North American Journal of Management 24:237±243, 2004 ᭧ Copyright by the American Fisheries Society 2004

Evidence of Handling Mortality of Adult Caused by Fish Wheel Capture in the , Alaska

TEVIS J. UNDERWOOD* Fairbanks Fish and Wildlife Field Of®ce, U.S. Fish and Wildlife Service, 101 12th Avenue, Box 17, Room 222, Fairbanks, Alaska 99701, USA

JEFFREY F. B ROMAGHIN AND STEVE P. K LOSIEWSKI Division of Fisheries and Habitat Conservation, U.S. Fish and Wildlife Service, 1011 East Tudor Road, Anchorage, Alaska 99503-6199, USA

Abstract.ÐFrom 1996 to 1998, marked ®sh from a United States and Canada (Milligan et al. 1985, mark±recapture experiment were used to examine po- 1986; Merritt and Roberson 1986; Link and En- tential effects of ®sh wheel capture, handling, and tag- glish 1996; W. Ambrogetti, personal communi- ging on adult chum salmon Oncorhynchus keta in the Yukon River, Alaska. Four ®sh wheels equipped with cation, U.S. Fish and Wildlife Service, retired). live holding boxes were used to capture ®sh, two at the Fish wheels provide a number of bene®ts, includ- marking site and two at the recapture site. During the 3 ing low manpower requirements to operate and years of the study we annually marked 8,513±18,632 relatively safe operating conditions for sampling ®sh with individually numbered spaghetti tags; annual fast-¯owing rivers. They provide constant effort, tag returns external to the mark±recapture experiment can have high catch rates, and produce live catch- (not by project ®sh wheels) ranged from 594 to 1,007. Individual salmon were captured from one to four times es. Data from ®sh wheels can assist in providing in the four project ®sh wheels used in the mark±recapture species composition, stock characteristics, run experiment. Tag returns, interviews, carcass surveys, timing, distribution, relative abundance, true abun- and data from other management projects indicated that dance, and any other information afforded by the the proportion of ®sh with marks decreased as distance capture of live migrating ®sh. The ®sh wheel's from the marking site increased. Nine possible expla- nations for these observations were considered, but ®sh utility has made it a regular part of ®shery man- mortality associated with capture and handling appeared agement programs in many areas (Milligan et al. to be the most likely cause. Tags returned outside of the 1986; Cappiello and Bromaghin 1997; Link and mark±recapture experiment were used to investigate the English 1996; Underwood et al. 2000a, 2000b). relationship between the capture history within the ex- New projects are beginning for other major ®sh- periment and upriver recapture. Recapture probabilities eries in Alaska on the Copper (K. Hyer, U.S. Fish declined signi®cantly as the number of times a ®sh was captured increased. Our results raise concern over the and Wildlife Service, Of®ce of Subsistence Man- relatively common use of ®sh wheels for gathering in- agement, Anchorage, personal communication) season management data and for other research purpos- and Kuskokwim rivers (C. Kerkvliet, Alaska De- es. We recommend more de®nitive investigation of these partment of Fish and Game, personal communi- phenomena, a review of ®sh wheel construction and op- cation) in 2001. Fish wheels have been assumed eration to minimize potential effects to salmon popu- to be a low-impact method of sampling ®sh until lations, reexamination of the ef®cacy of live box capture as a management tool, and development of alternatives recently when Underwood et al. (2000b) suggested to current live box capture practices. potential handling mortality and listed nine hy- potheses as possible explanations for an inverse relationship between mark rate and distance from First developed in North Carolina, ®sh wheels the marking site; hence our study. were used there and in the of Fish captured in ®sh wheels experience varied Oregon and Washington for commercial harvest of levels of trauma and stressors. Depending on the migrating ®sh before 1900 (Donaldson and Cramer 1971). Fish wheels were suggested as a sampling size of the ®sh wheel, some ®sh may be raised to tool in 1951 (Meehan 1961) and since have been a height of 3 m before dropping through the air commonly used for research and management onto a chute that diverts the ®sh into the live box. studies of Paci®c salmon Oncorhynchus spp. in the Other ®sh may gently slide from basket to chute to live box with minimal jarring. Sources of trauma from ®sh wheels include physical impacts from * Corresponding author: tevis࿞[email protected] vertical drops, lacerations and punctures from wire Received January 14, 2002; accepted February 26, 2003 or other basket construction materials, and effects

237 238 UNDERWOOD ET AL.

FIGURE 1.ÐMap of the Yukon River showing the 1996±1998 ®sh wheel marking and recovery (near Rampart) sites for chum salmon (denoted by dark triangles) and the location of villages (dark circles). from ¯ight behavior. In the live box ®sh may ex- in Alaska (Beacham et al. 1988). The Alaskan por- perience collisions with walls or other ®sh, and tion of the Yukon River upstream of the Tanana crowding. Lethal and sub-lethal effects caused by River drains portions of the Brooks Range on the ®sh wheels have not been examined or reported, north and numerous smaller highlands to the south. except for recovery and migration of radio-tagged In Canada, the northwestern extension of the ®sh after release from ®sh wheels (Eiler 1990). Rocky Mountains borders the drainage to the east, Effects of capture and processing of ®sh have been and the Wrangell±St. Elias Range lies to the south- considered to be minimal where study assumptions west. Numerous smaller mountain ranges lie with- require similar behavior of marked and unmarked in the drainage. The river is turbid in summer, but ®sh (Killick 1955; Merritt and Roberson 1986). clears to some degree in winter when the in¯uence Our objectives were to determine if mortality of of glacial runoff, erosion, and tannic lowlands are adult chum salmon Oncorhynchus keta varied with reduced (Buklis and Barton 1984). River ice distances from the marking site and to determine breaks apart in May and can cause pooling for if mortality was associated with ®sh wheel capture miles when ice jams dam the river. and cumulative handling. To address our objec- The study area of the mark±recapture experi- tives, we examined data on the proportion of ®sh ment conducted from 1996 to 1998 was on the having tags, compared the rate of recapture be- Yukon River main stem between river kilometer tween gear types, and examined tag loss at various (rkm) 1,170 at a canyon upstream of the con¯uence locations upriver of the mark site. We also cate- with the Tanana River and rkm 1,221 at the village gorized the number of times a ®sh was captured of Rampart, Alaska (Gordon et al. 1998; Under- during the course of a mark±recapture experiment wood et al. 2000a, 2000b). This area is character- and then calculated the probability of a tag being ized by a meandering single channel with three returned from somewhere other than our ®sh islands (Figure 1). wheels, referred to as external recapture. Methods Study Area Marking site sampling procedures.ÐThe two The Yukon River (Figure 1) is over 3,200 km ®sh wheels at the marking site were composed of in length and drains about 860,000 km2, of which ¯oatation logs, two baskets, padded chutes, and about 330,200 km2 lie in Canada and 529,800 km2 live holding boxes (Figure 2). The baskets on these MANAGEMENT BRIEFS 239

deep; the walls and ¯oors contained many 5-cm diameter holes to allow a continuous ¯ow of water but prevent a strong current that could potentially impinge or tire ®sh. Fish wheels were placed across the river from each other on the north and south banks. Fish wheels ¯oated next to the riverbank so that the shoreward tip of the basket swept within 30 cm of the bottom. Wheels were moved inshore or off- shore to maintain the same proximity to the sloped bottom. A lead similar to a submerged picket fence was placed between the wheel and the shore to direct ®sh towards the dipping baskets. Tagging commenced by August 3 and ceased approximately September 20 each year. Fish were marked 6 d/week, Monday through Saturday. Dur- ing 1996 most ®sh were marked between 1000 and 1400 hours In subsequent years, operations were modi®ed to balance the objectives of marking 400 ®sh/d, spreading the release of marks throughout the day, and reducing holding times in the live boxes. Crews marked ®sh starting at four different times (0800, 1200, 1600, and 1900 hours), at- tempting to mark 100 ®sh each time. Chum salmon were marked with individually numbered spaghetti tags applied with barbed (1996) or hollow (1997 and 1998) applicator needles. During 1996 a hole punched in the caudal ®n was used as a secondary mark for the ®rst9doftheseason. During 1997 and 1998, half the left pelvic ®n was clipped per- pendicular to the ®n rays as a secondary mark. Severely injured or diseased ®sh were released without marking. Fish wheels were operated up to 24 h/d when catch rates were low and about 6 h/ d when catch rates were high. Recovery site sampling procedures.ÐThe river FIGURE 2.Ð(A) Aerial view and (B) side view sche- at the recovery site was wider and shallower than matics of the two-basket ®sh wheel used to capture chum at the marking site, so the two recovery site ®sh salmon in the Yukon River, Alaska, for tagging and re- wheels were sized accordingly. Live boxes were capture in 1996±1998, showing (a) main spare, (b) fence of similar size to those downstream. The south or lead, (c) raft, (d) main cable, (e) axle, (f) chute, (g) bank wheel was placed about 2 km downstream chute extension, (h) live box, (i) baskets, (j) lifting frame for axle, and (k) paddles. from the north bank wheel. Sampling commenced at both recovery wheels approximately 1 d after tagging commenced. Recovery wheels were op- ®sh wheels were approximately 3.0 m wide and erated 24 h/d for 7d/week. The frequency of emp- dipped to a depth of 4.5 m below the water's sur- tying ®sh from the live box depended on the catch face. Baskets were lined with wire, nylon, plastic, rates but generally was two to four times a day. or chain link netting. Nylon seine netting was in- The recovery site protocol limited the number of stalled on the sides of the baskets to minimize ®sh in a live box to less 200 ®sh; however, this injury to ®sh as they were lifted from the water. number was exceeded at times in all years. Re- Closed-cell foam padding was placed along the corded data included a tally of marked and un- chute and the ramp on the path to the holding boxes marked ®sh and the tag number of recaptured ®sh. to reduce impact injury to ®sh. Live boxes were All ®sh were released alive, except during sched- approximately 2.4 m long by 1 m wide by 1.2 m uled openings of the subsistence ®shery and in 240 UNDERWOOD ET AL.

1998 when 60 ®sh were sacri®ced for blood anal- ysis and necropsy. External tag recovery.ÐFour methods were used to recover tags external to the mark and re- capture study: (1) ®shermen upstream returned tags, (2) ®shery research projects in the United States and Canada operating elsewhere within the drainage, (3) face-to-face interviews with ®sher- men in three upstream villages (Beaver, Fort Yu- kon and Circle, Alaska) or by telephone interviews at other locations, and (4) arrangements made with speci®c ®shermen to collect data in locations not close to a surveyed village. After 1996 some ®sh- ermen received a preseason brie®ng by telephone regarding identi®cation of the primary (a spaghetti tag) and secondary (a ventral ®n clip) marks. The tag-return data collected included the gear type, tag numbers, tallies of marked and unmarked ®sh, and tallies of ®sh with the secondary mark but missing the primary mark; however, some return data did not include all types of data. Analysis of data.ÐData regarding mark rates (proportion marked), tag loss, and gear type were tabulated. Mark rates were plotted on the y-axis against distance on the x-axis. Generalized linear models (Agresti 1990; McCulloch and Searle 2001) were used to model mark rates as a function of distance from the marking site. Because the number of ®sh marked in any one sample can be assumed to have a binomial distribution, model parametersÐan intercept and slope for each yearÐwere estimated using SAS PROC GEN- MOD with a binomial error term and an identity FIGURE 3.ÐProportion of tagged chum salmon versus link (SAS Institute 1999). This method weights the distance in river kilometers (rkm) from the Yukon observed mark rates by the number of ®sh ex- River, Alaska, tagging site by year, 1996±1998. Vertical amined in the sample, in contrast to linear regres- lines are the 95% con®dence intervals of plotted rates. Sloped lines were generated from estimated parameters sion that would weight all samples equally. We of the linear model used to test for nonzero slopes and tested whether slopes equaled zero within years slope differences among years. and whether slopes among years were equal. The probability of external recapture was mod- Results eled as a function of the number of times a ®sh The number of marked ®sh released were 17,568 was captured in project ®sh wheels (termed capture in 1996, 18,632 in 1997, and 8,513 in 1998. The history) by using generalized linear models number of tags recovered externally using all four (Agresti 1990; McCulloch and Searle 2001). Mod- data collection methods totaled 594 in 1996, 1,007 els were ®t to the data by using SAS PROC GEN- in 1997, and 1,002 in 1998. Some of the data were MOD (SAS Institute 1999) with an identity link obtained opportunistically, but trends were con- and a binomial error structure. This model struc- sistent among data sources and years. Within each ture results in parameter estimates that are the ob- year, tag rates decreased signi®cantly with in- served sample portions. Likelihood ratio tests creased distance from the tagging site (Figure 3). (Stuart et al. 1999) were used to test the hypothesis Line slopes indicate a signi®cant trend that dif- that recapture probabilities were equal for all cap- fered from zero in 1996 (␹2 ϭ 1274.9, df ϭ 1, P ture histories within each of the 3 years separately. Ͻ 0.001), 1997 (␹2 ϭ 1530.0, df ϭ 1, P Ͻ 0.001), MANAGEMENT BRIEFS 241

TABLE 1.ÐComparison of mark rates in 1997 between colocated gear types, location, river kilometers (rkm) from tagging site, source and gear type, sample sizes, and the number and percentage of marked ®sh. The sources listed were broken into ``management projects'' (MP), which were conducted by government agencies or supervised personnel, and ``®shery,'' which were data from ®shermen willing to participate.

Distance from tagging Number of ®sh Number of ®sh Percentage Location site (rkm) Source Method used examined with marks with marks Chandalar River 474 MP Carcass survey 1,414 43 3.0 Fort Yukon 437 MP Interview 1,240 36 2.9 Nation River 702 Gill net 983 11 1.1 Eagle City 777 Fishery Fish wheel 2,500 32 1.3 Eagle City 777 Fishery Fish wheel 2,700 32 1.2 and 1998 (␹2 ϭ 317.4, df ϭ 1, P Ͻ 0.001). Also, times in the project ®sh wheels were associated line slopes among years were not equal (␹2 ϭ with a reduced probability of recapture upriver. 123.2, df ϭ 2, P Ͻ 0.001). Different gear types, carcass surveys versus interviews and gill nets ver- Discussion sus ®sh wheels, had similar rates of recapture (Ta- Our results document the declining ratios of ble 1). Tag loss was low. Of the 48,574 ®sh ex- marked to unmarked salmon with increasing dis- amined for tag loss between 1996 and 1998, 1,255 tance from the marking site. Our data are corrob- ®sh had tags and 5 were reported as having lost orated by similar declines in mark rate with dis- their primary mark. Of the ®ve, one was from a tance observed in Canada (S. Johnson, Department main-stem survey and four were reported at the of Fisheries and Oceans Canada, personal com- furthest monitoring site which is on a spawning munication). As discussed by Underwood et al. ground. (2000a), possible explanations for these declines The proportion of ®sh recaptured externally include (1) nonreporting, (2) immigration, (3) trap ranged from 0.12 to 0.028 (Table 2). A trend of avoidance behavior, (4) excessive harvest of decreased tag returns with an increase in our pro- marks, (5) stock-speci®c selective sampling at the ject ®sh wheel captures was indicated by the sam- sample site, (6) nonstock-speci®c selective sam- ple proportions and 95% con®dence intervals (Fig- pling at the sample site, (7) external recovery se- ure 4). The results of likelihood ratio tests of the lective sampling upstream, (8) tag loss, and (9) equality of the recaptured proportions within each handling mortality. Only data regarding handling year were statistically signi®cant for 1996 (␹2 ϭ mortality provided an effect with the direction and 15.7, df ϭ 2, P Ͻ 0.001), 1997 (␹2 ϭ 40.1, df ϭ magnitude suf®cient to explain the observed de- 3, P Ͻ 0.001), and 1998 (␹2 ϭ 6.7, df ϭ 2, P Ͻ cline. Other explanations were considered unlikely 0.037). This suggests that ®sh caught multiple because they were either inconsistent with avail-

TABLE 2.ÐSummary of statistics by year and capture history (number of times recaptured) of the proportion of tagged ®sh recaptured, including number of ®sh tagged, external recaptures (not in project ®sh wheels), proportion recaptured, and standard errors.

Number of times captured in mark±recapture experiment Year Statistic 1234 1996 Number of ®sh tagged 15,492 2,052 24 0 Number of external recaptures 547 44 3 Proportion recaptured 0.035 0.021 0.125 SE 0.0015 0.0032 0.0690 1997 Number of ®sh tagged 15,136 3,111 351 34 Number of external recaptures 890 106 10 1 Proportion recaptured 0.059 0.034 0.028 0.029 SE 0.0019 0.0033 0.0089 0.0294 1998 Number of ®sh tagged 7,232 1,135 146 0 Number of external recaptures 876 115 11 Proportion recaptured 0.121 0.101 0.075 SE 0.0038 0.0090 0.0219 242 UNDERWOOD ET AL.

not a likely cause. Stock-based selective sampling was unlikely because only low mark rates were observed upstream; no high values were observed. Nonstock based selective sampling was unlikely because the magnitude of the dilution needed would result in run sizes larger than possible. Tag loss was unlikely because data clearly show that tags were retained. Mortality of marked ®sh was the most likely explanation for the observed reduced mark recov- ery rates upriver. Capture histories show the ef- fects of capture to be cumulative, and the decrease in proportion captured is of a direction and mag- nitude that is consistent with the decreased recov- ery rates with increased distance. Mortality caused by capturing and handling ®sh is common in tag- ging studies (Seber 1982). Mortality caused by stress can be delayed (Stichney 1983), and effects of multiple stressors can be cumulative (Wede- meyer et al. 1990). The magnitude of mortality indicated should be considered a minimum be- cause the ideal control group, ®sh not captured or handled, cannot be assessed. The total effect may be larger than indicated by this study. The implications of mortality are immediate for management and research. For example, the mark± recapture experiment handled as many as 60,000 ®sh during 1996 (Gordon et al. 1998). Even a mod- est increase in mortality rates could affect signif- icant numbers of ®sh needed for spawning es- capement. Of additional concern are the negative effects potentially caused by the numerous other ®sh wheels used for research and monitoring salm- on throughout Alaska and western Canada. Gen- eral concepts regarding handling, stress, and mor- tality are well-documented (Stichney 1983; Adams FIGURE 4.ÐProportion of chum salmon recaptured ex- ternally and 95% con®dence intervals, by capture his- 1990; Wedemeyer et al. 1990); however, speci®c tory (number of times captured). investigations into stress and morbidity caused by ®sh wheels have not been well documented. Pos- sible causes of elevated stress include trauma in able data, predicted impossible run sizes, or the the ®sh wheel, holding time in the live box, crowd- expected magnitude of the effect was insuf®cient ed conditions within the live box, handling pro- to produce the observed trends. Incomplete re- cedures, and tagging. Any one or a combination porting was unlikely because directed efforts to of these factors could be causing the majority of improve reporting did not change the trend, and the stress. Given the useful management data pro- the magnitude would be small. Immigration was duced by ®sh wheels, further investigations to iso- unreasonable because the magnitude needed would late individual stressors are warranted. Tests to iso- be outside the realm of possibility for the popu- late each potential cause may lead to procedures lation size. Trap avoidance was unlikely because that minimize harmful effects or reduce them to similar mark rates were found using different gear an acceptable level. Alternatives to holding ®sh in types (®sh wheel versus carcass counts versus gill live boxes for some uses, such as collection of nets) at similar distances from the tagging site (Ta- catch per unit effort data, might be explored. For ble 1). Excessive harvest of marked ®sh upstream example, video image capture via computer (Hatch of the marking site was not observed, so it was et al. 1998) could be applied to ®sh wheels, elim- MANAGEMENT BRIEFS 243 inating the need to retain captured ®sh in live box- Link, M. R., and K. K. English. 1996. The 1993 ®sh- es. wheel project on the Nass River and an evaluation of ®shwheels as an inseason management and stock Acknowledgments assessment tool for the Nass River. Canadian Tech- nical Report of Fisheries and Aquatic Sciences We thank Jeff Adams, James Finn, Judith Gor- 2372. don, Karen Hyer, Monty Millard, Rod Simmons, McCulloch, C. E., and S. R. Searle. 2001. Generalized, David Wiswar, peer reviewers, and editors who linear, and mixed models. Wiley, New York. reviewed and shaped this paper. Thanks also go to Meehan, W. R. 1961. Use of a ®sh wheel in salmon research and management. Transactions of the the many individuals in the United States and Can- American Fisheries Society 90:490±494. ada who gathered the data and took the time to Merritt, M. F., and K. Roberson. 1986. Migratory timing return tags. 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