wildlife (WDFW). Tribal commercial fishers (contracted through CRITFC) set 1,059 nets and captured 3,359 white sturgeon. Staff from ODFW and WDFW set 493 setlines and captured 3,952 white sturgeon. Combined sampling effort resulted in the capture of 7,316 white sturgeon, of which 5,337 were tagged with passive integrated transponder (PIT) tags. A total of 163 PITtagged sturgeon were recaptured, for an overall recapture rate of 3%. White sturgeon were distributed throughout The Dalles Reservoir with similar catch rates occurring in all reservoir sections. Between marking and subsequent recapture, white sturgeon in the Dalles Reservoir moved an average of 0.62 Rkm downstream. Using multiple mark-recapture estimates, the total population of white sturgeon 54 cm fork length (cm FL) in The Dalles Reservoir in 2005 was estimated at 102,757. The size distribution of white sturgeon in The Dalles Reservoir was estimated to be: 98.1% <110 cm FL, 1.1% cm FL, and 0.8% >137 cm FL. Transplant supplementation activities (Trawl-and-Haul) continued in 2005 with the transplant of juvenile white sturgeon from the lower Columbia River to John Day Reservoir. Juvenile white sturgeon were captured below Bonneville Dam by a private commercial trawler. We transplanted 800 of these fish into John Day Reservoir. Transplanted fish ranged in size from cm FL. All transplanted fish were marked by removal of two specific lateral scutes; one to identify them as a Trawl-and-Haul fish, and one to identify the year of capture. None of the transplanted fish were PIT-tagged. We assessed annual recruitment of young-of-year (YOY) white sturgeon in The Dalles, John Day, McNary, Ice Harbor, and Little Goose reservoirs. Sampling gear consisted of small mesh gill nets fished at standardized locations within each reservoir. Recruitment in 2005 appeared to be low in all reservoirs sampled, with only one YOY sturgeon captured in The Dalles Reservoir, one YOY sturgeon captured in McNary Reservoir, and no YOY sturgeon captured in any of the remaining reservoirs. 9

10 INTRODUCTION White sturgeon Acipenser transmontanus are the largest species of North American sturgeon (Scott and Crossman 1973). In the Columbia River basin, white sturgeon were severely overfished during the late 1800s, and populations declined enough to warrant the cessation of all sturgeon fishing. By the mid 1900s, sturgeon numbers had improved enough to once again support limited commercial and recreational fisheries. With the recent decline in anadromous salmonid abundance, there has been increased participation in the white sturgeon fishery. Total harvest of sturgeon doubled in the 1970 s and again in the 1980 s (Tracy 1993). Since 1986, ODFW has been working to monitor sturgeon populations and to take actions that will both increase the abundance of sturgeon and maintain productive sturgeon fisheries. Over time, project goals have changed as new information has clarified potential restoration actions. There are two primary goals of the current project: 1) Determine the need and identify potential measures for protecting and enhancing white sturgeon populations and mitigating for the effects of the hydropower system on production of white sturgeon in the Columbia and Snake rivers upstream from McNary Dam. 2) Implement and evaluate previously identified measures to protect and enhance white sturgeon populations and to mitigate for effects of the hydropower system on production of white sturgeon in Columbia River impoundments downstream from McNary Dam. We have developed protocols to monitor sturgeon abundance and recruitment throughout the basin to ensure that sturgeon populations remain healthy and abundant enough to allow fisheries now and into the future. To assess sturgeon abundance and population dynamics we conduct extensive annual mark-recapture surveys in the reservoirs between Bonneville Dam and McNary Dam on the Columbia River. These data allow for updates of the abundance and population characteristics of white sturgeon in the reservoirs, and for the assessment of existing management and mitigation approaches. To supplement the abundance of sturgeon in some of the less productive reservoirs in the basin, we have developed a transplant supplementation program. Our studies have shown that production of juvenile white sturgeon below Bonneville Dam is much greater than in either The Dalles or John Day reservoirs (citation). Therefore, each year we live-capture subadult sturgeon from below Bonneville Dam and transplant them into The Dalles or John Day reservoirs. Through this program we hope to increase abundance and improve production of sturgeon in these reservoirs. To evaluate the relative success of spawning by white sturgeon, we conduct annual recruitment indexing. To accomplish this, we sample for YOY sturgeon (i.e. sturgeon born that year) at specific index sites in three Columbia River and two Snake River reservoirs. By sampling these areas annually we can describe distribution and relative density of YOY white sturgeon in each reservoir. This information can then be used to identify recruitment trends among years and among reservoirs. 10

11 This report summarizes work performed by ODFW from April 2005 through March 2006 for the Bonneville Power Administration Project During this period, we participated in three distinct efforts to assess and/or enhance populations of white sturgeon in the Columbia River upstream from Bonneville Dam: 1) From June through August 2005 we assessed the abundance and population characteristics of white sturgeon in The Dalles Reservoir. 2) From October through November 2005, we coordinated the catch and transplant of juvenile white sturgeon from the lower Columbia River (downstream of Bonneville Dam) into John Day Reservoir. 3) From October through November 2005 we assessed annual recruitment of YOY white sturgeon in The Dalles, John Day, and McNary reservoirs in the Columbia River, and Ice Harbor and Little Goose reservoirs in the Snake River. These activities are conducted on an annual basis. Since 2001, stock assessment surveys have been conducted every year, rotating between the three reservoirs in Zone 6 (Bonneville, The Dalles, and John Day). Prior to 2001, stock assessment surveys in these reservoirs were conducted on a five-year rotation. Trawl-and-Haul supplementation and young-of-year indexing are both annual activities. METHODS Stock Assessment Sampling for white sturgeon in The Dalles Reservoir was divided into four distinct periods (periods 1-4). During period 1, gill nets were used to capture sturgeon. During periods 2-4, baited set lines were used to capture sturgeon. Sampling during period 1 took place from December 6, 2004 to January 21, During this time, CRITFC staff, working with tribal commercial fishers, used gill nets distributed throughout the reservoir to capture white sturgeon. Gill nets ranged from m in length and 5-9 m in height. Gill nets were constructed of cm stretched-measure nylon mesh and were fished on the river bottom for approximately 24 hours per set. Sampling during periods 2-4 took place from June through mid-august of 2005, and was conducted jointly by ODFW and WDFW. Period 2 was from June 6 to June 23. Period 3 was from June 27 to July 21. Period 4 was from July 25 to August 11. For sampling purposes, The Dalles Reservoir was divided into six sections from downstream to upstream (excluding all boat restricted zones). Each section ranged between 5.1 and 7.2 km in length (Figure 1). Sampling effort was distributed equally among and within the sections to obtain a representative sample of the population. All reservoir sections were sampled during each period. 11

12 During periods 2-4, setlines were used to capture white sturgeon. Setlines were chosen as the preferred sampling gear because, 1) they are less size selective than other sampling gear, 2) they are less damaging to white sturgeon than other sampling gear (Elliot and Beamesderfer 1990), and 3) setlines provide suitable catch rates for our objectives (Elliot and Beamesderfer 1990). Setlines measured 183 m in length and were equipped with 12/0, 14/0, and 16/0 circle hooks. Each setline contained 13 hooks of two sizes and 14 hooks of the remaining size (which was chosen randomly for each line), for a total of 40 hooks per line. Setlines were fished overnight for an average of 22.9 hours. All hooks were baited with pickled squid (Loligo spp.), which has been shown to yield higher catch rates than other baits (North et al. 1998). Fresh bait was applied to the hooks when necessary, or every 48 hours. All sturgeon were measured to the nearest 1.0 cm FL. All sturgeon were examined for external tags, lost tag scars, pectoral fin scars (from previous aging samples), and scute removal scars. A subsample of up to 30 fish per 20 cm length interval was used to obtain paired weight and aging samples. Weight was measured to the nearest 0.1 kg and a pectoral fin spine section was removed for subsequent aging. All recaptured fish were weighed. During period 1 (December and January), sturgeon 70 cm FL were tagged with a MHz ISO PIT-tag. During periods 2, 3, and 4, all white sturgeon were PIT tagged regardless of size. During all periods, sturgeon were externally marked by removing the second left lateral scute (to indicate a PIT-tagged fish) and the eleventh left lateral scute (to indicate the fish was captured in 2005) Figure 1. The Dalles Reservoir. Stock assessment sampling sections for 2005 are indicated by numbers and dashed lines. BRZ= boat-restricted zone. 12

13 Ages of captured white sturgeon were estimated from thin cross-sections of pectoral fin spines following procedures outlined in Beamesderfer et al. (1989). Up to 30 fish from each 20 cm length interval were aged. Each fin-spine section was aged three times by two experienced readers in a blind read design. In the cases where the age assigned to an individual fish did not match between readers, the primary reader assigned a final age to the fish. The relationship between sturgeon length (L) and age (x) in The Dalles reservoir was described by the von Bertalanffy growth function, L x = L [1-exp(-k(x-t 0 ))]. Parameters for the von Bertalanffy growth function were derived using the length and age data and nonlinear regression (SAS Institute 1988). The relationship between fork length (L) and weight (W) was described by the exponential function, W L = exp[a*ln(l)-b]. Parameters for the length-weight function were derived from nonlinear regression (SAS Institute 1998). The condition of white sturgeon 70 cm FL was assessed using estimates of relative weight (W r ) based on the standard weight equation, from Beamesderfer 1993, W= E-6*L Analysis-of-variance (ANOVA) and Tukey's pairwise comparison (SAS Institute 1988) were used to test for significant differences in relative weights of fish between 2002 (when the last stock assessment was completed in The Dalles Reservoir) and 2005, and among the 2005 sampling periods. Annual growth increments (AGI) for sturgeon from The Dalles Reservoir were estimated from: 1) the 2002 and 2005 von Bertalanffy growth functions, and 2) from all marked and recaptured sturgeon from The Dalles Reservoir ( ). Only sturgeon that were at large for one or more years between capture events were used to estimate the AGI s (n= 1,101). Annual growth increments derived using each method were compared to examine differences between predicted and actual growth. Overall population abundance (N) of sturgeon in The Dalles Reservoir was estimated using a Schnabel population estimator based on the number of PIT-tags applied and recaptured. The Schnabel estimate was calculated as: where m= the number of sampling periods, M i = total number of marked fish at the start of the ith sampling period (i = 1,..., m), C i = total samples taken in period i, R i = number of recaptures in the sample C i, and R= total recaptures during the experiment (sum of R i ) (Borchers et al. 2002). Although not noted in the above equation, the total number of marked fish at the start of a given period was adjusted to account for removals. Removals included mortalities during sampling and harvest estimated in sport and commercial fisheries. The Schnabel estimator was used to estimate abundance of the cm FL size class (group with the largest sample size). The number of size-specific recaptures was too small for reliable mark-recapture abundance estimates; therefore, the length-frequency distribution of the setline catch was used to apportion the Schnabel population estimate to the cm FL fish. The Schnabel estimate was then expanded to estimate abundance of the remaining size groups (<70 cm FL and >166 cm FL). Expansion was based on the relative frequency of the size class in the total 2005 setline catch, and differences in gear vulnerability (Beamesderfer et al. 1995). 13

14 Trawl and Haul Supplementation From October 18 to November 10, 2005, juvenile and sub-adult white sturgeon were captured in the lower Columbia River and transplanted into John Day Reservoir to supplement the existing population. Staff from ODFW contracted with a private fisher who conducted trawling activities downstream from Bonneville Dam between river kilometers (Rkm) 209 and 212. This area of the Columbia River has been used each year of this project and was originally selected because the bottom type is suitable for trawling, and catch rates of sub-adult white sturgeon were relatively high in previous years (McCabe and Hinton 1994). Trawl gear consisted of a 7.9 m (headrope length) semi-balloon otter trawl, with 38 mm stretched-mesh body and a 10 mm cod end liner to collect juvenile white sturgeon. All trawling was done on the river bottom for approximately 30 minutes per tow. The number and duration of daily tows varied with catch rates and collection goals. Tows were made in both upstream and downstream directions. After each tow, all fish were removed from the net and placed into 520 L plastic totes with circulating river water at ambient temperature and dissolved oxygen (DO) concentration. Bycatch was identified, counted, and returned to the river. All captured sturgeon were measured to the nearest 1.0 cm FL. Only white sturgeon between 30 and 90 cm FL were designated for transport to John Day Reservoir, all other sturgeon were returned to the river. The eleventh left lateral scute was removed from sturgeon designated for transport to signify capture in Additionally, the third right lateral scute was removed from sturgeon designated for transport to signify Trawl-and-Haul handling. No trawl captured sturgeon were PIT tagged. At the end of each day, all fish to be transported were loaded into either a 13,000 L or a 5,300 L ODFW fish liberation truck. All liberation trucks were equipped with supplemental oxygen. Fish were then transported and released into John Day Reservoir at the Arlington Boat Ramp (Rkm 390), Boardman Boat Ramp (Rkm 434), Irrigon Boat Ramp (Rkm 455), or Umatilla Boat Ramp (Rkm 468) (Figure 2). 14

15 Figure 2. Zone 6, Columbia River, and release sites in The Dalles and John Day reservoirs. Young-of-Year Indexing During October and November of 2005, staff from ODFW and WDFW conducted sampling in The Dalles, John Day, and McNary reservoirs in the Columbia River, and Little Goose and Ice Harbor reservoirs in the Snake River, to evaluate annual recruitment of YOY white sturgeon (Figure 3). Sampling took place in Little Goose Reservoir from October 3 to October 6, in Ice Harbor Reservoir from October 10 to October 13, in McNary Reservoir from October 17 to October 20, in John Day Reservoir from October 24 to October 28, and in The Dalles Reservoir from October 31 to November 3. In each reservoir, gill nets were used to sample for YOY white sturgeon. A single gill net was deployed at each of several predetermined, standardized locations within a given reservoir (Parsley et al. 1999) to allow for a comparison of catch between years. Sampling methodology was similar to past years (Burner et al. 1999), which involved fishing multiple overnight sets at the same site during the week. Gill nets measured 91.4 m in length and 3.7 m in height and were constructed with 5.1 cm stretched-measure multifilament nylon mesh. Nets were fished on the river bottom overnight for approximately 24 hours. Because nets were deployed during daylight hours and most catch of white sturgeon is believed to occur during darkness (McCabe and Tracy 1994), all nets were considered to have been sampling for equal amounts of effective fishing time. Therefore, each overnight set was treated as a single sampling effort. 15

16 With the exception of live salmonids, which were released immediately to reduce possible stress or injury from handling, all fish captured in the nets were carefully removed and placed in a holding tank filled with river water at ambient temperature and dissolved oxygen until they could be examined. All fish were identified to species, with the exception of sculpin and crayfish, which were identified to the genus Cottus and the genus Pacifastacus respectively. Any salmonid that had expired in the net was examined for marks, measured to the nearest 1 mm, and returned to the river. All white sturgeon were measured to the nearest 1 mm FL and weighed to the nearest 0.1 or kg, depending on size. For aging purposes, a pectoral fin spine section was taken from all captured sturgeon ( 90 cm FL) in each reservoir. Final age classification (YOY or older than YOY) was based on results from the age analysis. No marks or tags were applied to any captured fish. After examination, all fish were immediately returned to the river. For white sturgeon, both the catch-per-unit-effort (CPUE) (the number of sturgeon caught per overnight set) and the proportion of positive efforts (E p ) (the proportion of all sets that captured at least one sturgeon) were calculated from the sample and catch data. For small numbers of fish, the estimate of E p may provide a better measure of relative abundance than CPUE (Counihan et al. 1999), and is the parameter most often used in comparing catches of YOY white sturgeon among years in Columbia and Snake River reservoirs (Burner et al. 1999) CPUE and E p were estimated for both YOY white sturgeon, and for all white sturgeon captured. Figure 3. Map of sampling locations in the Columbia and Snake river basins. Highlighted river sections indicate the reservoirs in which young-of-year sampling took place during October and November of

17 RESULTS Stock Assessment Effort and Catch During period 1, tribal commercial fishers set 1059 gill nets in The Dalles Reservoir and caught 3,359 sturgeon. Of the 3,359 sturgeon captured, 1,633 sturgeon received PIT tags. During periods 2-4, staff from ODFW and WDFW set 493 setlines in The Dalles Reservoir and caught a total of 3,952 sturgeon (Tables 1 and 2). Of the 3,952 sturgeon captured, 3,704 sturgeon received PIT tags. A total of 163 PIT-tagged sturgeon were recaptured during the summer sampling periods (periods 2-4). All recaptured sturgeon measured <110 cm FL. The overall recapture rate of sturgeon PIT tagged during 2005 was 3.1%. White sturgeon were captured in all reservoir sections during all sampling periods. CPUE for all sections and weeks combined (periods 2-4) was 8.02 white sturgeon per setline (Table 3). Catch was distributed throughout the reservoir, with no significant difference in mean CPUE between reservoir sections (ANOVA, F= 1.1, P= 0.42). There was, however, a significant difference in mean CPUE between sampling periods (ANOVA, F= 7.0, P= 0.007). Mean CPUE during period 4 was significantly lower than mean CPUE during either period 2 or 3. Mean CPUE during periods 2 and 3 were not significantly different from each other. Most sturgeon recaptured during the stock assessment were recaptured near the original marking location. Of the 347 sturgeon that were marked and recaptured during sampling periods 1-4, 310 (or 89%) were recovered within +/- 5 Rkm of the original marking location (Table 4). On average, fish were recaptured 0.62 Rkm downstream from where they were originally marked. The furthest upstream movement observed was 35 Rkm, and the furthest downstream movement observed was 30 Rkm. Table 1. Sampling effort (number of setline sets) by ODFW and WDFW in The Dalles Reservoir by week and reservoir section, June through August Sampling Sampling Section Week Total Period Period Period Total

18 Table 2. Catch of white sturgeon by ODFW and WDFW in The Dalles Reservoir by week and reservoir section, June through August Sampling Section Week Total Period 2 Period 3 Period Total ,952 Table 3. Mean catch-per-unit-effort (CPUE) of white sturgeon in The Dalles Reservoir by week and reservoir section, June through August Sampling Section Week All Period 2 Period 3 Period All

19 Table 4. Frequency of movement of fish between marking and recapture events. Negative numbers indicate downstream movement and positive numbers indicate upstream movement. Number of River KM Moved Frequency of Recaptures % Frequency of Recaptures -30 (or more) % % % % % % % % % % % 30 (or more) % Size, Age, and Growth Lengths of sturgeon captured using setlines ranged from cm FL, with a median length of 68.0 cm FL (Figure 4). The length distribution of the setline catch was: 98.1% <110 cm FL, 1.2% cm FL, and 0.8% >137 cm FL Number Captured Fork Length Figure 4. Length frequency of white sturgeon captured using setlines from The Dalles Reservoir during the 2005 stock assessment (N= 3952). 19

20 Weights of sturgeon captured using setlines ranged from kg, with a median weight of 3.2 kg. The relationship between fork length (L) and weight (W) was described by the exponential function: W L = exp[3.109*ln(l) ] (Figure 5). Relative weights of captured sturgeon (from periods 2-4) ranged from , with a mean relative weight of (95% CI: ) (Figure 5). There was no significant difference (ANOVA, F= 2.52, P=0.081) in relative weights of captured sturgeon between sampling periods in The mean relative weight during period 2 was 102.9, during period 3 was 105.9, and during period 4 was Relative Weight (%) S.D. Period 2 (N = 170) Period 3 (N = 195) Period 4 (N = 111) Mean - 2 S.D. 20 Weight (kg) N = 761 Weight = e (3.109*(ln(FL) )) r 2 = Fork Length Figure 5. Relative weights and length-weight relationship of white sturgeon captured with setlines during stock assessment sampling, June-August 2005 (periods 2-4). 20

21 We estimated the age of 157 white sturgeon captured from The Dalles Reservoir during the 2005 stock assessment. Age estimates ranged from 5-40 years, with a median age of 11 years. Variation between ages assigned by primary readers was high (Table 5). There was 23% agreement in the final ages assigned by the primary readers, with reader one assigning older ages than reader two in 57% of the samples. The age estimates from 2005 were used to determine the parameters of a von Bertalanffy growth equation. The von Bertalanffy equation describing size at age for sturgeon from The Dalles Reservoir in 2005 was: L x = 289.1[1-e (x-2.4) ] (Figure 6). Annual growth increments (AGI) for sturgeon from The Dalles Reservoir were estimated from the 2002 and 2005 von Bertalanffy growth functions and from recaptures during (Figure 7). Predicted AGI s decreased as fish size increased, ranging from approximately 5.5 cm/year for sturgeon cm FL, to approximately 2 cm/year for sturgeon >200 cm FL. Annual growth increments calculated from actual recaptured fish show varied growth as fish size increased. Growth ranged from a low of approximately 2-3 cm/year for sturgeon cm FL and >200 cm FL, to a high of approximately 7 cm/year for sturgeon >200 cm FL. Table 5. Discrepancies in aging of white sturgeon collected from The Dalles Reservoir during the 2005 stock assessment. The shaded row indicates when the two age readers assigned an identical age. Final Assigned Age Age Difference >29 % Agreement N All

22 Total Length 60" Fork Length (cm) Total Length 48" Lx=L (1-e -k(x-t 0 ) ) 2005 N= N= N= L k t ageing data ageing data ageing data Age (years) Figure 6. Von Bertalanffy growth function for white sturgeon collected from The Dalles Reservoir during the 2005 stock assessment. 8 Annual Growth Increment (cm/year) Recapture Data VB Prediction 2005 VB Prediction >201 Length Class (cm FL) Figure 7. Mean AGI s by length class predicted by the 2002 and 2005 von Bertalanffy growth functions, and mean AGI s calculated from recaptures of tagged fish from The Dalles Reservoir. 22

23 Abundance The abundance of cm FL white sturgeon was estimated to be 45,695 (95% CI: 37,039-56,345) (Table 6). The abundance of cm FL sturgeon and the abundance of >166 cm FL sturgeon (broodstock-sized adults) was estimated to be 56,648 and 414 respectively (Table 7). The abundance of legally harvestable fish ( cm FL, in both the sport and commercial fishery) was estimated to be 1,125. The total population of white sturgeon ( 54 cm FL) in The Dalles Reservoir in 2005 was estimated to be 102,757 (Table 7) (Figure 8). Table 6. Mark/recapture data and Schnabel abundance estimate of white sturgeon cm fork length, The Dalles Reservoir Period Catch Marks Recaps Mortalities Marks at Large Estimate (t) (C) (M) (R) Unmarked Marked (Mt) (M t *C)/(R+1) 1 a 2,096 1, ,829 45, ,354 44, ,912 44,383 Sum 3,798 3, Estimate 45,695 95% CI (lower) 37,039 95% CI (upper) 56,345 a Sturgeon recaptured during period 1 are not included in the Schnabel estimate. Table 7. Estimated abundances of white sturgeon in The Dalles Reservoir from the 2005 stock assessment. Confidence intervals are given for the size group for which a Schnabel estimate was calculated, and not for size groups for which abundance was estimated by expansion from the length-frequency of the setline catch. Estimated Abundance Size Class (95% Confidence Interval) cm FL 56, cm FL 44, cm FL 1, cm FL 1, cm FL 45,695 (37,039-56,345) >166 cm FL 414 Total 102,757 23

24 24" 30" 36" 42" Total Length The Dalles Reservoir " 54" 60" 66" 72" 78" Estimated Abundance Sport/Commercial Legal N= 1, N= 102, Fork Length (cm) Figure 8. Length-frequency distribution of sturgeon ( 54 cm FL) in The Dalles Reservoir based on the 2005 stock assessment. Trawl and Haul Supplementation A total of 85 tows were conducted from October 18 to November 10, 2005 in the lower Columbia River. Tows were conducted at an average speed of 2.5 knots (2.8 mph), for an average time of 29 minutes. Tows were conducted in both upstream (32%) and downstream (68%) directions, at depths ranging from 6-25 m (12.8 m average) (Table 8). A total of 904 white sturgeon were captured using the trawl gear. Overall CPUE was sturgeon per tow. Captured white sturgeon ranged in length from 14 to 101 cm FL (not including one sturgeon >200 cm FL that was released without a length measurement) (Figure 9). Fish of transportable size (30-90 cm FL) composed the majority (96%) of the catch. Mean fork length of all sturgeon sampled was 44.6 cm (95% CI: cm). Mean fork length of transplanted sturgeon was 46.3 cm. 24

25 Of the 904 trawl-caught sturgeon, 800 (89%) were transplanted into John Day Reservoir, 73 (8%) were released alive into the lower Columbia River, and 31 (3%) were either dead at capture or died during holding (Figure 9). Incidental catch of other fish species during Trawl and Haul activities is presented in appendix Table A-1. Table 8. Effort and catch of juvenile and sub-adult white sturgeon captured in the Columbia River downstream of Bonneville Dam (river kilometers ) during October and November, Year, Agency Sampling days Number of trawls Total catch CPUE Mean trawl time (min) Mean fishing depth (m) 1993 NMFS b a USGS c a NMFS b ,428 a USGS c a NMFS b ,974 a NMFS b ,362 a NMFS b ,728 a Private trawler ,705 a Private trawler ,937 a Private trawler ,375 a Private trawler ,466 a Private trawler Private trawler a b c Approximate number since some white sturgeon were not counted and immediately released at the capture site when tow catches were very large. National Marine Fisheries Service, now NOAA Fisheries. U. S. Geological Survey 25

26 60 Number Captured Fish Transported Fish Released M ortalities Fork Length (cm) Figure 9. Length-frequency distribution of all trawl-caught sturgeon during Trawl-and-Haul activities, 2005 (N= 904). Young-of-Year Indexing During YOY indexing, a total of 60 white sturgeon were captured from 181 individual net sets (all reservoirs combined). Nets were fished for a combined 3,945 hours, with an average time of 22.3 hours per set. Of the 60 white sturgeon captured, only two (3%) were classified as YOY. One of these was captured in McNary Reservoir and the other in The Dalles Reservoir. Captured sturgeon ranged in length from 21 to 104 cm FL (Figure 10), and both YOY sturgeon were >25 cm FL. Incidental catch of other fish species during young-of-year sampling is presented in appendix Table A-2. In Little Goose Reservoir, a total of six white sturgeon were captured from 36 individual net sets. Nets were fished for a total of 802 hours, with an average of 22.3 hours per set. Of the six white sturgeon captured, none were classified as YOY. CPUE for all sites combined was 0.17 white sturgeon of all ages. White sturgeon older than YOY were captured in 14% of the sets (Table 9). In Ice Harbor Reservoir, a total of four white sturgeon were captured in 36 individual net sets. Nets were fished for a total of 810 hours, with an average of 22.5 hours per set. Of the four white sturgeon captured, none were classified as YOY. CPUE for all sites combined was 0.11 white sturgeon of all ages. White sturgeon older than YOY were captured in 11% of the sets (Table 9). 26

27 In McNary Reservoir, a total of two white sturgeon were captured in 36 individual net sets. Nets were fished for a total of 785 hours, with an average of 22.8 hours per set. Of the two white sturgeon captured, one was classified as YOY. CPUE for all sites combined was 0.06 white sturgeon of all ages and 0.03 for YOY white sturgeon. White sturgeon of any age were captured in 6% of the sets, while YOY white sturgeon were captured in 3% of the sets (Table 9). In John Day Reservoir, a total of 18 white sturgeon were captured in 40 individual net sets. Nets were fished for a total of 863 hours, with an average of 21.6 hours per set. Of the 18 white sturgeon captured, none were classified as YOY. CPUE for all sites combined was 0.45 white sturgeon of all ages. White sturgeon older than YOY were captured in 28% of the sets (Table 9). In The Dalles Reservoir, a total of 30 white sturgeon were captured in 33 individual net sets. Nets were fished for a total of 735 hours, with an average of 22.3 hours per set. Of the 30 white sturgeon captured, one was classified as YOY. CPUE for all sites combined was 0.91 white sturgeon of all ages and 0.03 for YOY white sturgeon. White sturgeon of any age were captured in 48% of the sets, while YOY white sturgeon were captured in 3% of the sets (Table 9). 27

28 White Sturgeon Catch Little Goose Oct 4 - Oct 6 36 sets 22.3 h/set 6 white sturgeon* Ep YOY=0.00 Ice Harbor Oct 11 - Oct sets 22.5 h/set 4 white sturgeon Ep YOY=0.00 McNary Oct 18 - Oct sets 22.8 h/set 2 white sturgeon Ep YOY=0.03 John Day Oct 25 - Oct sets 21.6 h/set 18 white sturgeon Ep YOY=0.00 The Dalles Nov 1 - Nov 3 33 sets 22.3 h/set 30 white sturgeon Ep YOY= Fork Length (cm) Figure 10. Length-frequency distributions and catch data for white sturgeon captured during young-of-year indexing, October November *Three of the six sturgeon captured in Little Goose Reservoir were estimated to be >166 cm FL and were released without measurement, and are therefore not included in this figure. 28

29 Table 9. Effort and catch of white sturgeon in Columbia and Snake River reservoirs during young-of-year sampling, October and November Reservoir Reservoir Quarter a Parameter All Little Goose Gill Net Sets Total Hours White Sturgeon Catch (all sizes) White Sturgeon Catch (FL<30 cm) White Sturgeon / Set White Sturgeon (FL<30 cm)/set Sets with >0 white sturgeon (all sizes) 33% 22% 0% 0% 14% Sets with >0 white sturgeon (FL<30 cm) 0% 0% 0% 0% 0% Ice Harbor Gill Net Sets Total Hours White Sturgeon Catch (all sizes) White Sturgeon Catch (FL<30 cm) White Sturgeon / Set White Sturgeon (FL<30 cm)/set Sets with >0 white sturgeon (all sizes) 0% 22% 0% 22% 11% Sets with >0 white sturgeon (FL<30 cm) 0% 0% 0% 0% 0% John Day Gill Net Sets Total Hours White Sturgeon Catch (all sizes) White Sturgeon Catch (FL<30 cm) White Sturgeon / Set White Sturgeon (FL<30 cm)/set Sets with >0 white sturgeon (all sizes) 10% 13% 33% 50% 28% Sets with >0 white sturgeon (FL<30 cm) 0% 0% 0% 0% 0% McNary Gill Net Sets Total Hours White Sturgeon Catch (all sizes) White Sturgeon Catch (FL<30 cm) White Sturgeon / Set White Sturgeon (FL<30 cm)/set Sets with >0 white sturgeon (all sizes) 4% 11% 6% Sets with >0 white sturgeon (FL<30 cm) 4% 0% 3% 29

30 Table 9 (continued). Effort and catch of white sturgeon in Columbia and Snake River reservoirs during young-of-year sampling, October and November Reservoir Reservoir Quarter a Parameter All The Dalles Gill Net Sets Total Hours White Sturgeon Catch (all sizes) White Sturgeon Catch (FL<30 cm) White Sturgeon / Set White Sturgeon (FL<30 cm)/set Sets with >0 white sturgeon (all sizes) 33% 67% 64% 29% 48% Sets with >0 white sturgeon (FL<30 cm) 0% 33% 0% 0% 3% a Reservoir quarters are assigned by dividing the reservoir lengthwise into four sections of equal length starting at the downstream dam (quarter 1) and ending at the upstream dam (quarter 4). DISCUSSION Stock Assessment The estimated total abundance of white sturgeon ( 54 cm FL) in The Dalles Reservoir in 2005 (102,757 fish) was only slightly lower than in 2002 (104,349 fish). However, the 2005 stock assessment indicated a substantial reduction in most size classes (Table 10). The stock assessment indicated an 81% reduction in legal-sized fish and a 55% reduction in over-legal sized fish from 2002 levels (Table 11). A decrease in both legal and over-legal size fish from 2002 to 2005 was expected from modeling done following the 2002 stock assessment; however, the magnitude was larger than anticipated. Offsetting the declines in all other size classes was the substantial increase in cm FL fish, which increased in abundance by approximately 70% (Table 10). At the current time, approximately 98% of sturgeon biomass in The Dalles Reservoir is comprised of fish <110 cm FL (Figure 11). The abundance of small fish is important, as these fish will eventually contribute to harvest. However, due to the relatively slow growth of sturgeon, it will take several years for these fish to reach a harvestable size ( cm FL). Abundance estimates from for Zone 6 reservoirs and the Hanford reach of McNary Reservoir are presented in appendix Table A-3. 30