bluuebunny/crossref_metadata_2025_split huggingface dataset:
Estimating the Size of Steelhead Runs by Tagging Juveniles and Monitoring Migrants
Authors: Boughton David A. 
Published: February 2011

Abstract
The number of individuals in a spawning run of anadromous fish can be estimated by tagging juveniles with passive integrated transponders during the freshwater phase and the subsequent monitoring of adult upstream migrants by use of instream tag readers. The method may enable monitoring of steelhead Oncorhynchus mykiss in systems where other methods are intractable. I developed a hierarchical capture–resighting model and applied it to simulated data to develop a relation between the number of marked juveniles and the precision of run size estimates. Precision is primarily controlled by the number of tagged spawners that ultimately return and are detected; only 30–90 tagged spawners are required to obtain relatively precise estimates of run size. For typical marine survival rates, 0.0033–0.0330, this translates to a tagging effort of between 3,400 and 45,000 juveniles/cohort. Estimates are robust to imperfect detection of tagged fish if at least two instream readers independently scan for tags. Reach sampling allows for estimation of run size in large stream systems. Based on my simulations, the number of reaches could be as low as 30–40 under scenarios of high marine survival. Computer code is provided for the estimator using the freely available statistical software R.
δ13C and δ15N Signatures in Muscle and Fin Tissues: Nonlethal Sampling Methods for Stable Isotope Analysis of Salmonids
Authors: Hanisch Justin R. , Tonn William M. , Paszkowski Cynthia A. , Scrimgeour Garry J. 
Published: February 2011

Abstract
Stable isotope analysis has emerged as an important tool in aquatic ecology. For fish, dorsal muscle from sacrificed individuals has traditionally been used in stable isotope studies; however, there are many instances when lethal sampling is undesirable. We evaluated the feasibility of using adipose and caudal fin clips as alternatives to muscle in stable isotope studies for five species of salmonids. Because fish size and water temperature can affect stable isotope ratios, we also determined whether fish length and sampling date affected the difference in isotope signatures between fins and muscle. Biopsied muscle plugs and fin clips were collected from rainbow trout Oncorhynchus mykiss, brook trout Salvelinus fontinalis, and lake trout S. namaycush as well as lake whitefish Coregonus clupeaformis and pygmy whitefish Prosopium coulterii and analyzed for stable isotopes of carbon and nitrogen. The isotope signatures of both adipose and caudal fins were significantly correlated (0.33 &lt; R2 &lt; 0.97) with those of dorsal muscle from the five salmonid species studied, and in some cases the signatures of fins did not differ from those of muscle. Fish length and sampling date occasionally had a small effect (0.042 &lt; R2 &lt; 0.49) on the relationship between the isotope signatures of fin and muscle. Although muscle biopsy provides a viable, nonlethal method of collecting muscle tissue from suitably sized fish, the strong relationships between the isotope signatures of fin and muscle demonstrate that fin clips should be considered good surrogates for muscle in stable isotope studies of salmonids.
Long-Term Evaluations of Length Limit Regulations for Northern Pike in Minnesota
Authors: Pierce Rodney B. 
Published: February 2011

Abstract
The effects of maximum, minimum, and slot length limits on the sizes and relative abundance of northern pike Esox lucius were evaluated in 22 Minnesota lakes. The regulations were implemented in 1989–1998 and lasted 9–15 years. As preregulation information was available back to the 1970s, the evaluation periods covered 21–37 years. Comparisons were made with reference populations from 47 ecologically similar lakes during the same extended period. Although the regulations did not achieve management objectives in every lake, the broader-scale, statewide finding was that they improved the size structure of northern pike populations but produced no consistent trends in relative abundance. The improvements were detected against the backdrop of reference populations that initially appeared to have similar sizes and relative abundances. Maximum length limits protecting fish over 20, 22, and 24 in produced significant long-term increases in the percentages of northern pike 24 in and longer and 30 in and longer compared with the reference populations. Lakes with 30-in minimum length limits had increased percentages of northern pike 20 in and longer, but the improvements did not carry over to fish 30 in and longer. A mix of slot length limits produced results that are more difficult to interpret but generally improved size structure. A metaanalysis incorporating all of the length regulations indicated that the changes in northern pike size structure in regulated lakes were very large for an ecological experiment. Length limits protected large northern pike, with the expectation that lower yields were an acceptable trade-off for producing larger fish for recreational fisheries. This study reveals the range and magnitude of responses we can reasonably expect from length limits as well as the substantial value of conserving large fish when the goal is improved population size structure.
Interactions between Walleyes and Smallmouth Bass in a Missouri River Reservoir with Consideration of the Influence of Temperature and Prey
Authors: Wuellner Melissa R. , Chipps Steven R. , Willis David W. , Adams Wells E. 
Published: February 2011

Abstract
Walleyes Sander vitreus are the most popular fish among South Dakota anglers, but smallmouth bass Micropterus dolomieu were introduced to provide new angling opportunities. Some walleye anglers have reported reductions in the quality of walleye fisheries since the introduction of smallmouth bass and attribute this to the consumption of young walleyes by smallmouth bass and competition for shared prey resources. We quantified the diets of walleyes and smallmouth bass in the lower reaches of Lake Sharpe (a Missouri River reservoir), calculated the diet overlap between the two predators, and determined whether they partitioned shared prey based on size. We also quantified walleye diets in the upper reach of the reservoir, which has a different prey base and allowed us to compare the growth rates of walleyes within Lake Sharpe. Age-0 gizzard shad Dorosoma cepedianum composed a substantial proportion of the diets of both predators, regardless of location, for most of the growing season; the patterns in shad vulnerability appeared to drive the observed patterns in diet overlap. Smallmouth bass appeared to consume a smaller size range of gizzard shad than did walleyes, which consumed a wide range. Smallmouth bass consumed Sander spp. in some months, but in very low quantities. Given that global climate change is expected to alter the population and community dynamics in Great Plains reservoirs, we also used a bioenergetics approach to predict the potential effects of limiting prey availability (specifically, the absence of gizzard shad and rainbow smelt Osmerus mordax) and increased water temperatures (as projected from global climate change models) on walleye and smallmouth bass growth. The models indicated that the absence of rainbow smelt from the diets of walleyes in upper Lake Sharpe would reduce growth but that the absence of gizzard shad would have a more marked negative effect on both predators at both locations. The models also indicated that higher water temperatures would have an even greater negative influence on walleye growth; however, smallmouth bass growth was predicted to increase with higher temperatures. Fisheries managers should consider strategies to enhance the prey base or mitigate the effects of increased water temperatures that may occur in the future as a result of global climate change. Such proactive actions may alleviate potential future competition between walleyes and smallmouth bass resulting from changes in the fish community.
Estimating the Spawning Escapement of Hatchery- and Natural-Origin Spring Chinook Salmon Using Redd and Carcass Data
Authors: Murdoch Andrew R. , Pearsons Todd N. , Maitland Travis W. 
Published: February 2011

Abstract
Redd abundance and the demographic characteristics of salmon carcasses are frequently used (in combination) to estimate the abundance and characteristics of populations of Pacific salmon Oncorhynchus spp. However, there is uncertainty about the quality of these estimates because they rely on untested assumptions. We evaluated the quality of spawning ground estimates of Wenatchee spring Chinook salmon O. tshawytscha by comparing the number and origin of fish migrating upstream of Tumwater Dam with estimates of (1) redd abundance and (2) spawner abundance partitioned by sex and origin. Redd counts were well correlated with the abundance of fish passing Tumwater Dam (r2 = 0.84) between 1999 and 2007, indicating that such counts are a suitable index of population abundance. However, between 2004 and 2007, when carcass data were used to partition escapement estimates, the abundance of hatchery spring Chinook salmon was underestimated (mean = 6%, range 0–19%) and that of naturally produced fish was overestimated (mean = 19%, range = 1–43%). In addition, male spring Chinook salmon were underestimated by 20% (range = 18–22%) and females were overestimated by 32% (range = 15–65%). These biases were related to size-related carcass recovery bias and differences in the sex ratio between fish of different origins. The length of male spring Chinook salmon was significant in explaining the variation in the probability of carcass recovery but that of females was not. The sex ratios of carcasses adjusted for recovery bias were not significantly different from that for the population measured at Tumwater Dam. Spawning escapement estimates based on uncorrected carcass data underestimated those based on corrected carcass data 13–39%. We conclude that data collected during spawning ground surveys can be used to estimate the abundance and composition by origin of the spawning population if the biases in carcass recovery data are corrected.
Rotenone Toxicity to Rainbow Trout and Several Mountain Stream Insects
Authors: Finlayson Brian , Somer William L. , Vinson Mark R. 
Published: February 2011

Abstract
The piscicide rotenone has been used for over 70 years to eradicate unwanted fish, but controversy exists regarding its impacts on nontarget organisms, particularly aquatic invertebrates. We evaluated the toxicity of synergized Nusyn-Noxfish and nonsynergized CFT Legumine rotenone formulations in 4- and 8-h exposures to rainbow trout Oncorhynchus mykiss and six species of mountain stream caddisflies, mayflies, and stoneflies. We then compared these results with historical treatment data and aquatic invertebrate collections surrounding rotenone treatments in the 1990s that were designed to restore Paiute cutthroat trout O. clarkii seleniris to the Silver King Creek basin in Alpine County, California. The toxicity of rotenone was greatest to the trout; the synergist piperonyl butoxide appeared to have no effect on the toxicity of rotenone to the trout but did increase the toxicity to the invertebrates. The mean 8-h concentrations (as rotenone) lethal to 50% of the rainbow trout were 5.3 μg/L for CFT Legumine and 6.2 μg/L for Nusyn-Noxfish; the mean values for invertebrates ranged from 34 to 174 μg/L for CFT Legumine and from 13 to 74 μg/L for Nusyn-Noxfish. These findings corresponded to that observed in Silver King Creek, where three annual treatments of 16–23 μg/L for 6–18 h were successful in extirpating rainbow trout hybrids but caused little change in aquatic insect assemblages. To lessen the impacts of rotenone treatment in mountain streams, project planners should (1) use the lowest rotenone concentration and duration needed to accomplish the treatment objective (we suggest 25–50 μg/L for &lt;8 h) and (2) avoid using formulations containing the synergist piperonyl butoxide.
Size Selectivity in Marine Mammal Diets as a Guide to Evolutionarily Enlightened Fisheries Management
Authors: Etnier Michael A. , Fowler Charles W. 
Published: February 2011

Abstract
Commercial fisheries have a long history of nonsustainable harvests—not through deliberate mismanagement but through an inability to simultaneously account for the complexity of relevant factors, including the ecological and coevolutionary interactions within ecosystems. We argue that these factors (e.g., natural selection and coevolution) are among the structuring processes behind the patterns of predation exhibited by species such as marine mammals. As such, these patterns provide an indication of harvest practices that are sustainable in the long term—that is, normal for the systems and circumstances involved. Thus, patterns in selectivity exhibited by predators in their consumption of prey species meet the needs for evolutionarily enlightened guidance in management, long seen as missing in current practice. Our analysis of data characterizing the diets of 63 species of marine mammals indicates that the majority of prey consumed are 30 cm or less in length. This pattern is common to all marine mammal taxa and is apparently independent of the body size of predator species and largely independent of the body size range of prey species, many of which exceed 100 cm in maximum length. The size selectivity of commercial fisheries differs from that of marine mammals for all but the smallest prey species and is positively correlated with size. When possible, commercial fisheries tend to target individuals greater than 30 cm. The selective pressure this exerts on large-bodied prey species is abnormal in comparison with that of the natural predator–prey systems that have evolved to sustain consumption of individual prey items of 30 cm or less. To minimize the abnormal effects of selective pressure imposed by fishing, we argue that the targeted size composition of catches should be modified to more closely match the patterns exhibited by marine mammals as another example of the application of systemic management, a holistic alternative to conventional management.
Mass-Marking Reveals Emerging Self Regulation of the Chinook Salmon Population in Lake Huron
Authors: Johnson James E. , DeWitt Steven P. , Gonder David J. A. 
Published: February 2011

Abstract
All Chinook salmon Oncorhynchus tshawytscha stocked in Lake Huron during 2000–2003 were marked with oxytetracycline (OTC), fin clips, or a combination thereof to determine the relative contributions of natural reproduction and stocking to recruitment. Oxytetracycline administered in feed proved to be an effective, low-cost method of marking spring fingerling Chinook salmon. Vertebrae proved to be suitable tissue for OTC detection, meeting standards for accuracy and reproducibility. Vertebrae were not suitable as aging structures, perhaps due to the slow somatic growth of Lake Huron's Chinook salmon during this study. Based on lakewide recoveries from recreational and commercial fisheries, we estimated that nearly 80% of Chinook salmon from the marked year-classes were from natural reproduction. Wild-origin Chinook salmon constituted 96% of open-water samples from Georgian Bay; 82, 80, and 68% of those from the central, southern, and northern portions of the main basin; and 64% of those from the North Channel. The percentage of wild-origin Chinook salmon in some tributaries in the Ontario watershed of Lake Huron approached 100%. There was less variation in wild recruitment between years than between lake areas. This Chinook salmon population was introduced in the late 1960s and until recently had been widely viewed as hatchery dependent; our findings suggest otherwise. A self-sustaining predator population would represent a paradigm shift from an era when predation rates could be manipulated by adjusting salmonid stocking (i.e., 1968 to about 1995). These findings should help managers to critically review the effects of stocked Chinook salmon on Lake Huron's fisheries and ecosystem, including prey consumption demand, and to assess future needs for propagated Chinook salmon in Lake Huron.
Evaluation of Methods for Identifying Spawning Sites and Habitat Selection for Alosines
Authors: Harris Julianne E. , Hightower Joseph E. 
Published: February 2011

Abstract
Characterization of riverine spawning habitat is important for the management and restoration of anadromous alosines. We examined the relative effectiveness of oblique plankton tows and spawning pads for collecting the eggs of American shad Alosa sapidissima, hickory shad A. mediocris, and “river herring” (a collective term for alewife A. pseudoharengus and blueback herring A. aestivalis) in the Roanoke River, North Carolina. Relatively nonadhesive American shad eggs were only collected by plankton tows, whereas semiadhesive hickory shad and river herring eggs were collected by both methods. Compared with spawning pads, oblique plankton tows had higher probabilities of collecting eggs and led to the identification of longer spawning periods. In assumed spawning areas, twice-weekly plankton sampling for 15 min throughout the spawning season had a 95% or greater probability of collecting at least one egg for all alosines; however, the probabilities were lower in areas with more limited spawning. Comparisons of plankton tows, spawning pads, and two other methods of identifying spawning habitat (direct observation of spawning and examination of female histology) suggested differences in effectiveness and efficiency. Riverwide information on spawning sites and timing for all alosines is most efficiently obtained by plankton sampling. Spawning pads and direct observations of spawning are the best ways to determine microhabitat selectivity for appropriate species, especially when spawning sites have previously been identified. Histological examination can help determine primary spawning sites but is most useful when information on reproductive biology and spawning periodicity is also desired. The target species, riverine habitat conditions, and research goals should be considered when selecting methods with which to evaluate alosine spawning habitat.
Testing Adult Pacific Lamprey Performance at Structural Challenges in Fishways
Authors: Keefer Matthew L. , Daigle William R. , Peery Christopher A. , Pennington Howard T. , Lee Steven R. , Moser Mary L. 
Published: February 2011

Abstract
Adult Pacific lampreys Lampetra tridentata migrate through areas of difficult passage and high water velocity by attaching their oral discs to substrate and then releasing and bursting upstream. In fishways at dams, this burst-and-attach behavior can be ineffective, particularly where suitable attachment surfaces are unavailable. We used an experimental fishway to test performance of adult Pacific lampreys when confronted with a series of structural challenges. These included vertical steps near fishway weir orifices, squared versus rounded orifice entrances, and floor-mounted metal grates. All experimental challenges simulated common existing structures in weir-and-orifice fishways at Columbia and Snake River dams. Most experiments were paired with field evaluations of radio-tagged Pacific lampreys or video observations of untagged individuals in situ. Field and experimental results consistently indicated that the structural challenges reduced passage efficiency and lengthened passage times. Improving Pacific lamprey passage may be facilitated by removing or modifying vertical steps and other sharp-edged corners and by providing adequate attachment surfaces. Such accommodations should be especially beneficial in areas with high water velocity. The findings demonstrate how fish morphology and behavior should be explicitly considered in the design or retrofitting of fish passage structures.
Validation of Nonlethal Sex Determination for Black Crappies during Spring
Authors: Isermann Daniel A. 
Published: February 2011

Abstract
I evaluated the accuracy of using differences in body coloration, gamete stripping, and abdominal distension in females as a nonlethal method for determining the sex of black crappies Pomoxis nigromaculatus collected from two Minnesota lakes during spring (late April–early June). Sex assignments based on these three attributes were 93% accurate for all black crappies (211 of 227) and 98% accurate (174 of 177) for black crappies of 200 mm or more total length. The difference in body coloration between sexes was the most useful trait for identifying sex, but the distended abdomen of females and gamete stripping aided in identifying sex in some instances. Nonlethal sex assignment was less reliable for black crappies less than 200 mm (74% accurate; 37 of 50), largely because of the lack of dark coloration in males. The sex of black crappies of 200 mm or more can be identified accurately without killing the fish, but that of smaller crappies should be determined by means of visual inspection of the gonads.
Estimation and Modeling of Electrofishing Capture Efficiency for Fishes in Wadeable Warmwater Streams
Authors: Price Alison L. , Peterson James T. 
Published: February 2011

Abstract
Stream fish managers often use fish sample data to inform management decisions affecting fish populations. Fish sample data, however, can be biased by the same factors affecting fish populations. To minimize the effect of sample biases on decision making, biologists need information on the effectiveness of fish sampling methods. We evaluated single-pass backpack electrofishing and seining combined with electrofishing by following a dual-gear, mark–recapture approach in 61 blocknetted sample units within first- to third-order streams. We also estimated fish movement out of unblocked units during sampling. Capture efficiency and fish abundances were modeled for 50 fish species by use of conditional multinomial capture–recapture models. The best-approximating models indicated that capture efficiencies were generally low and differed among species groups based on family or genus. Efficiencies of single-pass electrofishing and seining combined with electrofishing were greatest for Catostomidae and lowest for Ictaluridae. Fish body length and stream habitat characteristics (mean cross-sectional area, wood density, mean current velocity, and turbidity) also were related to capture efficiency of both methods, but the effects differed among species groups. We estimated that, on average, 23% of fish left the unblocked sample units, but net movement varied among species. Our results suggest that (1) common warmwater stream fish sampling methods have low capture efficiency and (2) failure to adjust for incomplete capture may bias estimates of fish abundance. We suggest that managers minimize bias from incomplete capture by adjusting data for site- and species-specific capture efficiency and by choosing sampling gear that provide estimates with minimal bias and variance. Furthermore, if block nets are not used, we recommend that managers adjust the data based on unconditional capture efficiency.