bluuebunny/crossref_metadata_2025 huggingface dataset:
Initial Attempts to Actively Manage Recreational Fishery Harvest in Minnesota
Authors: Radomski Paul
Published: June 2004

The theories and management style of commercial fisheries management have recently been applied to recreational fisheries. Several Minnesota recreational fisheries are now managed with target harvest levels based on sustainable yield predictors or quotas based on constant fishing mortality rate strategies. Creel limits and length-based regulations are being used to meet established targets or quotas. Three case histories are described. Both benefits and shortcomings have resulted from applying commercial fisheries management programs directly to recreational fisheries. However, recreational fisheries managers may not be controlling total fish harvest. To effectively manage recreational fisheries for “safe satisfaction returns,” fisheries managers may need to adopt conservative, robust harvest regulations, kill quotas, or aggressive regulations on how people fish. The distribution and mix of those options can be determined by good social science, but the efficacy of managing for safe satisfaction returns will depend on good fisheries data (biological and sociological) and great social skill. The lessons learned from the three case histories reviewed could be used to improve recreational fisheries management.
Active Management of Walleye Fisheries in Alberta: Dilemmas of Managing Recovering Fisheries
Authors: Sullivan Michael G.
Published: June 2004

Managers of the recreational fishery for walleyes Sander vitreus (formerly Stizostedion vitreum) in Alberta, Canada, face an unusual combination of very low productivity (related to the northern climate) and high fishing pressure. Passive management of the large recreational fishery and active management of the smaller commercial fishery failed to prevent declines and collapses of walleye stocks. During the 1990s, extensive consultations with the public resulted in the development of an active recreational fishery management system using set points to classify stocks. Catch and release and large, highly restrictive length limits were used to regulate the harvest. These restrictions on the recreational harvest resulted in a dramatic increase in the catch rates of growth-overfished stocks. Paradoxically, this recovery has created dilemmas and controversies in both the recreational and commercial fisheries. Anglers are now dissatisfied with the low harvest rates and absence of large fish attending the high catch rates of small fish. The total allowable catch, however, is being taken by hooking mortality and illegal harvest of undersize walleyes in the recreational harvest. In commercial gill-net fisheries for lake whitefish Coregonus clupeaformis, increasing bycatch of walleyes restricts the harvest of lake whitefish and has created uneconomical fisheries. Resolving these dilemmas will require dramatic changes to fisheries management techniques in Alberta.
Characteristics of Deep Pools Used by Adult Summer Steelhead in Steamboat Creek, Oregon
Authors: Baigún Claudio R. M.
Published: June 2004

This study examined environmental factors that affect deep-pool use by adult summer steelhead Oncorhynchus mykiss in Steamboat Creek, Umpqua River basin, Oregon. Deep pools (>0.8 m depth) represented only 4% of the available habitat area, and 39% of these pools had a mean bottom temperature not exceeding 19°C. Fish and habitat surveys were conducted in August and the first half of September of 1991 and 1992. The presence of adult summer steelhead in pools was determined by snorkeling and visual inspection, and the physical, chemical, and geomorphic characteristics were measured. Differences in deep-pool use by summer steelhead and their relationship to environmental characteristics were assessed by descriptive canonical discriminant analysis. The canonical function explained 69% of the variation in deep-pool use and defined a gradient from long, shaded deep pools with a coarse substrate and colder bottoms (which fish used) to shorter, shallower, sunny pools with fine particulate substrate, homogeneous water temperatures, and warmer bottoms (which fish did not use). This indicates that pool occupancy by adult summer steelhead in Steamboat Creek is a result of the interaction of geomorphic characteristics, cover, and thermal conditions. Future research should be directed toward understanding how biotic interactions within pools, deep-pool patchiness, and overall riverscape conditions influence summer steelhead distribution and pool use.
Evidence of Handling Mortality of Adult Chum Salmon Caused by Fish Wheel Capture in the Yukon River, Alaska
Authors: Underwood Tevis J. , Bromaghin Jeffrey F. , Klosiewski Steve P.
Published: June 2004

From 1996 to 1998, marked fish from a mark–recapture experiment were used to examine potential effects of fish wheel capture, handling, and tagging on adult chum salmon Oncorhynchus keta in the Yukon River, Alaska. Four fish wheels equipped with live holding boxes were used to capture fish, two at the marking site and two at the recapture site. During the 3 years of the study we annually marked 8,513–18,632 fish with individually numbered spaghetti tags; annual tag returns external to the mark–recapture experiment (not by project fish wheels) ranged from 594 to 1,007. Individual salmon were captured from one to four times in the four project fish wheels used in the mark–recapture experiment. Tag returns, interviews, carcass surveys, and data from other management projects indicated that the proportion of fish with marks decreased as distance from the marking site increased. Nine possible explanations for these observations were considered, but fish mortality associated with capture and handling appeared to be the most likely cause. Tags returned outside of the mark–recapture experiment were used to investigate the relationship between the capture history within the experiment and upriver recapture. Recapture probabilities declined significantly as the number of times a fish was captured increased. Our results raise concern over the relatively common use of fish wheels for gathering in-season management data and for other research purposes. We recommend more definitive investigation of these phenomena, a review of fish wheel construction and operation to minimize potential effects to salmon populations, reexamination of the efficacy of live box capture as a management tool, and development of alternatives to current live box capture practices.
A Comparison of Migration Rates of Radio- and PIT-Tagged Adult Snake River Chinook Salmon through the Columbia River Hydropower System
Authors: Matter Alicia L. , Sandford Benjamin P.
Published: June 2004

Documentation of adult salmonid migration behavior in the Columbia River drainage is critically needed to assess the effects of dams on travel time and passage. In 2000, we compared the upstream travel times of passive integrated transponder (PIT)-tagged and radio-tagged adult chinook salmon Oncorhynchus tshawytscha from Bonneville Dam on the lower Columbia River to Lower Granite Dam on the Snake River. We found no evidence that radio tagging negatively affected chinook salmon behavior. In fact, their median travel time (14.1 d, range = 7.8-44.4 d, N = 113) was actually faster (statistically significant at P = 0.005) than that for PIT-tagged fish (median = 15.9 d, range = 8.9-67.4 d, N = 164) after accounting for temporal effects (i.e., Bonneville Dam passage date). However, we concluded this difference was not biologically significant and was probably related to differences in study design or data complications. This study indicated that radio transmitters weighing less than 2% of chinook salmon body weight and the handling associated with implanting those tags did not negatively affect temporal rates of fish movement from dam to dam.
Scale Pattern Analysis of Selected Scale Characteristics and the First Annulus for Distinguishing Wild and Hatchery Steelhead in the Hood River, Oregon
Authors: Tattam Ian A. , Whitesel Timothy A. , Pan Yangdong
Published: June 2004

Resource managers need an accurate, reliable means of distinguishing hatchery-origin steelhead Oncorhynchus mykiss from wild stocks. We evaluated the effectiveness of scale pattern analysis at distinguishing between wild and hatchery (progeny of wild broodstock) winter steelhead collected at Powerdale Dam in the Hood River basin. The characteristics within the freshwater zone of hatchery (n = 126) and wild (n = 428) scales were quantified to determine whether the improved growth experienced in the hatchery environment would facilitate discrimination between hatchery and wild steelhead. Scale measurements that depended on the location of the first freshwater annulus were the most effective at distinguishing between hatchery and wild steelhead. Linear discriminant function analysis of key scale characteristics correctly classified a maximum of 73.9% of a blind-sampled population (n = 92) of known-stock winter steelhead. On average, estimates of the proportion of wild fish in known-origin test groups differed by 11.7% from the actual proportion of wild fish and had poor precision (mean coefficient of variation (100 · SD/mean), 259.9%). Our results suggest that scale pattern analysis could be an effective tool, but until ponding checks and true annuli can be accurately differentiated managers should not depend on scale patterns to distinguish between wild and hatchery steelhead similar to those from the Hood River.
Influences of Temperature and Environmental Variables on the Distribution of Bull Trout within Streams at the Southern Margin of Its Range
Authors: Dunham Jason , Rieman Bruce , Chandler Gwynne
Published: June 2004

The bull trout Salvelinus confluentus is believed to be among the most thermally sensitive species in coldwater habitats in western North America. We conducted a comprehensive field assessment of thermal habitat associations throughout the southern margin of the species' range. We developed models of thermal habitat associations using two data sets representing a geographically diverse range of sites and sampling methods. In both data sets, maximum temperature was strongly associated with the distribution of bull trout. In spite of the potential biases in these data sets, model predictions were similar. In both cases, the probability of the occurrence of bull trout exceeded 50% when the maximum daily temperature was less than 14-16°C, a result that is consistent with recent laboratory-based thermal tolerances. In one data set, we modeled the association between the distribution of bull trout and environmental variables, including temperature, instream cover, channel form, substrate, and the abundance of native and nonnative salmonid fishes. Only temperature was strongly associated with the distribution of bull trout. Our results and related studies of landscape habitat associations suggest that conservation efforts for bull trout would benefit from a focus on maintaining and restoring large and interconnected coldwater habitats.
Assessment of the Counting Accuracy of the Vaki Infrared Counter on Chum Salmon
Authors: Shardlow T. F. , Hyatt K. D.
Published: June 2004

Vaki, Ltd., of Iceland has designed a system for counting the in-river migration of salmonids via infrared sensors. The Vaki fish counter is used in Iceland, the United Kingdom, and Europe but is much less used in North America partly because of the system's unknown ability to count large populations accurately. In tests in the Big Qualicum River of Vancouver Island, British Columbia, we found the accuracy of the counter to be inversely correlated with migration rate of chum salmon Oncorhynchus keta. The fish counter was very accurate (>95%) for migration rates less than 500 fish/h but accuracy declined to 76% at a rates exceeding 1,500 fish/h. The principal cause for the decline in accuracy was the inability of the infrared sensors to count the passage of more than one fish simultaneously.
Influence of River Conditions on Survival and Travel Time of Snake River Subyearling Fall Chinook Salmon
Authors: Smith Steven G. , Muir William D. , Hockersmith Eric E. , Zabel Richard W. , Graves Ritchie J. , Ross Chris V. , Connor William P. , Arnsberg Billy D.
Published: June 2004

From 1995 to 2000, subyearling fall chinook salmon Oncorhynchus tshawytscha reared at Lyons Ferry Hatchery were PIT-tagged at the hatchery, trucked upstream, acclimated, and released into free-flowing sections of the Snake River weekly from early June to mid-July. We estimated survival probabilities and travel time through the lower Snake River and detection probabilities at dams for each weekly release group. The average median time between release and arrival at Lower Granite Dam was 43.5 d. For each group, we split this time into two nearly equal (on average) periods: one when most fish in the group were rearing and one when most fish had apparently begun active seaward migration. The estimated survival for hatchery fish from release to the tailrace of Lower Granite Dam decreased with release date each year. The estimated survival through this reach was significantly correlated with three environmental variables: survival decreased as discharge (“flow”) decreased, as water transparency increased, and as water temperature increased. Because the environmental variables were highly correlated among themselves, we were unable to determine whether any factors were more important than the others. All three factors have plausible biological consequences for rearing and actively migrating fish, and survival is probably influenced by all of them and possibly by interactions among them as well. Summer flow augmentation will increase discharge and decrease water temperature (provided the additional water is not too warm) and probably increase the speed of seaward migration of smolts, all of which are beneficial to the recovery of threatened Snake River fall chinook salmon.
Evaluating Recent Innovations in Bait Fishing Tackle and Technique for Catch and Release of Rainbow Trout
Authors: Jenkins Thomas M.
Published: June 2004

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 91%, 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.
Social Aspects of Muskellunge Management in Wisconsin
Authors: Margenau Terry L. , Petchenik Jordan B.
Published: June 2004

Public opinion plays an important part in the successful development of a fisheries management plan. We used a mail questionnaire to survey 1,400 anglers who fish for muskellunge Esox masquinongy in Wisconsin. The survey included defined groups of muskellunge anglers separated by muskellunge club affiliation and geographic location and general anglers selected from a random sample of angler license sales. The survey questions were designed to obtain opinions regarding muskellunge fishery and trophy management in Wisconsin in terms of angling behaviors, regulation options, and perceived problems. All anglers generally preferred fishing with artificial lures and practiced the voluntary live release of legal-length muskellunge. Muskellunge anglers considered a trophy muskellunge to be at least 40 in long, with a preferred length of 50 in or longer. Muskellunge anglers also supported regulations for muskellunge that were based on a water's biological potential, along with increased restrictions on regulations such as minimum length limits. General anglers were less supportive of restrictive regulations and were more likely to keep a legal muskellunge for consumptive purposes. The greatest perceived problems with muskellunge fishing were Native American spearing and conflicts with users of speedboats and jet skis. Opinion surveys such as this can help in formulating management strategies that satisfy most anglers within biological limits.
Responses of Benthic Fishes and Giant Salamanders to Placement of Large Woody Debris in Small Pacific Northwest Streams
Authors: Roni Philip
Published: June 2004

The placement of large woody debris (LWD) to improve or restore habitat for fishes is a common practice in North American streams, and the responses of salmonids to this practice have frequently been examined. In contrast, little information exists on the effects of LWD placement on nonsalmonid fishes and amphibians. In this study, I examined the responses of giant salamanders Dicamptodon spp., juvenile lampreyss Entosphenus tridentatus and Lampetra spp., reticulate sculpins Cottus perplexus, and torrent sculpins C. rhotheus to artificially placed LWD by sampling 29 small streams with paired treatment and reference reaches. Densities and mean lengths of giant salamanders, reticulate sculpins, torrent sculpins, and lampreyss did not differ significantly between treatment and references reaches. I also examined whether the observed responses were correlated with differences in physical habitat between reference and treatment reaches. Lampreys densities (log10(treatment) − log10(reference)) and length of age-1 and older reticulate sculpins (log10(treatment) − log10(reference)) among streams were positively correlated with LWD within the wetted channel. Lampreys length was also positively correlated with differences in percentages of pool area. These results indicate that artificial LWD placement may benefit lampreys and age-1 and older reticulate sculpins (two species known to prefer pools) but have little effect on other nonsalmonid species.
Electroshock-Induced Injury and Mortality in the Spotfin Chub, a Threatened Minnow
Authors: Michael Holliman F. , Reynolds James B. , Kwak Thomas J.
Published: June 2004

The effects of AC and pulsed DC (PDC) electroshock on mortality and injury (vertebral damage and hemorrhage) of spotfin chub Cyprinella monacha, a threatened minnow, were evaluated in a laboratory experiment. Groups of 18-20 captive-reared fish were either designated as a control or exposed for 3 s to one of five electrical treatments (60-Hz AC at a peak-to-peak voltage gradient of 1.7, 2.5, or 3.3 V/cm or 60-Hz PDC at a peak voltage gradient of 2.5 or 5.0 V/cm). Immobilization, which renders fish susceptible to capture during electrofishing, was the predominant response evoked in the groups exposed to electroshock, with the exception of the 1.7-V/cm AC group. No injury was detected in any fish in the experiment. Mortality was 10% or less in groups exposed to AC, regardless of voltage gradient. There was no significant variation in mortality among the groups exposed to AC (P = 0.487-1.00). Mortality varied significantly in the groups exposed to 60-Hz PDC (2.5 V/cm (0%) versus 5.0 V/cm (25%); P = 0.047). Our results indicate that electroshocking with 60-Hz AC and 60-Hz PDC may be safe for capturing spotfin chub when voltage (thus, voltage gradient) is limited to the immobilization threshold and the exposure period to 3 s. However, AC should be used only in low-conductivity waters (e.g., <80 μS/cm).
Evaluation of a Large-Mesh Panel to Reduce the Flatfish Bycatch in the Small-Mesh Bottom Trawls Used in the New England Silver Hake Fishery
Authors: Milliken Henry O. , DeAlteris Joseph T.
Published: June 2004

Fishermen must use small-mesh bottom trawls to capture certain species of fish that cannot be retained by standard groundfish mesh sizes. These fisheries are subject to bycatch limits when such trawls are used in areas where regulated species reside. Bycatch of regulated flatfish in the small-mesh bottom trawl fishery for silver hake Merluccius bilinearis in the northwestern Atlantic is a concern of management because silver hakes are captured in areas where juvenile regulated flatfish are common. An evaluation of flatfish and silver hake behaviors using low-light underwater cameras suggested that the two species could be separated within the mouth of a bottom trawl. Using the alternate tow method, four different large-mesh panels positioned in the lower belly of the trawl were separately evaluated. One of them proved to be effective in reducing flatfish bycatch while not reducing the catch of silver hakes; a large-mesh panel constructed of 40.6-cm (16-in) stretched mesh that was diamond shaped using orange-colored nylon twine 1.6 mm (0.06 in) in diameter in the lower belly resulted in a 73% reduction in flatfish catch with no effect on the catch of silver hakes.
Designing Tagging Programs for Pelagic Longline Fisheries: Trade-offs between the Number of Releases and Observer Coverage
Authors: Polacheck Tom , Hearn William
Published: June 2004

Tagging experiments are becoming increasingly important for providing an alternative to catch indices in large pelagic fisheries. The design of these experiments, in terms of the resources to devote to the number of releases versus recovery activity, has generally been ad hoc. We examined the relationship between the level of observer coverage and the variance in the estimates of annual exploitation rates from a tagging experiment in which the reporting rate is estimated from comparisons of tag returns from vessels with and without observers. The results indicate that the predicted precision will be a function of the level of observer coverage, the number of tags released, and the actual fishing exploitation rate. The results suggest that a direct tradeoff exists between the number of tags released and the level of observer coverage, such that a proportional increase in either one has similar effects on the predicted coefficient of variation. However, considering the assumptions (particularly multistage aspects of observer sampling and the need to estimate catches by age), higher observer coverage would be favored. In fact, substantial benefits in terms of ensuring accuracy and precision of the estimates would be gained from having 100% observer coverage. In any case, the results emphasize the importance of ensuring both adequate numbers of tag releases and robust estimation of reporting rates.
Evacuation of Passive Integrated Transponder (PIT) Tags from Northern Pikeminnow Consuming Tagged Juvenile Chinook Salmon
Authors: Petersen James H. , Barfoot Craig A.
Published: June 2004

Prey fish implanted with passive integrated transponder (PIT) tags can be used in predation studies if the timing of tag evacuation from the predators is understood. Laboratory experiments were conducted to determine how PIT tags in juvenile Chinook salmon Oncorhynchus tshawytscha that were consumed by northern pikeminnow Ptychocheilus oregonensis were evacuated in relation to various parameters. The rate of evacuation was directly related to temperature, while predator size and the number of prey consumed had less effect on the timing of tag evacuation. A power model was fitted to predict the proportion of tags expected to be evacuated at different intervals after ingestion. These results could be used in planning field or laboratory predation experiments with PIT-tagged prey fish.
Comparison of Three Underwater Antennas for Use in Radiotelemetry
Authors: Beeman John W. , Grant Cam , Haner Philip V.
Published: June 2004

The radiation patterns of three versions of underwater radiotelemetry antennas were measured to compare the relative reception ranges in the horizontal and vertical planes, which are important considerations when designing detection systems. The received signal strengths of an antenna made by stripping shielding from a section of coaxial cable (stripped coax) and by two versions of a dipole antenna were measured at several orientations relative to a dipole transmit antenna under controlled field conditions. The received signal strengths were greater when the transmit and receive antennas were parallel to each other than when they were perpendicular, indicating that a parallel orientation provides optimal detection range. The horizontal plane radiation pattern of the flexible, stripped coax antenna was similar to that of a rigid dipole antenna, but movement of underwater stripped coax antennas in field applications could affect the orientation of transmit and receive antennas in some applications, resulting in decreased range and variation in received signal strengths. Compared with a standard dipole, a dipole antenna armored by housing within a polyvinyl chloride fitting had a smaller radiation pattern in the horizontal plane but a larger radiation pattern in the vertical plane. Each of these types of underwater antenna can be useful, but detection ranges can be maximized by choosing an appropriate antenna after consideration of the location, relation between transmit and receive antenna orientations, radiation patterns, and overall antenna resiliency.
Population Dynamics of Channel Catfish in Brownlee Reservoir and the Snake River, Oregon
Authors: Shrader Terry M. , Moody Barron , Buckman Mary
Published: June 2004

To evaluate a perceived decrease in trophy channel catfish Ictalurus punctatus in Brownlee Reservoir and the Snake River, Oregon, we used gill nets in the reservoir and longlines and slat traps in the river to capture and tag channel catfish larger than 305 mm during 1995-1997. Angler recaptures of tagged fish demonstrated that some channel catfish moved up to 254.3 km upstream and 122.5 km downstream from their initial tagging locations and that 48% of the fish recovered in the reservoir had been tagged in the river and 21% of the fish recovered in the river had been tagged in the reservoir. Recruitment to the river and reservoir stocks between 1984 and 1992 was significantly correlated. Age structure of river and reservoir stocks did not differ significantly. Mean length at age of fish of ages 5-10 was not significantly different in 1996 or 1997, although equations describing growth of the two stocks were significantly different in 1996. Total instantaneous mortality of river and reservoir stocks did not differ significantly, but the angler exploitation rate for channel catfish was significantly higher in the river (0.315) than in the reservoir (0.062) in 1995. The similarity between the population parameters of the river and reservoir stocks suggests that these fish should be managed as one population.
A New Tool for Measuring Sediment Accumulation with Minimal Loss of Fines
Authors: Lachance Stephanie , Dubé Maryse
Published: June 2004

To measure the impact of culvert construction on brook trout Salvelinus fontinalis spawning beds, we collaborated with Bio-Innove, Inc., to develop a simple method for measuring the physical characteristics of streambeds and for quantifying the accumulation of fine sediment at spawning depth. We developed a modified version of the Wesche method that greatly limits fine-sediment loss at retrieval and the loss of the sediment collectors themselves. We found all 128 collectors after a 1–3-month period and all but 3 after 1 year in four experimental streams. The collectors are reusable and permit easy transfer of samples to the laboratory without any visible loss of fine sediment. The data collected allowed us to compare, by use of parametric statistics, the upstream and downstream sections from newly built culverts in terms of percent fines of different diameters, distance of sediment accumulation downstream, grading curves, and organic matter content of accumulated fine sediment.
Fish and Invertebrate Recolonization in a Missouri Prairie Stream after an Acute Pollution Event
Authors: Meade Richard
Published: June 2004

Recolonization of invertebrates and fish was monitored for 50 weeks and 241 weeks (4.6 years), respectively, after a chicken manure spill killed more than 18,000 fish and an undetermined number of invertebrates in 31.4 km of a prairie stream in west-central Missouri. I have characterized the postspill water quality in the affected portions of the stream to provide insight about the impacts of water quality on the rate of recolonization, determined the recolonization of invertebrate populations to provide insight into the return of a suitable food base for the fish population, and documented the chronology of fish recolonization in the affected portions of the stream to assist with a more appropriate determination of losses of recreational and economic values as a result of fish kills. Water quality had improved by week 15 postspill, but degraded water quality retarded recovery by invertebrates at one site for 50 weeks. Total and noninsect invertebrate abundance improved at some, but not all, sites by week 22 postspill. Abundance of most invertebrates had recovered by week 50, but the invertebrate community remained unstable. The total numbers of fish at two polluted sites and at a reference site were similar by week 33 postspill. However, sunfish Lepomis sp. 178 mm or larger and largemouth bass Micropterus salmoides 305 mm or larger remained relatively scarce in the polluted stream segment by week 241. The low numbers of large sport fish present at 241 weeks postspill have greatly diminished the attractiveness of Muddy Creek for angling. The value of a lost or degraded recreational fishery should be included with assessments of penalties to help deter future violations of water quality laws and recover losses that may affect a fishery for two or more years after a major fish kill.
The Effect of Light Intensity on Sockeye Salmon Fry Migratory Behavior and Predation by Cottids in the Cedar River, Washington
Authors: Tabor Roger A. , Brown Gayle S. , Luiting Victoria T.
Published: June 2004

We examined the relationship between light intensity, migratory behavior of sockeye salmon Oncorhynchus nerka fry, and predation by cottids Cottus spp. We tested the hypothesis that above-natural intensities of nighttime light would increase cottid predation of sockeye salmon fry. In circular tank experiments under controlled laboratory conditions, we tested the ability of cottids to prey on sockeye salmon fry under six different light intensities using minimal water circulation to separate the effect of the migratory behavior of fry from the ability of cottids to capture them. We found that cottids preyed most effectively in complete darkness, whereas the lowest predation occurred at the brightest light intensity. We next tested the predation ability of cottids at four light intensities in a pair of artificial streams to simulate more natural conditions. In experiments without cottids, the majority of fry passed quickly through the artificial streams under complete darkness, but as light intensity was increased, fewer fry emigrated and did so at a slower rate. With cottids present and increased light intensity, even fewer fry emigrated but they did so at a faster rate than did those in the stream without cottids. We determined that cottids probably consumed about 5% of the sockeye salmon fry under complete darkness and ate about 45% of the fry at the brightest light intensity tested. In experimental field trials, the shoreline abundance of fry and predation by cottids increased as light intensities increased. Using two small lights within an 8-m shoreline section on the Cedar River, Washington, we delayed as many as 550 sockeye salmon fry and observed predation of as many as 7.6 fry/cottid. At the end of the experiment, we turned the lights off and noted that the shoreline abundance of fry declined dramatically. At two locations on the Cedar River lit by city lights, the abundance of sockeye salmon fry and predation by cottids was substantially greater than at nearby sites with low light. Also, we demonstrated at one site that reducing light intensity substantially reduced predation on sockeye salmon fry. Overall, we conclude that increased light intensity appears to slow or stop out-migration of fry, making them more vulnerable to capture by predators such as cottids.
Injury and Mortality Induced by Four Hook Types on Bluegill and Pumpkinseed
Authors: Cooke Steven J. , Suski Cory D. , Barthel Brandon L. , Ostrand Kenneth G. , Tufts Bruce L. , Philipp David P.
Published: June 2004

Tackle manufacturers have responded to concerns regarding hooking injury and mortality by attempting to design and market hooks that are less damaging to fish (e.g., circle hooks). To date, studies investigating circle hooks have been primarily restricted to large marine species. We compared the injury and short-term (72-h) mortality of bluegills Lepomis macrochirus and pumpkinseeds L. gibbosus angled using number-6 circle hooks and three other conventional hook types (aberdeen, wide-gap, and baitholder) across three water temperatures (18, 22, and 26°C). Unlike other hook types, circle hooks were never lodged in the gullet, but they were frequently lodged in the eye. Some fish captured on conventional hooks were hooked deeply in the gullet, necessitating line cutting for release. Incidences of bleeding were low using all hook types, and when not lodged in the gullet, all hooks were generally easy to remove. Anatomical hooking locations differed among small (<145-mm) and large (>145-mm) bluegills for all hook types but not among pumpkinseeds. Hooking depth differed between small and large fish of both species captured on circle hooks; smaller fish were hooked more deeply. Mortality in both species was negligible at all water temperatures except for bluegills at 26°C (3% mortality). Bluegills that died were smaller than those that survived. Our results confirm the supposition that circle hooks are less susceptible to deeply hooking fish in the gullet. However, circle hooks permanently impaired vision of up to 22% of the fish, much more than for other hooks types. Although efficient at minimizing injury and mortality in marine fish, our study suggests that circle hooks perform similarly to more conventional hook types in fisheries for small sunfish.
Predicting the Occurrence and Success of Walleye Populations from Physical and Biological Features of Northern Wisconsin Lakes
Authors: Nate Nancy A. , Bozek Michael A. , Hansen Michael J. , Ramm Carl W. , Bremigan Mary T. , Hewett Steven W.
Published: June 2004

We developed a linear discriminant function (LDF) using surface area, mean depth, fetch, and three substrate descriptors to discriminate the presence and absence of walleyes Sander vitreus (formerly Stizostedion vitreum) in 120 northern Wisconsin lakes. The resulting LDF correctly classified 90% of walleye lakes and 85% of nonwalleye lakes. For model validation, the model classified 90% of walleye lakes and 93% of nonwalleye lakes in an independent set of 100 randomly selected lakes. In contrast, within walleye lakes, an LDF using the same variables correctly classified only 60% of 30 self-sustaining walleye lakes and 50% of 30 stocked walleye lakes. For model validation, the model classified 30% of self-sustaining walleye lakes and 73% of stocked walleye lakes in an independent set of 40 randomly selected lakes. To further assess the differences between walleye lakes with self-sustaining and stocked populations, the angler catch rates for largemouth bass Micropterus salmoides, smallmouth bass M. dolomieu, northern pike Esox lucius, and muskellunge E. masquinongy obtained from creel surveys during 1990-2001 were analyzed by means of a principal components analysis. The first principal component explained 29% of the variation and represented a linear contrast between the relative abundance of walleyes and muskellunge and the relative abundance of largemouth bass and northern pike. High largemouth bass and northern pike densities characterized lakes with stocked walleye populations, whereas high walleye and muskellunge densities characterized lakes with self-sustaining walleye populations. We conclude that physical features may be used to discriminate lakes where walleyes presently occur from lakes where walleyes do not presently occur, and that fish community differences exist between stocked and self-sustaining walleye populations in northern Wisconsin.
Using a Geographic Information System to Assess the Accuracy of Radio-Triangulation Techniques for Fish Telemetry
Authors: James Daniel A. , Erickson Jack W. , Barton Bruce A.
Published: June 2004

We evaluated the accuracy of several triangulation methods that produce quantified rather than inferred transmitter position data on the movements of brown trout Salmo trutta in an urbanized stream. Other telemetry studies have reported accuracies of 0.5-5 m based on visual observation of fish or detection of hidden transmitters from within streams. With our geographic information system (GIS) method, coordinate locations for each transmitter position were recorded without entering the water. A global positioning system (GPS) was used to record coordinate locations on the stream bank and compass bearings with signals of hidden transmitters in the stream. Signal locations were then triangulated to estimate the coordinates of transmitter locations. Location coordinates were placed onto a GIS coverage, and accuracy was determined by comparing the actual positions of hidden transmitters with the estimated positions. Three different triangulation methods produced slightly different accuracies. Our GIS method is less biased and supported by data and could provide a standard method for triangulation. Moreover, the GIS-based radio-triangulation approach enables tracking in the field without disturbing a tagged fish in its habitat or otherwise altering a fish's behavior due to human intervention.
Tag Location and Retention in Black Rockfish: Feasibility of Using PIT Tags in a Wild Marine Species
Authors: Parker Steven J. , Rankin Polly S.
Published: June 2004

Tag and recovery programs can provide valuable information on population size and exploitation rates in fishes. Passive integrated transponder (PIT) tags are ideal for use in such programs because they provide identification of individual fish and are invisible to anglers, circumventing problems with nonreporting of tags. Our objective was to determine whether PIT tags could be used successfully to tag black rockfish Sebastes melanops. We tested tag placement and tag retention using intramuscularly injected PIT tags (12 × 2.1 mm) in 227 black rockfish (25-47 cm); three tag placement sites located outside of the area normally filleted were evaluated. Tag retention for all tag sites was 100% after 49 weeks; however, two fish retained inoperative tags, which possibly sustained damage during the tagging procedure. The results indicated that the best tagging site is ventral and anterior to the origin of the pectoral fin. At this site, tag retention is excellent, risk of infection is low, tag movement is minimal, and little or no tissue damage results from the tagging procedure.
Influence of Fishway Placement on Fallback of Adult Salmon at the Bonneville Dam on the Columbia River
Authors: Reischel Tami S. , Bjornn Theodore C.
Published: June 2004

Using radiotelemetry, we observed and quantified the behavior of upstream migrating adult Chinook salmon Oncorhynchus tshawytscha and sockeye salmon O. nerka exiting the Bradford Island fishway at the Bonneville Dam on the Columbia River in 1997 and 1998. Nearly all of the fish that exited the fishway migrated upstream along the Bradford Island shoreline. Those fish that took the route nearest to the spillway were most likely to fall back over the spillway. From 14.5% to 21.3% of the fish tracked along the Bradford Island shore fell back over the spillway of the dam. The combined effects of spill, water temperature, and Secchi disk visibility were associated with route patterns and fallback behavior during each year. High spill was significantly and positively correlated with fallback behavior for Chinook salmon in 1998. Most of the fish we tracked that fell back reascended the fishway and migrated upstream (≥95% in 1997; ≥70% in 1998). We suggest that modifying the configuration of this fishway's exit would decrease the proportion of fish that fall back, perhaps reduce the risk of injury and fatigue, and improve the precision of counts of fish migrating upstream.
Injury and Mortality of Warmwater Fishes Immobilized by Electrofishing
Authors: Dolan C. R. , Miranda L. E.
Published: June 2004

Most studies of injury associated with electrofishing have focused on salmonids; few have given attention to warmwater fishes. Under controlled laboratory conditions, we treated bluegill Lepomis macrochirus, channel catfish Ictalurus punctatus, and largemouth bass Micropterus salmoides of various sizes to duty cycles ranging from 1.5% to 100%. This range of duty cycles represented continuous DC and pulsed-DC frequencies ranging from 15 to 110 Hz and pulse durations of 1 to 6 ms. At each duty cycle, fish were exposed to power densities in excess of those required to immobilize them within 3 s, and we subsequently determined the incidence of hemorrhage, spinal injury, and mortality. Incidence of hemorrhage averaged 3% (range, 0–25%), differed among species, and was not related to duty cycle or fish size. Incidence of spinal injury averaged 3% (range, 0–22%) and mortality averaged 10% (range, 0–75%); both differed among species and were related to duty cycle, fish size, and interactions among these variables. Largemouth bass was the species most vulnerable to hemorrhage, spinal injury, and mortality, channel catfish the least vulnerable; bluegills exhibited effects that were intermediate. Small centrarchids were especially susceptible to mortality. Fish tetanized by the electrical treatment were more likely to experience injury and mortality than fish that were only narcotized. However, mortality was not related to the injuries studied because hemorrhage and spinal injuries were similar in fish that survived electroshock and in those that died. We suggest that electrofishing with intermediate to high duty cycles could reduce electrofishing-induced injury and mortality to warmwater fish. Additionally, the power output and electrode system should be managed to induce narcosis and prevent tetany and to avoid the large peak powers required to immobilize small individuals.
Catchability of Walleyes to Fyke Netting and Electrofishing in Northern Wisconsin Lakes
Authors: Rogers Mark W. , Hansen Michael J. , Beard T. Douglas
Published: June 2004

We quantified relationships between both fyke-net catch rates (catch/net-night) and electrofishing catch rates (catch/mi) and population densities (number/acre) of walleye Sander vitreus (formerly Stizostedion vitreum) for adult population estimates and total population estimates to determine whether catchability was density dependent. Fyke-net catch rates were modeled as a nonlinear function of adult walleye density and of four size-classes of the adult population, and electrofishing catch rates were modeled as a nonlinear function of adult and total walleye density and four size-classes of the adult and total populations. The results showed nonlinear relationships between catch rate and density for the adult and total populations. We accounted for measurement errors in catch rates and densities by estimating bias-corrected slopes by means of Monte Carlo simulations and estimated measurement-error ratios by means of an errors-in-variables model. We found that the bias-corrected slopes were higher than ordinary-least-squares regression estimates and that measurement errors were greater in catch rates than in density estimates. Lastly, we sought to explain the residual variability in the relationships between (1), fyke-net catch rates and adult walleye densities and (2) electrofishing catch rates and adult and total walleye densities. We found that the fyke-net catch rate was positively related to adult walleye density and percent littoral zone (percentage of lake surface area ≤20 ft deep) and negatively related to conductivity. We found that the electrofishing catch rate of adult walleyes was positively related to adult walleye density and conductivity and that the electrofishing catch rate of the total walleye population was positively related to total walleye density. We concluded that the nonlinear relationship between catch rates and walleye abundance limits the use of catch rates to index walleye abundance in northern Wisconsin lakes.
Atlantic Sturgeon Marine Bycatch and Mortality on the Continental Shelf of the Northeast United States
Authors: Stein Andrew B. , Friedland Kevin D. , Sutherland Michael
Published: June 2004

Protected sturgeon Acipenser spp. are caught in a number of different commercial fishing gears along the east coast of the USA. During their life cycle, Atlantic sturgeon Acipenser oxyrinchus migrate into marine waters, where they are caught by otter trawls, sink gill nets, and drift gill nets targeting other species. We investigated fishing records collected by onboard observers to calculate Atlantic sturgeon bycatch and mortality rates for each fishing gear. Bycatch rates were based on fishing trips monitored between 1989 and 2000 and were indexed by landed species and state. Rates were then raised to fisherywide estimates of bycatch based on total landings for the relevant gears at each location. Where data were available, we estimated sturgeon mortality for each gear. The results showed that Atlantic sturgeon bycatch was highest for sink gill nets in specific areas of the coast. The observed immediate mortality rates of Atlantic sturgeon captured in sink gill nets and drift gill nets were 22% and 10%, respectively, suggesting that annual mortality in these fisheries may be on the order of 1,500 fish per year. The resulting mortality estimates are a source of concern for the continued recovery of Atlantic sturgeon resources.