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At least 541 records · Page 30Linked to original sources
USGS1989

Efficacy of benzocaine as an anesthetic for salmonid fishes

Benzocaine was tested in the laboratory to determine the effective concentrations for anesthetizing juvenile chinook salmon Oncorhynchus tshawytscha and rainbow trout O. mykiss (formerly Salmo gairdneri ). Tests were conducted at three water temperatures, in waters ranging from very soft to very hard, and with groups of rainbow trout from 5 to 47 cm long and chinook salmon 20 cm long. Effective concentrations were defined as those that rendered the fish fully handleable in 3 min or less, allowed recovery of most fish within 10 min, and caused no mortality after 15-min exposures. Concentrations of 25–45 mg/L anesthetized both species over the entire range of conditions tested. Although efficacy was essentially unrelated to species or water quality, it was related to water temperature and size offish; the concentrations of benzocaine required were highest at the lowest water temperatures and for the largest fish.

North American Journal of Fisheries Management↗
USGS1989

Variation in capture efficiency of a beach seine for small fishes

We determined the capture efficiency of a beach seine as a means of improving abundance estimates of small fishes in littoral areas. Capture efficiency for 14 taxa (individual species or species groups) was determined by seining within an enclosure at night over fine and coarse substrates in the John Day Reservoir, Oregon–Washington. Mean efficiency ranged from 12% for prickly sculpin Cottus asper captured over coarse substrates to 96% for peamouth Mylocheilus caurinus captured over fine substrates. Mean capture efficiency for a taxon (genus or species) was generally higher over fine substrates than over coarse substrates, although mean capture efficiencies over fine substrates were significantly greater for only 3 of 10 taxa. Capture efficiency generally was not influenced by fish density or by water temperature (range, 8–26°C). Conclusions about the relative abundance of taxa captured by seining can change substantially after capture efficiencies are taken into account.

North American Journal of Fisheries Management↗
USGS1989

Comparison of fish catches with buoyant pop nets and seines in vegetated and nonvegetated habitats

Two models of pop nets were developed to sample fish in shallow riverine waters, one for use in vegetated areas and the other for nonvegetated areas. Both nets have a mechanical release mechanism that can be tripped from the water surface. Replicated field tests were conducted to compare pop-net catches with bag-seine collections every 2 weeks from May through mid-October. Overall, total catch per effort did not vary significantly ( P < 0.05) between the two gears at either the vegetated or nonvegetated site. However, collections with the pop net were not as diverse as with the seine at either sampling site, perhaps because the area sampled by pop nets (5.6 m 2 ) was smaller than the area swept by the average seine haul (70-140 m 2 ). The pop net effectively sampled fish in shallow nonvegetated habitats and was useful in heavily vegetated areas where seining or electroshocking was difficult.

North American Journal of Fisheries Management↗
USGS1989

Side-scan sonar mapping of lake trout spawning habitat in northern Lake Michigan

Native stocks of lake trout Salvelinus namaycush were virtually or completely extirpated from the lower four Great Lakes by the early 1960s. The failure of early attempts to reestablish self-sustaining populations of lake trout was attributed partly to the practice of stocking hatcheryreared juveniles at locations and over substrates that had not been used in the past for spawning by native fish. Subsequent attempts to improve the selection of stocking locations were impeded by the lack of reliable information on the distribution of substrates on historical spawning grounds. Here we demonstrate the potential of side-scan sonar to substantially expand the data base needed to pinpoint the location of substrates where lake trout eggs, fry, or juveniles could be stocked to maximize survival and help ensure that survivors returning to spawn would encounter suitable substrates. We also describe the substrates and bathymetry of large areas on historical lake trout spawning grounds in the Fox Island Lake Trout Sanctuary in northern Lake Michigan. These areas could be used to support a contemporary self-sustaining lake trout population in the sanctuary and perhaps also in adjacent waters.

Great Lakes↗
USGS1989

Downstream migration of recently metamorphosed sea lampreys in the Ocqueoc River, Michigan, before and after treatment with lampricides

The objectives of this study were to determine the effectiveness ofchemical treatments of the Ocqueoc River, Michigan, in reducing the number of recently metamorphosed sea lampreys Petromyzon marinus migrating to Lake Huron and to estimate total numbers of migrants produced before and after treatment. Sea lampreys were captured during their downstream migration in a single fyke net fished in the same location from September 1963 through August 1975. The catch, which averaged 3,474 sea lampreys (range, 3,248-3,913) during four migration periods (September-June) before treatment in 1968, declined to 4 during the 1974-1975 migration period. Markrecapture studies were conducted to determine the capture efficiency of the net for recently metamorphosed sea lampreys and to estimate the total downstream migration for each migration period. Estimated downstream migrations before treatment averaged 62,036 sea lampreys (range, 58,000-69,875) for four migration periods and declined to 71 during the 1974-1975 migration period. Catches were usually greater in fall than in spring. The fall peak in migratory activity was in November or December, and the spring peak was in April; both peaks occurred while water levels were high and water temperatures were near 5°C.

Michigan↗
USGS1989

Effects of water temperature on the mortality of field-collected fish marked with fluorescent pigment

The cumulative effects of collection, handling, and marking with fluorescent pigment on the mortality of adult minnows, young-of-the-year centrarchids, and large centrarchids and percids was determined at five water temperatures (10-20.6 degree C) in field trials. There have been few field trials of this type. The mortality of centrarchids and percids was directly related to temperature and decreased noticeably when the temperature was below 19.5 degree C. The mortality of minnows decreased somewhat as river temperatures cooled but was always at least 50%. Variation was high in the temperature-related patterns of mortality in different taxa and sizes of fish. This variation complicates the accuracy and usefulness of pigment in marking field-collected fish for mark-recapture studies in warmwater systems.

North American Journal of Fisheries Management↗
USGS1990

Sample size requirements and analysis of tag recoveries for paired releases of lake trout

A simple chi-square test can be used to analyze recoveries from a paired-release experiment to determine whether differential survival occurs between two groups of fish. The sample size required for analysis is a function of (1) the proportion of fish stocked, (2) the expected proportion at recovery, (3) the level of significance (∝) at which the null hypothesis is tested, and (4) the power (1 – β) of the statistical test. Detection of a 20% change from a stocking ratio of 50: 50 requires a sample of 172 (∝ = 0.10; 1 – β = 0.80) to 459 (∝ = 0.01; 1 – β = 0.95) fish. Pooling samples from replicate pairs is sometimes an appropriate way to increase statistical precision without increasing numbers stocked or sampling intensity. Summing over time is appropriate if catchability or survival of the two groups of fish does not change relative to each other through time. Twelve pairs of identical groups of yearling lake trout Salvelinus namaycush were marked with coded wire tags and stocked into Lake Ontario. Recoveries of fish at ages 2–8 showed differences of 1–14% from the initial stocking ratios. Mean tag recovery rates were 0.217%, 0.156%, 0.128%, 0.121%, 0.093%, 0.042%, and 0.016% for ages 2–8, respectively. At these rates, stocking 12,100–29,700 fish per group would yield samples of 172–459 fish at ages 2-8 combined.

North American Journal of Fisheries Management↗
USGS1990

Sterilizing effects of cobalt-60 and cesium-137 radiation on male sea lampreys

Male spawning-run sea lampreys Petromyzon marinus were exposed to various doses of cobalt-60 or cesium-137 radiation in an attempt to sterilize them for use in a program for controlling sea lampreys through the release of sterile males. Males captured and irradiated during the early part of the upstream migration were not effectively sterilized at the doses tested. After irradiation, the sea lampreys were more susceptible to fungal infections by Saprolegnia sp., and many died without attempting to spawn. Males captured and irradiated during the middle and late parts of the spawning migration were effectively sterilized at a dose of 2,000 rads. However, some radiation-induced mortality was observed in males captured and irradiated during the middle part of the spawning migration. Radiation is not as effective as the chemosterilant bisazir for sterilizing male sea lampreys.

North American Journal of Fisheries Management↗
USGS1990

Evaluation of condition indices for estimation of growth of largemouth bass and white crappie

We evaluated the ability of three condition indices-condition factor ( K ), relative condition ( K n ), and relative weight ( W r )-to estimate annual growth rates of largemouth bass Micropterus salmoides and white crappies Pomoxis annularis collected during standardized autumn electrofishing and trap-net surveys of Texas reservoirs. Multiple-regression models for estimation of length increments from initial length (at the start of the growing season) and condition indices had R 2 values of 0.63-0.76 for largemouth bass and 0.46-0.83 for white crappie. However, these models are not useful for indirect estimation ofgrowth rates because growth must be known (initial length equals length at capture minus estimated annual growth). Models based on length at capture and condition indices had R 2 values of 0.22-0.68 for largemouth bass and less than 0.45 for white crappie. The low precision of models based on length at capture indicates that condition provides a weak basis for indirect estimation of growth rates from Texas reservoirs sampled during autumn and, therefore, is unreliable for detection of size-related growth phenomena such as "stockpiling" (size specific, density-dependent growth depression). Direct estimates of growth rates based on back-calculations or tagging data seem necessary for reliable detection of size-related growth patterns for largemouth bass and white crappies from Texas reservoirs.

North American Journal of Fisheries Management↗
USGS1990

Changes in Wisconsin's Lake Michigan salmonid sport fishery, 1969-1985

The modern sport fishery for salmonids in Wisconsin waters of Lake Michigan was begun during 1963-1969 with the stocking of rainbow trout ( Oncorhynchus mykiss ), lake trout (Salvelinus namaycush), brook trout ( S. fontinalis ), brown trout ( Salmo trutta ), coho salmon ( O. kisutch ), and chinook salmon ( O. tshawytscha ). The fishery grew rapidly during 1969-1985 as angler effort increased 10-fold, catch rate doubled, and catch increased 20-fold. The stocking and catch became increasingly dominated by chinook salmon, with coho salmon and lake trout of secondary importance and brown, rainbow, and brook trout of least importance. Trolling dominated the fishery, particularly by launched-boat anglers and, more recently, by moored-boat anglers. Charter boat trolling grew the most continuously and had the highest catch rates. The catch by trollers was dominated by chinook and coho salmon and lake trout. Pier, stream, and shore anglers fished less overall, but had catch rates that were similar to launched-boat anglers. The catch by pier and shore anglers was spread among chinook and coho salmon, and lake, brown and rainbow trout. The catch by stream anglers was dominated by chinook salmon. The percentage of stocked fish that were subsequently caught (catch ratio) was highest for fingerling chinook salmon (12.9%). Yearling brook trout, brown trout, coho salmon, lake trout, and rainbow trout had intermediate catch ratios (5.1-9.8%). Fingerling brook trout, brown trout, and lake trout had the lowest catch ratios (2.5-3.5%). The catch ratio for rainbow trout dropped from 9.8 to 5.1% after stocking with a different strain (the Shasta strain). Fingerling rainbow trout produced the lowest returns (<0.5%). We derived stocking recommendations for each species and life stage based on these catch ratios, and catch objectives based on maintaining catch levels recorded during 1983-1985.

North American Journal of Fisheries Management↗
USGS1991

Tolerance of subyearling American shad to short-term exposure to gas supersaturation

Subyearling American shad Alosa sapidissima normally migrate from rivers in the fall and may encounter changes in gas supersaturation levels while traversing hydroelectric dams. To determine whether changes in behavior or survival occur during these events, we exposed subyearling American shad to five levels of gas supersaturation that included pressure increases above equilibrium (▵P) from 10 to 205 mm Hg (101–128% saturation) for 4 h. Multifactor analysis of variance showed no significant differences in behavior or survival of fish before or after treatment. Gas bubbles were observed on external tissues of fish only at the highest treatment level (▵P = 205 mm Hg). Factor analysis elucidated three categories of behavioral organization under experimental conditions: boundary, social, and nonsocial behavior. Under gas supersaturation conditions thought to occur in dammed rivers of the eastern USA, the behavior of subyearling American shad does not appear to be affected in a way that might reduce survival during migration.

North American Journal of Fisheries Management↗
USGS1991

Rotenone persistence in freshwater ponds: Effects of temperature and sediment adsorption

The persistence of rotenone was compared between a cement-lined pond (0.04 hectare) and an earthen-bottom pond (0.02 hectare) treated with 5 μL Noxfish/L (250 μg rotenone/L) during spring, summer, and fall. Water temperatures on the days of treatment in each season were 8, 22, and 15°C, respectively. Both ponds were filled with pond water from a common source 1 week before each of the three treatments. Water samples (filtered and unfiltered) and sediment samples were analyzed by high-performance liquid chromatography to monitor the decrease of rotenone until residues were at or below the detection limit (<2.0 μg/L for water and < 25 ng/g for sediments). The loss of rotenone from water generally followed a first-order rate ofdecay. Rotenone disappeared two to three times faster in the earthen pond than in the concrete pond. The rotenone half-life times in the spring, summer, and fall treatments were 3.7, 1.3, and 5.2 d, respectively, in the concrete pond, and 1.8, 0.7, and 1.8 d in the earthen pond. Rates of decay in both ponds were directly correlated with water temperature. Filtered water samples from both ponds contained less rotenone than unfiltered water, indicating that some rotenone was bound to suspended material. The highest concentration of rotenone in sediment samples was 102 ng/g; residues decreased to below the detection limit within 14 d in the spring treatment and within 3 d in the summer and fall treatments.

North American Journal of Fisheries Management↗
USGS1991

Growth and survival of stocked lake trout with nuclear cataracts in Lake Ontario

Four strains of yearling lake trout Salvelinus namaycush from the 1985 and 1986 year-classes at the Allegheny National Fish Hatchery were evaluated for nuclear cataracts prior to stocking in Lake Ontario in June 1986 and 1987. Lake trout recaptured by bottom trawling from April to August 1987 and 1988 were examined for cataracts. Cataract frequencies in three strains of yearling lake trout at stocking in 1986 and after 14 and 26 months in the lake were: Seneca Lake&ndash;35, 24, and 29%; Lake Ontario&ndash;32,24, and 42%; and Lake Superior&ndash;7,4, and 6%. Cataract frequencies for yearlings at stocking in 1987 and after 2 and 14 months were: Seneca Lake&ndash;51, 37, and 51 %; Lake Superior&ndash;7,12, and 12%; and Jenny Lake&ndash;46,13, and 36%. Cataract frequency was lower ( P < 0.05) at capture in three of the six groups recaptured in 1987 and in two of the six groups in 1988. Fish with cataracts in the 1987 recovery had survival ratios of 17&ndash;186% after 2 months in the lake and 48&ndash;67% after 14 months, compared with normal-eyed fish of the same strain. Nuclear cataract frequency was relatively stable after the first year of lake residency, when equilibrium was achieved between the increased mortality of cataract phenotypes and the rate of cataract development in normal-eyed phenotypes. Within groups, weight and length were not different between healthy fish and fish with cataracts. The absence of growth depression in fish with cataracts and the reduced survival rate suggested that faster growing fish were more susceptible to cataract formation.

North American Journal of Fisheries Management↗
USGS1993

Modeling the response of native steelhead to hatchery supplementation programs in an Idaho River

A life history model was used to predict the response of native steelhead Oncorhynchus mykiss in the Lochsa River, Idaho, to long-term supplementation with hatchery fry and smolts. The four key factors affecting the response of the native fish to a stocking program were (1) the number of native spawners, (2) the number of stocked fish, (3) the number and fitness of progeny from stocked fish, and (4) the amount of mating between hatchery and native fish. Long-term stocking of fry or smolts led to the extinction of native fish in some scenarios. The model can be used to help assess the risks and benefits of proposed stocking programs.

North American Journal of Fisheries Management↗
USGS1992

Effect of stocking season and technique on survival of lake trout in Lake Ontario

To identify the stocking season and technique that resulted in maximum contribution of hatchery‐reared lake trout Salvelinus namaycush to the population in Lake Ontario, paired lots of yearlings were stocked near shore in March, near shore in May, and offshore by helicopter in May. All mortality associated with stocking season and technique apparently had occurred by age 2. Therefore, survival comparisons were based on combined recoveries of age‐2 and older fish. We found statistically significant differences in survival ratios for 19 of 30 comparisons among individual paired lots, but results were not consistent. For example, among 17 comparisons of lake trout stocked near shore in May and offshore in May, survival was significantly better for fish stocked near shore in four cases and for fish stocked offshore in six cases. With fish stocked near shore in May used as the control group, mean survival ratios (near shore March : near shore May : offshore May) were 0.86:1.00:1.12. However, the 95% confidence interval indicated that the survival ratios were not significantly different from 1:1:1. Variables other than stocking date and technique apparently had a major influence on survival of lake trout following stocking in Lake Ontario. Predation by large salmonids may have been the dominant mechanism affecting survival.

Lake Ontario↗
USGS1992

Fyke-net and gill-net size selectivities for yellow perch in Green Bay, Lake Michigan

We estimated a fyke‐net selectivity function for yellow perch Perca flavescens in Green Bay, Lake Michigan, by comparing length‐frequency distributions of yellow perch captured in fyke nets with different mesh sizes in 1986. Using a length—girth relationship for Green Bay yellow perch, we expressed selectivity as the ratio of girth ( G ) to effective mesh perimeter ( P ), which was 5–7% less than nominal mesh perimeter. Then, fitting an existing gill‐net selectivity function to the Green Bay yellow perch fishery, we found fyke‐net and gill‐net selectivities were similar, with similar G / P ratios, but fyke nets had smaller effective mesh perimeters and thus were more efficient at capturing smaller yellow perch for any given mesh size, The derived fyke‐net selectivity function can be used to determine mesh sizes that minimize the sublegal catch of yellow perch in this fishery and could be applied to entrapment gear in other yellow perch fisheries, given data on the length–girth relationships and effective mesh perimeters.

Wisconsin↗
USGS1992

Selective dipnetting of largemouth bass during electrofishing

We electrofished 10 north‐central Texas reservoirs from 1987 through 1990 by either dipnetting all electroshocked fish (intensive dipnetting) or selectively dipnetting only fish visually identified as largemouth bass Micropterus salmoides . We compared selected indices of population structure (proportional stock density, relative stock density, and young–adult ratio) and abundance (catch per unit effort) for largemouth bass derived from data obtained with these two dipnetting techniques. No significant differences ( P > 0.17) were detected between intensive dipnetting and selective dipnetting for any of these indices of population structure, Similarly, neither the total number of largemouth bass collected per hour nor the number of small largemouth bass (<20 cm total length) collected per hour differed significantly ( P > 0.31) between dipnetting techniques.

Texas↗