bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Spatially Explicit Open-Ocean DeLury Analysis to Estimate Gear Efficiency in the Dredge Fishery for Sea Scallop Placopecten magellanicus
Authors: Gedamke Todd , DuPaul William D. , Hoenig John M. 
Published: June 2004

Abstract
The translation of survey data into estimates of absolute abundance hinges on the availability of an accurate estimate of gear efficiency. In many fisheries, however, a wide range of estimates exists and research directed at quantifying this critical parameter has focused on relatively small, fishery-independent data sets. In the present study, a technique was developed to utilize the copious amounts of data available from an open-ocean fishery for sea scallops Placopecten magellanicus in a spatially explicit depletion model. In June 1999, Georges Bank Closed Area II was opened to the commercial scallop fleet after a 5-year multispecies fishing ban. During the 5-month opening, the spatial distribution and magnitude of fishing effort was tracked through vessel monitoring systems, and a relatively small but still substantial number of catch observations were made aboard vessels from the commercial fleet. A spatial analysis of both catch and effort data was utilized to select areas consistent with the assumptions of a DeLury analysis. Maximum likelihood estimation was then used to generate a single estimate of the catchability coefficient (and thus efficiency), while simultaneously estimating the initial abundance in each area. The gear efficiency of the New England-style scallop dredge used during the fishing season was estimated to be 42.7%. A sensitivity analysis of model results shows a potential range of 35.5–52.5%, depending on model assumptions.
Winter Habitat Use by Adult Largemouth Bass in the Pend Oreille River, Idaho
Authors: Karchesky Christopher M. , Bennett David H. 
Published: June 2004

Abstract
We evaluated the behavior and use of overwintering habitat of adult largemouth bass Micropterus salmoides in the Pend Oreille River, Idaho, using radiotelemetry after increases in winter water levels. Largemouth bass tagged in late summer remained in backwaters until the initiation of the fall drawdown, when they moved to deeper shoreline areas. As water temperatures declined further, all but 1 of the 19 largemouth bass tagged throughout a 44.2-km-long section of river migrated to one of two overwintering areas. Once there, largemouth bass either showed no movement or migrated freely between the two overwintering areas. The overwintering areas were adjacent to the river, had an abundance of aquatic macrophytes, were more than 1 m deep, and had zero water velocity. Higher winter lake levels of 0.6 m did not attract wintering largemouth bass to backwaters. We hypothesized that habitat in overwintering areas was preferred because water temperatures there were several degrees warmer than in shallow backwaters.
Use of Egg Surrogates to Estimate Sampling Efficiency of Striped Bass Eggs in the Savannah River
Authors: Reinert Thomas R. , Will Ted A. , Jennings Cecil A. , Davin William T. 
Published: June 2004

Abstract
Surface push nets have been employed in the Savannah River estuary (SRE) to monitor striped bass Morone saxatilis spawning activity since the 1960s, but most intensively since the mid-1980s. These methods provide relative catch-per-unit-effort data for comparing station-to-station and year-to-year changes in egg abundance but do not provide total annual production estimates. To quantify the sampling efficiency of our gear, we investigated the use of gellan beads as striped bass egg surrogates. Gellan beads were comparable to striped bass eggs in size and specific gravity, and are appropriate surrogates for efficiency trials. In 1999 and 2000, we released known quantities of gellan beads to evaluate the efficiency of our egg sampling gear. Efficiency ranged from 1 bead per 11,300 at large (0.009%) to about 1 bead per 300,000 at large (0.0003%), depending on release and recapture locations. The use of egg surrogates was an effective and informative technique for evaluating our standardized egg sampling gear and may be similarly useful for other systems and other species with semibuoyant pelagic eggs. Additionally, the use of egg surrogates uncovered previously unsuspected biases in sampling efficiency because of differences in channel morphology and hydrology within the SRE.
Accuracy and Precision of Age Estimates for Pallid Sturgeon from Pectoral Fin Rays
Authors: Hurley Keith L. , Sheehan Robert J. , Heidinger Roy C. 
Published: June 2004

Abstract
Accurate age information is critical to the biological understanding and management of most fish species, but particularly for species of concern, such as the pallid sturgeon Scaphirhynchus albus. The accuracy and precision of pallid sturgeon age estimates from pectoral fin ray sections has never been established, yet all accumulated age information for the species was collected using this technique. To examine the accuracy and precision of age estimates, 16 pectoral fin ray samples from age-6 pallid sturgeon were obtained from Gavins Point National Fish Hatchery, South Dakota. The fin rays were sectioned, mounted, and independently examined twice by each of two readers. Only 28.1% of the age estimates accurately reflected the known age of the fish. Multiple readings of the same sample by the same reader (within-reader precision) only agreed 25% of the time, differences being as great as 5 years between the two estimates. Between-reader agreement was 46.9%, the two readers' estimates of the same fish differing by as much as 2 years. Because of low accuracy and precision, estimated ages from pallid sturgeon pectoral fin rays should be viewed with caution.
Effect of Hypoxia on the Distribution of Fishes Associated with a Petroleum Platform off Coastal Louisiana
Authors: Stanley David R. , Wilson Charles A. 
Published: June 2004

Abstract
A combination of hydroacoustics and visual survey techniques were used to estimate the abundance, size distribution, and species composition of fishes at a petroleum platform in the northern Gulf of Mexico. The effect of dissolved oxygen (DO) concentration on the density and distribution of fishes at this de facto artificial reef was examined. The techniques used permitted surveys of the entire water column, providing a more accurate reflection of the effect of a highly variable phenomenon (i.e., hypoxia) that may not be measured with traditional fisheries sampling equipment. Hypoxic conditions were observed during two of the five trips to the petroleum platform, South Timbalier 54. When hypoxia was present, fish density was dramatically higher in the strata immediately above the hypoxia. It was difficult to determine the exact impact of hypoxia on target strength (a measure of fish size), as the larger mean target strengths observed in the spring and summer may be due to seasonal factors and not to hypoxia alone. With the exception of the fall 1995 survey (which had significantly higher density and abundance estimates than other surveys), the estimated number of fishes did not vary among any of the sample periods. Even when 32% (15–22 m) of the water column was hypoxic (summer 1996), abundance estimates were slightly higher than in other survey periods without hypoxia (except fall 1995). While hypoxia reduced the availability of the water column to fishes, they concentrated where favorable DO levels were found. This included demersal species such as red snapper Lutjanus campechanus, which were found higher in the water column than expected.
Use of Riffle and Run Habitats with Aquatic Vegetation by Juvenile Atlantic Salmon
Authors: Beland K. F. , Trial J. G. , Kocik J. F. 
Published: June 2004

Abstract
We examined the use of riffle and run habitats with varying aquatic macrophyte coverage by juvenile Atlantic salmon Salmo salar in the Narraguagus River, Maine, via electrofishing and individual fish observations. At the site level, large and small parr were more abundant in riffle habitats than in run habitats, and the abundance of small parr was lower at sites with heavy aquatic vegetation. At the individual-fish level, parr use of moderately vegetated areas was significantly higher than expected based on availability of such habitats, and use of heavily vegetated areas was lower than expected. The use of vegetated areas was not independent of dominant substrate type. Use of moderately vegetated habitats exceeded expectations for gravel- and sand-dominated areas; for cobble-dominated areas, use of sites with little or no vegetation exceeded expectations. Approximately 95% of the observed parr were found in the vicinity of a discrete cover item (i.e., cobble, vegetation, or other). Parr typically held position in the immediate vicinity of a cobble particle or other large stone when such cover items were available. In areas with limited cobble cover, parr often held position in the vicinity of rooted aquatic macrophytes. In the absence of cobble cover, areas with moderate levels of aquatic vegetation provide a cover component to juvenile Atlantic salmon and are used to a greater extent than similar areas lacking such cover.
Use of Resampling to Evaluate a Simple Random Sampling Design for General Monitoring of Fishes in Texas Reservoirs
Authors: Dumont Spencer C. , Schlechte Warren 
Published: June 2004

Abstract
Traditional formulae used to estimate sample sizes to achieve a desired level of precision have been proven to underestimate required sample sizes. Further, because these formulae typically focus on precision, they are unable to provide the information needed to evaluate the risk of not attaining other sampling objectives. Resampling approaches provide a framework for estimating realistic sample sizes, can handle complex objectives, and will provide probability-based statements that can be used to assess risk. We used a resampling approach to assess the performance of a simple random sampling design for the general monitoring of fishes with electrofishing, gill nets, and trap nets in Texas reservoirs. We evaluated median relative standard error (RSE = 100 × SE of the estimate/estimate) of catch-per-unit-effort (CPUE) estimates of stock length fish with current sampling methods. We estimated the effort necessary to achieve RSEs of (at worst) 25% or 15% (RSE25 and RSE15, respectively) at various probability levels. Resampling estimates of effort needed to achieve RSE25 were compared with estimates calculated from one commonly used formula (N = (CV/RSE)2) for all target species. Further, we estimated the effort necessary to collect 100 stock length fish of each target species. Median RSE ranged from 22 for largemouth bass Micropterus salmoides to 43 for crappies Pomoxis spp. The median number of stock length fish collected using the current sampling effort ranged from 16 for blue catfish Ictalurus furcatus to 43 for palmetto bass (male white bass Morone chrysops × female striped bass M. saxatilis) per sampling event. Estimated sampling effort needed to achieve RSE25 for largemouth bass and to collect 100 stock length largemouth bass at the 75th percentile of samples was 29 and 62 5-min stations, respectively. Estimated sampling effort needed to achieve RSE25 at the 75th percentile of samples for other target species ranged from 32 net-nights for channel catfish I. punctatus to 59 net-nights for crappies. Estimated sampling effort needed to collect 100 stock length fish from gill nets and trap nets at the 75th percentile of samples ranged from 72 net-nights for crappies to over 100 net-nights for blue catfish. Simple random sampling generally resulted in low catches of stock length fish and a poor precision of CPUE estimates, especially for target species collected with gill nets and trap nets. Sampling effort estimates (from N = (CV/RSE)2) underestimated the sampling effort needed for all species examined. Unlike traditional sample size formulae, the resampling approach presented here allows the user to determine sampling effort with an associated probability of success in achieving a particular level of precision or in collecting a given number of fish.
Summer Habitat Use by Rainbow Trout and Brown Trout in Jocassee Reservoir
Authors: Barwick D. Hugh , Foltz Jeffrey W. , Rankin Daniel M. 
Published: June 2004

Abstract
Temperature, dissolved oxygen, and depth preferences of Jocassee Reservoir rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta implanted with temperature-sensing radio transmitters were determined during July, August, and September 1994–1998. Specific knowledge of these preferences was needed to verify habitat criteria designed to assist in the management of water quality in this reservoir for trout survival in late summer and early fall. Rainbow trout exhibited temperature, dissolved oxygen, and depth preferences in the ranges 8.3–13.4°C, 2.9–8.7 mg/L, and 30.0–52.0 m, respectively, while brown trout exhibited preferences in the ranges 7.5–21.9°C, 4.2–10.0 mg/L, and 14.0–54.0 m, respectively. Even though rainbow trout selected cooler water temperatures and greater depths than brown trout, both species generally exhibited preferences for water 20°C or cooler and containing 5.0 mg/L or more of dissolved oxygen. Maintenance of these criteria in Jocassee Reservoir should ensure adequate habitat for the summer and early fall survival of rainbow and brown trout.
Injury of American Eels Captured by Electrofishing and Trap-Netting
Authors: Reynolds James B. , Holliman F. Michael 
Published: June 2004

Abstract
We compared the incidence of internal injuries in adult American eels Anguilla rostrata captured by trap-netting (N = 20) and by 30-Hz, pulsed-DC electrofishing (N = 18) in the St. Lawrence River, New York. On average, the lengths and weights of fish caught by the two methods were similar. Radiographic imaging revealed that spinal damage occurred in 60% of the electroshocked American eels but only 15% of the trap-netted American eels. Bilateral filleting showed hemorrhages in 30% of the electroshocked fish but none of the trap-netted fish. Electrofishing caused significantly higher incidences of both spinal damage and hemorrhage than did trap-netting. Most electroshocked American eels had multiple spinal injuries; hemorrhages occurred only in fish with multiple sites of vertebral damage. We recommend that workers avoid the use of 30-Hz, pulsed DC to capture American eels that are intended for release; a lower frequency, such as 15 Hz, may significantly reduce injury but may also result in unacceptably low capture rates. We hypothesize that electroshocked American eels are at high risk for injury because of their large size (&gt;90 cm) and high vertebral count (&gt;100).
Fish Size and Exposure to Air: Potential Effects on Behavioral Impairment and Mortality Rates in Discarded Sablefish
Authors: Davis Michael W. , Parker Steven J. 
Published: June 2004

Abstract
Fisheries models often assume that discarded undersized fish and target species will survive and contribute to future recruitment and yield. If smaller fish are more susceptible to capture stressors than larger fish, then the assumption that smaller discards would contribute to recruitment may not be true. We tested the hypothesis that small sablefish Anoplopoma fimbria show more behavioral impairment and mortality than large fish when exposed to air (10–60 min) at various temperatures (10–18°C). Sablefish captured by trawl, longline, or trap are commonly exposed to these conditions during warmer seasons when brought up on deck and sorted. Two size-classes of fish (small: 32–49 cm total length (TL); large: 50–67 cm TL) were used in the experiments. Behavior was measured as upright orientation and startle responses to visual and mechanical stimuli 1, 2, 3, and 24 h after air exposure; mortality was measured through 7 d after air exposure. Small fish mortality increased as air time increased and was at higher levels than in large fish. Only 10 min of air exposure caused behavioral impairment in small and large fish, which could lead to increased predation on discarded fish. At 24 h after air exposure, normal behavior had not generally resumed and small fish had more behavioral impairment than large fish.
Male Dominance in the New Zealand Longfin Eel Population of a New Zealand River: Probable Causes and Implications for Management
Authors: McCleave James D. , Jellyman Donald J. 
Published: June 2004

Abstract
The endemic New Zealand longfin eel Anguilla dieffenbachi (hereafter, longfin eel), is overfished, and in southern South Island, New Zealand, rivers have recently become predominated by males. This study examined length and age at sexual differentiation in male eels in the Aparima River catchment (area, 1,375 km2; mean flow, 20 m3 · s−1) and the sex ratio and distribution of eels throughout the catchment. Longfin eels differentiated into males mostly at lengths from 300 to 460 mm and ages from 10 to 25+ years. Females were rare: Of 738 eels examined for sexual differentiation, 466 were males and 5 were females, and a few others, not examined, were large enough to be female. These counts suggest a male : female ratio among differentiated longfin eels of 68:1. Of 31 differentiated shortfin eels A. australis, less common in the Aparima River, 26 were females. Male longfin eels were distributed throughout the main stem and tributaries; undifferentiated eels were more prevalent in lower and middle reaches and in the main stem than in upper reaches and tributaries. In other studies, male longfin eels predominated commercial catches in the Aparima and four other southernmost rivers, by 2.4:1 to 13.6:1 males to females. The Aparima River had the most skewed sex ratio. Longfin eel catches from the Aparima River will become more male predominated because few sublegal-size females were present. The length-frequency distributions of eels in the present samples and in the commercial catches were truncated just above minimum legal size (about 460 mm), showing that few females escape the fishery. Historically, females predominated these rivers. The recent change in sex ratio is attributable partly to selective harvest of females, and partly to changes in the structure of the population from fishing, such that differentiation into males has been favored. Longevity, delayed sexual maturity, semelparity, and endemism with restricted range make the longfin eel particularly vulnerable to overfishing.
Bias and Bias Correction in Fish Recruitment Prediction
Authors: Chen D. G. 
Published: June 2004

Abstract
A lognormal error is usually assumed in the traditional stock–recruitment (SR) analysis. In this paper, I demonstrate that a positive bias results when an SR model with lognormal error is used for fish recruitment prediction. Not only is this bias exponentially dependent on the structure of the model's residual variance and the historical SR data, it is also dependent on the specific value of spawner biomass used. I then derive a bias correction that is asymptotically unbiased with a finite-sample bias that is practically zero. Data from two Pacific salmon populations, southeast Alaska pink salmon Oncorhynchus gorbuscha and Chilko Lake sockeye salmon O. nerka, are used to demonstrate this approach. The results show that the relative bias is about 10% for a spawning biomass within the historical range and that the bias is substantial outside that data range. However, with the proposed bias correction, the bias is negligible both within (&lt;0.1%) and outside of (&lt;0.3%) the data range.
Movement Patterns of American Eels in an Impounded Watercourse, as Indicated by Otolith Microchemistry
Authors: Cairns D. K. , Shiao J. C. , Iizuka Y. , Tzeng W-N. , MacPherson C. D. 
Published: June 2004

Abstract
Otolith Sr:Ca ratios were used to determine migrational histories of American eels Anguilla rostrata in an eastern Canadian coastal stream that is impounded at the head of tide. American eels sampled from the estuary were smaller (41.0 ± 9.3 cm (mean ± SD), N = 324) and younger (ages 1–4) than those in a freshwater pond (65.0 ± 7.5 cm, N = 265; ages 11–26) 2.5 km upstream of the head of tide. The Sr:Ca ratios permitted identification of three migrational contingents. In 7 of 13 (54%) American eels taken in the estuary, Sr:Ca ratios declined to 4.76 ± 1.22 × 10−3, indicating direct migration from the sea to estuarine settlement sites. In the 6 other American eels (46%), Sr:Ca ratios indicated an approach to freshwater soon after arrival in continental waters, followed by settlement in the estuary where ratios stabilized at 4.50 ± 1.23 × 10−3. In all 15 American eels sampled from the freshwater pond, Sr:Ca ratios indicated settlement in freshwater in the elver year and no subsequent change of habitat salinity (postelver ratio, 0.64 ± 0.66 × 10−3). The lack of evidence for postelver movements between freshwater and brackish water contrasts with literature findings that such movements are common in systems where dams do not impede access to freshwater. Dams may hamper normal American eel movements between rivers and estuaries, even in watercourses in which some American eels are able to colonize freshwaters.
Sampling Fish in Streams with Seines: Costs of Recording Data by Haul
Authors: Winston Matthew R. 
Published: June 2004

Abstract
Data from stream fish community samples obtained with seines are often recorded in the form of a species list with abundances, measures of total effort, and overall measures of habitat in the reach sampled. With a little more effort, investigators can significantly enhance the value of the data by recording this information for each seine haul rather than aggregating by reach. The objective of this study was to measure the added cost, in terms of time, of recording data by seine haul. While doing 11 community samples with seines, I timed four components of each seine haul: the time that the seine was in the water sampling, the time spent processing the fish, the time spent recording data for each seine haul, and the time spent getting ready for the next seine haul. I found that recording data by seine haul increased the time to make seine hauls from 8% to 34% (median of 12% or 7 min added to each hour of work). The benefits of recording data by seine haul include providing the flexibility to standardize in unforeseen circumstances, providing better quality control, and providing data at two spatial scales instead of one.