USGS Science⌕ Search

SEARCH · USGS Science

Results for “Journal of Fisheries Management”

Search indexed USGS publications on groundwater, aquifers, geologic maps, mineral resources and earthquakes. Explore source records by subject and place.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
USGS2026

Gerrard strain Rainbow Trout are not piscivorous in a shallow, polymictic reservoir

Objective Georgetown Lake (Montana, USA) is renowned for its multispecies salmonid fishery. Although many anglers target kokanee Oncorhynchus nerka in Georgetown Lake, the body length of kokanee has typically been considered unsatisfactory. To reduce the density of kokanee and increase the average size, Montana Fish, Wildlife & Parks began stocking the piscivorous Gerrard strain of Rainbow Trout O. mykiss (hereafter “Gerrard”) in 2015 to consume kokanee. In 2020, preliminary evidence suggested that the average length of kokanee greater than 200 mm increased by almost 40 mm. Methods To assess the efficacy of biocontrol through the introduction of a piscivore to predate on kokanee, we examined the diet composition of all potential predators (three strains of Rainbow Trout and Brook Trout Salvelinus fontinalis ) to determine the amount of predation on kokanee and to understand the feeding ecology of all potential predators. Results There was little evidence of piscivory in any predator and no evidence of Gerrards consuming kokanee. Gerrards exhibited a generalist feeding strategy, and there was dietary overlap and no difference in trophic position among Gerrards and other predators. Conclusions From a biological-control perspective, there is no benefit in continuing to stock Gerrards to reduce kokanee densities in Georgetown Lake. These findings underscore the challenge of predicting predator–prey relationships, as diet plasticity can lead to unexpected dynamics based on resource availability and habitat structure within aquatic ecosystems, highlighting the importance of evaluating management interventions, such as biocontrols, in different ecosystems.

Montana↗
USGS2019

Submergence responses of cool-season annual plants and potential for fish habitat

Unnatural water regimes of flood control reservoirs limit vegetation establishment in littoral zones and produce mudflats with low structural complexity insufficient for many juvenile fishes. One strategy to enhance habitat on mudflats is to sow cool-season plants to provide submerged structure when inundated. However, how long the structure of these plants persists following inundation has not been evaluated. To investigate the species-specific responses of cool-season plants to inundation, we submerged six cool-season plant species in outdoor flow-through tanks and monitored maximum height and density of plant structures over time. Time-to-event analyses and generalized linear models were used to characterize differences in structural persistence between species over time. Plantings degraded rapidly if inundated before plant maturity. However, mature plants of Marshall Ryegrass Lolium multiflorum and Triticale Triticosecale provided dense structure for periods long enough to provide refuge for juvenile fish. As Ryegrass degraded, stem density decreased producing wide gaps relative to Triticale which remained dense and complex. Differences in plant architecture may influence the quality of habitat and which fish species and age class utilize each planting. Our results indicate that cool-season grasses planted in mudflats can persist after inundation long enough to enhance seasonal fish habitat and differences in plant structural characteristics may allow managers more flexibility to target desirable fish species.

North American Journal of Fisheries Management↗
USGS2019

Morphological identification of Bighead Carp, Silver Carp, and Grass Carp eggs using random forests machine learning classification

Visual identification of fish eggs is difficult and unreliable due to a lack of information on the morphological egg characteristics of many species. We used random forests machine learning to predict the identity of genetically identified Bighead Carp Hypophthalmichthys nobilis , Grass Carp Ctenopharyngodon idella , and Silver Carp H. molitrix eggs based on egg morphometric and environmental characteristics. Family, genus, and species taxonomic-level random forests models were explored to assess the performance and accuracy of the predictor variables. The egg characteristics of Bighead Carp, Grass Carp, and Silver Carp were similar, and they were difficult to distinguish from one another. When combined into a single invasive carp class, the random forests models were ≥ 97% accurate at identifying invasive carp eggs, with a ≤5% false positive rate. Egg membrane diameter was the most important predictive variable, but the addition of ten other variables resulted in a 98% success rate for identifying invasive carp eggs from 26 other upper Mississippi River basin species. Our results revealed that a combination of morphometric and environmental measurements can be used to identify invasive carp eggs. Similar machine learning approaches could be used to identify the eggs of other fishes. These results will help managers more easily and quickly assess invasive carp reproduction.

Iowa↗
USGS2022

Variation in Prairie Chub hatch relationships across wet and dry years in the upper Red River basin

Objective The Prairie Chub Macrhybopsis australis is a poorly studied minnow species endemic to the upper Red River basin and is of both state and federal conservation interest due to uncertainty about its life history and potential listing status. The upper Red River basin of Oklahoma and Texas is a harsh environment where drought and extreme flow events are exacerbated by human alterations. As an assumed pelagic-broadcast-spawning minnow, the Prairie Chub is capable of a protracted spawning season and larval fish survival is assumed to be linked to discharge and streamflow variability. Methods We systematically collected 2,017 age-0 Prairie Chub from seven sites (North Fork Red River, Salt Fork Red River, Pease River, Red River, Prairie Dog Town Fork Red River, North Wichita River, and South Wichita River) with variable flow patterns during April–September 2019 and May–August 2020. We used otolith age estimates and back calculations to determine successful spawning dates. We used a hurdle model framework to examine relationships between hatch probability and hatch frequency. Result Hatch probability had a negative relationship with calendar day and declined as calendar day increased. Hatch counts peaked in late June and early July and declined thereafter in 2019 but showed no discernible peak during the spawning season in 2020. Hatch probability during the spawning season increased with relative flow and air temperature. Increased hatch counts were also positively related to discharge variability (CV) for the 10 d prior to hatch dates. Conclusion Our findings indicated that successful hatches had considerable spatial and temporal variability, with some sites contributing minimally to the population during some years. Spatial and temporal variability of hatch probability and hatch frequencies pose a variety of considerations for future conservation and management efforts, particularly given the pending federal listing status of the species.

North American Journal of Fisheries Management↗
USGS2024

Processing time and precision of aging structures for Bighead Carp and Silver Carp in the lower Red River catchment in the southern Great Plains

Objective Population demographics of invasive species are commonly evaluated to better develop management actions that are useful for reducing their abundance or controlling the population. Bighead Carp Hypophthalmichthys nobilis and Silver Carp H. molitrix are emblematic invaders in the United States, where they continue to expand their range. There is currently no consensus about which hard structure from these species is best for age estimation. Our study objective was to compare the processing time and precision of five hard structures used for age estimation of both species. Methods We sampled fish in the lower Red River catchment of Oklahoma, Arkansas, and Texas during summer and autumn 2021–2022 and removed the lapillus otolith, left primary pectoral fin ray, postcleithrum, urohyal bone, and anterior-most pterygiophore of the dorsal fin from both Bighead and Silver carp. The structures ( n = 1204) were either embedded in epoxy or thin-sectioned and mounted on slides. Two readers estimated the age of the fish by using each structure and came to a consensus. Processing time was recorded from the onset of laboratory processing to the termination of polishing the cross sections for age estimation. Result Processing of otoliths was comparable to or faster than processing of the other structures and resulted in the highest between-reader agreement. The lowest coefficients of variation in age estimation were represented using lapillus otoliths for Bighead Carp and postcleithra for Silver Carp. Our age bias plots indicated that all other structures underestimated age relative to the lapillus otoliths. Conclusion Our results indicated that using lapillus otoliths for age estimation of these species would have the highest between-reader agreement and would incur no additional laboratory processing time. However, validation is needed to assess whether lapillus otoliths correctly age these species. From a management perspective, use of this structure would facilitate improved population comparisons.

Arkansas, Oklahoma, Texas↗
USGS2012

Backwaters in the upper reaches of reservoirs produce high densities of age-0 crappies

Reservoir backwaters are aquatic habitats in floodplains of reservoir tributaries that are permanently or periodically flooded by the reservoir. Like many reservoir arms, backwaters are commonly shallow, littoral habitats, but they differ from arms in various respects, including their support of primarily wetland plant assemblages that are tolerant to flooding. Elsewhere, the reservoir floods mainly upland plants that are less tolerant to flooding, producing a band of barren shoreline along the fluctuation zone. We investigated differences in relative abundance of age-0 crappies Pomoxis spp. in backwaters and arms of widely fluctuating flood control reservoirs, examined the effect of water level, and estimated the likelihood and timing with which these habitats are flooded annually. Higher catch rates of age-0 crappies were obtained in backwater habitats than in arm habitats. When inundated during the crappie spawning season, backwaters provided vegetated habitat at lower water levels than arms. Backwaters flooded earlier than arms and remained flooded longer to provide prolonged nursery habitat. Whereas vegetated habitat was inundated almost yearly in backwaters and arms, inundation that was timed to the onset of spawning occurred less regularly. Because of differences in water elevation, vegetated habitats were flooded in time for crappie spawning about every other year in backwaters but only every third year in arms. Recruitment of age-0 crappies was inversely correlated with high water levels during the months preceding the spawning period, perhaps because early flooding degraded the vegetation. Our results suggest that water levels may be managed during late winter and spring to regularly flood wetland vegetation communities in backwaters; however, water levels should be maintained at or below normal pool and should only irregularly flood upland vegetation in reservoir arms to promote the preservation of such vegetation. Furthermore, management efforts to enhance crappie recruitment should consider the enhancement and preservation of backwaters.

Mississippi↗
USGS2000

Forecasting survival and passage of migratory juvenile salmonids

We developed methods to forecast survival and cumulative percent passage for subyearling chinook salmon Oncorhynchus tshawytscha at a dam to help managers effectively time the release of reservoir water to mitigate for passage delays and reduced survival. We tagged Snake River subyearling chinook salmon upstream of a dam from 1993 to 1998 and determined when a subsample of the tagged fish passed the dam. We randomly selected data (1993, 1994, 1996, and 1998) to develop a quadratic discriminant function for predicting which fish would survive to the dam and to develop a multiple-regression equation to predict the date survivors would pass the dam. We used the predicted passage dates within a year to calculate a daily cumulative percent passage forecast and then calculated a 90% forecast interval that varied by year, depending on the number of predicted survivors. We validated the forecast method using data for 1995 and 1997. The 1995 forecasted passage curve differed from the observed passage curve for 25 d of the 168-d emigration season. The 1997 forecasted and observed passage curves were similar for the entire 168-d emigration season. The 90% forecast interval was ±18.8% in 1995 and ±22.4% in 1997. We conclude that our method is a valid tool for in-season water management but acknowledge the potential for interannual variability in forecast performance.

North American Journal of Fisheries Management↗
USGS1994

Declining survival of lake trout stocked during 1963-1986 in U.S. waters of Lake Superior

The average catch per effort (CPE) values for the 1963–1982 year-classes of stocked lake trout Salvelinus namaycush caught at age 7 in gill nets and for the 1976–1986 year-classes caught at ages 2–4 in trawls declined significantly in U.S. waters of Lake Superior. The declines in CPE were not explained by reduced stocking, but rather by significant declines in survival indices of the year-classes of stocked lake trout. Increases in mortality occurred in year-classes before the fish reached ages 2–4, before they were recruited into the sport and commercial fisheries, and before they reached sizes vulnerable to sea lamprey predation. We conclude that declining abundance of stocked lake trout resulted from increased mortality, which may have been caused by competition, predation, or by a combination of these and other factors. Restoration of lake trout in Lake Superior may now depend on prudent management of naturally reproducing stocks rather than on stocking of hatchery-reared fish.

North American Journal of Fisheries Management↗
USGS2008

Fish passage in a western Iowa stream modified by grade control structures

Grade control structures (GCSs) are commonly used in streams of western Iowa to control bank erosion and channel headcutting but may be barriers to fish passage. From May 2002 to May 2006, we used mark-recapture methods to evaluate fish passage over a total of five GCSs, ranging in slope (run : rise) from 13:1 to 18:1 in Turkey Creek, Cass County, Iowa. Three structures, over which limited fish movement was documented from 2002 to 2004, were modified in the winter of 2004-2005 to facilitate fish passage. Before modification, the majority of recaptured fish were recaptured at the station where they were originally marked; only 1% displayed movement between sites and either upstream or downstream over a GCS. After modification fish passage improved, 14% of recaptured fish displayed movement either upstream or downstream over a GCS. Individuals of four target species - channel catfish Ictalurus punctatus, yellow bullhead Ameiurus natalis, black bullhead A. melas, and creek chub Semotilus atromaculatus - passed over at least one modified structure. The majority of documented movements over GCSs were in the upstream direction and occurred in late spring and early summer, when streamflow was relatively high. Although we documented low numbers of fish passing both upstream and downstream over GCSs, these structures are probably barriers to fish movement during periods of low flow and when there is a structural failure, such as in-channel movement of riprap. Grade control structures are pervasive in western Iowa streams; nearly every low-order stream contains at least one instream structure. To sustain fish populations, management efforts should focus on constructing or modifying GCSs to allow fish passage. ?? Copyright by the American Fisheries Society 2008.

North American Journal of Fisheries Management↗
USGS2024

Cold blood in warming waters: Effects of air temperature, precipitation, and groundwater on Gulf Sturgeon thermal habitats in a changing climate

Objective In a changing climate, the effects of air temperature, precipitation, and groundwater on water temperature and thermal habitat suitability for Gulf Sturgeon Acipenser desotoi , listed as threatened under the U.S. Endangered Species Act, are not well understood. Hence, we incorporated these factors into thermal habitat models to forecast how Gulf Sturgeon may be affected by wide‐ranging climate change scenarios in 2024–2074. Methods Using data from the Choctawhatchee River, Florida, we developed precipitation‐ and groundwater‐corrected air–water temperature models, compared their accuracy with that of conventional air–water temperature models used in fisheries management, and projected future Gulf Sturgeon thermal habitat suitability for normal physiological functioning and fieldwork (i.e., population sampling and telemetry surgeries) in summer (May–August) under 16 climate change scenarios. Result Precipitation‐ and groundwater‐corrected models were more accurate than conventional air–water temperature models (mean improvement in adjusted R 2 = +0.45; range = +0.09 to +0.75). Water temperature was projected to warm at widely variable rates across climate change scenarios encompassing different air temperature, precipitation, and groundwater regimes. Importantly, Gulf Sturgeon summer aggregation areas were cooler and influenced more by precipitation and groundwater and less by air temperature than were non‐aggregation areas. If precipitation and groundwater—as drivers of cooling—become warm in a changing climate, summer aggregation areas were projected to exhibit thermal habitat degradation equivalent to or greater than that of non‐aggregation areas. Conclusion Our results add hydrological context to the premise that aggregation areas provide cool water and energetic savings for Gulf Sturgeon during summer, underscoring the importance of protecting these habitats through groundwater conservation, water quality monitoring, and riparian/watershed habitat management. Our findings indicate that identifying thermally appropriate times for fieldwork activities will be increasingly important and time‐restricted as climate change intensifies. However, our research provides managers with a portfolio of water temperature models and an accurate, cost‐effective, management‐relevant approach to forecasting thermal habitat conditions for Gulf Sturgeon and other species in a changing climate.

Alabama, Florida↗
USGS2022

Suppression of invasive fish in the west: Synthesis and suggestions for improvement

Reservoirs are ubiquitous features on the landscape of the western United States. Although reservoirs provide numerous benefits (e.g., irrigation, flood control, hydropower, recreational use), these systems are often a concern from an ecological perspective. Reservoirs support fisheries primarily composed of nonindigenous sport fishes that may become invasive and negatively influence recipient ecosystems. Furthermore, reservoirs alter adjacent riverine habitats, further increasing the threat of invasive fishes to aquatic systems. As such, most western natural resource management agencies focus considerable effort on managing the threat of invasive fish species. Unfortunately, controlling invasive fish is expensive and rarely effective because of a lack of clear objectives, appropriate fishing mortality, and long-term commitment. In an effort to improve management of invasive fish in the western United States, we reviewed existing literature to identify the steps necessary to effectively suppress these species. Specifically, we provide guidance on defining achievable objectives, assessing feasibility, evaluating success, and improving the efficiency of invasive fish suppression. This iterative approach provides managers with a framework to effectively address the challenge of suppressing invasive fish in the western United States.

North American Journal of Fisheries Management↗
USGS2012

Strategies to control a common carp population by pulsed commercial harvest

Commercial fisheries are commonly used to manage nuisance fishes in freshwater systems, but such efforts are often unsuccessful. Strategies for successfully controlling a nuisance population of common carp Cyprinus carpio by pulsed commercial harvest were evaluated with a combination of (1) field sampling, (2) population estimation and CPUE indexing, and (3) simulation using an exponential semidiscrete biomass dynamics model (SDBDM). The range of annual fishing mortalities ( F ) that resulted in successful control ( F = 0.244–0.265) was narrow. Common carp biomass dynamics were sensitive to unintentional underharvest due to high rates of surplus production and a biomass doubling time of 2.7 years. Simulations indicated that biomanipulation never achieved successful control unless supplemental fishing mortality was imposed. Harvest of a majority of annual production was required to achieve successful control, as indicated by the ecotrophic coefficient (EC). Readily available biomass data and tools such as SDBDMs and ECs can be used in an adaptive management framework to successfully control common carp and other nuisance fishes by pulsed commercial fishing.

North American Journal of Fisheries Management↗
USGS2023

Synthesis of larval lamprey responses to dewatering: State of the science, critical uncertainties, and management implications

Objective Dewatering of fine sediments in rivers and streams can kill many thousands of larval lampreys (order Petromyzontiformes) that are burrowed in these habitats. The larval life stage for lampreys lasts 3–10 years, and because larvae often aggregate in large numbers, negative impacts from dewatering could potentially deplete local populations and affect multiple year-classes. Larval lampreys have not traditionally been considered during instream projects, but recent efforts to increase awareness of lamprey habitats have resulted in guidance on dewatering approaches to limit impacts to lampreys. Salvage efforts to rescue and relocate lampreys aim to mitigate losses, but a lack of understanding of lamprey responses limits the optimization of dewatering and salvage procedures. Methods We summarize the state of the science for nine factors that influence larval lamprey ( Entosphenus and Lampetra spp.) responses to dewatering, including burrowing depth, the prevalence and timing of emergence, movements, survival, shoreline slope, dewatering rate, light, and lamprey size. Result Research suggests that (1) shoreline slope influences movement capability, (2) hot and sunny conditions increase the risk of mortality, (3) salvage activities cause minimal direct mortality, and (4) smaller larvae are especially vulnerable to negative impacts from dewatering because they are more likely to emerge and are less capable of movement. Critical uncertainties associated with dewatering include cues that drive emergence, the influence of sediment composition and stratigraphy, vertical distribution of larvae in natural settings, use of the hyporheic zone, the scale of predation losses, and the effectiveness and impacts of salvage activities. Conclusion Balancing investments in salvage operations and lamprey exclusion efforts (e.g., screening) and developing field survey approaches to evaluate lamprey use of the hyporheic zone are identified management implications and research needs. Addressing the critical uncertainties discussed here and providing updated, science-based guidance on dewatering and salvage practices are suggested management actions to support lamprey conservation.

North American Journal of Fisheries Management↗
USGS2013

To stock or not to stock? Assessing restoration potential of a remnant American shad spawning run with hatchery supplementation

Hatchery supplementation has been widely used as a restoration technique for American Shad Alosa sapidissima on the East Coast of the USA, but results have been equivocal. In the Penobscot River, Maine, dam removals and other improvements to fish passage will likely reestablish access to the majority of this species’ historic spawning habitat. Additional efforts being considered include the stocking of larval American Shad. The decision about whether to stock a river system undergoing restoration should be made after evaluating the probability of natural recolonization and examining the costs and benefits of potentially accelerating recovery using a stocking program. However, appropriate evaluation can be confounded by a dearth of information about the starting population size and age structure of the remnant American Shad spawning run in the river. We used the Penobscot River as a case study to assess the theoretical sensitivity of recovery time to either scenario (stocking or not) by building a deterministic model of an American Shad population. This model is based on the best available estimates of size at age, fecundity, rate of iteroparity, and recruitment. Density dependence was imposed, such that the population reached a plateau at an arbitrary recovery goal of 633,000 spawning adults. Stocking had a strong accelerating effect on the time to modeled recovery (as measured by the time to reach 50% of the recovery goal) in the base model, but stocking had diminishing effects with larger population sizes. There is a diminishing return to stocking when the starting population is modestly increased. With a low starting population (a spawning run of 1,000), supplementation with 12 million larvae annually accelerated modeled recovery by 12 years. Only a 2-year acceleration was observed if the starting population was 15,000. Such a heuristic model may aid managers in assessing the costs and benefits of stocking by incorporating a structured decision framework.

North American Journal of Fisheries Management↗
USGS2016

A paired-laser photogrammetric method for in situ length measurement of benthic fishes

Photogrammetry, a technique to obtain measurements from photographs, may be a valid method for measuring lengths of rare, threatened, or endangered species. Photogrammetric methods of measurement are nonintrusive and reduce the possibility of physical damage or physiological stress associated with the capture and handling of individuals. We evaluated precision and accuracy of photogrammetric length measurements relative to board measurements of Greenside Darters Etheostoma blennioides and Variegate Darters E. variatum in an aquarium and applied photogrammetry in a field study of the Diamond Darter Crystallaria cincotta , a federally listed endangered species. Digital photographs were taken of each individual using a waterproof camera equipped with two parallel lasers. Photogrammetric length measurements were digitized with ImageJ software. Agreement between board and photogrammetric measurements were high for Greenside and Variegate darters. The magnitude of differences was small between direct and photogrammetric measurements, ranging from 0.6% to 3.1%, depending on the species measured and the type of measurement taken. These results support photogrammetry as a useful method for obtaining length measurements of benthic stream fishes. Photogrammetric methods allowed for length measurements and an assessment of length frequency of 199 Diamond Darters, informative data for management that could not be collected with conventional measuring-board methods.

North American Journal of Fisheries Management↗
USGS1996

Natural thermal refugia for temperate warmwater stream fishes

The seasonal use of an Ozark spring branch by fishes was evaluated from January 1993 to January 1995. Temperatures in the spring branch were fairly constant, at 13.5 ± 1°C, and usually exceeded the temperature of a receiving stream during the November–March coldwater period. Black redhorse Moxostoma duquesnei , smallmouth bass Micropterus dolomieu , shadow bass Ambloplites ariommus , and longear sunfish Lepomis megalotis showed a temporal pattern of use in the spring branch. The lowest use was during the April–October warmwater period, and the greatest use was during the coldwater period. During cold periods, biomass of these four species in the spring branch was significantly greater and fish size significantly larger than in similar habitats in the adjoining stream. The weight per unit length of fish using the spring branch during cold periods was also significantly greater. Shadow bass and longear sunfish had significantly greater relative stomach contents than conspecifics in equivalent habitats from the adjoining stream, but had similar relative numbers of eggs. Large concentrations of adult fish used spring branches during the coldwater period, and these fish may be more vulnerable to angling than conspecifics in similar habitats in adjoining streams dominated by surface water. Thus, we suggest that stream managers consider the usefulness of fish refuges in spring branches and adjacent thermally influenced areas.

Missouri↗
USGS2025

Population dynamics of White Sturgeon in the upper Snake River, Idaho: Evaluation of management options for a harvest fishery

Objective Understanding how fish populations will respond to management actions is critical for making effective management ­decisions. This study provides important information regarding population demographics for a nonnative, hatchery-implemented population of White Sturgeon Acipenser transmontanus . We investigated the population dynamics of White Sturgeon in the upper Snake River, Idaho, and developed an age-structured population model to evaluate potential stocking and harvest scenarios (e.g., length limits and annual quotas). Methods White Sturgeon were sampled from June to October 2022 and from June to August 2023 using angling (i.e., rod and reel) and setlines from a 260-km-long section of the Snake River. Capture histories from 261 known-age White Sturgeon informed age and growth analysis and an evaluation of movement trends. A closed-population capture–recapture model and an estimate of setline-specific catchability were used to estimate the total abundance of White Sturgeon in the upper Snake River. Apparent survival for the population was estimated using a Cormack–Jolly–Seber model. Finally, a population model was parameterized using information on the population dynamics of White Sturgeon in the upper Snake River. The model was used to estimate the effects of varying stocking rates and harvest scenarios (i.e., harvest slot of 76–122 cm fork length [FL] and annual quotas of 0–25 White Sturgeon harvested) on the population. Results In total, 340 individual White Sturgeon were captured throughout the study area, with 181 recapture events. Individuals varied in FL from 54 to 205 cm, and the mean relative weight for captures was 105.2 (SD = 14.4), suggesting relatively high body condition. Age varied from 2 to 25 years, and White Sturgeon moved an average of 8.1 km (SD = 23.5) downstream from stocking locations. Estimated abundance of White Sturgeon in the tailwaters of American Falls Dam was 428 fish (95% CI = 403–463). That abundance estimate was used to inform a total abundance estimate of 887 White Sturgeon (95% CI = 835–960) in the study area. Apparent annual survival was 0.79 (95% CI = 0.64–0.89). A stocking rate of 285 age-2 White Sturgeon/year was necessary to maintain current abundance. For every five fish harvested (harvest slot = 76–122 cm FL) per year, estimated abundance decreased by about 2.2% over 20 years. Conclusions Our research identified fast growth of White Sturgeon relative to other populations and relatively high mortality for a White Sturgeon population without exploitation. Also, like other studies evaluating harvest, a population model was used to illustrate the effect of varying rate functions on a fishery. The age-structured population model suggested that a harvest fishery is possible while still meeting management goals for the upper Snake River White Sturgeon fishery.

Idaho↗
USGS1995

Abundance indices for determining the status of lake trout restoration in Michigan waters of Lake Superior

Self-sustaining populations of lake trout Salvelinus namaycush have returned to most areas in Lake Superior, but progress toward achieving historic commercial yields has been difficult to measure because of unrecorded losses to predation by sea lamprey Petromyzon marinus and to fisheries. Consequently, we developed restoration targets (catch per effort, CPE; geometric mean number per kilometer of 114-mm stretch-meaure gill net during 1929-1943, when historic yields were sustained) from linear relationships between CPE in commercial and assessment fisheries in Michigan. Target CPEs for lake trout restoration were higher and less variable than the modern CPEs in all areas. Modern CPEs generally increased during the 1970s and early 1980s but declined during the late 1980s and early 1990s. Modern CPEs were highest in western Michigan from the Keweenaw Peninsula to Marquette (71 to 81% of target CPEs), but coefficients of variation (CV,SD/mean) of mean CPEs were 1.4 to 2.4 times greater than target CVs. Around Munising, the modern CPE was lower (41% of the target CPE), whereas the CV was 1.9 times greater than the target CV. Around Grand Marais, the modern CPE was lowest among all areas (17% of the target CPE), but the CV was nearly the same (1.1 times the target CV). In Whitefish Bay, the modern CPE was only 28% of the target CPE and the CV was 9.0 times greater, though the modern period was based on only the years 1979-1982 and 1984-1985. Further progress in restoration in most areas can be achieved only if fishery managers adequately protect existing stocks of wild fish from sea lamprey predation and fishery exploitation.

North American Journal of Fisheries Management↗