bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative Hooking Mortality among Walleyes Caught on Barbed and Barbless Octopus Hooks and Barbed Jigs
Authors: Reeves Keith A. , Staples David F.
Published: December 2011

Anglers sometimes use alternatives or modifications to J-shaped hooks to reduce hooking mortality in fish that are caught with live baits and then released. One such modification, the removal of barbs, has been evaluated for several fish species but has shown little promise for reducing hooking mortality; however, barbless hooks have not been evaluated for walleye Sander vitreus. We evaluated relative mortality for walleyes (228–419 mm total length) that were caught by means of bobber fishing with leeches on barbed (n = 179 fish) or barbless (n = 209) live-bait octopus hooks or on barbed jigs (n = 193); after capture, the fish were held for 120 h in net pens. Holding mortality was a function of water temperature, cage density, bleeding level, and hook location; fish length and angler handling time did not significantly affect mortality. We combined hook location and bleeding level to create a single variable, hooking damage, which was used to replace the two variables in the initial model. This second model was similar to the first, indicating that hooking damage was correlated with mortality when controlling for the effects of water temperature and cage density. We also determined that hooking damage was correlated with hook type. For the 228–419-mm walleyes in our study, barbed jigs caused less damage than live-bait hooks and damage levels were similar between barbed and barbless live-bait hooks. Given specified levels of hooking damage, holding mortality was independent of hook type. We hypothesize that the fish in this study were too small to swallow the jigs well and thus were hooked less critically and bled less than fish that were caught with live-bait hooks. This study illustrates how gear type can affect hooking mortality based on the amount of damage caused when the fish is caught and adds to the body of literature indicating that the removal of barbs from hooks does not increase fish survival.

Received March 15, 2010; accepted November 17, 2010
Movement of Lake-Origin Burbot Reared in a Hatchery Environment and Released into a Large River Drainage
Authors: Neufeld Matthew D. , Cain Kenneth D. , Jensen Nathan R. , Ireland Susan C. , Paragamian Vaughn L.
Published: December 2011

Burbot Lota lota in Kootenay Lake and the Kootenay River of British Columbia, Idaho, and Montana (U.S. spelling: “Kootenai River”) are at risk of demographic extinction. We conducted a pilot study to evaluate poststocking dispersal and movement of hatchery-reared, lake-strain burbot (Moyie Lake, British Columbia) in a riverine environment to determine the potential utility of this hatchery strain for future burbot rehabilitation efforts in this system. We implanted ultrasonic tags into 30 hatchery-reared burbot (ages 2 and 3) and released them into the Goat River, a tributary to the Kootenay River, in October 2009. Dispersal over a distance of 2 km from the Goat River release site to the Kootenay River occurred within 1–9 d after release (mean = 3.1 d; n = 28 active tags). Thereafter, 14 burbot remained in the Kootenay River for the rest of the 144-d study period; nine of these fish were observed moving upstream from the Goat River confluence, and five were observed both upstream and downstream from the confluence. The other 14 burbot were observed in Kootenay Lake; of these fish, eight were detected in the lake for the duration of the study, and six were observed to move regularly between the lake and the river. Dispersal distances (distance between the upstream-most and downstream-most detections per individual) within the Kootenay River ranged from 10 to 138 km (mean = 80 km), and tagged fish were detected over a 236-km reach (from 135 km downstream to 101 km upstream of the Goat River confluence). We also observed burbot in the vicinity of known spawning locations during the February spawning season. The observed dispersal suggests that a limited number of stocking locations may be sufficient to allow burbot to access available habitats within a few months postrelease. Our observations therefore suggest that lake-origin, hatchery-reared burbot may be suitable for stocking in a riverine environment.

Received June 11, 2010; accepted December 4, 2010
Assessing the Feasibility of Native Fish Reintroductions: A Framework Applied to Threatened Bull Trout
Authors: Dunham Jason , Gallo Kirsten , Shively Dan , Allen Chris , Goehring Brad
Published: December 2011

Translocations to recover native fishes have resulted in mixed success. One reason for the failure of these actions is inadequate assessments of their feasibility prior to implementation. Here, we provide a framework developed to assess the feasibility of one type of translocation—reintroduction. The framework was founded on two simple components of feasibility: the potential for recipient habitats to support a reintroduction and the potential of available donor populations to support a reintroduction. Within each component, we developed a series of key questions. The final assessment was based on a scoring system that incorporated consideration of uncertainty in available information. The result was a simple yet transparent system for assessing reintroduction feasibility that can be rapidly applied in practice. We applied this assessment framework to the potential reintroduction of threatened bull trout Salvelinus confluentus into the Clackamas River, Oregon. In this case, the assessment suggested that the degree of feasibility for reintroduction was high based on the potential of recipient habitats and available donor populations. The assessment did not provide a comprehensive treatment of all possible factors that would drive an actual decision to implement a reintroduction, but it did provide a fundamental level of feasibility assessment that is often lacking in practice.

Received May 28, 2010; accepted December 22, 2010
Survival and Straying of Hatchery Steelhead following Forced or Volitional Release
Authors: Clarke Lance R. , Flesher Michael W. , Warren Shelby M. , Carmichael Richard W.
Published: December 2011

In this study, conducted over four release years, we compare the performance of hatchery steelhead Oncorhynchus mykiss that were force-released (FR) from acclimation ponds with that of fish given a 2-week volitional release (VR). After fish were released into streams, we monitored smolt out-migration travel times and survival to Lower Granite Dam on the Snake River using passive integrated transponder (PIT) tags in a subsample of each release group. To better understand the out-migration characteristics of volitionally departing fish, we also captured and PIT-tagged fish as they exited ponds in the first and last 24 h of VR. Across all release groups, travel time was 3% faster for fish that were forced from acclimation ponds than for VR groups; however, the average survival of VR groups (65.0%) was significantly higher than that of FR groups (58.6%). On average, fish that departed acclimation ponds in the first 24 h of VR took 6 d longer to reach Lower Granite Dam and had lower survival (50.3%) than those departing in the last 24 h (56.9%), though these differences were not statistically significant. We estimated smolt-to-adult survival and a stray rate index for the FR and VR groups based on recoveries of coded-wire-tagged adults. Across all releases, smolt-to-adult survival was not significantly different between groups (FR = 0.63%, VR = 0.59%), and the same was true for the stray rate index (FR = 10.9%, VR = 10.6%). Our finding that VR provided no postrelease survival benefit is consistent with the results of other published studies, but this is the first study to quantify the stray rate in relation to VR.

Received September 14, 2010; accepted November 15, 2010
The Impact of Different Performance Measures on Model Selection for Fraser River Sockeye Salmon
Authors: Cummings Jonathan W. , Hague Merran J. , Patterson David A. , Peterman Randall M.
Published: December 2011

Uncertainties prevalent in fisheries systems result in deviations between management targets and observed outcomes. As an example of attempting to deal with such uncertainty, fishery managers of sockeye salmon Oncorhynchus nerka from the Fraser River, British Columbia, use environmentally based management adjustment (MA) models to forecast indices of in-river loss of adults as they migrate upstream to spawn. Losses forecasted by MA models are directly incorporated into estimates of total allowable catch, resulting in harvest reductions that aim to increase the probability of achieving spawning escapement targets. However, the relative forecasting success of different MA models has not been rigorously assessed. Therefore, we used a suite of forecasting and hindcasting metrics to rank the performance of numerous MA models. We found that the rank of each model varied across sockeye salmon stock aggregates (i.e., run timing groups) and depended on the performance measures chosen for evaluation. Although model selection in fisheries research is often determined solely by model-fitting criteria, such as R2 and Akaike's information criterion (corrected for small-sample bias), in our case the models with the largest mean R2 value, the smallest mean corrected Akaike's information criterion, or both often ranked poorly for measures of model forecast performance (i.e., mean raw error, mean absolute error, and root mean square error). Although no single model performed best across all run timing groups, failure to apply an MA produced the worst outcome (for 3 of the 4 run timing groups) or second-worst outcome (for the fourth group). We provide a framework for model selection based on the relative importance of different model selection criteria and their associated performance measures. We urge scientists and managers to work closely together to develop appropriate metrics for assessing model performance and for objectively selecting forecast models that will best meet management objectives.

Received April 29, 2010; accepted December 6, 2010
Winter Catch-and-Release Hooking Mortality of Saugers below Lock and Dam 3 of the Mississippi River
Authors: Meerbeek Jonathan R. , Hoxmeier R. John H.
Published: December 2011

We evaluated the effect of length and depth of capture of saugers Sander canadensis on winter hooking mortality below Lock and Dam 3 of the Mississippi River (i.e., Pool 4) by catching saugers using the most common recreational fishing gear in these fisheries (jig and plastic, jig and minnow, and jigging spoons) and holding the fish for 72 h in a net-pen. Sauger winter hooking mortality was 26.4% and increased with depth of capture. Thirty-three percent (56 of 172) of the saugers caught at depths of 9 to 24 m died, compared with only 2% (1 of 41) of those caught at depths of 9 m or less. There was no relationship between fish length and mortality; however, fish caught at depths of 12 m or less were significantly larger. We applied our hooking mortality estimates (26.4%) to a concurrent creel census and estimated that 2,500–2,900 kg of saugers were lost each year to winter hooking mortality. The percentage of total angling mortality (harvest and hooking) resulting from catch and release each winter was 30.5% (2,515 kg/8,256 kg) in 2005–2006 and 33.0% (2,812 kg/8,529 kg) in 2006–2007. Based on the historical abundance and annual mortality estimates available for Pool 4 saugers, winter hooking mortality did not substantially reduce the population. However, anglers may reduce winter catch-and-release hooking mortality by fishing in shallower water (<9 m).

Received May 12, 2010; accepted December 30, 2010
Effects of Hatchery Fish Density on Emigration, Growth, Survival, and Predation Risk of Natural Steelhead Parr in an Experimental Stream Channel
Authors: Tatara Christopher P. , Riley Stephen C. , Berejikian Barry A.
Published: December 2011

Hatchery supplementation of steelhead Oncorhynchus mykiss raises concerns about the impacts on natural populations, including reduced growth and survival, displacement, and increased predation. The potential risks may be density dependent. We examined how hatchery stocking density and the opportunity to emigrate affect the responses of natural steelhead parr in an experimental stream channel and after 15 d found no density-dependent effects on growth, emigration, or survival at densities ranging from 1–6 hatchery parr/m2. The opportunity for steelhead parr to emigrate reduced predation by coastal cutthroat trout O. clarkii clarkii on both hatchery and natural steelhead parr. The cutthroat trout exhibited a type-I functional response (constant predation rate with increased prey density) for the hatchery and composite populations. In contrast, the predation rate on natural parr decreased as hatchery stocking density increased. Supplementation with hatchery parr at any experimental stocking density reduced the final natural parr density. This decline was explained by increased emigration from the supplemented groups. Natural parr had higher mean instantaneous growth rates than hatchery parr. The proportion of parr emigrating decreased as parr size increased over successive experimental trials. Smaller parr had lower survival and suffered higher predation. The final density of the composite population, a measure of supplementation effectiveness, increased with the hatchery steelhead stocking rate. Our results indicate that stocking larger hatchery parr (over 50 d postemergence) at densities within the carrying capacity would have low short-term impact on the growth, survival, and emigration of natural parr while increasing the density of the composite population; in addition, a stocking density greater than 3 fish/m2 might be a good starting point for the evaluation of parr stocking in natural streams.

Received June 28, 2010; accepted December 30, 2010
Recreational Freshwater Angler Success Is Not Significantly Different from a Random Catch Model
Authors: Seekell David A.
Published: December 2011

Most fish are caught by a small number of anglers. This striking empirical regularity has been attributed to angler skill, equipment, food-web structure, and fisheries management. I use long-term angler log data from Montana and creel survey data from the lower Current River of Missouri to test the hypothesis that inequality in fish catch is consistent with random chance. Catch data for largemouth bass Micropterus salmoides and lake trout Salvelinus namaycush recorded in angler logs for six Montana lakes were highly unequal (Gini coefficients = 0.26–0.64) but not significantly different from the theoretical expectation that chance determines success. The catch data from the lower Current River creel survey were more unequal than the Montana angler log data (Gini coefficient = 0.71) but, again, not significantly different from the theoretical expectation that chance determines success. As the amount of time spent fishing increases, the mean catch increases and the shape of the probability distribution of obtaining a certain size catch changes from being positively skewed to being symmetrical. Effective tests of skill and other factors that might promote larger catches require better measures and appropriate data with which to evaluate alternative models.

Received September 8, 2010; accepted January 3, 2011
Retention of Passive Integrated Transponder Tags in Stream-Dwelling Rainbow Trout
Authors: Meyer Kevin A. , High Brett , Gastelecutto Nick , Mamer Elizabeth R. J. , Elle F. Steven
Published: December 2011

Passive integrated transponder (PIT) tags have been widely used as a tool for various monitoring and research needs, but the retention of PIT tags has rarely been tested in resident salmonids. We quantified the short-term (≤1 week), annual (1 year), and long-term (≥1 year) retention rates of PIT tags placed in the peritoneal cavity of small resident rainbow trout Oncorhynchus mykiss in 11 study streams and assessed whether fish size and gender affected tag retention. Short-term retention rates were at least 92% and averaged 96% for all streams, but a paired t-test nevertheless indicated that experienced taggers had significantly higher short-term retention rates (mean, 98%) than did inexperienced taggers (mean, 95%). Annual retention rates for PIT tags averaged 81% among all study streams, ranging from a low of 67% to a high of 92%. Annual retention rates were lower for larger rainbow trout than for their smaller counterparts. Long-term tag loss for females was the same as for males for fish smaller than 15 cm but significantly higher for fish 15 cm or more, suggesting that egg expulsion was the primary cause of tag loss.

Received August 27, 2010; accepted January 3, 2011
Radiotelemetry to Estimate Stream Life of Adult Chum Salmon in the McNeil River, Alaska
Authors: Peirce Joshua M. , Otis Edward O. , Wipfli Mark S. , Follmann Erich H.
Published: December 2011

Estimating salmon escapement is one of the fundamental steps in managing salmon populations. The area-under-the-curve (AUC) method is commonly used to convert periodic aerial survey counts into annual salmon escapement indices. The AUC requires obtaining accurate estimates of stream life (SL) for target species. Traditional methods for estimating SL (e.g., mark–recapture) are not feasible for many populations. Our objective in this study was to determine the average SL of chum salmon Oncorhynchus keta in the McNeil River, Alaska, through radiotelemetry. During the 2005 and 2006 runs, 155 chum salmon were fitted with mortality-indicating radio tags as they entered the McNeil River and tracked until they died. A combination of remote data loggers, aerial surveys, and foot surveys were used to determine the location of fish and provide an estimate of time of death. Higher predation resulted in tagged fish below McNeil Falls having a significantly shorter SL (12.6 d) than those above (21.9 d). The streamwide average SL (13.8 d) for chum salmon at the McNeil River was lower than the regionwide value (17.5 d) previously used to generate AUC indices of chum salmon escapement for the McNeil River. We conclude that radiotelemetry is an effective tool for estimating SL in rivers not well suited to other methods.

Received July 21, 2010; accepted January 9, 2011
Simulated Population Responses of Common Carp to Commercial Exploitation
Authors: Weber Michael J. , Hennen Matthew J. , Brown Michael L.
Published: December 2011

Common carp Cyprinus carpio is a widespread invasive species that can become highly abundant and have deleterious ecosystem effects. Thus, aquatic resource managers are interested in controlling common carp populations, but control is difficult, in part, because of the inherent uncertainty as to how populations respond to exploitation. To better understand this response, we evaluated the population dynamics (recruitment, growth, and mortality) of common carp in three natural lakes in eastern South Dakota. Common carp exhibited similar population dynamics across these three systems, which were characterized by consistent recruitment (ages 3–15 being present), fast growth (K = 0.37–0.59), and low mortality (A = 1–7%). We then modeled the effects of commercial exploitation on size structure, abundance, and egg production to determine its utility as a management tool to control populations. All three populations responded similarly to exploitation simulations in which a 575-mm length restriction represented commercial gear selectivity. Simulated common carp size structure declined modestly (9–37%) in all simulations. The abundance of common carp declined dramatically (28–56% of starting levels) at low levels of exploitation (0–20%), but exploitation greater than 40% had little additive effect, the final populations only being reduced 49–79% despite high exploitation (>90%). At a moderate level of exploitation (40%), maximum lifetime egg production was reduced to 77–89% of starting levels, indicating the potential for recruitment overfishing. Exploitation further reduced common carp size structure, abundance, and egg production when simulations were not size selective. Our results provide insights into the ways in which common carp populations may respond to exploitation. Although commercial exploitation may be able to partially control populations, an integrated removal approach that removes all sizes of common carp has a greater chance of controlling population abundance and reducing the perturbations induced by this invasive species.

Received July 23, 2010; accepted January 6, 2011
Comparing Size, Movement, and Habitat Selection of Wild and Streamside-Reared Lake Sturgeon
Authors: Mann Kevin A. , Holtgren J. Marty , Auer Nancy A. , Ogren Stephanie A.
Published: December 2011

A streamside rearing facility (SRF) on the Big Manistee River, Michigan, was constructed for the purpose of rearing larval and age-0 lake sturgeon Acipenser fulvescens. Size, movement, and habitat selection were studied from 2007 to 2008 to determine whether there were differences between age-0 lake sturgeon reared in the streamside facility and natural cohorts. Lake sturgeon reared streamside showed no significant difference in length from their wild counterparts. Movement patterns were studied by attaching external radio transmitters to 17 age-0 streamside (198–250 mm total length) and 17 age-0 wild lake sturgeon (206–262 mm). The average weekly distances traveled by SRF fish ranged from 0.05–2.28 km (of 46 km surveyed) while wild fish traveled 0.04–2.81 km. In the river sections sampled, sand, pebble, and gravel comprised over 92.5% of the encountered substrates and Strauss index values indicated no differences in the presence of wild and SRF sturgeon over these substrates. Age-0 lake sturgeon were most often found in water 1.7 m deep with a velocity of 0.5 m/s, and no statistically significant differences were observed between wild and SRF sturgeon for either depth or velocity during the study years. By September, streamside-reared age-0 lake sturgeon attained a size similar to that of their wild cohorts and exhibited similar movement patterns and substrate association.

Received February 8, 2010; accepted January 27, 2011
Movements of Radio- and Acoustic-Tagged Adult Koi Carp in the Waikato River, New Zealand
Authors: Daniel Adam J. , Hicks Brendan J. , Ling Nicholas , David Bruno O.
Published: December 2011

The movement of koi, a highly colored variant of common carp Cyprinus carpio, was monitored for 18 months in the Waikato River, New Zealand, with both radiotelemetry and acoustic telemetry. Koi had large total linear ranges (mean, 39 km), and most fish (74%) monitored for more than 250 d traveled between the Waikato River and lateral habitat. Differences in total linear range and mean daily movement between years suggest a behavioral response associated with reduced habitat availability during periods of low flow. The movements of koi were highly variable and infrequent, suggesting that important long-range movements are missed in short-term studies (<250 d), resulting in underestimations of total linear range. Our data suggest that large numbers of koi could have been intercepted traveling between lateral habitat and the Waikato River during 1 of 2 years, indicating that point source removal would be highly effective.

Received June 12, 2009; accepted January 20, 2011
Testing the Severity of Ill Effects Model for Predicting Fish Abundance and Condition
Authors: Smedley Rosalyn A. , Curry R. Allen , Gray Michelle A.
Published: December 2011

We tested the severity of ill effects (SEV) model as a predictor of the potential impacts of suspended sediment in small streams in an agricultural region of New Brunswick. Proposed by Newcombe and Jensen, the SEV uses the concentration of suspended sediment and the duration of exposure to predict the impacts on fish. In 2007, eight streams with brook trout Salvelinus fontinalis and slimy sculpin Cottus cognatus were used to test the SEV model. Total suspended solids measured from May to August were used to calculate the SEV index using two different methods. Our analyses indicated poor correlations between the SEV index and measures of fish densities and condition factor. A survey of an additional eight streams in the region over 2 years indicated that local habitat and landscape features and temperature were better predictors of fish density and species occurrence. These results demonstrate the complexity of interpreting stressor impacts and the challenges inherent in developing indices of stress for fish in natural streams.

Received January 20, 2010; accepted January 28, 2011
Characterization of Plasma Vitellogenin and Sex Hormone Concentrations during the Annual Reproductive Cycle of the Endangered Razorback Sucker
Authors: Hinck Jo Ellen , Papoulias Diana M. , Annis Mandy L. , Tillitt Donald E. , Marr Carrie , Denslow Nancy D. , Kroll Kevin J. , Nachtmann Jason
Published: December 2011

Population declines of the endangered razorback sucker Xyrauchen texanus in the Colorado River basin have been attributed to predation by and competition with nonnative fishes, habitat alteration, and dam construction. The reproductive health and seasonal variation of the reproductive end points of razorback sucker populations are currently unknown. Using nonlethal methods, we characterized the plasma hormonal fluctuations of reproductively mature female and male razorback suckers over a 12-month period in a hatchery by measuring their vitellogenin (VTG) and three sex hormones: 17β-estradiol (E2), testosterone (T), and 11-ketotestosterone (KT). Fish were identified as reproductive or nonreproductive based on their body weight, VTG, and sex hormone profiles. In reproductive females, the E2 concentration increased in the fall and winter, and increases in T and VTG concentrations were generally associated with the spawning period. Mean T concentrations were consistently greater in reproductive females than in nonreproductive females, but this pattern was even more pronounced during the spawning period (spring). Consistently low T concentrations (<3 ng/mL) in adult females during the spawning period may indicate reproductive impairment. In reproductive males, spring increases in KT and T concentrations were associated with spawning; concentrations of E2 (<0.48 ng/mL) and VTG (<0.001 mg/mL) were low in males throughout the study. In addition, the E2 : KT ratio and T were the best metrics by which to distinguish female from male adult razorback suckers throughout the year. These metrics of reproductive health and condition may be particularly important to recovery efforts of razorback suckers given that the few remaining wild populations are located in a river where water quality and quantity issues are well documented. In addition to the size, age, and recruitment information currently considered in the recovery goals of this endangered species, reproductive end points could be included as recovery metrics with which to monitor seasonal trends and determine whether repatriated populations are cycling naturally.

Received September 24, 2010; accepted February 18, 2011
Natural Mortality in Relation to Age and Fishing Mortality on Walleyes in Escanaba Lake, Wisconsin, during 1956–2009
Authors: Hansen Michael J. , Fayram Andrew H. , Newman Steven P.
Published: December 2011

To evaluate the dynamics of fishing and natural mortality, we used a catch–age cohort analysis model of the population dynamics of walleye Sander vitreus in Escanaba Lake, Wisconsin, during 1956–2009. The catch–age model was based on angling catches at age from a compulsory creel census, abundance at age from mark–recapture studies, and recruitment at age 0 from mark–recapture studies. Harvest of age-3 and older (age-3+) walleyes averaged 12.5 fish/ha and varied 55% among years during 1956–2002, before the imposition of a 71-cm (28-in) minimum length limit that eliminated harvest. The population density of age-3+ walleyes averaged 34.8 fish/ha and varied 51% among years during 1956–2009. Annual exploitation of age-3+ walleyes averaged 34% during 1956–2002 and varied 35% among years during that period. The variation in population density explained only 0.5% of the variation in annual exploitation during 1956–2002. Natural mortality was best described by a model with decreasing age-specific vulnerability and a negative relationship with angling exploitation. Relative vulnerability to natural mortality declined gradually with age from 100% at age 0 to 83% at age 3, 50% at age 9.4, and 24% at age 17. Relative vulnerability to fishing mortality increased sharply from less than 1% at age 0 to 98% at age 3, peaked at 100% at age 4, and declined gradually to 66% at age 17. Fully vulnerable natural mortality (M) declined from 0.70 to 0.10 (mean = 0.41) as annual angling exploitation (u) on age-3+ walleyes increased from 0.0 to 0.65 (mean = 0.30). Our findings suggest that natural mortality declines with age and is inversely related to fishing mortality, so that it varies among ages and years. We conclude that stock assessment models for walleye fisheries should evaluate the effects of year-specific and age-specific natural mortality on model predictions.

Received September 4, 2010; accepted February 24, 2011
Efficiency of Gastric Lavage on Age-0 Brook Trout and the Influence on Growth and Survival
Authors: Hafs Andrew W. , Niles Jonathan M. , Hartman Kyle J.
Published: December 2011

Accurate knowledge of food webs is important in understanding aquatic ecology. One common way to determine the food web structure of an aquatic ecosystem is to perform stomach content analysis. Gastric lavage has developed into the preferred method for collecting dietary data from live fish. The objective of this study was to determine the efficiency of gastric lavage for age-0 brook trout Salvelinus fontinalis. Also, to assess the effects on short- and long-term growth and survival, age-0 brook trout were monitored for 2 months following the gastric lavage procedure. Gastric lavage was extremely efficient (>97% of dry weight; >98% by number) at removing Ephemeroptera, Plecoptera, and Trichoptera larvae fed live to age-0 brook trout larger than 50 mm total length (TL). Neither growth nor survival was significantly influenced by gastric lavage. Long-term survival was excellent (94%) and did not differ from that of control fish. Gastric lavage is thus an efficient, safe method for stomach content analysis of age-0 brook trout larger than 50 mm TL.

Received September 29, 2010; accepted March 16, 2011
Survival of Angled Saugers in the Lower Tennessee River
Authors: Kitterman Christy L. , Bettoli Phillip W.
Published: December 2011

An intense winter fishery for sauger Sander canadensis exists in the lower Tennessee River, and the objective of this study was to estimate the survival of angled saugers. In February 2008 and January–March 2009, 81 angled saugers (72 live plus 9 euthanized) were affixed with ultrasonic tags. The movements (or lack thereof) by saugers released alive were compared with those of euthanized fish to assess survival. Sixty-eight percent of the tagged saugers that were released alive exhibited maximum daily movements exceeding the greatest movement of any euthanized fish (0.5 km/d), and those fish were subsequently classified as survivors. The upstream movements of several euthanized fish indicated that their carcasses were ingested by piscivorous scavengers. In logistic models, the probability of mortality was significantly and inversely related to total length but not to capture depth, water temperature, handling time, or ascent rate. In 2 × 2 contingency tables, the fate of released saugers was not found to be associated with either the presence or absence of bleeding from the hooking wound or whether or not the fish displayed gastric distension. Most released fish survived despite the fact that gastric distension was observed in 72% of the angled saugers.

Received August 11, 2010; accepted April 21, 2011
Information Flow within the Social Network Structure of a Joint Strategic Plan for Management of Great Lakes Fisheries
Authors: Leonard Nancy J. , Taylor William W. , Goddard Chris I. , Frank Kenneth A. , Krause Ann E. , Schechter Michael G.
Published: December 2011

Transboundary fish stocks are governed by multiple entities, involving individuals with different expertise and sociocultural backgrounds and representing various institutions and jurisdictions. At times, individuals from these entities collaboratively make fishery governance decisions, and the existence of collegial or personal relationships may facilitate the decision-making process and result in better management of fish stocks. Although studies have assessed several aspects of fisheries institutional structures, very few have looked at the impact of social network structure. In this study, we found evidence for the perceived effectiveness of A Joint Strategic Plan for Management of Great Lakes Fisheries in its social network structure. We focused on the frequency of interactions for exchanging information about Great Lakes fish stocks in general and lake sturgeon Acipenser fulvescens in particular. These informational exchanges correspond to distinct social network structures, the fish stocks network and the lake sturgeon network. Similarities in participants’ attributes and perceptions about fisheries governance may have facilitated the formation of social ties within these networks. The lake sturgeon network had significant subgroups wherein flow was more concentrated. The formation of these subgroups appears to have been influenced by individuals’ employer type, committee affiliation, and perception about lake sturgeon governance. These subgroups were found to have 11 central individuals and two central subgroups. When comparing the central and noncentral individuals’ attributes and perceptions, we did not find a significant difference that explains why the 11 individuals were central. Similarly, no significant differences were found in comparing the central and noncentral subgroups. In assessing the flow of information within and across these subgroups, we found that it was evenly distributed with some specialization of flow between subgroups, the latter probably related to the presence of bridging individuals connecting the subgroups.

Received March 24, 2010; accepted March 23, 2011
Preliminary Evaluation of a Large-Scale American Eel Conservation Stocking Experiment
Authors: Pratt Thomas C. , Threader Ron W.
Published: December 2011

Significant declines in the recruitment of American eels Anguilla rostrata to formerly productive habitats in the upper St. Lawrence River and Lake Ontario resulted in the implementation of an experimental conservation stocking program. Nearly 3.8 million American eels (glass eel and elver stages) were stocked during 2006–2009. Our study objectives were to (1) assess the adequacy of sampling procedures for following temporal changes in stocked eel abundance, (2) examine captured eels for evidence of spinal trauma, (3) qualitatively evaluate whether stocked eels would disperse outside of stocking locations, and (4) provide initial data on biological variables describing young stocked yellow eels. Boat electrofishing was successful at capturing all four stocked year-classes, and the densities of stocked eels in the main stocking locations ranged from 25 to 275 eels/ha. Estimated sampling precision ranged from 0.15 to 0.28, and the estimated sample sizes required to detect a 50% change in stocked eel densities ranged from 27 to 112 electrofishing transects depending on location and season. The stocked American eels dispersed throughout Lake Ontario and demonstrated among the fastest recorded growth rates for this species: 60 to 123 mm/year. The first male American eels ever identified in the St. Lawrence River watershed were among the stocked individuals assessed for gender. We conclude that boat electrofishing for yellow American eels has the potential to measure stocking effectiveness along shallow shorelines with limited aquatic vegetation. We also recognize that the ultimate assessment of the conservation stocking experiment will not be made until future studies on the population demographics, migratory behavior, and spawning physiology of stocked American eels are complete.

Received December 10, 2010; accepted May 11, 2011
Selectivity Evaluation for Two Experimental Gill-Net Configurations Used to Sample Lake Erie Walleyes
Authors: Vandergoot Christopher S. , Kocovsky Patrick M. , Brenden Travis O. , Liu Weihai
Published: December 2011

We used length frequencies of captured walleyes Sander vitreus to indirectly estimate and compare selectivity between two experimental gill-net configurations used to sample fish in Lake Erie: (1) a multifilament configuration currently used by the Ohio Department of Natural Resources (ODNR) with stretched-measure mesh sizes ranging from 51 to 127 mm and a constant filament diameter (0.37 mm); and (2) a monofilament configuration with mesh sizes ranging from 38 to 178 mm and varying filament diameter (range = 0.20–0.33 mm). Paired sampling with the two configurations revealed that the catch of walleyes smaller than 250 mm and larger than 600 mm was greater in the monofilament configuration than in the multifilament configuration, but the catch of 250–600-mm fish was greater in the multifilament configuration. Binormal selectivity functions yielded the best fit to observed walleye catches for both gill-net configurations based on model deviances. Incorporation of deviation terms in the binormal selectivity functions (i.e., to relax the assumption of geometric similarity) further improved the fit to observed catches. The final fitted selectivity functions produced results similar to those from the length-based catch comparisons: the monofilament configuration had greater selectivity for small and large walleyes and the multifilament configuration had greater selectivity for mid-sized walleyes. Computer simulations that incorporated the fitted binormal selectivity functions indicated that both nets were likely to result in some bias in age composition estimates and that the degree of bias would ultimately be determined by the underlying condition, mortality rate, and growth rate of the Lake Erie walleye population. Before the ODNR switches its survey gear, additional comparisons of the different gill-net configurations, such as fishing the net pairs across a greater range of depths and at more locations in the lake, should be conducted to maintain congruence in the fishery-independent survey time series.

Received January 5, 2011; accepted May 13, 2011
Relationship between Electrofishing Catch Rate and Adult Trout Abundance in Wisconsin Streams
Authors: Bergman Paul S. , Hansen Michael J. , Nate Nancy A.
Published: December 2011

The relative quickness and cost effectiveness of single-pass electrofishing samples (catch per effort [CPE]) argues for their use over multiple-pass estimates for enumerating stream fish populations. However, CPE can be an imprecise index of fish abundance and therefore may be less useful than more-precise indices of abundance, such as those obtained from mark–recapture or depletion methods, for assessing trout populations. We evaluated the use of single-pass electrofishing samples (catch/mi) as abundance (number/mi) predictors of adult brook trout Salvelinus fontinalis and brown trout Salmo trutta in Wisconsin streams by quantifying the relationship between electrofishing CPE and adult trout abundance. First, we tested for linearity of the relationship between CPE and adult trout abundance while accounting for measurement error. Next, we explained the residual variability in the relationship using physical and biological attributes of surveyed streams. We found that the relationship between CPE and adult trout abundance was proportional (linear) for both brook trout and brown trout. Electrofishing catchability did not differ significantly between trout species or among seasons or ecoregions. However, catchability was significantly greater for towed-barge electrofishing (0.64; 95% confidence interval, 0.55–0.73) than backpack electrofishing (0.23; 0.09–0.59). Adult trout abundance alone explained 82% of the variation in CPE for backpack units and 87% of the variation in CPE for towed-barge units. Stream habitat features such as stream slope, mean stream width, and pool density failed to explain additional variation in catchability. Our results indicate that CPE can provide a reliable index of adult trout abundance in Wisconsin streams, but mark–recapture methods may still be needed to obtain a more precise estimate of abundance. However, because time and effort can be reduced 50% if single-pass CPEs are used instead of mark–recapture abundance estimates to predict adult trout abundance, managers may choose to sacrifice higher precision for reduced sampling effort.

Received December 20, 2010; accepted June 17, 2011
Education in the Era of the Millennials and Implications for Future Fisheries Professionals and Conservation
Authors: Millenbah Kelly F , Wolter Bjørn H K , Taylor William W
Published: December 2011

Fisheries and other natural resource professionals face growing challenges in their fields and the resources that they manage. Many are well aware of the pending impacts of retirement of the Baby Boomers and the loss of collective knowledge held by those individuals. We are also acutely aware of the damaging impacts of reduced budget allocations for natural resources–based programs. Concomitant to the decrease in funding is the ever-increasing complexity of the fisheries discipline that brings with it new and more complicated ecological and governance challenges. These, and the evolving preferences, morals, and values of today's college students, pose a unique and difficult dynamic for engaging the next generation in the stewardship of fish and wildlife resources. Critical to the success of future conservation efforts will be the modification of educational and workplace systems, including the American Fisheries Society, to prepare and support future professionals so that they may handle this suite of complex, interdisciplinary issues. Understanding the characteristics of the next generation of natural resource leaders, and the individuals with whom they will interact in pursuit of conservation, is key to ensuring that they can meet the challenges of a new era in resources management. The purpose of this article is to describe the next generation of fisheries professionals (the Millennials) and to provide suggestions for how higher education and the fisheries profession can best prepare to support the success of this generation and ultimately the future of fisheries conservation and management.
Contrasting Global Game Fish and Non-Game Fish Species
Authors: Donaldson Michael R , O'Connor Connie M , Thompson Lisa A , Gingerich Andrew J , Danylchuk Sascha E , Duplain René R , Cooke Steven J
Published: December 2011

We compared biological and ecological traits between global game fish and non-game fish species using an analysis with randomly chosen fish species from each group and an analysis where species were matched by body length. We used data from the International Game Fish Association (IGFA), FishBase, and the International Union for Conservation of Nature (IUCN) Red List of Threatened Species. Game fish species were defined as being present in the IGFA world record list. The random comparison revealed that on average game fish were significantly larger (155.0 ± 121.5 versus 34.1± 59.5 cm), occupied shallower minimum depths (19.4 ± 58.8 versus 130.0± 359.0 m), had a broader latitudinal range (51°.2 ± 29.4° versus 31.1°± 25.9°), and significantly higher trophic levels (4.1 ±0.1 versus 3.4± 0.1 trophic units) than non-game fish species. The length-matched analysis simüarly identified that game fish species occupied higher trophic levels than non-game fish (3.9 ± 0.4 versus 3.6± 0.6 trophic units), but latitudinal range and depth associations did not differ between groups. Both the random and length-matched analyses revealed that game fish were more commonly found in freshwater than non-game fish. Both analyses found that game fish species were more migratory and that both groups differed in their geographical distributions. The random comparison revealed that game fish were significantly more targeted by commercial fisheries, less resilient, and more threatened relative to non-game fish. Caution must be exercised when synthesizing data from broad data sources, yet this study identifies important differences between game fish and non-game fish species, which are relevant to management and conservation initiatives.
Mortality and Carrier Status of Bluegills Exposed to Viral Hemorrhagic Septicemia Virus Genotype IVb at Different Temperatures
Authors: Goodwin Andrew E. , Merry Gwenn E.
Published: December 2011

The emergence of the viral hemorrhagic septicemia virus (VHSV) genotype IVb (VHSV-IVb) in the Great Lakes of North America has led to concern that the virus might spread to natural fisheries and aquaculture in the southern USA. We exposed bluegills Lepomis macrochirus to VHSV-IVb by intraperitoneal injection at six temperatures from 10°C to 30°C and followed the disease course by quantitative real-time reverse transcriptase polymerase chain reaction (qrt-RT-PCR). Mortality of injected fish was 90% at 10°C, 35% at 14°C, and 10% at 18°C; no mortality attributable to VHSV was observed at temperatures of 22–30°C. In survivors tested at 21 d postchallenge, viral copies and prevalence determined by qrt-RT-PCR were inversely related to temperature, and VHSV-IVb could not be detected in fish held at temperatures above 22°C. Similar results were obtained for bluegills that were exposed by cohabitation with the intraperitoneally injected fish. Acclimation of the fish to 12°C after 21 d at higher temperatures did not appear to cause a re-emergence of the virus. Based on our findings, the temperature range of VHSV-IVb appears to be the same as published values for VHSV genotype I, which has an optimum of 9–12°C and an upper limit of 18–20°C.

Received September 29, 2010; accepted February 10, 2011
The Effect of High Total Ammonia Concentration on the Survival of Channel Catfish Experimentally Infected with Flavobacterium columnare
Authors: Farmer Bradley D. , Mitchell Andrew J. , Straus David L.
Published: December 2011

Ammonia concentrations in water can affect the severity of Flavobacterium columnare infections in fish. Two trials lasting 7 d each were conducted to determine the effect of a single immersion flush treatment of total ammonia nitrogen (TAN; 15 mg/L) on the survival of channel catfish Ictalurus punctatus infected with F. columnare; the chemical was added while the water flowed continuously through the tanks. Both trials consisted of four treatments: (1) no ammonia exposure and no bacterial challenge (control), (2) ammonia exposure only, (3) bacterial challenge only, and (4) both ammonia exposure and bacterial challenge. Two hours after exposure to ammonia, the highest un-ionized ammonia level was 0.43 mg/L. The percent un-ionized ammonia is based on TAN, temperature, and pH. Caudal fins from three fish in each treatment were sampled at 24 h posttreatment to be analyzed by quantitative real-time polymerase chain reaction (qPCR). No significant difference in survival (mean ± SE) was noted between the channel catfish in treatment 1 (95.2 ± 1.2%) and those in treatment 2 (95.6 ± 1.0%); however, survival in both treatments 1 and 2 differed significantly from that in treatments 3 (8.5 ± 4.5%) and 4 (41.8 ± 12.7%). Treatment 4 catfish had significantly higher survival than treatment 3 catfish. Quantitative PCR data showed that treatment 4 fish had significantly less F. columnare (7.6 × 105) than did treatment 3 fish (1.2 × 107), and treatment 2 fish (8.5 × 103) had significantly less bacteria than did treatment 1 fish (6.9 × 104), indicating that ammonia limited the F. columnare infection. The highest mean concentration of the bacteria (3.9 × 107) was found on moribund fish. The ammonia concentrations tested did not negatively influence fish survival but interfered with the infection process. An in vitro assay was also conducted to evaluate the direct effects of ammonia on F. columnare.

Received September 15, 2010; accepted May 7, 2011