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At least 1,369 records · Page 76Linked to original sources
USGS2014

A capture-recapture model of amphidromous fish dispersal

Adult movement scale was quantified for two tropical Caribbean diadromous fishes, bigmouth sleeper Gobiomorus dormitor and mountain mullet Agonostomus monticola, using passive integrated transponders (PITs) and radio-telemetry. Large numbers of fishes were tagged in Rio Mameyes, Puerto Rico, U.S.A., with PITs and monitored at three fixed locations over a 2-5 year period to estimate transition probabilities between upper and lower elevations and survival probabilities with a multistate Cormack-Jolly-Seber model. A sub-set of fishes were tagged with radio-transmitters and tracked at weekly intervals to estimate fine-scale dispersal. Changes in spatial and temporal distributions of tagged fishes indicated that neither G. dormitor nor A. monticola moved into the lowest, estuarine reaches of Rio Mameyes during two consecutive reproductive periods, thus demonstrating that both species follow an amphidromous, rather than catadromous, migratory strategy. Further, both species were relatively sedentary, with restricted linear ranges. While substantial dispersal of these species occurs at the larval stage during recruitment to fresh water, the results indicate minimal dispersal in spawning adults. Successful conservation of diadromous fauna on tropical islands requires management at both broad basin and localized spatial scales.

Journal of Fish Biology↗
USGS2014

Otolith microchemistry of tropical diadromous fishes: spatial and migratory dynamics

Otolith microchemistry was applied to quantify migratory variation and the proportion of native Caribbean stream fishes that undergo full or partial marine migration. Strontium and barium water chemistry in four Puerto Rico, U.S.A., rivers was clearly related to a salinity gradient; however, variation in water barium, and thus fish otoliths, was also dependent on river basin. Strontium was the most accurate index of longitudinal migration in tropical diadromous fish otoliths. Among the four species examined, bigmouth sleeper Gobiomorus dormitor , mountain mullet Agonostomus monticola , sirajo goby Sicydium spp. and river goby Awaous banana , most individuals were fully amphidromous, but 9-12% were semi-amphidromous as recruits, having never experienced marine or estuarine conditions in early life stages and showing no evidence of marine elemental signatures in their otolith core. Populations of one species, G. dormitor , may have contained a small contingent of semi-amphidromous adults, migratory individuals that periodically occupied marine or estuarine habitats (4%); however, adult migratory elemental signatures may have been confounded with those related to diet and physiology. These findings indicate the plasticity of migratory strategies of tropical diadromous fishes, which may be more variable than simple categorization might suggest.

Journal of Fish Biology↗
USGS1953

A modification in the technique of computing average lengths from the scales of fishes

In virtually all the studies that employ scales, otollths, or bony structures to obtain the growth history of fishes, it has been the custom to compute lengths for each individual fish and from these data obtain the average growth rates for any particular group. This method involves a considerable amount of mathematical manipulation, time, and effort. Theoretically it should be possible to obtain the same information simply by averaging the scale measurements for each year of life and the length of the fish employed and computing the average lengths from these data. This method would eliminate all calculations for individual fish. Although Van Oosten (1929: 338) pointed out many years ago the validity of this method of computation, his statements apparently have been overlooked by subsequent investigators.

Progressive Fish-Culturist↗
USGS1965

Lake trout fin-clipping rates at two national fish hatcheries

The successful stocking of the hatchery-reared lake trout (Salvelinus namaycush) in Lake Superior has imporved the outlook for rehabilitating stocks reduced to an extremely low level by predation from the sea lamprey (Petromyzon marinus). Marking the fish by fin-clipping to determine growth and survival benefits from holding young-of-the-year lake trout in the hatchery overwinter was begun in 1952-53 and continued through 1954-55. Boat and shore--and spring and fall--plants of yearlings were compared in subsequent experiments to reduce costs of planting and improve survival. Hatchery lake trout now are marked primarily to distinguish them from wild fish in assessment of natural reproduction. Year-to-year and local variations of the mark also supply information on individual plants. Recent large increases in numbers of lake trout stocked required development of an efficient, economical system of clipping fins on a mass-production basis. Data on marking rates were collected in 1958-63 at the Bureau of Sport Fisheries and Wildlifes's Pendills Creek and Charlevois National Fish Hatcheries (both in Michigan), where more than 3.5 million fish were fin-clipped.

Progressive Fish-Culturist↗
USGS1965

A review of advances in the study of diseases of fish: 1954-1964

STUDY OF DISEASE IN ANIMALS, INCLUDING MAN, has progressed rapidly in the past decade. Looking back, we find amazing success in the study of man's diseases and possibly only a little less success in studies of diseases of domesticated homeothermic animals. We who are interested in the poikilothermic animals may feel at times that we have not advanced so rapidly in our field. The reason for this may be closely associated with economics. The market for drugs and therapeutic agents is greater for domestic livestock than for cultured fishes. A larger income is derived from rearing domestic livestock. Therefore, more public funds are available for study of diseases of man and domestic livestock, while such funds are limited for the study of diseases of fish. The Federal and State fish-cultural systems, as well as colleges and universities, have been most active in research on fish disease and probably will continue to be so.

Progressive Fish-Culturist↗
USGS1988

Interrelations of oxygen concentrations, fish density, and performance of Atlantic salmon in an ozonated water reuse system

In a 16‐week study, we stocked duplicate groups of 3.3‐g Atlantic salmon ( Salmo salar ) in 25‐fish increments (25 to 100 fish/6.5‐L jar) and in 250‐fish increments (250 to 1,000 fish/144‐L trough), in an ozonated, 100% closed water reuse system, to examine changes in fish performance in response to rearing at different densities and loadings within the system. Maximum rearing density (kg!m 3 ) reached 219 in jars and 125 in troughs. Maximum loading (ratio of fish weight to water flow) reached 0.45 kg/(L/min) in jars, and 0.79 kg/(L/min) in troughs. A rise in water temperature from 18.9 to 21°C during weeks 11 and 12 was accompanied by a drop in effluent dissolved oxygen (DO), followed by an increase in mortality and a decline in biweekly weight gain. Later declines in water temperature to 18.4°C, and reductions in biomass, were followed by reduced mortality and increased weight gain. In both jars and troughs, mortality increased when dissolved oxygen dropped to 6.5 mg/L or lower, water temperature reached 19.6°C, and biomass reached 50–75 kg/m 3 , or 0.1–0.2 kg/(L/min) flow. Changes in DO, weight gain, and mortality per unit change in density (kg biomass/m 3 ), were lower in jars than in troughs, but changes in these responses in terms of flow (kg/[L/min]) were lower in troughs. Results of this study suggest that, for optimum growth, survival, and feed conversion of Atlantic salmon in an ozonated water reuse system, dissolved oxygen should be at least 6.5 mg/L. Maintenance of an acceptable level of oxygen should minimize detrimental effects offish density or elevated water temperature.

Progressive Fish-Culturist↗
USGS1958

A possible cause of sunburn in fish

A LESION DESCRIBED AS A GRAY ΡATCH GENERALLY LOCATED ΑΝΤΕRIOR TO THE DORSAL FIN has been associated with high mortality of fish on numerous occasions in production hatcheries throughout the United States. This lesion has been called "sunburn" or "backpeel." No bacteria or other pathogens have been found in fish with these symptoms. For example, at a Montana hatchery in April 1956, mortality of 10 to 15 percent occurred daily and this lesion was the only syndrome found. On occasion, shade has prevented this condition and even restored affected fish to an apparent normal condition; thus there has seemed to be a correlation between sunshine and the condition in fish. To our knowledge, this has been the only therapy attempted.

Progressive Fish-Culturist↗
USGS1960

Collection and preservation of fish and other materials exposed to pesticides

The effects of pesticides on fish have become improtant to fish conservation since World War II, when DDT first came into common use. With the development of other potent insecticides and the increasing use of massive dosages in more recent years, the threat to fish and fish foods has increased. Fishery biologists have conducted some studies on the effects of insecticides, but it has been impossible for fishery science to keep pace with chemistry and agriculture.

Progressive Fish-Culturist↗
USGS2018

What environmental conditions reduce predation vulnerability for juvenile Colorado River native fishes?

The incompatibility of native Colorado River fishes and nonnative warm-water sport fishes is well documented with predation by nonnative species causing rapid declines and even extirpation of native species in most locations. In a few rare instances native fishes are able to survive and recruit despite the presence of nonnative warm water predators, indicating that specific environmental conditions may help reduce predation vulnerability. We experimented with turbidity, artificial blue water colorant, woody debris, rocks, and aquatic vegetation in a laboratory setting to determine if any of these types of cover could reduce predation vulnerability and confer survival advantages for juvenile bonytail Gila elegans, (mean = 70 mm TL), roundtail chub Gila robusta, (mean = 35 mm TL), humpback chub Gila cypha, (mean = 67 mm TL), and razorback sucker Xyrauchen texanus (mean = 74 mm TL). Juvenile native fishes were exposed to predation by adult largemouth bass Micropterus salmoides, smallmouth bass Micropterus dolomieu, green sunfish Lepomis cyanellus, flathead catfish Pylodictis olivaris, and black bullhead catfish Ameiurus melas, in overnight trials. Turbidity above 500 NTU reduced predation vulnerability by up to 50%, for the sight-feeding predators, but increased predation vulnerability to non-sight feeding predators such as flathead catfish and bullhead catfish. Turbidity was the only treatment which appeared to significantly alter predation mortality of native prey. These results may help to explain recent patterns of wild juvenile razorback sucker recruitment at the inflow of the San Juan River into Lake Powell and the inflow of the Colorado River into Lake Mead. These are both areas of high turbidity where flathead catfish are not currently present but other nonnative sportfish are relatively abundant.

Journal of Fish and Wildlife Management↗
USGS2014

Gear and seasonal bias associated with abundance and size structure estimates for lentic freshwater fishes

All freshwater fish sampling methods are biased toward particular species, sizes, and sexes and are further influenced by season, habitat, and fish behavior changes over time. However, little is known about gear-specific biases for many common fish species because few multiple-gear comparison studies exist that have incorporated seasonal dynamics. We sampled six lakes and impoundments representing a diversity of trophic and physical conditions in Iowa, USA, using multiple gear types (i.e., standard modified fyke net, mini-modified fyke net, sinking experimental gill net, bag seine, benthic trawl, boat-mounted electrofisher used diurnally and nocturnally) to determine the influence of sampling methodology and season on fisheries assessments. Specifically, we describe the influence of season on catch per unit effort, proportional size distribution, and the number of samples required to obtain 125 stock-length individuals for 12 species of recreational and ecological importance. Mean catch per unit effort generally peaked in the spring and fall as a result of increased sampling effectiveness in shallow areas and seasonal changes in habitat use (e.g., movement offshore during summer). Mean proportional size distribution decreased from spring to fall for white bass Morone chrysops , largemouth bass Micropterus salmoides , bluegill Lepomis macrochirus , and black crappie Pomoxis nigromaculatus , suggesting selectivity for large and presumably sexually mature individuals in the spring and summer. Overall, the mean number of samples required to sample 125 stock-length individuals was minimized in the fall with sinking experimental gill nets, a boat-mounted electrofisher used at night, and standard modified nets for 11 of the 12 species evaluated. Our results provide fisheries scientists with relative comparisons between several recommended standard sampling methods and illustrate the effects of seasonal variation on estimates of population indices that will be critical to the future development of standardized sampling methods for freshwater fish in lentic ecosystems.

Iowa↗
USGS2020

Carbon dioxide-induced mortality of four species of North American fishes

Fisheries managers have a growing interest in the use of carbon dioxide (CO 2 ) as a tool for controlling invasive fishes. However, limited published data exist on susceptibility of many commonly encountered species to elevated CO 2 concentrations. Our objective was to estimate the 24-h 50% lethal concentration (LC 50 ) and 95% lethal concentration (LC 95 ) of CO 2 for four fishes (Rainbow Trout Oncorhynchus mykiss , Common Carp Cyprinus carpio , Channel Catfish Ictalurus punctatus , and Westslope Cutthroat Trout Oncorhynchus clarkii lewisi ). In the laboratory, we exposed juvenile fish to a range of CO 2 concentrations for 24 h in unpressurized, flow-through tanks. We developed a Bayesian hierarchical model to estimate the dose-response relationship for each fish species with associated uncertainty, and estimated 24-h LC 50 and LC 95 values based on laboratory trials for each species. The minimum concentration inducing mortality differed among cold water–adapted species and warm water–adapted species groups: 150 mg CO 2 /L for Westslope Cutthroat Trout and Rainbow Trout and 225 mg CO 2 /L for Common Carp and Channel Catfish. We observed complete mortality at 275 mg CO 2 /L (38,672 microatmospheres [μatm]), 225 mg CO 2 /L (30,711 μatm), and 495 mg CO 2 /L (65,708 μatm [Common Carp]; 77,213 μatm [Channel Catfish]) for Westslope Cutthroat Trout, Rainbow Trout, and both Common Carp and Channel Catfish, respectively. There was evidence of a statistical difference between the 24-h LC 95 values of Westslope Cutthroat Trout and Rainbow Trout (245.0 [222.2–272.2] and 190.6 [177.2–207.8] mg CO 2 /L, respectively). Additionally, these values were almost half the estimated 24-h LC 95 values for Common Carp and Channel Catfish (422.5 [374.7–474.5] and 434.2 [377.2–492.2] mg CO 2 /L, respectively). Although the experimental findings show strong relationships between increased CO 2 concentration and higher mortality, additional work is required to assess the efficacy and feasibility of a CO 2 application in a field setting.

Journal of Fish and Wildlife Management↗
USGS1979

Ethyl-p-aminobenzoate (Benzocaine): efficacy as an anesthetic for five species of freshwater fish

Ethyl-p-aminobenzoate (benzocaine) was tested for its efficacy as an anesthetic for rainbow trout (Salmo gairdnerii, brown trout (Salmo truttas, northern pike (Esox lucius). carp (Cyprinus carpio), and largemouth bass (Mieropterus salmoidesi. Since benzocaine is not water soluble, it was applied with acetone as a carrier. Concentrations of 100 to 200 mg!l were required for large adult northern pike, compared with 50 to 100 mg/l for small fish. Rates of sedation and recovery were slower in cold water than in warm water. Water hardness had little influence on the activity of benzocaine. Fish were anesthetized faster and recovered more slowly in acid than in alkaline water. Benzocaine produced deep anesthesia, but concentrations that rendered the fish handleable within 5 min were generally not safe for exposures longer than 15 min. Concentrations of benzocaine efficacious for fish were not acutely toxic to eggs of coho salmon (Oncorhynchus kisutch), chinook salmon (Oncorhynchus tshauiytschas, rainbow trout, brown trout, or lake trout (Salvelinus namaycush). Benzocaine is not registered for fishery use and is neither more effective nor safer than the registered anesthetic, tricaine methanesulfonate (MS-222l.

Investigations in Fish Control↗
USGS1967

A comparison of Oregon pellet and fish-meat diets for administration of sulfamethazine to Chinook salmon

The absorption of sulfamethazine by yearling spring chinook salmon ( Oncorhynchus tshawytscha ) was compared when administered in the Oregon Pellet and a fish-meat diet. The pelleted diet delivered the drug to the fish approximately twice as efficiently as the fish-meat diet. Dosage levels are recommended for both diets, and the efficacy of administering drugs in fish feed is discussed.

Oregon↗
USGS2022

Climate change and fishes in estuaries

This chapter provides an overview of the main drivers of change in estuarine systems, their expected causes and impacts on estuarine fish and fisheries. An analysis of global, regional and local patterns of estuarine fish and how climate-induced change may impact estuarine systems and their fish communities is provided. We also examine the main environmental, climatic and biological stressors likely to impact estuarine fish and associated fisheries. A set of case studies is used to illustrate the differences in potential impacts associated with various global regions and types of estuaries. An understanding of climate change in estuaries will support estuarine ecosystem resilience, inform management and facilitate adaptation.

Book chapter↗
USGS2013

Effects of isolation and fishing on the marine ecosystems of Easter Island and Salas y Gómez, Chile

1. An expedition to Salas y Gómez and Easter islands was conducted to develop a comprehensive baseline of the nearshore marine ecosystem, to survey seamounts of the recently created Motu Motiro Hiva Marine Park (MMHMP) – a no-take marine reserve of 150 000 km2 – and to compare these results with Easter Island where the marine ecosystem is similar but has no marine protection. 2. Live coral cover was surprisingly high at both Easter Island (53%) and Salas y Gómez (44%), especially considering their sub-tropical location, high wave energy environments, and geographic isolation. 3. Endemic and regionally-endemic species comprised 77% of the fish abundance at Easter Island and 73% at Salas y Gómez. Fish biomass at Salas y Gómez was relatively high (1.2 t ha-1) and included a large proportion of apex predators (43%), whereas at Easter Island it was almost three times lower (0.45 t ha-1) with large predators accounting for less than 2% of the biomass, despite good habitat quality. 4. The large cohort of small sharks and the absence of larger sharks at Salas y Gómez suggest mesopredator release consistent with recent shark fishing. The fish fauna at the seamounts between Easter Island and Salas y Gómez, outside of MMHMP, harboured 46% endemic species, including a new species of damselfish (Chromis sp. nov.) and probably a new species of Chimaera (Hydrolagus). Numerous seamounts adjacent to Salas y Gómez are currently not included in the MMHMP. 5. This expedition highlights the high biodiversity value of this remote part of the Pacific owing to the uniqueness (endemicity) of the fauna, large apex predator biomass, and geographic isolation.

Aquatic Conservation: Marine and Freshwater Ecosys↗
USGS2020

Spatial and temporal trends in Potomac River fish abundance linked to species traits

Analysis of species abundance trends can inform an understanding of the underlying mechanisms. We evaluated spatial and temporal trends in fish species abundance in the non-tidal Potomac River (USA) from a dataset comprising 2841 seine-hauls with > 250,000 individual fish records across 10 sites and 43 years (1975-2017). The dataset contained 47 species from 7 taxonomic families, with species richness and abundance dominated by leuciscids, centrarchids, and percids (85% and 95% of the total dataset, respectively). We used linear modeling and bootstrapping techniques to estimate spatial and temporal trends in abundance (CPUE) for 38 species, excluding the rarest taxa (< 30 individuals). Spatial trends in abundance were detected for 22 species (58%), of which 15 were more abundant downstream than upstream and 7 were more abundant upstream than downstream. Temporal trends in abundance were detected for 25 species (66%), of which 15 increased over time and 10 decreased over time. Spatial trends were associated with reproductive life history strategies: egg-attachers and viviparous fishes generally increased in a downstream direction, whereas species with other reproductive modes and relatively short spawning durations (< ~2 months) showed the opposite spatial trend. Temporal trends were associated with reproductive guilds and range area (a surrogate for environmental tolerance): egg-attachers and nest-associates generally increased in abundance over time, whereas broadcast spawners, clean-gravel spawners, and nest-guarders with relatively small range areas (< ~ 1.2 million km2) tended to decrease over time. This study provides an analysis of one of the largest systematic collections of freshwater fishes to our knowledge and provides a framework to evaluate mechanisms underlying observed trends.

Potomac River↗
USGS2025

Linking permafrost to the abundance, biomass, and energy density of fish in Arctic headwater streams

Permafrost thaw alters groundwater flow, river hydrology, stream-catchment interactions, and the availability of carbon and nutrients in headwater streams. The impact of permafrost on watershed hydrology and biogeochemistry of headwater streams has been demonstrated, but there is little understanding of how permafrost influences fish in these ecosystems. We examined relations among permafrost characteristics, the resulting changes in water temperature, stream hydrology (e.g., discharge flashiness), and macroinvertebrates, with the abundance, biomass, and energy density of juvenile Dolly Varden ( Salvelinus malma ) and Arctic Grayling ( Thymallus arcticus ) across 10 headwater streams in northwestern Alaska. Macroinvertebrate density was driven by concentrations of dissolved carbon and nutrients supporting stream food webs. Dolly Varden abundance was primarily related to water temperature with fewer fish in warmer streams, whereas Dolly Varden energy density decreased with the flashiness of the headwater streams. Dolly Varden biomass was related to both temperature and bottom-up food web effects. The energy density of Arctic Grayling decreased with warmer temperatures and discharge flashiness. These relations demonstrate the importance of terrestrial–aquatic connections in permafrost landscapes and indicate the complexity of landscape effects on fish. Because permafrost thaw is one of the most impactful changes occurring as the Arctic warms, an improved understanding of how stream temperature, hydrology, and bottom-up food web processes influence fish populations can aid forecasting of future conditions across the Arctic.

Alaska↗
USGS2025

Invasive predatory fish occupies highest trophic position leading to expansion of isotopic niches in a riverine food web

Invasive species are drivers of ecological change with the potential to reshape the structure and function of terrestrial and aquatic ecosystems. The invasive flathead catfish ( Pylodictis olivaris ) is an opportunistic predator that has established a rapidly growing population in the Susquehanna River, Pennsylvania, USA, since they were first detected in 2002. Although the predatory effects of invasive catfishes on native fish communities have been documented, the effects of invasion on riverine food webs are poorly understood. This study quantified the effects of invasive flathead catfish on the trophic position (TP) and isotopic niche of the river's food web by comparing invaded and non-invaded sites. In addition to flathead catfish, the food web components examined included crayfish, minnows, and two ecologically and socioeconomically important fish species: the smallmouth bass ( Micropterus dolomieu ) and channel catfish ( Ictalurus punctatus ). We found that flathead catfish occupied the highest TP, with a posterior mean TP of 3.08 (95% credible interval = [2.71, 3.42]), exceeding that of the two resident fish predators, the smallmouth bass and channel catfish. The TP of the resident channel catfish, which occupies a similar ecological niche, declined after flathead catfish invasion. In fact, there was a 0.92 posterior probability that channel catfish TP was lower in invaded sites than at non-invaded sites. Using a Bayesian bivariate ellipses analysis, we found overwhelming evidence of isotopic niche expansion and overlap for all components of the food web in the presence of flathead catfish. These findings support the “trophic disruption hypothesis,” where an introduced species prompts resident species to change diets in an attempt to avoid competition and predation following invasion. Our results indicate that flathead catfish invasion is altering food web structure and energy flow in a large riverine ecosystem and contributes to the breadth of knowledge regarding how ecosystems may respond to the introduction of a large predatory fish species.

Pennsylvania↗