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At least 307 records · Page 17Linked to original sources
USGS2014

Fishing for Northern Pike in Minnesota: A comparison of anglers and dark house spearers

In order to project fishing effort and demand of individuals targeting Northern Pike Esox lucius in Minnesota, it is important to understand the catch orientations, management preferences, and site choice preferences of those individuals. Northern Pike are specifically targeted by about 35% of the approximately 1.5 million licensed anglers in Minnesota and by approximately 14,000–15,000 dark house spearers. Dark house spearing is a traditional method of harvesting fish through the ice in winter. Mail surveys were distributed to three research strata: anglers targeting Northern Pike, dark house spearing license holders spearing Northern Pike, and dark house spearing license holders angling for Northern Pike. Dark house spearers, whether spearing or angling, reported a stronger orientation toward keeping Northern Pike than did anglers. Anglers reported a stronger orientation toward catching large Northern Pike than did dark house spearers when spearing or angling. Northern Pike regulations were the most important attribute affecting site choice for respondents in all three strata. Models for all strata indicated a preference for lakes without protected slot limits. However, protected slot limits had a stronger negative influence on lake preference for dark house spearing licensees (whether spearing or angling) than for anglers.

Minnesota↗
USGS1990

Management implications of a model of predation by a resident fish on juvenile salmonids migrating through a Columbia River reservoir

We constructed a model ofpredation by northern squawfish Ptychocheilus oregonensis on juvenile salmonids migrating through John Day Reservoir. The model predicts salmonid survival as a function of number and distribution of northern squawfish, number and timing of juvenile salmonids entering the reservoir, salmonid residence time, water temperature, and flow. The model predicted survival similar to independent estimates for 1983–1986 and also approximated differences among areas and months. Uncertainty analyses showed that the number of salmonids surviving predation may vary ±5% with normal annual variation in predator number, temperature, and flow. Survival in 1983–1986 was near the average predicted from 30 years of historic environmental data. Sensitivity analyses implied that the best avenues ofreducing predation are to reduce the number of northern squawfish, pass salmonids earlier in the year, and maintain sizes of runs of juvenile salmonids at or above present levels. Survival of salmonids, as simulated by the model, is weakly affected by changes in predator distribution, changes in predator consumption rate near the upstream dam, residence time, or flow.

North American Journal of Fisheries Management↗
USGS2015

Origin of Atlantic Sturgeon collected off the Delaware coast during spring months

Atlantic Sturgeon Acipenser oxyrinchus oxyrinchus was federally listed under the U.S. Endangered Species Act as five distinct population segments (DPS). Currently, at least 18 estuaries coastwide host spawning populations and the viability of these vary, requiring differing levels of protection. Subadults emigrate from their natal estuaries to marine waters where they are vulnerable to bycatch; one of the major threats to the rebuilding of populations. As a result, identifying the population origin of Atlantic Sturgeon in coastal waters is critical to development of management plans intended to minimize interactions of the most imperiled populations with damaging fisheries. We used mitochondrial DNA control region sequencing and microsatellite DNA analyses to determine the origin of 261 Atlantic Sturgeon collected off the Delaware coast during the spring months. Using individual-based assignment (IBA) testing and mixed stock analysis, we found that specimens originated from all nine of our reference populations and the five DPSs used in the listing determination. Using IBA, we found that the Hudson River population was the largest contributor (38.3%) to our coastal collection. The James (19.9%) and Delaware (13.8%) river populations, at one time thought to be extirpated or nearly so, were the next largest contributors. The three populations combined in the South Atlantic DPS contributed 21% of specimens; the Altamaha River, the largest population in the South Atlantic DPS, only contributed a single specimen to the collection. While the origin of specimens collected on the Delaware coast was most likely within rivers of the New York Bight DPS (52.1%), specimens that originated elsewhere were also well represented. Genetic analyses provide a robust tool to identify the population origin of individual sturgeon outside of their natal estuaries and to determine the quantitative contributions of individual populations to coastal aggregations that are vulnerable to bycatch and other anthropogenic threats.

Delaware↗
USGS2021

Accuracy and precision of otolith-derived age Interpretations for known-age lake trout

Catch-at-age data are used to inform important management decisions for recovering populations of Lake Trout Salvelinus namaycush . Age data for Lake Trout are commonly derived from interpretation of annual growth marks (annuli) on the fish’s otoliths. Due to the tendency for annuli to vary in appearance and the subjectivity that is inherent to any age interpretation method, it is important that the common sources of interpretation error be well understood for any aging method used to inform management plans. In this study, coded wire tags were used to establish true ages for 153 Lake Trout to measure the precision and accuracy of age interpretations made from transverse-sectioned otoliths and to identify sources of potential age interpretation error that researchers and managers may encounter when using this method. Precision of age interpretations, as measured by average coefficient of variation, ranged from 7.9% to 9.2%. Accuracy of age interpretations varied among readers, with exact matches ranging from 41.8% to 53.6% and accuracy within ±1 year ranging from 81.0% to 83.0%. Age interpretation errors were more likely to be overestimates of true age for Lake Trout under age 7 and underestimates for Lake Trout over age 13. However, only reader 1 exhibited significant systematic bias in their age interpretations. Poor clarity of the first annuli, growth checks resembling annuli, and faintness of narrow annuli near otolith margins in older fish were identified as likely sources of interpretation error in this study. A digital reference collection of known-age Lake Trout otoliths is provided as supplemental material in the online version of this article. This collection can be used for training new readers, measuring the accuracy of age interpretations, and monitoring for aging bias by anyone using otoliths to obtain age data for Lake Trout.

North American Journal of Fisheries Management↗
USGS2023

Spawning locations, movements, and potential for stock mixing of walleye in Green Bay, Lake Michigan

Effective fishery management in large systems relies on understanding how individual stocks contribute to a fishery over spatial and temporal scales. The current conceptual model for management of Walleye Sander vitreus in Green Bay designates Walleye in the northern and southern parts of the bay as distinct stocks, with little mixing between the northern and southern fisheries, and assumes that Walleye in both northern and southern Green Bay primarily spawn in tributaries as opposed to shoreline or offshore reef areas. We used acoustic telemetry to test this conceptual model for Walleye management in Green Bay. Telemetry indicated that the majority of Green Bay Walleye use tributaries for spawning. However, many individuals were assigned to open-water spawning locations during consecutive years in both northern (26%) and southern (21%) Green Bay, suggesting that open-water spawners may represent a larger proportion of the Walleye stocks than previously thought. Differential movement was observed between northern and southern portions of Green Bay, with 56% of Walleye tagged in northern Green Bay crossing receiver lines to move south compared to only 19% of Walleye tagged in southern Green Bay crossing receiver lines to move north. Walleye typically transitioned across these boundaries in summer and fall, suggesting that stock contributions to the fishery in each zone may differ seasonally. Differential movements of northern Green Bay Walleye may be influenced by broad-scale differences in habitat and prey availability, which are likely related to the differential effects of dreissenid mussel invasion in Green Bay. Our results suggest that adjustment of monitoring efforts to account for open-water spawners may provide a more complete picture of stock status. Additionally, more research examining potential food web effects of northern Green Bay Walleye moving into southern Green Bay may be needed to determine how these movements might influence other important species.

Wisconsin↗
USGS2018

Proactive Rainbow Trout suppression reduces threat of hybridization in the Upper Snake River Basin

Preserving remaining nonhybridized populations Cutthroat Trout Oncorhynchus clarkii is a conservation priority often requiring management action. Although proactive programs for Rainbow Trout O. mykiss and hybrid suppression offer a flexible tool, particularly in large interconnected river basins, this management approach is used less frequently than alternatives such as barriers and piscicides. We describe the results of a targeted Rainbow Trout hybrid suppression program spanning 15 years in the upper Snake River, Wyoming, a core stronghold for Yellowstone Cutthroat Trout O. clarkii bouvieri . Initially, Rainbow Trout hybrids were relatively common in the Gros Ventre River, a major tributary to the Snake River. Between 2002 and 2016, 926 individuals of Rainbow Trout ancestry were removed from the Gros Ventre River. Relative abundance of Rainbow Trout hybrids decreased over this time, while the Yellowstone Cutthroat Trout population increased. Temporal genetic data collected in 2007–2008 and again in 2014 demonstrate that the overall proportion Rainbow Trout admixture and the proportion of hybrids in a sample both significantly decreased in the Gros Ventre River and did not increase elsewhere in the Snake River basin. In conclusion, proactive Rainbow Trout suppression appears to have reduced the threat of Rainbow Trout hybridization in this river basin and helped protect an interconnected metapopulation that has a highly diverse life history and genetic variation important for long-term persistence.

Idaho, Wyoming↗
USGS2015

Status and conservation of interior Redband Trout in the western United States

In this article we describe the current status and conservation of interior (potamodromous) Redband Trout Oncorhynchus mykiss sspp. throughout its range in the western United States using extant data and expert opinion provided by fish managers. Redband Trout historically occupied 60,295 km of stream habitat and 152 natural lakes. Currently, Redband Trout occupy 25,417 km of stream habitat (42% of their historical range) and 124 lakes or reservoirs. Nonhybridized populations are assumed to occupy 11,695 km (46%) of currently occupied streams; however, fish from only 4,473 km (18%) have been genetically tested. Approximately 47% of the streams occupied by Redband Trout occur on private land, 45% on government lands, and 8% in protected areas. A total of 210 Redband Trout populations, occupying 15,252 km of stream habitat (60% of the current distribution) and 95,158 ha of lake habitat (52%), are being managed as “conservation populations.” Most conservation populations have been designated as weakly to strongly connected metapopulations (125; 60%) and occupy much more stream length (14,112 km; 93%) than isolated conservation populations (1,141 km; 7%). The primary threats to Redband Trout include invasive species, habitat degradation and fragmentation, and climate change. Although the historical distribution of interior Redband Trout has declined dramatically, we conclude that the species is not currently at imminent risk of extinction because it is still widely distributed with many populations isolated by physical barriers and active conservation efforts are occurring for many populations. However, the hybridization status of many populations has not been well quantified, and introgression may be more prevalent than documented here. We recommend (1) collecting additional genetic data and estimating distribution and abundance by means of a more rigorous spatial sampling design to reduce uncertainties, (2) collecting additional information to assess and predict the impacts of climate on populations, and (3) continuing to use this database to evaluate the status of Redband Trout and inform conservation efforts through time.

North American Journal of Fisheries Management↗
USGS2000

Seasonal changes in ruffe abundance in two Lake Superior tributaries: Implications for control

Since the discovery of ruffe Gymnocephalus cernuus in the St. Louis River in 1987, state, federal, and tribal management agencies have sought to slow its spread to areas outside the western end of Lake Superior. A debate over control strategies highlighted uncertainties about seasonal movements of this species between Lake Superior and its western tributaries. One strategy called for eliminating reproducing populations in tributaries on the periphery of the range using chemical piscicides. That strategy rested on the assumption that ruffe congregate in tributaries during a predictable time of year. This study was designed to explore that assumption. Ruffe collections from the Iron and Sand rivers during 1995 indicated that ruffe were present in those tributaries throughout the summer but that abundance was not highest at the predicted time: June 19–22. Maximum abundance in the Iron River did not coincide with that in the Sand River and did not occur during June 19–22 in either river. The timing of peak abundance was not clearly related to changes in water temperature. Ruffe were present in substantial numbers in Lake Superior during June 19–22 when aggregations in the tributaries had been predicted. These findings do not support the assumption of the chemical control strategy.

North American Journal of Fisheries Management↗
USGS2017

A refined electrofishing technique for collecting Silver Carp: Implications for management

Detecting nuisance species at low abundance or in newly established areas is critical to developing pest management strategies. Due to their sensitivity to disturbance and erratic jumping behavior, Silver Carp Hypophthalmichthys molitrix can be difficult to collect with traditional sampling methods. We compared catch per unit effort (CPUE) of all species from a Long Term Resource Monitoring (LTRM) electrofishing protocol to an experimental electrofishing technique designed to minimize Silver Carp evasion through tactical boat maneuvering and selective application of power. Differences in CPUE between electrofishing methods were detected for 2 of 41 species collected across 2 years of sampling at 20 sites along the Illinois River. The mean catch rate of Silver Carp using the experimental technique was 2.2 times the mean catch rate of the LTRM electrofishing technique; the increased capture efficiency at low relative abundance emphasizes the utility of this method for early detection. The experimental electrofishing also collected slightly larger Silver Carp (mean: 510.7 mm TL versus 495.2 mm TL), and nearly four times as many Silver Carp independently jumped into the boat during experimental transects. Novel sampling approaches, such as the experimental electrofishing technique used in this study, should be considered to increase probability of detection for aquatic nuisance species.

North American Journal of Fisheries Management↗
USGS2016

Simulation modeling to explore the effects of length-based harvest regulations for Ictalurus fisheries

Management of Blue Catfish Ictalurus furcatus and Channel Catfish I. punctatus for trophy production has recently become more common. Typically, trophy management is attempted with length-based regulations that allow for the moderate harvest of small fish but restrict the harvest of larger fish. However, the specific regulations used vary considerably across populations, and no modeling efforts have evaluated their effectiveness. We used simulation modeling to compare total yield, trophy biomass ( B trophy ), and sustainability (spawning potential ratio [SPR] > 0.30) of Blue Catfish and Channel Catfish populations under three scenarios: (1) current regulation (typically a length-based trophy regulation), (2) the best-performing minimum length regulation (MLR best ), and (3) the best-performing length-based trophy catfish regulation (LTR best ; “best performing” was defined as the regulation that maximized yield, B trophy , and sustainability). The B trophy produced did not differ among the three scenarios. For each fishery, the MLR best and LTR best produced greater yield (>22% more) than the current regulation and maintained sustainability at higher finite exploitation rates (>0.30) than the current regulation. The MLR best and LTR best produced similar yields and SPRs for Channel Catfish and similar yields for Blue Catfish; however, the MLR best for Blue Catfish produced more resilient fisheries (higher SPR) than the LTR best . Overall, the variation in yield, B trophy , and SPR among populations was greater than the variation among regulations applied to any given population, suggesting that population-specific regulations may be preferable to regulations applied to geographic regions. We conclude that LTRs are useful for improving catfish yield and maintaining sustainability without overly restricting harvest but are not effective at increasing the B trophy of catfish.

North American Journal of Fisheries Management↗
USGS2007

Tag return models allowing for harvest and catch and release: Evidence of environmental and management impacts on striped bass fishing and natural mortality rates

Catch-and-release fisheries have become very important in the management of overexploited recreational fish stocks. Tag return studies, where the tag is removed regardless of fish disposition, have been used to assess the effectiveness of restoration efforts for these fisheries. We extend the instantaneous rate formulation of tag return models to allow for catch and release as well as harvest. The key point of our methods is that, given an estimate of the tag reporting rate, the fishing mortality rate (F) is separated into two components: the mortality on harvested fish and the "mortality" on tags (because the lags are removed) of fish released alive. The total fishing mortality rate for untagged fish is the sum of the Fs due to harvest and hooking mortality suffered by fish released alive. Natural mortality rates can also be estimated. Both age-independent models and age-dependent models are constructed, and the age-dependent models are illustrated by application to data from a study of striped bass Morone saxatilis in Chesapeake Bay from 1991 to 2003 by the Maryland Department of Natural Resources. By fitting models of the natural mortality rate with limited age and year dependence, we demonstrate an overall decrease in natural mortality rates as fish age and provide evidence of an increase in natural mortality beginning in the late 1990s, when an outbreak of the disease mycobacteriosis is thought to have begun. Our results indicate that fishing mortality is age dependent; selectivity increases up to age 6, when fish appear to be fully recruited to the fishery. There is also evidence of an increase in fishing mortality since 1995, when regulations were relaxed. ?? Copyright by the American Fisheries Society 2007.

North American Journal of Fisheries Management↗
USGS2020

Targeting aggregations of telemetered Lake Trout to increase gillnetting suppression efficacy

Conserving Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri by suppressing invasive Lake Trout Salvelinus namaycush in Yellowstone Lake is a high priority for Yellowstone National Park resource managers. Here, we tested whether targeting telemetered Lake Trout could increase the efficacy of Lake Trout suppression by gill netting. Mobile acoustic tracking surveys were performed to identify aggregations of tagged Lake Trout in summer (June–August) 2017. Lake Trout aggregations were relayed daily to suppression crews by phone, radio, or text and a printed map. Suppression crews set 30 large-mesh gill nets targeting telemetered Lake Trout aggregations (target treatment) and 124 large-mesh gill nets not targeting telemetered aggregations (nontarget treatment). Mean log e (CPUE) was higher for the target treatment (0.37; 95% credible interval [CRI] = 0.08–0.65) than for the nontarget treatment (−0.37; 95% CRI = −0.51 to −0.21). Mean of the target treatment was higher than the mean of the nontarget treatment for over 99% of the 1,000 draws from the joint posterior distribution. Because of telemetry costs, mean CPUE per US$10,000 spent was similar between the target treatment (0.20; 95% CRI = 0.15–0.26) and the nontarget treatment (0.15; 95% CRI = 0.13–0.17). Telemetry is an effective strategy for improving Lake Trout CPUE, which corresponds to an increased efficiency in the Lake Trout suppression program.

Wyoming↗
USGS2004

Consumption dynamics of the adult piscivorous fish community in Spirit Lake, Iowa

At Spirit Lake, one of Iowa's most important fisheries, walleye Sander vitreus (formerly Stizostedion vitreum) is one of the most popular species with anglers. Despite a century of walleye stocking and management in Spirit Lake, walleye growth rate, size structure, and angler harvest continue to decline. Our purpose was to determine the magnitude and dynamics of walleye population consumption relative to those of other piscivorous species in Spirit Lake, which would allow managers to judge the feasibility of increasing the abundance, growth rate, and size structure of the walleye population. We quantified food consumption by the adult piscivorous fish community in Spirit Lake over a 3-year period. Data on population dynamics, diet, energy density, and water temperature from 1995 to 1997 were used in bioenergetics models to estimate total consumption by walleye, yellow perch Perca flavescens, smallmouth bass Micropterus dolomieu, largemouth bass Micropterus salmoides, black crappie Pomoxis nigromaculatus, and northern pike Esox lucius. Estimated annual consumption by the piscivorous community varied roughly fourfold, ranging from 154,752 kg in 1995 to 662,776 kg in 1997. Walleyes dominated total consumption, accounting for 68, 73, and 90% (1995-1997, respectively) of total food consumption. Walleyes were also the dominant consumers of fish, accounting for 76, 86, and 97% of piscivorous consumption; yellow perch followed, accounting for 16% of piscivorous consumption in 1995 and 12% in 1996. Yellow perch were the predominant fish prey species in all 3 years, accounting for 68, 52, and 36% of the total prey consumed. Natural reproduction is weak, so high walleye densities are maintained by intensive stocking. Walleye stocking drives piscivorous consumption in Spirit Lake, and yearly variation in the cannibalism of stocked walleye fry may be an important determinant of walleye year-class strength and angler success. Reducing walleye stocking intensity, varying stocking intensity from year to year, and attempting to match stocking intensity with the abundance of prey species other than walleye may improve the walleye fishery in Spirit Lake.

North American Journal of Fisheries Management↗
USGS2019

A statewide evaluation of Florida Bass genetic introgression in Tennessee

Largemouth Bass (Micropterus salmoides) are one of the most popular freshwater sport fish in the United States and managers in southeastern states have stocked the Florida Bass (M. s. floridanus) subspecies outside of its natural range to increase size structure of existing Largemouth Bass populations. In Tennessee, fisheries for Largemouth Bass are concentrated in reservoirs of the Cumberland and Tennessee River systems; however, Florida Bass stockings have to date been restricted to two reservoirs of the Tennessee River and have varied significantly in extent and duration. We quantified levels of genetic admixture between Florida Bass and Largemouth Bass using 38 species-diagnostic single nucleotide polymorphisms for 979 fish sampled from 14 reservoirs from the Cumberland and Tennessee River systems. We tested for differences in genetic admixture across river systems and evaluated the relative importance of fish stockings in explaining observed levels of genetic admixture. Levels of genetic admixture and associated variation was higher in reservoirs of the Tennessee River (range = 6.3 – 30.4 average percent Florida Bass alleles) relative to the Cumberland River (range = 5.7 – 13.4 %), but admixture was not solely related to stocking rates. The highest levels of Florida Bass introgression were detected in Chickamauga Reservoir, the most extensively stocked reservoir in the state. Linear models identified fish stocked as a significant overall predictor of admixture, but we also observed stocked and unstocked reservoirs with similar levels of admixture, suggesting factors other than stocking influence population genetics. Our statewide assessment of reservoir-level patterns of hybridization among black bass was performed prior to the recent expansion of Florida Bass stocking efforts in Tennessee, and thus, represents a baseline for evaluating future stocking.

Tennessee↗
USGS2026

Tag retention, growth, condition, and survival of externally marked Yellow Perch

Objective: Determining the movement and survival of Yellow Perch Perca flavescens that inhabit Lake Erie is a priority management concern, yet contemporary understanding of their cross-jurisdictional movements and exploitation is lacking. To support future movement and survival studies, we evaluated the retention rates, condition, growth, and survival associated with four external tagging methods. Methods: One-hundred hatchery- reared Yellow Perch (188–257 mm) were tagged and held in recirculating aquaculture systems over a 168- d period. We tested four external tag types, including loop tags, ring tags, streamer tags, and T- bar anchor tags, and quantified tag retention rates, as well as tagging effects on condition, growth, and survival. Results: T- bar anchor and loop tags had 100% retention, whereas ring (54%) and streamer (0%) retention was poor. The condition and growth of fish were not affected by any of the tagging methods; however, the loop tags caused abrasive wounds near the tagging site that could lead to secondary infection and latent effects on survival. We found no evidence that tagging resulted in mortality. Conclusion: External T- bar tags were the most efficient to apply and provided a marking option that was highly visible, had high retention, and had no effects on condition, growth, or survival in Yellow Perch over the 168- d study period.

North American Journal of Fisheries Management↗
USGS2016

Life history characteristics and vital rates of Yellowstone Cutthroat Trout in two headwater basins

The Yellowstone Cutthroat Trout Oncorhynchus clarkii bouvieri is native to the Rocky Mountains and has declined in abundance and distribution as a result of habitat degradation and introduced salmonid species. Many of its remaining strongholds are in headwater basins with minimal human disturbances. Understanding the life histories, vital rates, and behaviors of Yellowstone Cutthroat Trout within headwater stream networks remains limited yet is critical for effective management and conservation. We estimated annual relative growth in length and weight, annual survival rates, and movement patterns of Yellowstone Cutthroat Trout from three tributaries of Spread Creek, Wyoming, and two tributaries of Shields River, Montana, from 2011 through 2013 using PIT tag antennas within a mark–recapture framework. Mean annual growth rates varied among tributaries and size-classes, but were slow compared with populations of Yellowstone Cutthroat Trout from large, low-elevation streams. Survival rates were relatively high compared with those of other Cutthroat Trout subspecies, but we found an inverse relationship between survival and size, a pattern contrary to what has been reported for Cutthroat Trout in large streams. Mean annual survival rates ranged from 0.32 (SE = 0.04) to 0.68 (SE = 0.05) in the Spread Creek basin and from 0.30 (SE = 0.07) to 0.69 (SE = 0.10) in the Shields River basin. Downstream movements from tributaries were substantial, with as much as 26.5% of a tagging cohort leaving over the course of the study. Integrating our growth, survival, and movement results demonstrates the importance of considering strategies to enhance headwater stream habitats and highlights the importance of connectivity with larger stream networks.

North American Journal of Fisheries Management↗
USGS2020

Influence of population density and length structure on angler catch rate in kokanee fisheries

Management agencies are often charged with providing fisheries that lead to angler participation. Catch rate is one of the primary drivers of angler participation but can be influenced by a suite of factors, including population structure (e.g., density and size structure). The complexity of understanding how population structure influences angler catch rate is typified in kokanee Oncorhynchus nerka fisheries. Previous research suggests that angler catch rates of kokanee are positively influenced by fish density and total length. However, that research was based on data collected using size-selective midwater trawls. Due to the potential limitation of previous research, we sought to (1) understand the relative bias of midwater trawls and gill nets for describing the size structure of kokanee available to anglers and (2) re-evaluate the influence of fish density and fish length on angler catch rates in kokanee fisheries. Midwater trawl, gill-net, and creel data were collected on five prominent kokanee fisheries throughout Idaho in 2016 and 2017. Catch composition and percent overlap of midwater trawls, gill nets, and angler-caught fish were compared to understand the efficacy of midwater trawls and gill nets for representing the size structure of kokanee available to anglers. In addition, the influence of kokanee density and length on angler catch rates was evaluated. Midwater trawls primarily sampled small kokanee (<330 mm) and exhibited little overlap with angler-caught fish, whereas gill nets sampled more large fish (>330 mm) and exhibited higher overlap with angler-caught fish when compared to midwater trawls. Fish length was not positively associated with angler catch rates. However, fish density exhibited a positive relationship with angler catch rates. Our results highlight the importance of gear choice for understanding how kokanee populations function and elucidate the tradeoffs associated with population density, fish length, and resulting kokanee fisheries.

Idaho↗
USGS2011

Radiotelemetry to estimate stream life of adult chum salmon in the McNeil River, Alaska

Estimating salmon escapement is one of the fundamental steps in managing salmon populations. The area-under-the-curve (AUC) method is commonly used to convert periodic aerial survey counts into annual salmon escapement indices. The AUC requires obtaining accurate estimates of stream life (SL) for target species. Traditional methods for estimating SL (e.g., mark–recapture) are not feasible for many populations. Our objective in this study was to determine the average SL of chum salmon Oncorhynchus keta in the McNeil River, Alaska, through radiotelemetry. During the 2005 and 2006 runs, 155 chum salmon were fitted with mortality-indicating radio tags as they entered the McNeil River and tracked until they died. A combination of remote data loggers, aerial surveys, and foot surveys were used to determine the location of fish and provide an estimate of time of death. Higher predation resulted in tagged fish below McNeil Falls having a significantly shorter SL (12.6 d) than those above (21.9 d). The streamwide average SL (13.8 d) for chum salmon at the McNeil River was lower than the regionwide value (17.5 d) previously used to generate AUC indices of chum salmon escapement for the McNeil River. We conclude that radiotelemetry is an effective tool for estimating SL in rivers not well suited to other methods.

Alaska↗