Evaluating Recent Innovations in Bait Fishing Tackle and Technique for Catch and Release of Rainbow Trout

Transcription

1 North American Journal of Fisheries Management 23:098 07, 2003 Copyright by the American Fisheries Society 2003 Evaluating Recent Innovations in Bait Fishing Tackle and Technique for Catch and Release of Rainbow Trout THOMAS M. JENKINS, JR.* Spooky Meadow Institute for Trout Ecology, Post Office Box 336, June Lake, California 93529, USA Abstract. Since some recent innovations in bait tackle and technique appear to reduce or eliminate the immediate mortality of released rainbow trout Oncorhynchus mykiss, this study tested the hypothesis that they are as effective for hook and release as artificial flies. Hatchery rainbow trout from aquaculture pens were caught using circle hooks, the new Shelton self-releasing hooks, standard J and treble hooks, and artificial flies (all barbless), noting hook location, 26-d weight change, and survival. Except for those caught on artificial flies, the fish were encouraged to swallow the hook, which was baited with a pasty attractant popular in eastern California (Berkley Powerbait). Most Shelton, J, and treble hooks (78, 65, and 63%, respectively) lodged in the esophagus, whereas all artificial flies and at least 70% of the circle hooks lodged in the mouth or jaw. Flies, circle hooks, and Shelton hooks were extracted from the fish, and the lines were cut on the J and treble hooks. The fish caught with flies, J hooks (line cut), and netted controls all survived the observation period. The survival of fish caught on the Shelton, cut-line treble, and extracted circle hooks was 98, 98, and 9%, respectively. The mean growth of cut-line J-hook fish was somewhat below that in other groups. The results from a second experiment showed that the Shelton hooks can be effective (0.7% mortality in 60 d) with no fish handling, and a third study suggested that much larger fish suffer only slightly greater mortality from flies, cut-line circle hooks, and Shelton hooks (0.7, 3.3, and 4.7%, respectively). Since significant differences in the long-term mortality and growth effects of some bait techniques and artificial flies could not be demonstrated, the use of the former should be recommended to anglers and perhaps reconsidered in waters where bait angling is not currently allowed. In areas with intense fishing pressure such as California s eastern Sierra Nevada, the successful release of both hatchery-reared and wild salmonids can help sustain fish populations and acceptable levels of catch per unit effort. Most anglers in the region use bait tackle, and while many have expressed an interest in contributing to this conservation effort, no consistent means for doing so has been demonstrated. Managers and fishers can reasonably expect results like those of Taylor and White (992), who estimated from nine studies that rainbow trout Oncorhynchus mykiss released from bait tackle suffer almost six times the mortality of fish caught on artificial lures. A few bait fishers have tried to overcome this problem by using less traditional techniques, some of which appear to kill virtually no fish during the immediate postrelease period. If these released fish are actually surviving and contributing to a fishery, the techniques should be widely promoted. If the reduction in mortality is illusory, however, the use of these methods might be counterproductive, with anglers catching and releasing numerous fish with * Corresponding author: tjenk@gte.net Received March 3, 2002; accepted January 3, 2003 little prospect of survival. Therefore, the hypothesis considered was that artificial flies (widely accepted for the catch and release of salmonids) and these nontraditional bait techniques have equal, long-term effects on the survival and growth of cultured rainbow trout, provided equal care is exercised by anglers. If this prediction cannot be falsified for one or more of the tested bait methods, they should be considered for use in restrictive management scenarios. This study focused on three techniques for reducing bait fishing mortality. One was the use of a hook that, by virtue of its shape, tends to lodge in the mouth or jaw more often than standard hooks. Schisler and Bergersen (996) reported average mortality of 55.3% for rainbow trout when deeply lodged bait hooks were removed, but only 5.2% if superficially lodged hooks were removed. A circle hook was selected in this category because it is used in some marine fisheries but has not been evaluated thoroughly for rainbow trout. A second technique involves a new hook (the Shelton selfreleasing hook) that can be removed easily regardless of where it is lodged, generally without pulling a fish from the water. A third technique involves circle hooks or more traditional gear (J and treble hooks), but the line is cut on some or 098

2 BAIT FISHING INNOVATIONS FOR RAINBOW TROUT CATCH AND RELEASE 099 all of the fish to avoid the trauma and handling stress of hook removal. Compared with a 55.3% mortality from the removal of deeply imbedded hooks, Schisler and Bergersen (996) observed an average 20.6% mortality when they cut the line. Similarly, Mason and Hunt (967) reported a 82 95% mortality of rainbow trout when deep hooks were removed, but 34.5% if they were not. Although these studies suggest that the mortality associated with cut-line methods will be higher than that with artificial lures, these methods were included because many anglers are convinced of their efficacy. First, an experiment was conducted to compare long-term mortality and growth among the bait techniques and artificial flies; Shelton hooks were then further evaluated with minimal handling over a longer period; finally, testing was done to determine the effects of fish size when using Shelton hooks, cut-line circle hooks, and artificial flies. Methods The core experiment. In the core or hook comparison experiment, a single angler caught hatchery rainbow trout from three 2.4-m 4.9-m 2.4-m-deep floating pens in June Lake, Mono County, California. The pens contained several thousand fish for an aquaculture program. The angler alternated between six methods until 50 fish were caught by each method over a period of 6 d, 8 3 July The fish from each day (approximately equal in number) were placed in separate.8-m.8-m 2.4-m-deep observation pens so they could be observed for the same number of days after capture. The fishing methods used were: () Berkley Powerbait on a barbless Shelton Release hook (Shelton hook, SHEL) which has a J shape and a gap of 5 mm between the point and the shank, reverses 80 when a tag line activates the release mechanism, and exits the fish under light tension (see Appendix); (2) a barbless wet fly (FLY) with a 4-mm gap between the point and the shank, removed by fingers or hemostats; (3) Berkley Powerbait on a debarbed Eagle Claw model L circle hook (CC-E) with a 3-mm gap between the point and the shank, differing from a J hook by its inturned point ( 45 ) and more rounded configuration (these hooks were extracted from the fish s body with fingers or hemostats); (4) Berkley Powerbait on a barbless J-shaped worm hook (JCL) with a 5-mm gap between the point and the shank (to minimize handling and direct trauma, these hooks were all left in the fish by cutting the line where it exited the jaws); (5) Berkley Powerbait on a barbless, brass-coated treble hook (TCL), with a gap of 3 mm between the points and the shank and a greatest width of 7 mm (these hooks were also left in the fish by cutting the line); and (6) control fish removed individually from the pens with a dip net (CNTL). Powerbait is a proprietary mixture of substances with physical and chemical properties conducive to catching rainbow trout. It may be similar to the scented artificial baits used by Schisler and Bergersen (996). This bait was selected because it can be molded to any type of hook, is aggressively approached and ingested by rainbow trout, and is popular with anglers on Sierra Nevada waters. The fish were allowed to ingest the bait for at least 30 s under low tension to facilitate deep hooking; artificial flies were set immediately. Circle hooks were not set (i.e., tension was gradually increased), as per manufacturer s recommendation. Fish were then played until they could be easily netted and placed in a bucket of tricaine methanesulfonate (MS-222) anesthetic. When the fish slowed enough to be grasped underwater without struggling, the hook location was recorded, the hook was removed (or left in by cutting the line), and incidents of bleeding were noted. Control fish were anesthetized and manipulated in a manner comparable with that used for the angled fish. All fish were weighed (nearest g), measured (nearest mm, fork length [FL]), and marked for later identification. The first 02 fish from each 50 fish group were fin-clipped according to the treatment and marked with a unique combination of subcutaneous dye spots on the fins (Pitcher and Kennedy 977). The last 48 fish in a treatment were fin-clipped to indicate the capture method but not individually marked. Following processing, the fish were allowed to recover in a bucket and were then moved to an observation pen. The observation pens were checked daily, and any dead fish were removed, identified, and autopsied. Survivors were fed the same type of sinking trout pellets they were accustomed to before capture, at a rate slightly above maintenance. The surface temperature in the pens was then recorded. After 26 d (3 8 August 2000), the surviving fish were removed from a cage, anesthetized, identified, weighed, measured, and returned to the aquaculture program. The minimal-handling experiment. Between 0720 and 600 hours on 9 September 2000, an angler caught 300 rainbow trout from the aquaculture pens; these fish were released to a floating

3 00 JENKINS observation pen measuring.8 m 3.4 m 2.4 m deep. The fish were caught with Berkley Powerbait on Shelton hooks like those in the core experiment. Each fish was allowed to ingest the hook under low tension for s, then played until it could be led over a submerged plastic bucket. The bucket was then pulled from the pen, the fish was released underwater by a jerk on the tag line (see Appendix), and the water and fish were transferred to the holding cage. The fish were not touched during the operation nor was anesthetic added to the water. This procedure simulated the actual use of the hook from a fish s perspective, although the brief confinement in the bucket elicited a vigorous response from the subjects and made them more difficult to release. Between 0700 and 0730 hours the following day (20 September), 300 control fish were netted and placed in a cage like that described above. On subsequent days, the fish were fed once with sinking trout pellets, and the dead fish were removed and counted. The mortalities in the hooked group were autopsied to determine the cause of death. After 60 d (on 8 November 2000), 98 control fish and 00 Shelton fish were removed at random, weighed, measured, and returned to the aquaculture pens with the other survivors. The large fish experiment. This study was conducted in a channel fed by the upper Owens River (Mono County, California), within the confines of the Alpers Owens River Ranch. The fish were caught from a reach of natural meanders with barriers at the ends to confine fish and maintain depth at reduced flow. It measured approximately 90 m 5.5 m.5 m deep, with a flow of about 30 L/s. The channel was characterized by steep banks with extensive undercuts and a substrate of mud, sand, and gravel with patches of rooted vegetation (mostly the waterweed Elodea canadensis). At the time of the study, this reach contained approximately,000 rainbow trout weighing from 0.5 to over 5 kg. These fish were being held on a maintenance diet of floating pellets and natural food, but the artificial feeding was stopped a few days before the experiment. Adjacent upstream was a straight reach 70 m 5m.5 m deep, with similar substrate, vegetation, and channel cross section. Ranch staff seined this reach to remove residents and divided it into three sections by soft netting to hold fish from the three treatments. For the first 3 d of the experiment (20 22 August 200), fish were alternately caught by an angler using size 2 barbless flies, and by another angler using Berkley Powerbait on a Shelton Release barbless hook measuring 6 mm across the opening. The fish were played until they could be led over a net and released (by jerking the tag line on the Shelton hooks or by unhooking the fly with fingers or hemostats). The elapsed time from the initial hooking to the final release was recorded. Most of the fish were not touched, but a few caught with each method had to be reoriented underwater or grasped by the jaw to aid in hook extraction or the removal of line wrapped around fins, gill covers, or teeth. After fish were released into the net, they were moved to a large container of water and then to individual holding sections. Note that this procedure simulates catch and release with these methods, except for the added stress of a momentary removal from the water and transportation in a container. One hundred fifty fish were caught by each of the two methods. On the fourth and fifth days of the experiment (23 24 August 200), 50 fish were caught by two anglers using size 2 Eagle Claw Featherlite circle hooks with the barbs removed. The hooks measured 3 mm at the opening and 6 mm at the widest span, with the point angled 45. Like Shelton hooks, they were baited with Powerbait and fished according to the manufacturer s recommendation, which specifies that the hook not be set. If circle hooks were not easily removable from the fish by hand or with hemostats, the line was cut as near to the hook as possible. After release, the fish were transferred to the holding area in the same manner as the Shelton and the fly individuals. The fish in the holding sections were not artificially fed during the time more were being added, but on subsequent days were given a generous diet of floating pellets. The mortalities were recorded daily for each treatment until all fish had been observed a minimum of 2 d. The fish dying during the experiment were weighed, measured, and examined for injuries related to hooking. The temperature was measured every hour during the angling phase and every morning thereafter. At the experiment s end (2 September for Shelton fish, 3 September for fly-caught fish, and 4 September for circle-hook fish), all surviving fish were weighed, measured, and returned to the holding stream. Statistical tests. In all three experiments, the observed numbers of deaths were compared pairwise among treatments (hook type) with chisquare contingency tables, using the null hypothesis of no difference in effect. In one instance the Fisher exact probability test was substituted because computation with the chi-square test yielded

4 BAIT FISHING INNOVATIONS FOR RAINBOW TROUT CATCH AND RELEASE 0. Percent of 50 fish in each treatment FIGURE hooked in indicated areas. Mouth Low Risk upper and lower jaws, sides of mouth, and roof of mouth; Mouth High Risk gill arches, tongue, and pharynx; FLY barbless fly, removed; CC-E barbless circle hook, removed; SHEL Shelton barbless hook, removed; JCL barbless worm hook, line cut; and TCL barbless treble hook, line cut. a nonsense value. Null hypotheses concerning the mean proportional weight change (weight change/ initial weight) were tested with the Mann Whitney U-test, and the differences among condition factors (K 0 5 [weight/fl 3 ]) with confidence intervals were based on the Z statistic. Significance levels ( ) were set at When possible (mortality 0), 95% binomial confidence intervals for mortality were approximated using the formula s2 m( m)/(n ), where s 2 is the variance of the estimated proportion, m is the proportion dying in a treatment, and n is the original number in the treatment (Zar 984). Results The Core Experiment As expected, all flies and most circle hooks lodged in the mouth, although a substantial number of circle hooks had to be removed from the esophagus as well. J, Shelton, and treble hooks were usually, but not always, swallowed (Figure ). Bleeding was uncommon, with the least occurring from cut-line J hooks (2%) and the most from extracted circle hooks (9%). Nineteen of 900 fish (2.%) died during the experiment, but none was from the control (net caught), barbless fly, or J-hook treatment (Table ). Nine circle-hook fish died of esophagus damage within the first 5 d, and the remaining four died within 2 weeks, for a total mortality of 8.7%. When delayed mortality could be related to the initial hooking location (i.e., for the 02 individually marked fish in each treatment), 27% of the fish having circle hooks removed from their esophagus eventually died (Table 2). The last two mortalities had damage to gill filaments, although both were initially hooked in the jaw. Since circle hooks are designed to be swallowed and subsequently pulled to a safer location, the gill area was presumably contacted as the hook moved toward the jaw. Three fish (2%) caught on Shelton hooks died during the experiment, but the cause of death was not apparent for any of the three. They did not die for several days (days 4, 9, and 26), and their digestive tracts were empty when examined. Three fish caught with treble hooks died (2%), all late in the experiment (days 7, 2, and 23), but again the causes of death were not apparent. Only mortality from extracted circle hooks differed significantly from the other methods, presumably due to the technique rather than the gear itself (Shelton and treble versus fly, net and J: P 0.0; Shelton and treble versus circle: P 0.025; fly, net, and J versus circle: P 0.00; Table ). Fish initially averaged 254 mm FL ( TABLE. Sample percent mortalities (n 50, all treatments), sample mean weight changes (n 02, all treatments), and binomial confidence intervals around mortality parameters in the core experiment. Values followed by the same letter are not different at the 0.05 level (see text). Abbreviations are as follows: CNTL netted control; FLY barbless artificial fly, removed; CC-E barbless circle hook, removed; SHEL barbless Shelton self-releasing hook, removed; JCL barbless J hook, line cut; TCL barbless treble hook, line cut. Percent mortality 95% confidence interval Percent weight gain (g) Treatment CNTL FLY CC-E SHEL JCL TCL 0.0 y 0.0 y 8.7 z 2.0 y 0.0 y 2.0 y z 6.29 z 7.03 z 7.44 z 3.63 y 5.63 z

5 02 JENKINS TABLE 2. Number of fish from each treatment that were hooked at indicated anatomical locations, and number (percent) of fish hooked at said locations that died during experiment. Only the 02 individually marked fish from each 50-fish treatment are included; therefore, percent hooked is approximately equal to number hooked. Abbreviations are defined in Table. Treatment FLY CC-E SHEL JCL TCL Hook location Hooked Died Hooked Died Hooked Died Hooked Died Hooked Died Upper jaw Lower jaw Side of mouth Roof of mouth Upper gill arch Lower gill arch Tongue Upper pharynx Lower pharynx Esophagus Foul hooked Hook thrown (.7) 4 7 (26.9) (4.3) (6.7) (2.5) (.6) mm) and 98 g ( g). All but the occasional moribund fish appeared to feed vigorously, and the mean length and weight (Table ) increased in all treatments. Relative to control and fly fish, the mean weight of treble-hook and J-hook fish increased less, and that of the Shelton-hook and circle-hook fish increased more, but only the J-hook fish increased significantly less than the others (Table ). Condition factors (K ) were not significantly different among treatments at the start or at the end. The afternoon surface temperature in the pens fluctuated between 7 C and 20 C, but spot measurements of temperature profiles indicated that the fish spent nearly all of their time at 8 9 C. The Minimal-Handling Experiment Of 300 fish caught on Shelton hooks, four bled to some extent after release. Two fish (0.7%, 95% confidence interval 0.6%) failed to recover fully from the procedure and died during the first 24 h. One had suffered a ripped stomach lining, but no cause of death was apparent for the second. Five netted fish (.7%, 95% confidence interval %) died of unknown cause during the experiment. The difference in mortality between the Shelton and control fish was not statistically significant (P 0.25). Growth was not measured directly since fish were not handled, but the mean condition factor (K ) was not significantly different between treatments (Net:.375, SE 0.09; Shelton:.39, SE 0.02). The water temperature varied widely during the experiment as the weather alternated between summer and winter conditions, dropping in stages from about 6 C at the start to 0 C at the end. The Large Fish Experiment All 450 fish fought vigorously when hooked (most leaping from the water repeatedly), recovered after release, and survived through the day they were captured. The mean fighting time was over min in all groups (Table 3). Due to their shape, the circle hooks were occasionally more difficult to remove from the mouth, accounting for longer fighting times (which included the release period). Bleeding after release was relatively infrequent (Table 3) and was usually caused by a puncture wound in the mouth or jaw. Although some fish were hooked in the gill arches and bled TABLE 3. Summary of large fish experiment. Abbreviations are as follows: SHEL Shelton barbless hook; FLY barbless artificial fly; CC barbless circle hook; K 0 5 (weight/fl 3 ). Treatment Sample size Mean (SE) fighting time (s) Mean weight (kg) Percent bleeding Sample percent mortality 95% binomial confidence interval Mean condition factor K (SE) SHEL FLY CC (2.2) 63 (.6) 86 (.2) (0.02).375 (0.03).366 (0.02)

6 BAIT FISHING INNOVATIONS FOR RAINBOW TROUT CATCH AND RELEASE 03 profusely, none died immediately from the injury, as noted above. Mortality was less than 5% in all groups, with a difference of 4% between the artificial flies and the Shelton hooks (Table 3). Five extra fish were discovered in the SHEL holding area at the final census (48 fish rather than the expected 43), so all SHEL mortalities were not necessarily caused by hooking. Since all fish in the fly and circle groups were accounted for and there were no failures in the confinement barriers, either fish of unknown health were missed in the initial seining or ranch hands discarded some dead fish from the source channel in the Shelton holding area immediately upstream. Even if all of the mortalities were due to the direct and indirect effects of capture, none of the differences between treatments was statistically significant (Shelton versus fly: P 0.05; Shelton versus circle, P 0.75; fly versus circle: P 0.0). Although the results may not be strictly comparable due to differences in fish strain, history, and habitat, the fly and Shelton mortalities were not statistically different from those in the core experiment (Shelton, P 0.25; fly, P 0.5, Fisher exact probability test). The survivors to the end of the study fed vigorously and maintained high condition factors that did not differ significantly among treatments (Table 3). The water temperature ranged from 0.5 C before sunrise on the coldest day to 4.5 C in the afternoon of the warmest day, but otherwise varied from 2 C during the experiment. Discussion In the core or hook-comparison experiment, barbless flies, barbless Shelton hooks, and cut-line barbless J and treble hooks caused negligible mortality of rainbow trout ( 2%) during the first 3 weeks after release, and the hypothesis of equal effect could not be rejected statistically. Obviously this compares favorably with 6.9% (artificials) and 4% (bait) estimated for this species by Taylor and White (992), based on nine previous studies. The circle hooks caused 27% mortality when they were removed from the esophagus, but 77% were hooked in the mouth and could be extracted safely, or the hook fell out when tension was reduced on the line (versus 34% and 36% for the J and treble hooks, respectively; Figure ). This high frequency of superficial hooking kept total deaths from circle hooks below 0%. Although the hypothesis of equal effect was rejected for this gear, mortality from circle hooks almost certainly would have been minimal had deeply imbedded hooks been left in the fish (cf. no mortality from cut-line J hooks). It is interesting that Parmenter (2000) reported no difference between circle hooks and J hooks in the incidence of deep hooking if circle hooks were not used as recommended (50% versus 49%), but circle hook fish suffered only half the mortality of J-hook fish (0.4% versus 9.0%). Participating anglers were allowed to cut lines on deep hooks, but handling and release methods were not optimal for postrelease survival (T. Jenkins, personal observation). Although bait tackle has been banned from many waters based on studies employing similar methods, the low mortality observed in this study might render its procedures and conclusions somewhat controversial. One might suggest, for example, that the use of only one angler to catch fish, and the personal handling and release of the fish, might have led to unrealistically low mortality. In fact, the investigation design was quite conservative in this respect. The study assistant was instructed to drop bait in the pen with a slack line and to let fish swallow it; hooks (except for the circle type) were then set in what appeared to be standard fashion, and fish were played until they ceased resisting. In other words, the methods used were no different from those used by any bait angler intending to keep fish. All fish were personally netted and handled to ensure that fly-caught and bait-caught fish would be treated with equal (but not extraordinary) care. Little discretion was available for handling and release when the lines were cut, a tag line was jerked (Shelton hook), or a hook was removed with fingers or hemostats. It is difficult to see how numerous anglers using these methods under the contraints of the initial assumption (that bait fishers will use the same precautions as fly fishers to keep fish alive) would have produced substantially different results. A second objection might be that fish caught from pens are less likely to suffer damage than those caught in open water. This argument appears to have little merit since our technique for bait simulated an inattentive angler and resulted in a high incidence of risky hook placement (e.g., in the gills or the esophagus). Once a hook enters the digestive tract, for example, there seems to be no reason why the physical environment would influence subsequent damage. Schill (996) pointed out that fish he has studied in hatchery raceways and ponds suffered considerably higher mortality than comparable fish in a natural stream because passive fishing (resulting in deep hooking) is more

7 04 JENKINS difficult in a stream. A third objection might be that removing hooks under light anesthesia could have reduced handling stress and mortality. Aside from the fact that no anesthetic was used in the second and third experiments (with similar results), the elaborate procedure of netting, weighing, measuring, marking, and letting fish recover in a bucket may be more stressful than cutting the line or pulling the tag line (for Shelton hooks) while fish are in the water. As for artificial fly- and circle hook-caught fish, the former might have benefited somewhat from anesthesia, and the latter almost certainly did, so it might be concluded that both suffered artificially low mortality. Seltzer tablets (CO 2 ) are used routinely to anesthetize fish in small containers, so anglers could easily achieve the same presumptive benefit. A fourth objection might be that postrelease observation in a pen causes unusually low mortality, so the results cannot be generalized to a fishery. Actually, there is no reason to suppose that releasing a fish in its lake or stream habitat would be more stressful than confining it at density. In fact, the few fish that declined in vigor during the first experiment were attacked by other fish, probably hastening their demise. There appears to be no literature support for the idea that easier access to food increases the rate of healing or otherwise enhances the survival of fish with gut wounds, especially if they must compete for abrasive dry pellets in a feeding melee. The water temperature seems not to have been a factor, because it was always above the point where the mortality of hatchery rainbow trout might have been reduced (Dotson 982; Schisler and Bergersen 996). A last objection might be that fish of hatchery origin were studied and therefore do not represent wild fish under similar circumstances. Although wild rainbow trout might have fared worse in my experiments due to confinement in an unfamiliar and therefore stressful habitat (Taylor and White 992), no anatomical reason or literature support seems apparent for the notion that hatchery fish confined for weeks after release would better tolerate comparable hook wounds or more easily pass loose hooks than wild fish released immediately to their accustomed habitat. Lacking convincing arguments to the contrary, the results of this study predict the relative performance of these gear types in a fishery, assuming that bait anglers wishing to spare fish will take the same precautions as fly anglers. Perhaps this assumption has not traditionally been reasonable, but neither has the fishing public been widely acquainted with effective bait techniques. This issue is likely more sociological than biological and should be dealt with as such by local fishery managers. The success of Shelton hooks is not surprising given their easy removal regardless of where they lodge and the fact that the fish need not be held or even touched. Likewise, circle hooks were expected to have potential because they favor mouth locations, and they could have been left in if swallowed. In contrast, the more traditional cut-line approach with standard hooks was more effective than anticipated. Mason and Hunt (967) lost 35% of their hook-in fish during 4 months of observation, with 99% dying in the first 3 weeks. Schill (996) observed 47% mortality with J hooks left in for 2 months, and 83% died the first week. Similarly, Schisler and Bergersen (996) reported a 20.6% mortality of cut-line fish in 3 weeks (presumably a long enough time period to bracket most mortality), but 36.2% died at the temperature of the present study. The comparable figure for cutline fish in this study is 0.8%, or one mortality out of 24 esophagus hooks in 26 d (Table 2). Speculating as to the reason for this substantial difference in cut-line performance, the use of barbless bait hooks is a possibility and will be discussed below. Obviously long-term mortality is important, but the actual impact of catch and release on a fishery depends on resumed foraging and growth. The fish caught on bait hooks in the core study continued to grow after release as much as the control and barbless fly individuals, although there was a tendency for J-hooked fish, and to a lesser extent treble-hooked fish, to grow less than fish in the other treatments (Table ). Schill (996) found slightly lower average K in cut-line fish than in unfished controls, but Mason and Hunt (967) saw no effect. In this experiment differences in K for survivors were not significant. Some anglers believe that a minimal handling of fish during release can reduce subsequent mortality, even if longer playing time might be required. Although limited evidence suggests that neither playing to exhaustion (Marnell and Hunsaker 970) nor handling (i.e., dry hands or holding out of water, Hulbert and Engstrom-Heg 980; Hegen et al. 987; Loftus et al. 988) is necessarily harmful, it seems reasonable that either could cause sublethal stress (Wydoski 977). Since fish can be released from Shelton hooks even more readily than fish hooked in the jaw on artificial flies (because the tag line extends several centi-

8 BAIT FISHING INNOVATIONS FOR RAINBOW TROUT CATCH AND RELEASE 05 meters from the mouth), the minimal-handling experiment was conducted to see if mortality could be eliminated if fish were not touched during release. Only two (0.7%) of the Shelton-caught fish died within 60 d after capture, a period during which all hooking-related mortality is likely to occur (Mason and Hunt 967). Although this reduction in mortality is not significant, the hint of delayed mortality in the first experiment (a fish lost on day 26) was not repeated. The results from the core and minimal-handling experiments showed that fish with weights from 62 to about 500 g can be safely released from several types of bait tackle. In the third experiment, there was interest in the possibility that large rainbow trout would be more likely to injure themselves on bait hooks than would smaller trout, simply because they require more time and line tension to subdue and they jerk on the hook more violently (Warner 979). Since there were no facilities to duplicate the core experiment with large fish, circle hooks were selected to represent an ideal cut-line tackle (because many are superficially lodged), Shelton hooks because they caused little mortality in the first two experiments, and artificial flies for comparison. The mortality was slightly higher than in the core experiment for both fly and Shelton treatments (0.7% and 4.7%, respectively, versus 0% and 2%, respectively), and cut-line circle hooks caused greater mortality (3.3%) than cut-line J and treble hooks in the earlier study; mortalities within the experiment were statistically equivalent, however, and quite low compared with most literature values. If we assume that important variables were the same in both experiments, the between-experiment increases for the fly and the Shelton fish were not statistically significant. Warner (979) speculated that the unusually high mortality of his cut-line Atlantic salmon Salmo salar (57% in 4 d) was due to their large size, but they were only about 300 mm total length compared with 450 mm FL in this study. Since his fish suffered 90% mortality when the bait hooks were removed (on the high side of results reported for all salmonids), it is possible that the species studied or the conditions in the experiment contributed to a lower overall survival. Warner (976) suggested that the mortality rates in hatchery experiments underestimate those in normal fishery conditions because anglers can see the fish and prevent them from swallowing hooks (although Schill [996] concludes the opposite). This was not the case in the present study because we purposely let fish swallow hooks, and turbulence in the channel made observation of the strike as difficult as it would be in any stream. It should also be mentioned that several fish that died in this experiment had no obvious hook damage, but were distended with small rocks in the digestive tract or unused eggs in the body cavity when autopsied. According to the ranch owner, natural mortalities in this group of fish usually show one or the other of these conditions. Thus, there is a possibility that the slightly higher mortality associated with fish size was not directly caused by hook injury but by a higher susceptibility to stress or accidental trauma. Although they are decidedly nonstandard for bait tackle, barbless hooks were used exclusively in this study. Shelton hooks are barbless, and Westerman (932) reported that barbless bait hooks cause more reduction in mortality than anyone has observed for barbless artificials (where results have been contradictory; Taylor and White 992; Muoneke and Childress 994), so I assumed that this was an important variable to control. Is it possible that this factor alone reduced bait fishing mortality to the level of fly fishing mortality? Certainly the absence of a barb assisted in the removal of the Shelton hooks when they were reversed, and perhaps even limited mortality from the removal of deeply imbedded circle hooks to 27% (compared with values as high as 95% for J hooks in other studies; e.g., Mason and Hunt 967). As for leaving hooks in so they can work their way through the digestive tract, the lack of a barb might have facilitated hooks exiting tissue and reduced trauma when they did. Yet this effect does not seem adequate to explain fully the surprising performance of cut-line hooks in this study. The complete explanation probably involves such factors as unusual care in fish handling and the design of holding facilities, or the superior initial health of the subjects, all of which (it is personally believed) better mimicked conditions in a real fishery. Conclusions and Recommendations The bait techniques evaluated herein killed, at most, 33 out of,200 fish (97.3% survival). If the mortalities resulting from the unnecessary extraction of deeply lodged circle hooks (at least seven) are disregarded, the figure is closer to 98%. Should bait anglers be inclined (or required) to spare their catches, this level of success would justify the extra effort and/or expense involved. There appears to be no reason why these methods should not be tried on species in different taxonomic groups, although which to choose would depend on the an-

9 06 JENKINS atomical and behavioral characteristics of the fish and the physical properties of the habitat. The choice among the nearly equivalent methods for rainbow trout and other salmonids would depend on the situation and angler preference. Artificial lures cause little mortality in most fisheries and appear to be effective in multiple recapture scenarios (Schill et al. 986). If bait is more productive or is merely preferred by anglers, Shelton hooks are equally effective and have the same advantages of distinctive appearance (if enforcement of gear restrictions is an issue) and removability. Hook-in (cut-line) methods are also promising, especially when hooks have the circle configuration (because fewer are lost in the gut), but mouth hooking should be encouraged because higher hook-in mortality has been reported from other studies. Acknowledgments This study was supported by U.S. Department of Agriculture Forest Service Economic Recovery grant 00-DG to Friends of Sierra Trout and the City of Bishop, California, and by numerous government bodies, private organizations, and individuals in Inyo and Mono counties. J. Frederickson of the June Lake Marina and T. Alpers of the Alpers Owens River Ranch provided use of their facilities. R. Noles, N. Upham, S. Marti, E. Rummel, W. Wright, and J.-B. Brown assisted in various phases of the project. For technical assistance, I am grateful to J. Pelechowski, S. Jenkins, E. Smith, D. Jenkins, M. Niles, W. Power, and J. Daughenbaugh. S. Parmenter of the California Department of Fish and Game, Bishop Office, provided useful comments. References Dotson, T Mortalities in trout caused by gear type and angler-induced stress. North American Journal of Fisheries Management 2: Hegen, H. E., G. E. Saul, and G. C. Matlock Survival of hook-caught spotted seatrout held in cages. Proceedings of the Annual Conference Southeastern Association of Fish and Wildlife Agencies 38(984): Hulbert, P. J., and R. Engstrom-Heg Hooking mortality of worm-caught hatchery brown trout. New York Fish and Game Journal 27: 0. Loftus, A. J., W. W. Taylor, and M. Keller An evaluation of lake trout (Salvelinus namaycush) hooking mortality in the upper Great Lakes. Canadian Journal of Fisheries and Aquatic Sciences 45: Marnell, L. F., and D. Hunsaker Hooking mortality of lure-caught cutthroat trout (Salmo clarki) in relation to water temperature, fatigue, and reproductive maturity of released fish. Transactions of the American Fisheries Society 99: Mason, J. W., and R. L. Hunt Mortality rates of deeply hooked rainbow trout. Progressive Fish- Culturist 29:87 9. Muoneke, M. I., and W. M. Childress Hooking mortality: a review for recreational fisheries. Reviews in Fisheries Science 2: Parmenter, S. C Circle hooks: remedy for bait angling mortality? Pages 6 65 in D. A. Schill, S. Moore, P. Byorth, and B. Hamre, editors. Management in the new millenium: are we ready? Wild trout VII. Yellowstone National Park, Old Faithful, Wyoming. Pitcher, T. J., and G. J. A. Kennedy The longevity and quality of fin marks made with a jet inoculator. Fisheries Management 8:6 8. Schill, D. J Hooking mortality of bait-caught rainbow trout in an Idaho trout stream and a hatchery: implications for special-regulation management. North American Journal of Fisheries Management 6: Schill, D. J., J. S. Griffith, and R. E. Gresswell Hooking mortality of cutthroat trout in a catch-andrelease segment of the Yellowstone River, Yellowstone National Park. North American Journal of Fisheries Management 6: Schisler, G. J., and E. P. Bergersen Postrelease hooking mortality of rainbow trout caught on scented artificial baits. North American Journal of Fisheries Management 6: Taylor, M. J., and K. R. White A meta-analysis of hooking mortality of nonanadromous trout. North American Journal of Fisheries Management 2: Warner, K Hooking mortality of landlocked Atlantic salmon, Salmo salar, in a hatchery environment. Transactions of the American Fisheries Society 05: Warner, K Mortality of landlocked Atlantic salmon hooked on four types of fishing gear at the hatchery. Progressive Fish-Culturist 4: Westerman, F. A Experiments show insignificant loss of hooked immature trout when they are returned to the water. Michigan Department of Conservation Monthly Bulletin 2(2): 6. Wydoski, R. S Relation of hooking mortality and sublethal hooking stress to quality fishery management. Pages in R. A. Barnhart and T. D. Roelofs, editors. Catch-and-release fishing as a management tool. Humboldt State University, Aracata, California. Zar, J. H Biostatistical analysis. Prentice-Hall, Englewood Cliffs, New Jersey.

10 BAIT FISHING INNOVATIONS FOR RAINBOW TROUT CATCH AND RELEASE 07 Appendix: Manufacturer s Description of Shelton Hook Function