Bureau of Fisheries Management

Oshkosh, WI, United States

Bureau of Fisheries Management

Oshkosh, WI, United States

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Koenigs R.P.,Bureau of Fisheries Management | Bruch R.M.,Bureau of Fisheries Management | Kamke K.K.,Bureau of Fisheries Management
North American Journal of Fisheries Management | Year: 2013

The age data used to manage Walleye Sander vitreus fisheries are not always accurate, as otoliths typically provide more accurate age estimates for larger, older Walleyes than dorsal spines. We assessed the impacts that the aging error associated with the use of dorsal spines has on the estimated age distribution, growth and mortality rates, and yield per recruit for Walleyes in the Winnebago system, Wisconsin. Age distributions derived from otolith age estimates more accurately portrayed variable recruitment than those derived from dorsal spine age estimates. The mean estimates of instantaneous total annual mortality developed from sex-specific catch curves were greater when dorsal spine age estimates were used (0.515 for males, 0.493 for females) than when otolith age estimates were (0.349 for males, 0.396 for females), with most of the differences being observed in natural mortality estimates. The von Bertalanffy growth models were not significantly different, but the yield-per-recruit models (which rely heavily on von Bertalanffy model parameters) incorporating spine age data produced average yield estimates 50-70% lower than the models developed from otolith ages. The yield-per-recruit models derived from spine-determined ages also resulted in lower recommendations as to the age and size of fish for maximum yield at all exploitation levels than the models developed from otolith age data. The mean dorsal spine and otolith age estimates were similar for male Walleyes <457 mm and female Walleyes <508 mm, but for larger fish otoliths yielded significantly older ages than spines. Given the economic and social impacts of the Winnebago system Walleye fishery, we recommend exclusive use of otoliths to obtain the most accurate estimates of fish age, growth, mortality, and yield. In populations in which the sacrifice of large quantities of fish is not acceptable, we recommend using spines to estimate the ages of smaller fish (males <457 mm, females <508 mm) and otoliths to estimate the ages of fish larger than these critical lengths. © 2013 Copyright Taylor and Francis Group, LLC.


Koenigs R.P.,Bureau of Fisheries Management | Bruch R.M.,Bureau of Fisheries Management | Kamke K.K.,Bureau of Fisheries Management
North American Journal of Fisheries Management | Year: 2013

Rates of tag loss should be estimated and accounted for when using mark-recapture surveys and angler tag returns to estimate fish population abundance and exploitation rates. Walleyes Sander vitreus sampled during April 2010 spawning assessments conducted in the Winnebago system, Wisconsin, were marked with anchor tags and upper caudal fin clips to estimate tag loss rates during three time intervals: 0-11 d posttagging, 0-90 d posttagging, and 1 year posttagging. Tag loss was negligible (<0.5%) within the first 11 d but increased to 4.7% within the first 90 d and to 21.9% after 1 year. After we corrected for the tag loss occurring within the first 90 d, estimates of population abundance decreased 4.3% for females and 4.4% for males, while estimates of exploitation increased 4.9% for both sexes. Accounting for 21.9% annual tag loss led to more severe decreases in the estimates of population abundance (20.0% for females and 21.2% for males) and increases in the estimates of exploitation (28.0% for both sexes) than not accounting for any tag loss. Higher exploitation rates resulted in higher estimates of fishing mortality and lower estimates of natural mortality. When used in yield-per-recruit models, the estimated natural mortality rates derived from exploitation rates that accounted for tag loss resulted in higher yields through the implementation of larger minimum length limits to maximize yield. We recommend that managers evaluate the effectiveness of their tagging operations by estimating tag loss and assessing the potential impacts of quantified loss on management metrics. We also caution against the application of population models without an accurate estimate of tag loss and the associated impacts on estimates of population abundance and exploitation and, in turn, fishing and natural mortality rates. © 2013 Copyright Taylor and Francis Group, LLC.


Mosel K.J.,University of Wisconsin - Stevens Point | Mosel K.J.,U.S. Fish and Wildlife Service | Isermann D.A.,University of Wisconsin - Stevens Point | Hansen J.F.,Bureau of Fisheries Management
North American Journal of Fisheries Management | Year: 2015

Abstract: Harvest regulations for Black Crappie Pomoxis nigromaculatus and Yellow Perch Perca flavescens in the northern USA and Canada have not been thoroughly evaluated, and specific guidance regarding where minimum length limits (MLLs) might improve these fisheries is lacking. We examined whether: (1) transitioning from an aggregate statewide daily creel limit of 25 panfish to species-specific daily creel limits of <25 fish or implementing statewide MLLs could reduce harvest of Black Crappie and Yellow Perch in Wisconsin by ≥25%, and (2) MLLs would improve yield by ≥10% and mean TL of harvested fish by ≥25 mm in Wisconsin fisheries. Creel surveys indicated that ≥94% of Wisconsin anglers did not harvest a Black Crappie or Yellow Perch, and ≤0.12% of anglers harvested a daily creel limit of 25 fish. Daily creel limits would need to be ≤7 fish/ angler to reduce harvest by ≥25%. Statewide MLLs would need to be ≥229 mm for Black Crappie and ≥203 mm for Yellow Perch to reduce harvest by ≥25%, but predicted responses to MLLs varied among simulated populations. In general, MLLs were not predicted to improve yield, indicating that growth overfishing was not a widespread problem. Minimum length limits could improve mean TL of harvested fish, but increases ≥25 mm were only observed under 254-mm and 279-mm MLLs, and anglers would have to accept predicted reductions in harvest of ≥30% to achieve these improvements. A 229-mm MLL offered a more equitable trade-off between increases in mean TLs of harvested fish (11–21-mm improvements) and reductions in harvest (22–37% reductions). Our modeling provides a framework for managers to make more informed decisions regarding harvest regulations, but more information regarding angler preferences is needed for selecting appropriate management objectives and harvest regulations. © 2015, © American Fisheries Society 2015.


Bocast C.,University of Wisconsin - Madison | Bruch R.M.,Bureau of Fisheries Management | Koenigs R.P.,Bureau of Fisheries Management
Journal of Applied Ichthyology | Year: 2014

The primary goal of this study was to obtain accurate data of previously undocumented lake sturgeon (Acipenser fulvescens Rafinesque, 1817) spawning sounds, generated during wild sturgeon reproduction. Biologists have long known that lake sturgeon produce low-frequency sounds during spawning bouts; energy from these sounds can break the surface of the water occasionally and propagate harmonics in the terrestrial atmosphere, creating a faint drumming popularly known as 'sturgeon thunder'. Understanding the contribution of this sonic behavior in context is essential for gaining a more comprehensive scientific appreciation of the process of sturgeon spawning, and accurate acoustic data should prove useful for fisheries managers seeking to monitor or enhance sturgeon stocks for reproductive activity. Recordings were made at several locations on the Wolf and Embarrass rivers during the 2011-2013 spawning seasons. Drumming sounds ranging from 5 to 8 Hz fundamental frequency were evident. Other characteristic noises associated with spawning lake sturgeon, including low-frequency rumbles and hydrodynamic sounds, were identified. Other high frequency sounds were also discovered. All of these sounds coalesce into a distinctive acoustic signature of lake sturgeon spawning activity. Knowledge of this sonic signature can be used to accurately document reproductive activity at multiple locations over extended periods using remote recording tools and techniques. © 2014 Blackwell Verlag GmbH.


Jennings M.J.,Bureau of Science Services | Sloss B.L.,U.S. Geological Survey | Hatzenbeler G.R.,Bureau of Science Services | Kampa J.M.,Bureau of Science Services | And 4 more authors.
Fisheries | Year: 2010

Conservation of genetic resources is a challenging issue for agencies managing popular sport fishes. To address the ongoing potential for genetic risks, we developed a comprehensive set of recommendations to conserve genetic diversity of muskellunge (Esox masquinongy) in Wisconsin, and evaluated the extent to which the recommendations can be implemented. Although some details are specific to Wisconsin's muskellunge propagation program, many of the practical issues affecting implementation are applicable to other species and production systems. We developed guidelines to restrict future brood stock collection operations to lakes with natural reproduction and to develop a set of brood lakes to use on a rotational basis within regional stock boundaries, but implementation will require considering lakes with variable stocking histories. Maintaining an effective population size sufficient to minimize the risk of losing alleles requires limiting brood stock collection to large lakes. Recommendations to better approximate the temporal distribution of spawning in hatchery operations and randomize selection of brood fish are feasible. Guidelines to modify rearing and distribution procedures face some logistic constraints. An evaluation of genetic diversity of hatchery-produced fish during 2008 demonstrated variable success representing genetic variation of the source population. Continued evaluation of hatchery operations will optimize operational efficiency while moving toward genetic conservation goals.


Koenigs R.P.,Bureau of Fisheries Management | Bruch R.M.,Bureau of Fisheries Management | Stelzer R.S.,University of Wisconsin - Oshkosh | Kamke K.K.,Bureau of Fisheries Management
Fisheries Research | Year: 2015

Although accurate age data are essential when estimating somatic growth and mortality rates required to effectively manage exploited walleye (. Sander vitreus) populations, aging structures have not been validated for age ranges present in most walleye populations. Otoliths and dorsal spines were collected from 302 walleye considered known age in the Winnebago System, Wisconsin, USA: 142 that were assigned ages via progression of discrete length modes following an individual strong year class (ages 0-3), and 160 (ages 4-10, 12-13, 16, 18) that were initially tagged at lengths small enough to accurately assign age ±1 year (<380. mm) and later recaptured and assigned an age (assigned age at tagging plus number of years at liberty). Paired aging structures were also collected from over 2000 additional walleye sampled during spawning assessments, tournament monitoring, and other surveys to better understand the relationship between spine and otolith age estimates and to compare catch curve residuals from structure and sex-specific catch curves to standard walleye recruitment indices. We found otoliths were accurate for walleye ages 0-10, while dorsal spines yielded relatively accurate age estimates for walleye ages 1-5, but underestimated age of walleye age-6 and older. Age distributions within catch curves constructed from otolith age estimates correlated well with measured year class strength, while age distributions from dorsal spine age estimates correlated poorly. Our results from fish considered known age validate the accuracy of otolith age estimates for walleye up to age-10, with corroborating evidence from catch curves and accurate recruitment indices strongly suggesting that otoliths are valid for all ages of Winnebago System walleye. We recommend the use of otoliths to accurately estimate walleye age, growth, and mortality, and to provide accurate age data for other population analyses. © 2015 Elsevier B.V.


Fayram A.H.,Office of the Great Lakes | Tober Griffin J.D.,Office of the Great Lakes | Wendel J.L.,Bureau of Fisheries Management
Aquatic Ecosystem Health and Management | Year: 2014

Walleye (Sander vitreus) populations in Wisconsin are near the center of their geographical range and support valuable fisheries. The role of seasonal temperature and precipitation in Walleye recruitment was examined using regression tree analysis. Climatological variables were estimated at the 8 km2 scale and Walleye recruitment was estimated based on 298 individual electrofishing surveys. Estimated changes in Walleye recruitment between 1950 and 2006 were examined based on changes in explanatory climatological variables. Spring precipitation and summer maximum temperature were significant predictors of age-0 Walleye density and mean estimated changes in these variables between 1950 and 2006 were used to estimate changes in Walleye recruitment. The model predicted a small overall increase in Walleye recruitment and provides insight into the direct role of climatological variables in Walleye recruitment. However, given the low explanatory power (R2 = 0.103), it is likely that historic climatological changes have had a limited effect on recruitment levels. © 2014 Copyright © 2014 AEHMS.


Schueller A.M.,National Oceanic and Atmospheric Administration | Fayram A.H.,Bureau of Fisheries Management | Hansen M.J.,University of Wisconsin - Stevens Point
North American Journal of Fisheries Management | Year: 2012

Understanding the dynamics of angling effort and how fish populations are affected by angler effort is an important and often unappreciated component of fisheries management. Our objective was to determine the extent to which angling-induced mortality limits walleye Sander vitreus population density in northern Wisconsin lakes. We developed a simulation model to evaluate the effects on long-term equilibrium walleye population density caused by effort limitations, density-dependent angling effort, and angling regulations. Equilibrium density was limited by angling effort when effort was held constant but was generally lower when effort was density dependent. Equilibrium density ranged from 3.46 to 21.79 adults/ha when effort was density dependent, similar to the observed median density in lakes sustained by natural reproduction (8.7 adults/ha). Median equilibrium density was 23.3 adults/ha when effort was zero. Equilibrium density was higher when harvest was regulated by a minimum length limit as opposed to no length limit and with no postrelease mortality than with postrelease mortality. Population collapse was more likely and equilibrium density was lower when the population density and effort/ha relationship was strongest. Because the observed relationship between adult walleye population density and effort/ha was weaker, we conclude that open-access walleye fisheries in northern Wisconsin are generally self-regulating. However, populations likely persist at lower population densities than would be expected if angling effort were limited to lower levels than those currently observed. Our results are intuitive; however, they suggest that density increases may be on the order of 100% when effort is severely restricted compared with open-access fisheries with unlimited effort. Other fish species may experience different expected density increases with restricted angler effort depending on a number of factors, but our results suggest that population density changes can be dramatic and that similar modeling exercises may be useful to managers of other fish species if increasing density is of interest. © American Fisheries Society 2012.


Hansen J.F.,Bureau of Fisheries Management | Fayram A.H.,Bureau of Fisheries Management | Hennessy J.M.,Bureau of Fisheries Management
North American Journal of Fisheries Management | Year: 2012

Walleyes Sander vitreus are an important cultural and economic resource in northern Wisconsin, both as a recreational fishery and a tribal subsistence fishery. Understanding the recruitment of age-0 walleyes to the adult population could be of great utility in effectively managing harvest and informing stocking efforts in this mixed use fishery. Our objective was to determine the relationship between abundance of age-0 walleyes in the fall and the subsequent adult year-class 4 years later and to explain additional residual variation related to environmental variables. Since 1986, fall electrofishing surveys have been conducted to estimate the densities of age-0 walleyes and spring mark-recapture surveys to estimate spawning adult walleyes. We fit a gamma stock-recruitment curve to a data set of 104 paired surveys (age-0 survey with adult survey conducted 4 years later) on 58 lakes and attempted to explain residual variation related to additional environmental variables. Our analysis suggests that the maximum number of age-4 fish (3.36/ha) is not produced by the maximum number of age-0 fish but by a somewhat intermediate density (243/ha) and that this relationship varies with the complexity of the shoreline. This density-dependent relationship should help managers refine models forecasting walleye abundance, as well as optimize stocking rates. © American Fisheries Society 2012.


Snobl Z.R.,Bureau of Fisheries Management | Koenigs R.P.,Bureau of Fisheries Management | Bruch R.M.,Bureau of Fisheries Management | Binkowski F.P.,University of Wisconsin - Milwaukee
North American Journal of Fisheries Management | Year: 2015

Abstract: A common guideline for attaching or imbedding transmitters for fish is that the transmitter weight should not exceed 2% of the total weight in air of a fish. This guideline is thought to limit the negative effects of tagging, but little research supports it. Our objectives were to compare the postrelease dispersal rates of 48 hatchery-reared fingerling Lake Sturgeon Acipenser fulvescens (265–305 mm, 80–100 g) surgically implanted with sonic transmitters equating to 2% and 4% of fish body weight, and to compare the dispersal rates between fish stocked in two river systems in Wisconsin. Downstream dispersal rates of the 2% and 4% treatments were not significantly different within the individual rivers but were significantly different between rivers. We recommend that transmitters weighing up to 4% of total body weight can be used without effects on the movement of fingerling Lake Sturgeon. Received January 6, 2015; accepted June 29, 2015 © 2015, © American Fisheries Society.

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