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At least 1,729 records · Page 96Linked to original sources
USGS1968

Rehabilitation of lake trout in the Apostle Islands region of Lake Superior

Marked success of rehabilitation of lake trout in Lake Superior has been due principally to the control of the sea lamprey and closure of the lake trout fishery in 1962 and large-scale plantings of yearling lake trout in 1959-66. After the sea lamprey became established in the late 1940s, spawning stocks of lake trout began to decrease and were almost nonexistent by 1960-61. After control of the sea lamprey and closure of the commercial fishery for lake trout in 1962, the abundance of spawning stocks began to rise and reached the highest levels on record in 1964-66. Successful spawning in 1964 and 1965 was demonstrated by catches of age-0 lake trout in 1965 and 1966, the first evidence of natural reproduction since 1959. Plantings of hatchery-reared lake trout in Wisconsin waters of Lake Superior began in 1952. The percentage of hatchery-reared fish in catches of juvenile lake trout increased almost steadily from 1953 to 1965 (when nearly all were of hatchery origin). The abundance of juvenile fish increased from 1959 to 1962 and remained nearly constant in 1962-66. The success of lake trout plantings was highest in 1959-61 but generally declined after 1961; the success of the plantings was inversely related to the abundance of older lake trout. Annual increments of growth of hatchery-reared lake trout varied from 1.1 to 5.0 inches after planting. The average lengths of fish of identical age-groups varied according to gear of capture, depth of water, and season. More than 65% of the season's growth of age-III lake trout took place after September. The findings indicate that the present rate of stocking lake trout may be higher than necessary to maintain optimum abundance.

Journal of the Fisheries Research Board of Canada↗
USGS2025

Dead giveaway: Rising mortality rates suggest effectiveness of Lake Erie grass carp (Ctenopharyngodon idella) response

Grass carp ( Ctenopharyngodon idella ) are large, invasive fish that threaten Lake Erie’s economy and ecosystem. Incidental catches of grass carp have occurred since the 1980s in Lake Erie, while multi-day removal events were carried out in 2014 and 2017. To mitigate ecosystem impacts, a large-scale, multi-agency response to remove as many grass carp as possible from the Lake Erie basin (“strike teams”) began in 2018 and has increased every year. To date, total annual removals of fish has been the primary measure of progress; however, total annual removals do not indicate how efforts are affecting the grass carp population. Population vital rates, such as mortality rate, can indicate population demographic changes and may provide an alternative approach to measure how removals have impacted the grass carp population. We estimated annual mortality rates using 553 grass carp, representing 82.9 % of all grass carp removed in the Lake Erie basin, using a hierarchical catch-curve model and catch-at-age data from 2014 to 2022. Annual average mortality rates were initially low (4.3 %) and increased between 2017 and 2022 with the highest mortality (13.6 %) observed in 2021. Positive correlations between mortality and the number of fish harvested per year suggest that removals may be driving increases in the grass carp mortality rate. This increase in mortality rate shows promise for controlling the spread of grass carp within the Lake Erie ecosystem. This research supports the needs of fishery managers to better understand grass carp population dynamics and the adaptive management framework identified in the Lake Erie Grass Carp Adaptive Response Strategy.

Lake Erie↗
USGS1997

Potential error with in situ surveys of smallmouth bass, Micropterus dolomieu Lacepede, as determined by radio-telemetry

In situ surveys using scuba are important tools in the management of smallmouth bass (Micropterus dolomieu) in boreal, clear lakes of North America. Population estimates that are derived from such surveys may be erroneous if the size composition of the fish observed by divers differs from that of the entire population. Forty-four adult smallmouth bass of three size classes were radio-tagged and tracked during the summer of 1993 (mid June to early September) in Green Lake, Maine, USA, to investigate possible size-related error from observations by divers being towed along the lake shore. Our results indicate that scuba divers may fail to count a significant portion of large smallmouth bass during late summer (mid July to early September), compared to small- or medium-sized fish. The results suggest that scuba surveys should be conducted during early summer (mid June to mid July) to derive more accurate population estimates.

Fisheries Research↗
USGS2011

Abundance, stock origin, and length of marked and unmarked juvenile Chinook salmon in the surface waters of greater Puget Sound

This study focuses on the use by juvenile Chinook salmon Oncorhynchus tshawytscha of the rarely studied neritic environment (surface waters overlaying the sublittoral zone) in greater Puget Sound. Juvenile Chinook salmon inhabit the sound from their late estuarine residence and early marine transition to their first year at sea. We measured the density, origin, and size of marked (known hatchery) and unmarked (majority naturally spawned) juveniles by means of monthly surface trawls at six river mouth estuaries in Puget Sound and the areas in between. Juvenile Chinook salmon were present in all months sampled (April–November). Unmarked fish in the northern portion of the study area showed broader seasonal distributions of density than did either marked fish in all areas or unmarked fish in the central and southern portions of the sound. Despite these temporal differences, the densities of marked fish appeared to drive most of the total density estimates across space and time. Genetic analysis and coded wire tag data provided us with documented individuals from at least 16 source populations and indicated that movement patterns and apparent residence time were, in part, a function of natal location and time passed since the release of these fish from hatcheries. Unmarked fish tended to be smaller than marked fish and had broader length frequency distributions. The lengths of unmarked fish were negatively related to the density of both marked and unmarked Chinook salmon, but those of marked fish were not. These results indicate more extensive use of estuarine environments by wild than by hatchery juvenile Chinook salmon as well as differential use (e.g., rearing and migration) of various geographic regions of greater Puget Sound by juvenile Chinook salmon in general. In addition, the results for hatchery‐generated timing, density, and length differences have implications for the biological interactions between hatchery and wild fish throughout Puget Sound.

Washington↗
USGS2012

Habitat associations of fish species of greatest conservation need in wadeable Iowa streams

Fish and habitat data were collected from 84 wadeable stream reaches in the Mississippi River drainage of Iowa to predict the occurrences of seven fish species of greatest conservation need and to identify the relative importance of habitat variables measured at small (e.g., depth, velocity, and substrate) and large (e.g., stream order, elevation, and gradient) scales in terms of their influence on species occurrences. Multiple logistic regression analysis was used to predict fish species occurrences, starting with all possible combinations of variables (5 large-scale variables, 13 small-scale variables, and all 18 variables) but limiting the final models to a maximum of five variables. Akaike's information criterion was used to rank candidate models, weight model parameters, and calculate model-averaged predictions. On average, the correct classification rate (CCR = 80%) and Cohen's kappa (κ = 0.59) were greatest for multiple-scale models (i.e., those including both large-scale and small-scale variables), intermediate for small-scale models (CCR = 75%; κ = 0.49), and lowest for large-scale models (CCR = 73%; κ = 0.44). The occurrence of each species was associated with a unique combination of large-scale and small-scale variables. Our results support the necessity of understanding factors that constrain the distribution of fishes across spatial scales to ensure that management decisions and actions occur at the appropriate scale.

Iowa↗
USGS2025

Staying alive: Post-translocation apparent survival of fishes in headwater springs following drought

Objective Increasing fragmentation from constructed barriers, increased water use, and climate change limits the resiliency of stream fish metapopulations by reducing colonization. Management actions such as stocking or translocating fish may help contribute to the resilience of isolated habitats and increase redundancy of populations in intermittent stream networks. Our objective was to determine whether translocating fish into prairie headwater refuges could reestablish or supplement isolated populations. Methods We examined apparent survival and probability of detection of four native, small-bodied fishes that were translocated in 2022 and 2023 to prairie headwater refuges that were affected by a severe drought and experienced slow recovery of their fish assemblages. All the fish were marked with passive integrated transponder tags, allowing us to use a mark–recapture framework to track the fate of these fish. Results Apparent survival was predicted by an interaction between time and translocation site, indicating an important consideration of environmental factors. Approximately one-quarter of the fish remained at site A through the summer of both years, whereas estimates were near zero at site B in both years and mixed across years at site C. The decreases in apparent survival probabilities following flow events suggest that fish may be emigrating during these periods of reconnection. During the lower flow year, more fish remained at the headwater sites and young-of-year fish were captured during long-term sampling, suggesting that the translocated fish reproduced. Conclusions The success of translocation projects will depend on a variety of factors, including management goals, habitat, and hydrology, but the initially high survival reported in this study is encouraging. Difficulties with examining the movement of small fish during hydrologic events limited our conclusions about the relative contributions of mortality and emigration to apparent survival estimates. Despite low yearly apparent survival, we found evidence of reproduction from translocated fish, suggesting that the reestablishment of a viable population is possible.

North American Journal of Fisheries Management↗
USGS2012

Oceanographic gradients and seabird prey community dynamics in glacial fjords

Glacial fjord habitats are undergoing rapid change as a result of contemporary global warming, yet little is known about how glaciers influence marine ecosystems. These ecosystems provide important feeding, breeding and rearing grounds for a wide variety of marine organisms, including seabirds of management concern. To characterize ocean conditions and marine food webs near tidewater glaciers, we conducted monthly surveys of oceanographic variables, plankton, fish and seabirds in Kenai Fjords, Alaska, from June to August of 2007 and 2008. We also measured tidal current velocities near glacial features. We found high sediment load from glacial river runoff played a major role in structuring the fjord marine ecosystem. Submerged moraines (sills) isolated cool, fresh, stratified and silt-laden inner fjord habitats from oceanic influence. Near tidewater glaciers, surface layers of turbid glacial runoff limited availability of light to phytoplankton, but macrozooplankton were abundant in surface waters, perhaps due to the absence of a photic cue for diel migration. Fish and zooplankton community structure varied along an increasing temperature gradient throughout the summer. Acoustic measurements indicated that low density patches of fish and zooplankton were available in the surface waters near glacial river outflows. This is the foraging habitat occupied most by Kittlitz's murrelet (Brachyramphus brevirostris), a rare seabird that appears to be specialized for life in glacially influenced environments. Kittlitz's murrelets were associated with floating glacial ice, and they were more likely to occur near glaciers, in deeper water, and in areas with high acoustic backscatter. Kittlitz's murrelet at-sea distribution was limited to areas influenced by turbid glacial outflows, and where prey was concentrated near the surface in waters with low light penetration. Tidewater glaciers impart unique hydrographic characteristics that influence marine plankton and fish communities, and this has cascading effects on marine food webs in these ecosystems.

Fisheries Oceanography↗
USGS2021

It’s complicated…environmental DNA as a predictor of trout and char abundance in streams

The potential to provide inferences about fish abundance from environmental (e)DNA samples has generated great interest. However, the accuracy of these abundance estimates is often low and variable across species and space. A plausible refinement is the use of common aquatic habitat monitoring data to account for attributes that influence eDNA dynamics. We therefore evaluated the relationships between eDNA concentration and abundance of bull trout ( Salvelinus confluentus ), westslope cutthroat trout ( Oncorhynchus clarkii lewisi ) and rainbow trout ( Oncorhynchus mykiss ) at 42 stream sites in the Intermountain West (USA and Canada) and tested whether accounting for site-specific habitat attributes improved the accuracy of fish abundance estimates. eDNA concentrations were positively associated with fish abundance, but these relationships varied by species and site, and there was still considerable variation unaccounted for. Random site-level differences explained much of this variation, but specific habitat attributes of those sites explained relatively small amounts of this variation. Our results underscore that either eDNA sampling or environmental characterization will require further refinement before eDNA can be used reliably to estimate fish abundance in streams.

Idaho, Montana, Oregon, Washington↗
USGS2021

Partial migration and spawning movements of humpback chub in the Little Colorado River are better understood using data from autonomous PIT tag antennas

Choosing whether or not to migrate is an important life history decision for many fishes. Here we combine data from physical captures and detections on autonomous passive integrated transponder (PIT) tag antennas to study migration in an endangered fish, the humpback chub (Gila cypha). We develop hidden Markov mark-recapture models with and without antenna detections and find that the model fit without antenna detections misses a large proportion of fish and underestimates migration and survival probabilities. We then assess survival and growth differences associated with life history strategy and migration for different demographic groups (small male, small female, large male, large female). We find large differences in survival according to life history strategy, where residents had much lower over-winter survival than migrants. However, within the migratory life history strategy, survival and growth were similar for active migrants and skipped migrants for all demographic groups. We discuss some common challenges to incorporating detections from autonomous antennas into population models and demonstrate how these data can provide insight about fish movement and life history strategies.

Arizona↗
USGS1965

Oral immunization of rainbow trout ( Salmo gairdneri ) against an etiologic agent of "redmouth disease"

Rainbow trout were fed a pelleted diet containing killed cells of the etiologic agent of a bacterial disease, redmouth. These fish in addition to appropriate controls were subsequently challenged with virulent homologous organisms. Ninety per cent of the redmouth immunized fish survived the basic challenge using virulent organisms in contrast to 20% survival for the controls. Multiple challenge doses at increased levels also are discussed.

Journal of the Fisheries Research Board of Canada↗
USGS1942

Growth of the rock bass, Ambloplites rupestris (Rafinesque), in five lakes of northeastern Wisconsin

The forms of the growth curves of rock bass from four lakes in northeastern Wisconsin with medium-hard to hard water bore a general resemblance to each other, but differed sharply from the curve for rock bass from a lake with extremely soft water. With the exception of a slight increase in growth in the third year of life the annual increments of length of the rock bass of Nebish Lake (4.0 p.p.m. of bound CO 2 ) tended to decrease consistently beyond the first year. The good first-year growth in length of rock bass of Allequash, Silver, and Trout Lakes (16.8, 15.0, and 18.7 p.p.m., respectively, of bound CO 2 ) was followed by poor growth in the second, third, and fourth years of life. This poor growth was followed in turn by good growth in the fifth and sixth years. The annual increments of length tended to decline beyond the sixth year of life. The growth of rock bass of Muskellunge Lake (10.0 p.p.m. of bound CO 2 ) declined sharply in the second year of life. The annual increments of length were fairly constant in the second to seventh years, inclusive, but declined beyond the seventh year. In each lake the males grew more rapidly than the females. The time of attainment of the legal total length of 7 inches in the different lakes ranged from late in the sixth growing season in Nebish and Trout Lakes to the middle of the eighth growing season in Muskellunge Lake. Rock bass of corresponding length from Allequash, Silver, and Trout Lakes were so nearly of the same weight that one curve described the length-weight relationship of the three stocks. Muskellunge Lake rock bass were considerably lighter than fish of the same length from these three lakes, and Nebish Lake rock bass were somewhat lighter than those from Muskellunge Lake.

Transactions of the American Fisheries Society↗
USGS1963

Diffusion of herbicides through plastic film

Plastic film have been used by fishery workers as barriers to subdivide experimental ponds in order to assess the value of some chemical treatment, and as test vessels to contain dilute solutions or suspensions of toxic chemicals in experiments conducted to establish tolerance levels of these chemicals for fish.

Progressive Fish-Culturist↗
USGS1963

Persistence of DDT and its metabolites in a farm pond

A farm pond near Morrison, Colorado, was treated with 0.02 p.p.m. of DDT in June 1961. The persistence and distribution of the insecticide in materials sampled from the aquatic environment were studied until November 1962. Detectable amounts of DDT were not found in the water after 3 weeks. Residues in the mud had declined within 8 weeks after the treatment to levels not significantly higher than pre-treatment levels, but a sample of vegetation still contained relatively high levels of residues. From this time until the second summer, sufficient vegetation was not present to provide a sample for chemical analysis. A new crop of vegetation sampled 1 year after the treatment contained residues approximating pre-treatment levels. Fish accumulated 3 to 4 p.p.m. of DDT and its metabolites within 1 month after the treatment. The residue levels slowly declined after this, but when the study was terminated, 2 to 3 p.p.m. of the metabolites DDD and DDE still remained in the fish. The highest residue levels measured in crayfish were about one-half of those found in fish. Some mortality of the more susceptible fish and invertebrates occurred as a result of the DDT treatment; however, severe adverse effects were not demonstrated.

Transactions of the American Fisheries Society↗
USGS1984

Biotic and abiotic influences on corticosteroid hormone rhythms in channel catfish

Plasma‐corticosteroid concentrations in resting channel catfish Ictalurus punctatus held at 21 C varied only slightly during a 24‐hour period; further, increases in hormone concentrations induced by confinement stress were independent of time of day and photoperiod. Temperature strongly affected both resting corticosteroid concentrations and the dynamics of hormone secretion when fish were stressed. Resting concentrations were greatest in fish acclimated to 5 and 10 C (25–29 ng/ml), sharply lower in fish held at 15, 20, or 21 C (5–9 ng/ml), and intermediate in fish maintained at 25, 30, or 35 C (12–13 ng/ml). Hormone concentrations increased when fish were stressed by confinement. Corticosteroid concentrations hardly changed in fish held at 5 or 10 C, but increased markedly in fish at higher temperatures; in addition the response was more delayed at the lower temperatures.

Transactions of the American Fisheries Society↗
USGS1988

Use of diagnostic bones to identify and estimate original lengths of ingested prey fishes

We examined and measured cleithra, dentaries, opercles, and pharyngeal arches – bones found to persist during digestion of most prey fish – to identify 24 prey fish species and back-calculate their original fork length. Eighteen of the 24 species examined could be easily distinguished; however, for certain congenerics, identification was neither consistent nor reliable for all bones within the size ranges examined. Relations between bone length and fish length were linear for 14 species for which the sample sizes were adequate ( N > 30); coefficients of determination ( r 2 ) ranged from 0.79 to 0.99. Diagnostic characteristics and measurements of these bones provided reliable identification of genera and species and estimates of original fork lengths of partly digested prey fish from three predators. This method, compared with that of examining only prey fish in a measurable condition, greatly increased the amount of dietary information available from gut analysis.

Transactions of the American Fisheries Society↗
USGS1991

Variation in feeding, aggression, and position choice between hatchery and wild cutthroat trout in an artificial stream

I compared feeding, aggressive behavior, and spatial distribution of differently ranked individuals of hatchery and wild coastal cutthroat trout Oncorhynchus clarki clarki in an artificial stream. Both hatchery and wild groups established stable dominance hierarchies that seemed to be based on size differences. Hatchery and wild fish within a hierarchical rank fed at similar rates. Hatchery fish were more aggressive than their wild conspecifics, irrespective of rank. Dominant hatchery fish were evenly distributed in pools and riffles, whereas dominant wild fish were three times more often in pools than in riffles. In both groups, socially intermediate fish were almost evenly distributed between pools and riffles, and subordinate fish spent most of their time in pools. On average, hatchery fish spent 57% of their time in pools and 43% in riffles, whereas wild fish spent 71% of their time in pools and 29% in riffles. These results support the hypothesis that excessive expenditure of energy for unnecessary aggression, use of fast-flowing water, or other purposes contributes to poor survival of hatchery fish after they are stocked in streams. Poor survival would reduce the efficacy of using hatchery stocks to supplement wild production.

Transactions of the American Fisheries Society↗
USGS1991

An intergeneric hybrid of a native minnow, the golden shiner, and an exotic minnow, the rudd

The hybrid golden shiner Notemigonus crysoleucas × rudd Scardinius erythrophthalmus is the first known nonsalmonid, intergeneric hybrid of an exotic species and a North American native species. The cross is also the first valid record of a viable hybrid involving the native golden shiner. Meristic and mensural characters of 30 artificially produced hybrids of male golden shiners and female rudds were analyzed. Forty-seven percent of the meristic traits exhibited character states intermediate between those of parents. Twenty-seven percent of the meristic characters were supernumerary, suggesting developmental instability of the hybrid genome. Mensural hybrid characters were significantly skewed to the golden shiner phenotype. The skewed mensural inheritance and other skewed patterns of morphological inheritance also suggest problems in canalization of the hybrid phenome or atypical patterns of dominance. All hybrids were identifiable by intermediate squamation of the cultrate abdomen: the keel was mostly scaled but exhibited a small fleshy ridge posteriorly. This minnow hybrid allows general inferences to be made about the phylogenetic affinity of the golden shiner to other cultrate cyprinids of Eurasia. The hybrid cross has important management and conservation implications for fishes in North America. The hybrid is an example of how an exotic species may negatively affect a native species.

Transactions of the American Fisheries Society↗
USGS1998

Early life history stages of Gulf sturgeon in the Suwannee River, Florida

Egg sampling confirmed that Suwannee River Gulf sturgeon Acipenser oxyrinchus desotoi , a subspecies of Atlantic sturgeon A. o. oxyrinchus use the same spawning site at river kilometer (rkm) 215 from the mouth of the river each year. Forty-nine eggs were recorded in 1995, and 368 were recorded in 1996. Spawning began 4–7 d after the March new moon in both years and lasted 10–11 d; in 1996, a second 10-d spawning round began on the April new moon. Developmental synchrony among eggs recovered suggested several discrete spawning events in both years. Total eggs deposited for three 1996 sampling days was estimated as 405,600–711,000/d, approximating the fecundity range of a large female Gulf sturgeon . Eggs were found only in the southern half of the river , an area with surface currents of 0.5–1.5 m/s and numerous eddies producing reverse bottom currents of 0.1–0.5 m/s. Egg substrate consisted of bedrock limestone thinly overlain by fine sand and densely distributed elliptical gravel 2–10 cm in diameter. Eggs were found predominantly in depths of 2–4 m at water temperatures of 17–21°C, conductivities of 50–100 μS, and dissolved oxygen levels exceeding 5.0 mg/L. The Cody Scarp, 15 rkm above the spawning ground, may mark the upstream limit of spawning areas in the river . Three 2–4-month-old riverine juveniles (82–115 mm total length, TL) collected are the smallest yet captured from any river . Data for 18 riverine age-0 juveniles (to 350 mm TL) suggest that this stage lasts 6–10 months, terminating with migration of fish to the river mouth in January–February. Less than 2% of 461 juveniles captured at the estuarine river mouth (1990–1993) were under 350 mm TL. Riverine age-0 fish were collected over long shallow stretches (typically <4 m deep) of relatively barren sand (rkm 12–238).

Florida↗