bluuebunny/crossref_metadata_2025_split huggingface dataset:
Injury and Mortality of Warmwater Fishes Immobilized by Electrofishing
Authors: Dolan C. R. , Miranda L. E. 
Published: June 2004

Abstract
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

Abstract
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

Abstract
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.
Statistical Properties of the Relative Weight (W
r) Index and an Alternative Procedure for Testing W
r Differences between Groups
Authors: Brenden Travis O. , Murphy Brian R. , Birch Jeffrey B. 
Published: June 2004

Abstract
Fishery managers commonly test for differences in relative weight (Wr) between or within populations using standard parametric or nonparametric statistical tests. However, the statistical properties of the Wr index have not been studied; consequently, we cannot be certain that Wr data satisfy the theoretical assumptions upon which many standard tests are based. In particular, we do not know if Wr data are independent and identically distributed (i.i.d.), which is an assumption made by most standard statistical tests and which can increase the type I error rate of a statistical test when it is violated. We derived approximations to the expectation, variance, and covariance of the Wr index using the Delta method and estimated these parameters with sample data for muskellunge Esox masquinongy, largemouth bass Micropterus salmoides, and black crappie Pomoxis nigromaculatus. Additionally, we devised a likelihood ratio test (R-test) that tests for differences in Wr between groups and that does not assume i.i.d. data. We applied the R-test to the sample data and compared the results with those obtained from traditional statistical tests. The statistical properties of the Wr index were conditionally dependent on fish length. This conditionality prevents the covariance from equaling zero across an entire fish sample, so that Wr data will be inherently correlated. For the sample data, parameter estimates increased with fish length and typically were above realistic Wr values. This bias was attributed to variability in sample length-weight data. Traditional statistical tests were more liberal than the R-test in declaring statistical significance when testing for differences in Wr between groups. Based on our derivations, we conclude that Wr data will violate an i.i.d. assumption to some extent. To avoid falsely declaring statistical significance when testing group differences, we recommend that the R-test be used with Wr data.
Regurgitation Rates of Intragastric Radio Transmitters by Adult Chinook Salmon and Steelhead during Upstream Migration in the Columbia and Snake Rivers
Authors: Keefer M. L. , Peery C. A. , Ringe R. R. , Bjornn T. C. 
Published: June 2004

Abstract
Regurgitation rates for radio tags gastrically implanted into adult salmon Oncorhynchus spp. and steelhead O. mykiss are difficult to estimate in the wild because most fish are never recaptured to allow inspection of secondary tags. During 1996–2000, 9,006 Chinook salmon O. tshawytscha and steelhead with both radio tags and secondary tags were released near Bonneville Dam on the Columbia River (Washington–Oregon), and 1,764 fish were recaptured in mid-migration 460 km upstream on the lower Snake River. Minimum annual regurgitation rates ranged from 0.4% to 10.9% for spring–summer Chinook salmon (pooled rate = 3.0%; n = 838), from 3.5% to 4.3% for steelhead (pooled rate = 4.0%; n = 881), and from 0% to 5.6% for fall Chinook salmon (pooled rate = 2.2%; n = 45). Fish that lost transmitters retained them a median of 7 d (average = 14.1 d) before regurgitation, and a majority of losses occurred in the lower Columbia River. Transmitter retention was improved by placing rubber bands or a ring of surgical tubing around part of each tag.
Great Blue Heron Predation on Stocked Rainbow Trout in an Arkansas Tailwater Fishery
Authors: Hodgens Lynn S. , Blumenshine Steven C. , Bednarz James C. 
Published: June 2004

Abstract
Fisheries managers seldom have adequate information to assess their stock losses to avian piscivores, which function as apex predators in many aquatic food webs. Our primary objective was to estimate the number of stocked rainbow trout Oncorhynchus mykiss consumed by great blue herons Ardea herodias on the Bull Shoals and Norfork tailwaters of north-central Arkansas. Between November 2000 and December 2001, we periodically surveyed great blue herons along 150.7 river km on the tailwaters of the Bull Shoals and Norfork dams. Heron density (number/km) in or along the river ranged from 0 to 4/km per survey, with the highest mean number located near the Bull Shoals Dam (2.31 herons/km). We recorded 467 prey captures by herons during 202 observation hours. Sculpin Cottus spp. were the most common prey (N = 120). Most prey (87%) measured 14 cm or less in length, and most captured live trout (85.4%) fell between 10.5 and 28.0 cm in length. While live trout represented only 48 of 359 identifiable prey items (13%), they comprised an estimated 62.8% of heron diet biomass. We developed a bioenergetics model that combined our observations with published metabolic coefficients and relationships to estimate heron energy demand during breeding and nonbreeding seasons. This analysis revealed that trout comprised an estimated 67% of heron daily energy demand in the study area. Heron daily energy demand peaked during the breeding season (March–May). Based on a mean monthly population estimate of 227 great blue herons requiring 156 million kJ of total energy/year, we calculated that herons consumed just under 50,000 catchable-sized stocked trout annually. This loss to great blue herons represents an estimated 2.4% of the approximately 2 million trout stocked in the study area. Thus, great blue heron predation likely represents only a minor source of trout mortality in the Bull Shoals and Norfork tailwaters.
Applications of New Technologies to Instream Flow Studies in Large Rivers
Authors: Gard Mark , Ballard Ed 
Published: June 2004

Abstract
An acoustic Doppler current profiler, underwater video system, hand-held laser range finder and global positioning receiver were used to collect data for instream flow studies on the Sacramento and lower American rivers in California. The use of the equipment decreased the time required to collect spawning criteria data for Chinook salmon Oncorhynchus tshawytscha in deep water in a given area by a factor of 3.4 and doubled the number of transects that could be modeled with the same budget. With the application of quality control criteria, discharges could be measured with an average accuracy of 2.7% versus gauge data with an accuracy of 5%. The total time required to collect data for two-dimensional habitat sites varied with the length and complexity of the sites, and was equivalent to the total time required for physical habitat simulation (PHABSIM) data collection for shorter sites, and less for longer sites.
Simple Control Method to Limit the Spread of the New Zealand Mudsnail Potamopyrgus antipodarum
Authors: Richards David C. , O'Connell Pat , Shinn Dianne Cazier 
Published: June 2004

Abstract
The invasive New Zealand mudsnail Potamopyrgus antipodarum is now well established in rivers in the western United States and is rapidly expanding its range. Potamopyrgus antipodarum is most likely to be spread to new waters via contaminated equipment. To assess a possible method for controlling their spread, we conducted a desiccation and freezing experiment on seven size-classes of P. antipodarum to determine mortality at different temperatures and low or high humidity. Our results show that P. antipodarum does not survive freezing or desiccation at high temperatures with low humidity. At all temperatures, larger P. antipodarum generally survived desiccation longer than smaller ones, and for all size-classes mortality generally increased with increased exposure time. We recommend thoroughly freezing or drying potentially contaminated equipment to limit the spread of P. antipodarum to uninfected aquatic ecosystems.
Effect of Electrofishing Effort on an Index of Biotic Integrity
Authors: Dauwalter Daniel C. , Pert Edmund J. 
Published: June 2004

Abstract
We sampled fishes at 15 stream sites in the Ozark Highlands ecoregion of Arkansas and examined the effects of sampling effort on an index of biotic integrity (IBI). We found that sampling effort affected component metric scores, IBI scores, and qualitative site classifications. The scores of taxonomic richness metrics increased with increasing effort, while relative abundance metrics were inconsistently affected by sampling effort. The scores of all metrics stabilized with increasing effort. Although some deviation from the sampling effort designated for the IBI appeared acceptable, we found that even a sampling effort deviation of 10 mean stream widths from the designated effort (19.6%) caused one qualitative site classification to change. Our results showed that differences in sampling effort can affect IBI scores and result in erroneous stream assessments. They also indicated that an accurate assessment of regional stream conditions relies on incorporating the specific sampling effort designated for the Ozark Highlands IBI.
Producing Fluorescent Marks on Atlantic Salmon Fin Rays and Scales with Calcein via Osmotic Induction
Authors: Mohler Jerre W. 
Published: June 2004

Abstract
Calcified tissues of Atlantic salmon in both larval and postscale developmental life stages became labeled with the fluorochrome dye known as calcein in 7 min by sequential immersion in salt and calcein solutions. I introduce the term “osmotic induction” to describe this process. At 47 d posttreatment, fish that had been exposed to osmotic induction of calcein as nonfeeding larvae exhibited mortality and growth equivalent to that of nonexposed fish (P &lt; 0.05). Atlantic salmon parr (at 5 months posthatch) exposed to osmotic induction of calcein exhibited no mortality during a 120-d posttreatment period. In addition to inducing a calcein mark on fin rays of all larvae and parr, the procedure also produced a distinct calcein mark on scales of parr. A second exposure of parr to osmotic induction 90 d after the first produced a conspicuous 2-band pattern on scales which corresponded to the two separate marking events. Calcein marks are invisible to the unaided eye but were observed without sacrificing the experimental fish by employing a calcein detection device (patent applied for) and fluorescence microscopy. Osmotic induction of calcein marks is a potentially useful technique for batch-marking fish because it greatly reduces the amount of contact time between the fish and marking solution and produces an easily identified mark; this may enable salmon fishery managers and researchers to perform a variety of nonlethal fisheries evaluations not practical or possible using previous marking and tagging techniques.
Immersion Marking of Juvenile Midas Cichlids with Oxytetracycline
Authors: Barker Jennifer M. , McKaye Kenneth R. 
Published: June 2004

Abstract
Laboratory experiments were conducted on the use of oxytetracycline hydrochloride (OTC) for marking juvenile Midas cichlids Amphilophus citrinellus. Juveniles were immersed in tris-buffered OTC solutions of 200, 400, or 600 mg/L for 4, 8, or 16 h. Marked juveniles were detected by the presence of a fluorescent mark on spines and rays when viewed under an ultraviolet light. Immersion in 600-mg/L OTC solution for 8 h produced the optimum mark intensity. No immediate mortality occurred after the marking procedure. Retention of the externally visible marks and effect of OTC treatment on long-term survival were examined by rearing both marked and unmarked juveniles for 6 weeks. Marks were visible for 2–7 weeks, depending on the size of the juveniles when marked. Marking with OTC had no effect on survival over the 6-week period. The effects of light exposure on retention and intensity of externally visible marks were examined by rearing marked fry under both dark and light conditions. Retention and intensity of externally visible marks were greater in juveniles held in the dark. The effect of OTC treatment on the vulnerability of juveniles to predation was determined by subjecting both marked and unmarked juveniles to predation by bigmouth sleepers Gobiomorus dormitor 72 h after OTC treatment. OTC marking did not affect the vulnerability of juveniles to predation. Our results indicate that this OTC marking technique would be suitable for short-term mark–recapture, growth, and alloparental care studies of Midas cichlids.
Effectiveness of Electrical Fish Barriers Associated with the Central Arizona Project
Authors: Clarkson Robert W. 
Published: June 2004

Abstract
The Central Arizona Project (CAP) canal delivers Colorado River water into the Gila River basin. During its planning and construction, issues arose regarding the unwanted entrainment and transport of nonindigenous fishes and other aquatic biota into, through, and out of the canal. One control strategy was the emplacement of electrical fish barriers on two CAP distributary canals to prevent fishes from moving upstream into the Gila River drainage. The operation, maintenance, and effectiveness of these barriers are described for the period 1988–2000. Documented outages totaled more than 100 h, representing less than 0.001% downtime since installation. It is nearly certain that outages allowed immigration by undesired fish(es). Immigrations that occurred when the barriers were operating according to design criteria indicate that the barriers do not totally block the passage of upstream-migrating fish. The proximate sources of electrical barrier outage included component damage from lightning strikes, component breakdowns, failure to adhere to component maintenance and replacement schedules, failure to incorporate adequate protection and redundancies to certain system components, inadequate training of personnel, and unknown causes. Known outages of remote monitoring systems (which are necessary to document outages and understand the potential for undocumented barrier outages) totaled more than 400 d, representing about 3% of the period of barrier operations. The complexity of electrical barrier systems and the problems such intricacy creates for operation and monitoring may always preclude absolute effectiveness. Additional refinements to system components, personnel training, and operation procedures may reduce barrier failures but add further to that complexity. Management agencies will have to determine the cost-effectiveness of such refinements.
Largemouth Bass Abundance and Angler Catch Rates following a Habitat Enhancement Project at Lake Kissimmee, Florida
Authors: Allen Mike S. , Tugend Kimberly I. , Mann Marty J. 
Published: June 2004

Abstract
A habitat enhancement project was conducted at Lake Kissimmee, Florida, during 1995-1996 to improve fish habitat and remove dense inshore vegetation caused by stabilized water levels. We evaluated abundance of age-1 (&lt;250 mm total length (TL)) and adult (fish at least 356 mm TL and all sizes of fish caught by anglers) largemouth bass Micropterus salmoides before and after the habitat enhancement. Mean electrofishing catch per hour (CPH) of age-1 largemouth bass increased significantly after the 1995-1996 habitat enhancement, suggesting strong year-classes for 2 years after the habitat enhancement (i.e., 1997-1998 year-classes). Growth of age-1 largemouth bass also increased following habitat enhancement; mean total length of age-1 fish averaged 143 mm before enhancement and 186 mm after enhancement. Catch curves conducted in 2001 and 2002 corroborated historical electrofishing data indicating that the 1997 and 1998 year-classes were abundant as adults compared with other year-classes in the age frequencies. Age-1 largemouth bass electrofishing catch rates were not related to seasonal water levels or coverage of hydrilla Hydrilla verticillata. Despite the rapid growth rates and high abundance of the 1997 and 1998 year-classes, neither electrofishing catch rates of largemouth bass at least 356 mm TL nor angler catch rates of largemouth bass (fish/h, all sizes of fish, harvested or released; data from creel surveys) differed significantly between preenhancement and postenhancement periods. Thus, we were unable to detect a change in adult largemouth bass abundance or angler catch rates following the habitat enhancement. Fishing effort directed toward largemouth bass declined after enhancement for the winter period (November-February) but did not differ significantly between preenhancement and postenhancement periods for the summer (May-August) period. Benefits of muck removal concurrent with lake drawdowns include increased recreational opportunities and improved habitat. However, our results indicate that fish population responses to drawdowns and muck removals may vary and detecting effects on the adult largemouth bass populations can be difficult. Therefore, habitat enhancement efforts should focus on lakewide recreational benefits rather than benefits to a single preferred species (e.g., largemouth bass).
Seasonal Daphnia Biomass in Winterkill and Nonwinterkill Glacial Lakes of South Dakota
Authors: Isermann Daniel A. , Chipps Steven R. , Brown Michael L. 
Published: June 2004

Abstract
We compared the seasonal biomass (μg dry weight/L) and body size of Daphnia pulex populations between South Dakota lakes that experienced nearly complete winterkill (n = 2) and those that did not experience fish winterkill the previous winter (n = 2). In spring (March–May), D. pulex biomass was substantially lower in winterkill lakes (0.4–1.9 μg/L) than in nonwinterkill lakes (13.8–129.4 μg/L). In summer months (June–July), D. pulex biomass increased in all lakes but was generally higher in winterkill lakes (332.1–469.3 μg/L) than in nonwinterkill lakes (88.6–204.2 μg/L). By September, D. pulex biomass was substantially higher in winterkill lakes (243.8 μg/L) than in nonwinterkill lakes (1.0 μg/L). The mean size of D. pulex increased significantly from March to August in winterkill lakes but not in nonwinterkill lakes. The seasonal differences in D. pulex biomass and size may have been related to size-selective predation by planktivorous fishes because the ratio of spine length to body length in D. pulex was significantly lower in winterkill lakes (mean, 0.34) than in nonwinterkill lakes (mean, 0.43). Moreover, seasonal patterns in chlorophyll-a biomass were inversely related to D. pulex biomass. The production and subsequent hatching of resting eggs may be important for recolonization of Daphnia populations after severe winter conditions. The survival and growth of zooplanktivorous fish that are stocked to repopulate winterkill lakes may be increased by delaying stocking until Daphnia populations recover from severe winterkill.