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At least 883 records · Page 49Linked to original sources
USGS2017

Response of fish population dynamics to mitigation activities in a large regulated river

Extensive water development in large rivers has precipitated many negative ecological effects on native fish populations. Mitigation for such development often focuses on restoring biological integrity through remediation of the physical and chemical properties of regulated rivers. However, evaluating and defining the success of those programs can be difficult. We modeled the influence of mitigation-related environmental factors on growth and recruitment of two ecologically important native fish species (Largescale Sucker Catostomus macrocheilus and Mountain Whitefish Prosopium williamsoni ) in the Kootenai River, Idaho. Artificial nutrient (phosphorus) addition best predicted the variability in annual growth of both species. Nutrient addition was positively related to Largescale Sucker growth but negatively related to Mountain Whitefish growth. The best model explained 82% of the annual variability in incremental growth for Largescale Suckers and 61% of the annual variability for Mountain Whitefish. Year-class strength of Largescale Suckers was not closely related to any of the environmental variables evaluated; however, year-class strength of Mountain Whitefish was closely associated with nutrient addition, discharge, and temperature. Most research has focused on biotic assemblages to evaluate the effects of mitigation activities on fishes, but there is an increased need to identify the influence of rehabilitation activities on fish population dynamics within those assemblages. Here, we demonstrate how fish growth can serve as an indicator of rehabilitation success in a highly regulated large river. Future fish restoration projects can likely benefit from a change in scope and from consideration of an evaluation framework involving the response of population rate functions to mitigation.

Idaho↗
USGS2013

Hybrid seine for full fish community collections

Seines are simple and effective fish collection gears, but the net mesh size influences how well the catch represents the fish communities. We designed and tested a hybrid seine with a dual-mesh bag (1/4″ and 1/8″) and compared the fish assemblage collected by each mesh. The fine-mesh net retained three times as many fish and collected more species (as many as eight), including representatives of several rare species, than did the coarser mesh. The dual-mesh bag permitted us to compare both sizes and species retained by each layer and to develop species-specific abundance correction factors, which allowed comparison of catches with the coarse-mesh seine used for earlier collections. The results indicate that a hybrid seine with coarse-mesh wings and a fine-mesh bag would enhance future studies of fish communities, especially when small-bodied fishes or early life stages are the research focus.

Journal of Freshwater Ecology↗
USGS2015

The influence of a severe reservoir drawdown on springtime zooplankton and larval fish assemblages in Red Willow Reservoir, Nebraska

Reservoirs can be dynamic systems, often prone to unpredictable and extreme water-level fluctuations, and can be environments where survival is difficult for zooplankton and larval fish. Although numerous studies have examined the effects of extreme reservoir drawdown on water quality, few have examined extreme drawdown on both abiotic and biotic characteristics. A fissure in the dam at Red Willow Reservoir in southwest Nebraska necessitated an extreme drawdown; the water level was lowered more than 6 m during a two-month period, reducing reservoir volume by 76%. During the subsequent low-water period (i.e., post-drawdown), spring sampling (April–June) showed dissolved oxygen concentration was lower, while turbidity and chlorophyll- a concentration were greater, relative to pre-drawdown conditions. Additionally, there was an overall increase in zooplankton density, although there were differences among taxa, and changes in mean size among taxa, relative to pre-drawdown conditions. Zooplankton assemblage composition had an average dissimilarity of 19.3% from pre-drawdown to post-drawdown. The ratio of zero to non-zero catches was greater post-drawdown for larval common carp and for all larval fishes combined, whereas we observed no difference for larval gizzard shad. Larval fish assemblage composition had an average dissimilarity of 39.7% from pre-drawdown to post-drawdown. Given the likelihood that other dams will need repair or replacement in the near future, it is imperative for effective reservoir management that we anticipate the likely abiotic and biotic responses of reservoir ecosystems as these management actions will continue to alter environmental conditions in reservoirs.

Nebraska↗
USGS2012

A prototype splitter apparatus for dividing large catches of small fish

Due to financial and time constraints, it is often necessary in fisheries studies to divide large samples of fish and estimate total catch from the subsample. The subsampling procedure may involve potential human biases or may be difficult to perform in rough conditions. We present a prototype gravity-fed splitter apparatus for dividing large samples of small fish (30–100 mm TL). The apparatus features a tapered hopper with a sliding and removable shutter. The apparatus provides a comparatively stable platform for objectively obtaining subsamples, and it can be modified to accommodate different sizes of fish and different sample volumes. The apparatus is easy to build, inexpensive, and convenient to use in the field. To illustrate the performance of the apparatus, we divided three samples (total N = 2,000 fish) composed of four fish species. Our results indicated no significant bias in estimating either the number or proportion of each species from the subsample. Use of this apparatus or a similar apparatus can help to standardize subsampling procedures in large surveys of fish. The apparatus could be used for other applications that require dividing a large amount of material into one or more smaller subsamples.

North American Journal of Fisheries Management↗
USGS2017

Earning their stripes: The potential of tiger trout and other salmonids as biological controls of forage fishes in a western reservoir

Maintaining a balance between predator and prey populations can be an ongoing challenge for fisheries managers, especially in managing artificial ecosystems such as reservoirs. In a high-elevation Utah reservoir, the unintentional introduction of the Utah Chub Gila atraria and its subsequent population expansion prompted managers to experimentally shift from exclusively stocking Rainbow Trout Oncorhynchus mykiss to also stocking tiger trout (female Brown Trout Salmo trutta × male Brook Trout Salvelinus fontinalis ) and Bonneville Cutthroat Trout O. clarkii utah (hereafter, Cutthroat Trout) as potential biological control agents. We measured a combination of diet, growth, temperature, and abundance and used bioenergetic simulations to quantify predator demand versus prey supply. Utah Chub were the predominant prey type for tiger trout, contributing up to 80% of the diet depending on the season. Utah Chub represented up to 70% of the total diet consumed by Cutthroat Trout. Although Utah Chub dominated the fish biomass in the reservoir, we still estimated abundances of 238,000 tiger trout, 214,000 Cutthroat Trout, and 55,000 Rainbow Trout. Consequently, when expanded to the population level of each predator, tiger trout and Cutthroat Trout consumed large quantities of Utah Chub on an annual basis: tiger trout consumed 508,000 kg (2,660 g/predator) of the standing prey population, and Cutthroat Trout consumed an estimated 322,000 kg (1,820 g/predator). The estimated combined consumption by Cutthroat Trout and tiger trout exceeded the estimate of Utah Chub annual production. As such, our results suggest that the high rates of piscivory exhibited by Cutthroat Trout and tiger trout in artificial lentic ecosystems are likely sufficient to effectively reduce the overall abundance of forage fishes and to prevent forage fishes from dominating fish assemblages. Collectively, this research provides the first documented findings on tiger trout ecology and performance, which will aid managers in designing and implementing the best stocking strategy to optimize sport fish performance, control undesirable forage fish, and enhance and maintain angler satisfaction.

Utah↗
USGS2012

Use of a storm water retention system for conservation of regionally endangered fishes

Maintaining aquatic biodiversity in urban or suburban areas can be problematic because urban landscapes can be nearly devoid of aquatic habitats other than engineered basins for storm water management. These areas are usually of questionable value for fish, but we examined a case study in which five regionally imperiled fish species were reintroduced into an artificial storm water detention pond and subsequently thrived. Although not a formal experiment, postintroduction survey data suggested that three of the five species maintained high population densities for 10 years after initial stocking, and two persisted in lower numbers. Success was likely due to a combination of unique design features and prior habitat preparation that resulted in clear water conditions that supported dense vegetation. Stocked fish persisted despite occasional bouts of low dissolved oxygen and increased chloride levels resulting from road salt application within the watershed. Transplanted fish served as a source population for both research and further reintroduction experiments. We suggest that, for some fish species, habitat preservation has a middle ground between natural habitats and completely artificial environments that require constant husbandry and that storm water systems could be used to create engineered sanctuaries within the human landscape that have many potential benefits for both humans and fish.

Fisheries↗
USGS2012

Assessment of freshwater fish assemblages and their habitats in the National Park Service system of the southeastern United States

The southeast region of the United States contains the highest diversity of freshwater fish species in the country: approximately 662 species. Existing protected areas like units of the National Park Service (NPS) should reflect this biodiversity, but there has been no broad-scale assessment. We compiled several data sets identifying native freshwater fish species distributions in and surrounding NPS units and threats to those resources. Focusing on the 26 NPS units containing only freshwater fish species, we documented 288 species within NPS boundaries. The largest NPS units tended to have the most fish species and aquatic habitat but also the greatest amount of alteration. Increasing rates of urbanization, declines in percentage agriculture land cover, and increased density of road-stream crossings in surrounding watersheds were good predictors of nonindigenous species presence within NPS unit boundaries. These results help document the role of NPS units in conserving freshwater fish diversity and, in this region, suggest that measures aimed at controlling urbanization in the adjacent watersheds could affect the diversity of freshwater fish communities in these units.

Fisheries↗
USGS2015

A simple web-based tool to compare freshwater fish data collected using AFS standard methods

The American Fisheries Society (AFS) recently published Standard Methods for Sampling North American Freshwater Fishes. Enlisting the expertise of 284 scientists from 107 organizations throughout Canada, Mexico, and the United States, this text was developed to facilitate comparisons of fish data across regions or time. Here we describe a user-friendly web tool that automates among-sample comparisons in individual fish condition, population length-frequency distributions, and catch per unit effort (CPUE) data collected using AFS standard methods. Currently, the web tool (1) provides instantaneous summaries of almost 4,000 data sets of condition, length frequency, and CPUE of common freshwater fishes collected using standard gears in 43 states and provinces; (2) is easily appended with new standardized field data to update subsequent queries and summaries; (3) compares fish data from a particular water body with continent, ecoregion, and state data summaries; and (4) provides additional information about AFS standard fish sampling including benefits, ongoing validation studies, and opportunities to comment on specific methods. The web tool—programmed in a PHP-based Drupal framework—was supported by several AFS Sections, agencies, and universities and is freely available from the AFS website and fisheriesstandardsampling.org . With widespread use, the online tool could become an important resource for fisheries biologists.

Fisheries↗
USGS2016

Biological and communication skills needed for introduced fish biologists

What skills and knowledge will a new graduate seeking employment need to work with introduced fishes? Clearly, success in introduced species management—similar to other disciplines in fisheries—requires a mixture of scientific and communication skills. However, specific abilities especially important to a biologist who manages introduced fishes should be highlighted. Unlike most other management strategies, stocking an introduced species can result in unintended and irreversible impacts, so particular care must be employed when stocking is considered. Furthermore, fish populations in areas outside of the introduced species management area might also be affected, usually negatively, if the introduced fish escapes. Therefore, rock-solid knowledge of basic aquatic ecology, including risk management; fish taxonomy (so the wrong fish species is not mistakenly stocked!); familiarity with human values of both the time and the place (which requires communication skills); and a strong understanding of human history are all important.

Fisheries↗
USGS2017

Grand challenges in the management and conservation of North American inland fishes and fisheries

Even with long-standing management and extensive science support, North American inland fish and fisheries still face many conservation and management challenges. We used a grand challenges approach to identify critical roadblocks that if removed would help solve important problems in the management and long-term conservation of North American inland fish and fisheries. We identified seven grand challenges within three themes (valuation, governance, and externalities) and 34 research needs and management actions. The major themes identified are to (1) raise awareness of diverse values associated with inland fish and fisheries, (2) govern inland fish and fisheries to satisfy multiple use and conservation objectives, and (3) ensure productive inland fisheries given nonfishing sector externalities. Addressing these grand challenges will help the broader community understand the diverse values of inland fish and fisheries, promote open forums for engagement of diverse stakeholders in fisheries management, and better integrate the inland fish sector into the greater water and land use policy process.

Fisheries↗
USGS2013

Water levels shape fishing participation in flood-control reservoirs

We examined the relationship between fishing effort (hours fished) and average March–May water level in 3 flood control reservoirs in Mississippi. Fishing effort increased as water level rose, peaked at intermediate water levels, and decreased at high water levels. We suggest that the observed arched-shaped relationship is driven by the shifting influence of fishability (adequacy of the fishing circumstances from an angler's perspective) and catch rate along a water level continuum. Fishability reduces fishing effort during low water, despite the potential for higher catch rates. Conversely, reduced catch rates and fishability at high water also curtail effort. Thus, both high and low water levels seem to discourage fishing effort, whereas anglers seem to favor intermediate water levels. Our results have implications for water level management in reservoirs with large water level fluctuations.

Mississippi↗
USGS2010

Stomach emptiness in fishes: Sources of variation and study design implications

This study summarizes fish stomach content data from 369,000 fish from 402 species in 1,096 collections and reports on the percentage of individuals with empty stomachs. The mean percentage of individuals with empty stomachs among all species, locations, habitats, seasons, regions, and collection methods was 26.4%. Mean percentage of individuals with empty stomachs varied significantly among fish collection gear types, taxonomic orders, trophic groups, feeding behaviors, and habitats, and with species length at maturity. Most of the variation in percentage of individuals with empty stomachs was explained by species length at maturity, fish collection gear type, and two autecological factors: trophic group (piscivore percentage of individuals with empty stomachs > non-piscivore percentage of individuals with empty stomachs) and feeding habitat (water column feeder percentage of individuals with empty stomachs > benthic feeder percentage of individuals with empty stomachs). After accounting for variation with fish length, the percentage of individuals with empty stomachs did not vary with the stomach removal collection method (dissection vs. gastric lavage), feeding time (diurnal or nocturnal), or time of collection (day or night). The percentage of individuals with empty stomachs was similar between fresh and saltwater fish, but differed within finer habitat classifications and appeared to follow a general prey availability or productivity gradient: percentage of individuals with empty stomachs of open ocean collections > estuary collections, lentic > lotic, and pelagic > littoral. Gear type (active or passive) was the most influential factor affecting the occurrence of empty stomachs that can be readily controlled by researchers.

Reviews in Fisheries Science↗
USGS2001

Biological structure and dynamics of littoral fish assemblages in the eastern Finger Lakes

Fish assemblages from three of the New York Finger Lakes were examined for structure within and between lakes and over time. Species-area relationships indicated that local fish assemblages are the result of recent, lake-specific events that altered the regional species pool. Fish assemblages varied among seasons and those occupying eutrophic waters had different characteristics from those in oligotrophic waters. Bluntnose minnows ( Pimephales notatus ) were a persistent and important component of most assemblages, but abundance of bluegill ( Lepomis macrochirus ) was the most distinguishing feature. Species associations indicated that interactions among the fishes had little influence on assemblage structure. Correlations between community structure and abiotic factors were identified. Ten abiotic variables were strongly associated with the species assemblages, but could not fully explain differences between assemblages. Results indicate that the abundance and diversity of water column feeders was related to productivity of lake habitat. In general, fish populations were smaller in oligotrophic waters and water column feeders were poorly represented in those assemblages. Productivity at various trophic levels was implicated as a major factor determining lake fish assemblage structure.

New York↗
USGS2012

Habitat use by fishes of Lake Superior. I. Diel patterns of habitat use in nearshore and offshore waters of the Apostle Islands region

Diel patterns of distribution of fishes in nearshore (15–80 m depth) and offshore (>80 m) waters of the Apostle Islands region of Lake Superior were described using bottom trawls, mid-water trawls, and acoustic gear during day and night sampling. These data revealed three types of diel migration: diel vertical migration (DVM), diel bank migration (DBM), and no migration. DVM was expressed by fishes migrating from benthopelagic to pelagic strata and DBM was expressed by fishes migrating horizontally from deeper waters in the day to shallower waters at night while remaining within the benthopelagic stratum. Most fishes that did not exhibit diel migration showed increased nighttime densities as a result of increased activity and movement from benthic to benthopelagic strata. Rainbow Smelt ( Osmerus mordax), Cisco ( Coregonus artedi ), Bloater ( C. hoyi ), Kiyi ( C. kiyi ), juvenile Trout-Perch (Percopsis omiscomaycus ), and adult siscowet ( Salvelinus namaycush siscowet ) exhibited DVM. Lake Whitefish ( C. clupeaformis ), lean Lake Trout ( Salvelinus namaycush namaycush ), and juvenile siscowet exhibited DBM. Adult Trout-Perch and adult Pygmy Whitefish ( Prosopium coulteri ) exhibited a mixture of DBM and DVM. Burbot ( Lota lota ), Slimy Sculpin ( Cottus cognatus ), Spoonhead Sculpin ( C. ricei ), and Deepwater Sculpin ( Myoxocephalus thompsonii ) did not exhibit diel migration, but showed evidence of increased nocturnal activity. Ninespine Stickleback ( Pungitius pungitius ) exhibited a mixture of DVM and non-migration. Juvenile Pygmy Whitefish did not show a diel change in density or depth distribution. Species showing ontogenetic shifts in depth distribution with larger, adult life stages occupying deeper waters included, Rainbow Smelt, lean and siscowet Lake Trout, Lake Whitefish, Pygmy Whitefish, Ninespine Stickleback and Trout-Perch. Of these species, siscowet also showed an ontogenetic shift from primarily DBM as juveniles to primarily DVM as adults. Across all depths, fishes expressing DVM accounted for 73% of the total estimated community areal biomass (kg ha −1 ) while those expressing DBM accounted for 25% and non-migratory species represented 2% of the biomass. The proportion of total community biomass exhibiting DVM increased with depth, from 59% to 95% across ≤30 m to >90 m depth zones. Along the same depth gradient, the proportion of total community biomass exhibiting DBM declined from 40% to 1%, while non-migrators increased from 1% to 4%. These results indicate that DVM and DBM behaviors are pervasive in the Lake Superior fish community and potentially provide strong linkages that effect coupling of benthic and pelagic and nearshore and offshore habitats.

Aquatic Ecosystem Health & Management↗
USGS2014

A portable freshwater closed-system fish egg incubation system

To identify fish eggs collected in the field to species, a portable closed‐system fish egg incubation system was designed and used to incubate and hatch the eggs in the laboratory. The system is portable, small in scale (2.54 × 1.52 × 2.03 m), and affordable, with the approximate cost of the system being US$8,300 (2012). The main tank is 678 L and holds a battery of up to 21 (egg) incubation jars. The system includes three independent water pumping systems to (1) provide aerated water to hatching jars, (2) filter and sterilize incubation water, and (3) provide temperature‐controlled water in the main tank bath and the incubation jars. The system was successfully used to incubate freshwater fish eggs to raise resulting larvae to the post‐yolk‐sac stage for three seasons (spring 2012, spring 2013, and fall 2013) over two consecutive years, at two different locations, enabling us to identify fish eggs to species by providing identifiable fish larvae from incubated fish eggs.

North American Journal of Aquaculture↗
USGS2017

Light climate and dissolved organic carbon concentration influence species-specific changes in fish zooplanktivory

Dissolved organic carbon (DOC) in lakes reduces light penetration and limits fish production in low nutrient lakes, reportedly via reduced primary and secondary production. Alternatively, DOC and light reductions could influence fish by altering their visual feeding. Previous studies report mixed effects of DOC on feeding rates of zooplanktivorous fish, but most investigators tested effects of a single concentration of DOC against clear-water, turbid, or algal treatments. We used a controlled laboratory study to quantify the effects of a DOC gradient (3–19 mg L −1 ) on average light climate and the zooplankton feeding rate of 3 common, north temperate fishes. Light availability, which was inversely related to DOC concentration, had a positive and linear effect on zooplankton consumption by juvenile largemouth bass ( Micropterus salmoides ) and bluegill ( Lepomis macrochirus ), explaining 22% and 28% of the variation in consumption, respectively. By contrast, zooplankton feeding rates by fathead minnow ( Pimephales promelas ) were best predicted by a nonlinear, negative influence of light ( R 2 = 0.13). In bluegill feeding trials we found a general trend for positive selection of larger zooplankton (Cladocera and Chaoboridae); however, the light climate did not influence the selection of prey type. Largemouth bass selected for larger-bodied zooplankton, with weak evidence that selectivity for large Cladocera changed from negative to neutral selection based on electivity values across the light gradient. Our results suggest that the effect of DOC on the light climate of lakes may directly influence fish zooplanktivory and that this influence may vary among fish species.

Inland Waters↗
USGS2020

Reservoir fish habitats: A perspective on coping with climate change

Climate change is the defining environmental problem for our generation. The effects of climate change are increasingly evident and are anticipated to profoundly affect our ability to conserve fish habitats and fish assemblages. Reservoirs are important structures for coping with projected shifts in water supply, but they also provide refuge for riverine fishes and retain distinct fish assemblages that support diverse fisheries. The effects of climate change on reservoirs are unique among aquatic systems because reservoirs have distinctive habitat characteristics due to their terrestrial origin and strong linkage to catchments. This article reviews (1) the projected effects of rising temperature and shifting precipitation on reservoir fish habitats, and (2) adaptation strategies to cope with the anticipated effects. Climate warming impacts to reservoirs may include higher water temperatures and shifts in hydrology that can result in reduced water levels in summer and fall, altered water residence cycles, disconnection from upstream riverine habitats and backwaters, increased stratification, eutrophication, anoxia, and a general shift in biotic assemblages including plants, invertebrates, and fishes. What is needed to adapt to these changes is a perspective that focuses on maintaining ecosystem functionality rather than on retaining a certain species composition. To that end, various strategies organized into planning, monitoring, and managing compartments are identified.

Reviews in Fisheries Science & Aquaculture↗
USGS1955

A mycosis-like granuloma of fish

Mycoses of systemic distribution are rarely observed in fresh-water fish in this country. In a recent review of atypical cell growths in fishes, Nigrelli cited the only known instance of a mycetoma in a North American fresh-water fish which occurred in the head of fingerling landlocked salmon from an Idaho hatchery. The fungus associated with this granuloma was characterized by a branching septate mycelium. Rucker reported a streptomycete which was pathogenic to blueblack salmon. This organism produced internal nodules containing masses of hyphae but no inflammatory response. A pathogenic fungus has been observed frequently in marine fish, however, and in both marine and fresh-water fish in Europe. This organism was tentatively classified as a Phycomycete in or near the order Chytridiales and was assigned to the genus and species Ichthyophonus hoferi , later reclassified as Ichthyosporidium hoferi . The graduloma described in this report occurs in fresh-water trout and is apparently caused by a budding, yeast-like form with no hyphae which evokes a tremendous inflammatory reaction. Morphologically, the organism does not resemble the previously described Ichthyosporidium. The lesions were first seen accidentally in sections prepared from a diplobacillus infection of brook trout termed “kidney disease.” Subsequently, the granuloma was observed in three widely separated infections involving the diplobacillus in each instance. The histological material was received in a fixed condition; thus, no cultural data was available and the nomenclature and classification of the mycotic organism were not attempted. The present distribution of the disease, however, with its potential threat to domestic fish populations, seemed to warrant a description and discussion of the disease. Efforts are in progress to culture the organism.

Journal of Infectious Diseases↗