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USGS2020

Effects of latitude, season, and temperature on Lake Sturgeon movement

Ecologists have a limited understanding of the rangewide variation in movement behavior in freshwater fishes, but recent expansion of biotelemetry allows biologists to investigate how fish movement can help to predict behavioral shifts in response to changing environments. The Lake Sturgeon Acipenser fulvescens is a wide-ranging, migratory, coolwater species, making it a candidate species for studying patterns in movement ecology. We conducted a literature review and meta-analysis of seasonal movement data compiled from 38 Lake Sturgeon telemetry studies in North America to build an understanding of spatiotemporal variation in movement behavior. Lake Sturgeon movement studies were underrepresented for low-latitude populations in the Mississippi, Missouri, and Ohio/Tennessee River basins. Highest movement usually occurred during spring spawning migrations, whereas other populations exhibited their highest movement in the fall, potentially in order to overwinter near spawning grounds. Our meta-regression analysis indicated that latitude or summer maximum temperature best predicted standardized mean difference between spring and summer movement in Lake Sturgeon populations across the species’ range. Our results suggest that Lake Sturgeon populations at lower latitudes and those that experience warmer summer temperatures have lower summer movement relative to spring movement. Managers may use this information to prioritize actions promoting the conservation of seasonally important habitats for the continued recovery of migratory coolwater fish (e.g., Lake Sturgeon) that potentially experience stressful thermal conditions.

North American Journal of Fisheries Management↗

USGS2020

Assessing establishment and growth of agricultural plantings on reservoir mudflats

Winter drawdowns in flood control reservoirs create expansive mudflats that lack the vegetation typical of littoral zones, which reduces the amount of structure available for fish habitat. This study investigated the feasibility of establishing agricultural plantings as a management action to ameliorate mudflats by providing structural cover following reservoir refilling. We tested cool-season annual grasses and clovers applied in several mixed and monoculture treatments that were sown on the mudflats of Enid Reservoir, Mississippi, during the winter drawdown in three consecutive years. Soil samples were taken for analysis of pH and macronutrients prior to planting. Plantings were monitored until the following spring to evaluate effectiveness of establishment through ground coverage, height, and stem density sampling. Plots were assigned a seeding treatment of either grasses (ryegrass Lolium spp. or triticale x Triticosecale sp.), clovers (balansa clover Trifolium michelianum or berseem clover Trifolium alexandrinum ), or both (mixed plantings) or left as an unseeded control. Differences among plant treatments were assessed via repeated measures analysis of variance and differences among means evaluated with Tukey's honestly significant difference test. Soil productivity within the study area was poor all 3 years. Grasses germinated both when disked into the soil and when top sown, while clover only germinated when disked. Plots seeded with grasses performed better than control plots with respect to stem density, height, and ground coverage, while plots seeded with grass and clover mixtures performed better than control plots only with respect to height, and plots seeded with only clover did not perform significantly better than control plots. Results serve as an evaluation of the efficacy of agricultural plant establishment on the mudflats of a flood control reservoir, inform the direction of future research, and identify considerations regarding the application of agricultural plantings as a management tool to create fish habitat.

Mississippi↗

USGS2021

Winter habitat selection and efficacy of telemetry to aid Grass Carp removal efforts in a large reservoir

Grass Carp Ctenopharyngodon idella were introduced in North America to control aquatic vegetation in small, closed systems. However, when they escape into larger systems in which they can reproduce, they have the potential to cause significant declines and alterations in aquatic vegetation communities. These alterations can in turn affect native species that are dependent on aquatic vegetation. Increased captures and observations of spawning have elevated concerns about Grass Carp establishment in new locations, with particular concern for establishment in Lake Erie and its tributaries. Recent efforts using telemetered fish that co-locate with wild conspecifics, sometimes in aggregations that are susceptible to harvest, have been used successfully to control invasive Common Carp Cyprinus carpio populations. If Grass Carp aggregate in winter similarly to Common Carp, they might be susceptible to similar control or harvest methods. During the winters (December–March) of 2017–2019, we tracked 86 Grass Carp tagged with acoustic transmitters in Truman Reservoir, Missouri, to evaluate winter habitat selection and to determine the effectiveness of using tagged fish in locating and removing wild fish by comparing harvest at locations of tagged fish to harvest at control sites that we believed were suitable Grass Carp habitat. Discrete-choice models showed that Grass Carp exhibited strong selection for shallow water, as 75% of locations were in littoral habitats with depths of 3 m or less. On average, we harvested more fish at sites where tagged fish were located (3.6 fish/attempt) than at control sites (1.2 fish/attempt). Full guts in individuals that were harvested may indicate that fish were using shallow-water habitats to feed. Our results suggested that Grass Carp did not usually form large winter aggregations, and although targeting locations with tagged fish slightly increased harvest success compared to efforts without them, efforts to reduce populations via harvest may be difficult in large systems when fish are widely dispersed.

Missouri↗

USGS2023

Drawdown, habitat, and kokanee populations in a western U.S. reservoir

Greater drought frequency and severity due to climate change will result in greater drawdown of water storage reservoirs. However, changes to oxythermal regimes due to drawdown are reservoir specific and interface with fish species-specific habitat requirements, producing varying effects on coldwater fish populations. We examined the effect of drawdown on the oxythermal habitat and relative abundance of kokanee Oncorhynchus nerka , a coldwater salmonid, in Island Park Reservoir on the Henrys Fork of the Snake River, Idaho. A measure of relative kokanee abundance was negatively, exponentially related to drawdown. Oxythermal patterns measured in the reservoir during 2021, a severe drought year, revealed that drawdown reduced kokanee habitat by increasing water temperatures and decreasing dissolved oxygen concentrations. Oxythermal refugia for kokanee appeared to relate to inflow from the spring-fed Henrys Fork and other groundwater inflows. However, we did not quantify groundwater flow or connections, and we did not study kokanee population demographics or mortality. Reducing these sources of uncertainty is a priority for future study. Still, our study highlights a potential mechanism connecting reservoir drawdown to fish populations and the unique yet predictable mechanisms by which reservoir drawdown interacts with reservoir morphometry to affect fish habitat availability.

Idaho↗

USGS2024

Food habits of nonnative Walleyes in Lake Pend Oreille, Idaho

Objective Walleye Sander vitreus is an important species that has been widely introduced outside of its native distribution. The goal of this study was to assess the effects of an established Walleye population in the Lake Pend Oreille (LPO) system, Idaho. Methods Food habits of Walleyes were described using stomach contents and stable isotopes (δ 15 N, δ 13 C). Trophic structure of the LPO system's food web was identified using stable isotopes. Annual consumption by Walleyes of important prey items was estimated using a bioenergetics model. Result Walleyes consumed a diversity of prey items, including macroinvertebrates and fishes. Kokanee Oncorhynchus nerka , the most frequently consumed prey item, occurred in 23% of all Walleye diets. Combined, native cyprinids and catostomids occurred in 31% of all Walleye stomachs. Select taxa (e.g., native cyprinids, kokanee) were consistently consumed by Walleyes across seasons, regions, and cohorts, whereas other taxa (e.g., Westslope Cutthroat Trout O. lewisi , Smallmouth Bass Micropterus dolomieu ) were consumed inconsistently. Stable isotope analysis suggested that Walleyes occupied similar trophic positions as other top‐level piscivores in the system . As Walleye age increased, δ 15 N increased and δ 13 C decreased, indicating increased consumption of pelagic prey resources and prey at higher trophic positions. The estimated biomass of kokanee consumed annually by Walleyes was 27,121 kg (95% confidence interval = 9178–61,603). Comparatively, native cyprinids represented about 46% of the total biomass of kokanee consumed by Walleyes, whereas native catostomids represented about 11% and native salmonids represented about 15% of the total biomass of kokanee consumed by Walleyes. Conclusion This study revealed that Walleyes consumed various fishes across the LPO system. Although kokanee were the most frequently consumed prey item, native cyprinids and catostomids (combined) occurred at similar proportions. This study contributes to our growing knowledge of the effects of nonnative Walleyes on important salmonids and native fishes in western systems.

Idaho↗

USGS2006

Predictable hotspots and foraging habitat of the endangered short-tailed albatross (Phoebastria albatrus) in the North Pacific: Implications for conservation

The short-tailed albatross ( Phoebastria albatrus ) is a rare and endangered seabird that ranges widely over the northern North Pacific. Populations are slowly recovering but birds face several threats at sea, in particular the incidental capture of birds in long-line fisheries. Conservation efforts are hampered by a lack of information about the at-sea distribution of this species, especially knowledge of where it may predictably co-occur with long-line fishing effort. During 18 years of transiting the Aleutian Islands Unit of the Alaska Maritime National Wildlife Refuge on a research vessel, we observed short-tailed albatross on 65 occasions. They were consistently observed near Ingenstrem Rocks (Buldir Pass) in the western Aleutians and near Seguam Pass in the central Aleutians. Based on the oceanographic characteristics of the locations where we saw most of the birds, we hypothesized that short-tailed albatross “hotspots” were located where tidal currents and steep bottom topography generate strong vertical mixing along the Aleutian Archipelago. As a test of this hypothesis, we analyzed a database containing 1432 opportunistic observations of 2463 short-tailed albatross at sea in the North Pacific. These data showed that short-tailed albatross were closely associated with shelf-edge habitats throughout the northern Gulf of Alaska and Bering Sea. In addition to Ingenstrem Rocks and Seguam Pass, important hotspots for short-tailed albatross in the Aleutians included Near Strait, Samalga Pass, and the shelf-edge south of Umnak/Unalaska islands. In the Bering Sea, hotspots were located along margins of Zhemchug, St. Matthews and Pervenets canyons. Because these short-tailed albatross hotspots are predictable, they are also protectable by regulation of threatening activities at local spatial scales.

Deep-Sea Research Part II: Topical Studies in Ocea↗

USGS2013

Use of classification trees to apportion single echo detections to species: Application to the pelagic fish community of Lake Superior

Acoustic methods are used to estimate the density of pelagic fish in large lakes with results of midwater trawling used to assign species composition. Apportionment in lakes having mixed species can be challenging because only a small fraction of the water sampled acoustically is sampled with trawl gear. Here we describe a new method where single echo detections (SEDs) are assigned to species based on classification tree models developed from catch data that separate species based on fish size and the spatial habitats they occupy. During the summer of 2011, we conducted a spatially-balanced lake-wide acoustic and midwater trawl survey of Lake Superior. A total of 51 sites in four bathymetric depth strata (0–30 m, 30–100 m, 100–200 m, and >200 m) were sampled. We developed classification tree models for each stratum and found fish length was the most important variable for separating species. To apply these trees to the acoustic data, we needed to identify a target strength to length (TS-to-L) relationship appropriate for all abundant Lake Superior pelagic species. We tested performance of 7 general (i.e., multi-species) relationships derived from three published studies. The best-performing relationship was identified by comparing predicted and observed catch compositions using a second independent Lake Superior data set. Once identified, the relationship was used to predict lengths of SEDs from the lake-wide survey, and the classification tree models were used to assign each SED to a species. Exotic rainbow smelt (Osmerus mordax) were the most common species at bathymetric depths <100 m with their population estimated at 755 million (3.4 kt). Kiyi (Coregonus kiyi) were the most abundant species at depths >100 m (384 million; 6.0 kt). Cisco (Coregonus artedi) were widely distributed over all strata with their population estimated at 182 million (44 kt). The apportionment method we describe should be transferable to other large lakes provided fish are not tightly aggregated, and an appropriate TS-to-L relationship for abundant pelagic fish species can be determined.

Lake Superior↗

USGS2021

Estimating the effects of fish quality and size on the economic value of fishing in Oklahoma streams and rivers: A revealed preference and contingent behavior approach

Fishing in Oklahoma’s rivers and streams provides a unique experience for anglers in the state. Despite its popularity, information on total demand and economic benefits associated with stream fishing is limited in the state. Research on the role of site quality indicators, such as fish size and quantity, on recreational fishing has shown mixed results. Whether fish size or quantity plays an important role in determining fishing demand and economic value may have important management implications. We estimated the demand and economic value of fishing under varying scenarios by using anglers’ responses to hypothetical behavioral questions related to fishing in Ozark Highland streams and rivers in Oklahoma. We asked how intended number of trips might change in the future given hypothetical increases in catch rates of fish, catch rates of trophy-sized fish, and catch rates of preferred fish species, in combination with anglers’ trip-related data. Under current conditions, we estimated consumer surplus per person per trip to be $55 and aggregate value across all stream anglers in Oklahoma to be $68.51 million. Changes in marginal benefits varied among hypothetical scenarios of fish size and abundance but was maximized with a 25% increase in catch rates of trophy-sized fish. The study findings contribute to the understanding of the economic benefit of fishing in streams and suggest that fish size, rather than fish quantity, is more important to stream anglers in the area.

Oklahoma↗

USGS2011

Who's your momma? Recognizing maternal origin of juvenile steelhead using injections of strontium chloride to create transgenerational marks

We sought to determine whether a strontium chloride injection could be used to create a transgenerational otolith mark in steelhead Oncorhynchus mykiss . Two strontium injection trials and a survey of strontium: calcium (Sr:Ca) ratios in juvenile steelhead from various steelhead hatcheries were conducted to test the feasibility of the technique. In both trials, progeny of fish injected with strontium had significantly higher Sr:Ca ratios in the primordial region of their otoliths, as measured by an electron wavelength dispersive microprobe. In trial 1, the 5,000-mg/L treatment level showed that 56.8% of the otoliths were correctly classified, 12.2% being misclassified as belonging to the 0-mg/L treatment. In trial 2, the 20,000-mg/L treatment level showed that 30.8% of the otoliths were correctly classified, 13.5% being misclassified as belonging to the 0-mg/L treatment. There were no differences in the fertilization rates of eggs or survival rates of fry between the treatment and control groups. The Sr:Ca ratios in otoliths collected from various hatchery populations of steelhead varied and were greater than those found in otoliths from control fish in both of our injection trials. This study suggests that the marking technique led to recognizable increases in Sr:Ca ratios in some otoliths collected from fry produced by injected females. Not all progeny showed such increases, however, suggesting that the method holds promise but requires further refinement to reduce variation. Overall, there was a correct classification of about 40% across all treatments and trials; the variation in Sr:Ca ratios found among experimental trials and hatcheries indicates that care must be taken if the technique is employed where fish from more than one hatchery could be involved.

Transactions of the American Fisheries Society↗

USGS2015

Effects of effects of suspended sediment on early-life stage survival of Yaqui chub, an endangered USA–Mexico borderlands cyprinid

High levels of total suspended sediment (TSS) can have negative consequences on fishes, such as altering food supply, lowering food acquisition, clogging gills, and disrupting reproduction. While effects of TSS on salmonids and estuarine fish are well studied, less is known about possible negative impacts of suspended sediment on desert fishes. Several imperiled desert fishes inhabit streams and springs near the U.S.–Mexico border and are potentially threatened by increased sediment loads from borderlands activity such as livestock grazing, road building, illegal traffic, and law enforcement patrols. One such species is the Yaqui Chub Gila purpurea, a federally listed endangered cyprinid. We exposed Yaqui Chub embryos and fry (mean TL = 12.6 mm; SE = 0.42) to a range of TSS levels commonly found in one of the only streams they inhabit, Black Draw, which crosses the Arizona–Mexico border. We tested effects of 0; 300; 500; 1,000; 5,000; and 10,000 mg/L TSS loads on fry and embryos over a 5-d period in three replicate containers for each treatment. Fifty percent hatch rate (i.e., median lethal concentration, LC50) was 3,977 mg/L for embryos. The LC50 for fry (concentration at which half died) was 8,372 mg/L after 12 h of exposure; however, after 5-d exposure, LC50 leveled at 1,197 mg/L. The TL of fry did not change significantly in any treatment over the 5-d period. Suspended sediment in Black Draw reached concentrations lethal to Yaqui Chub embryo and fry during four floods in 2012. Although some desert fishes have evolved in rivers and streams subject to elevated TSS and are tolerant to high TSS concentrations, other fish species are less tolerant and may be impacted by land practices which increase erosion into stream systems. Management of critically endangered desert fishes should include considerations of the effects of increased suspended sediment.

Transactions of the American Fisheries Society↗

USGS2013

Comparison of harvest scenarios for the cost-effective suppression of Lake Trout in Swan Lake, Montana

Given the large amount of resources required for long-term control or eradication projects, it is important to assess strategies and associated costs and outcomes before a particular plan is implemented. We developed a population model to assess the cost-effectiveness of mechanical removal strategies for suppressing long-term abundance of nonnative Lake Trout Salvelinus namaycush in Swan Lake, Montana. We examined the efficacy of targeting life stages (i.e., juveniles or adults) using temporally pulsed fishing effort for reducing abundance and program cost. Exploitation rates were high (0.80 for juveniles and 0.68 for adults) compared with other lakes in the western USA with Lake Trout suppression programs. Harvesting juveniles every year caused the population to decline, whereas harvesting only adults caused the population to increase above carrying capacity. Simultaneous harvest of juveniles and adults was required to cause the population to collapse (i.e., 95% reduction relative to unharvested abundance) with 95% confidence. The population could collapse within 15 years for a total program cost of US$1,578,480 using the most aggressive scenario. Substantial variation in cost existed among harvest scenarios for a given reduction in abundance; however, total program cost was minimized when collapse was rapid. Our approach provides a useful case study for evaluating long-term mechanical removal options for fish populations that are not likely to be eradicated.

Montana↗

USGS2016

Developing recreational harvest regulations for an unexploited lake trout population

Developing fishing regulations for previously unexploited populations presents numerous challenges, many of which stem from a scarcity of baseline information about abundance, population productivity, and expected angling pressure. We used simulation models to test the effect of six management strategies (catch and release; trophy, minimum, and maximum length limits; and protected and exploited slot length limits) on an unexploited population of Lake Trout Salvelinus namaycush in Follensby Pond, a 393-ha lake located in New York State’s Adirondack Park. We combined field and literature data and mark–recapture abundance estimates to parameterize an age-structured population model and used the model to assess the effects of each management strategy on abundance, catch per unit effort (CPUE), and harvest over a range of angler effort (0–2,000 angler-days/year). Lake Trout density (3.5 fish/ha for fish ≥ age 13, the estimated age at maturity) was similar to densities observed in other unexploited systems, but growth rate was relatively slow. Maximum harvest occurred at levels of effort ≤ 1,000 angler-days/year in all the scenarios considered. Regulations that permitted harvest of large postmaturation fish, such as New York’s standard Lake Trout minimum size limit or a trophy size limit, resulted in low harvest and high angler CPUE. Regulations that permitted harvest of small and sometimes immature fish, such as a protected slot or maximum size limit, allowed high harvest but resulted in low angler CPUE and produced rapid declines in harvest with increases in effort beyond the effort consistent with maximum yield. Management agencies can use these results to match regulations to management goals and to assess the risks of different management options for unexploited Lake Trout populations and other fish species with similar life history traits.

New York↗

USGS2015

Strontium isotopes delineate fine-scale natal origins and migration histories of Pacific salmon

Highly migratory organisms present major challenges to conservation efforts. This is especially true for exploited anadromous fish species, which exhibit long-range dispersals from natal sites, complex population structures, and extensive mixing of distinct populations during exploitation. By tracing the migratory histories of individual Chinook salmon caught in fisheries using strontium isotopes, we determined the relative production of natal habitats at fine spatial scales and different life histories. Although strontium isotopes have been widely used in provenance research, we present a new robust framework to simultaneously assess natal sources and migrations of individuals within fishery harvests through time. Our results pave the way for investigating how fine-scale habitat production and life histories of salmon respond to perturbations—providing crucial insights for conservation.

Alaska↗

USGS2015

Climate change and vulnerability of bull trout (Salvelinus confluentus) in a fire-prone landscape.

Linked atmospheric and wildfire changes will complicate future management of native coldwater fishes in fire-prone landscapes, and new approaches to management that incorporate uncertainty are needed to address this challenge. We used a Bayesian network (BN) approach to evaluate population vulnerability of bull trout ( Salvelinus confluentus ) in the Wenatchee River basin, Washington, USA, under current and future climate and fire scenarios. The BN was based on modeled estimates of wildfire, water temperature, and physical habitat prior to, and following, simulated fires throughout the basin. We found that bull trout population vulnerability depended on the extent to which climate effects can be at least partially offset by managing factors such as habitat connectivity and fire size. Moreover, our analysis showed that local management can significantly reduce the vulnerability of bull trout to climate change given appropriate management actions. Tools such as our BN that explicitly integrate the linked nature of climate and wildfire, and incorporate uncertainty in both input data and vulnerability estimates, will be vital in effective future management to conserve native coldwater fishes.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS2011

Mysid and fish zooplanktivory in Lake Ontario: quantification of direct and indirect effects

Mysis relicta and planktivorous fish feed on zooplankton in Lake Ontario and form a trophic triangle that includes intraguild predation by fish on mysids. Thus, fish affect zooplankton both directly and indirectly. To evaluate the importance of alewife (Alosa pseudoharengus), rainbow smelt (Osmerus mordax), and mysids as zooplanktivores in Lake Ontario, we measured abundances and distributions, assessed diets, and computed mysid and fish consumption rates based on bioenergetics models. We further estimated indirect effects by comparing clearance rates given observed and potential mysid distributions. Estimated consumption rates varied widely with season and water depth and ranged between 2.6 x 10-3 and 1.3 gm-2day-1 for mysids and between 1.4 x 10-3 and 0.5 gm-2day-1 for fish, representing a daily removal of zooplankton of up to 10.2%-day-1 and 2.0%-day-1 by mysids and fish, respectively. Mysid planktivory exceeded fish planktivory in May and August, but fish planktivory dominated in October. Estimated mysid planktivory rates were 2- to 90-fold lower than the potential rate if mysids moved to temperatures that maximized their predation rates, suggesting an indirect positive effect of fish on zooplankton.

Canadian Journal of Fisheries and Aquatic Sciences↗

USGS1972

Virulence and persistence of rough and smooth forms of Aeromonas salmonicida inoculated into coho salmon (Oncorhynchus kisutch)

Virulent isolates of Aeromonas salmonicida showed a majority of smooth colonies, while the attenuated isolates displayed mostly rough colonies. A lesion occurred at the site of inoculation when one of the rough forms was inoculated into yearling coho salmon, but few mortalities were recorded even though the rough forms were readily recovered from both the lesion and the kidney. The fish inoculated with the same dosage of smooth forms all died within 96&ensp;hr of inoculation.

Journal of the Fisheries Research Board of Canada↗

USGS1966

Clinostomum marginatum in steelhead trout ( Salmo gairdneri ) and cutthroat trout ( Salmo clarki ) in a western Washington lake

Clinostomum marginatum (Trematoda: Clinostomatidae), the yellow grub parasite, was recorded in epizootic proportions from Lynch Lake, King County, Washington, in 1961 and 1962. The parasite larvae occurred principally in steelhead trout (Salmo gairdneri); cutthroat trout (S. clarki) were infected to a relatively minor degree. Fish and snail host populations were destroyed by rotenone and copper sulfate treatments.

Washington↗

USGS1980

Channelization and livestock impacts on salmonid habitat and biomass in western Washington

We examined salmonid habitat and biomasses in 50–70‐m pairs of altered and control sections of small (discharges less than 0.3 m 3 second −1 ) streams around Puget Sound in western Washington in 1978–1979. Altered sections had been channelized or used by livestock. Channelization significantly reduced overhead cover, sinuosity, wetted area, and woody bank cover while increasing bank grasses. Total habitat area declined in altered areas. These impacts most damaged the quality of habitat for cutthroat trout (Salmo clarki) over 70 mm in length. Biomass of coho salmon (Oncorhynchus kisutch) did not decline significantly in altered sections except in areas severely damaged. Zero‐age trout (cutthroat and steelhead, Salmo gairdneri) suffered no loss of habitat quality, although larger trout did, except in areas of severe physical impact. Short‐term effects of machinery operation in the one stream for which data were obtained included biomass depletions of all salmonid species and size classes. Channelization and livestock use appeared to reduce quality of winter habitat for salmonids. In altered sections with stable bottoms, no recent damage history, relatively little silt and sand, and adequate riffle areas, the reduction in overhead cover appeared to lead to higher standing crops of salmonids, suggesting that fish production in many streams of the Puget Sound area may be light‐limited.

Washington↗