Andrew H. Fayram

Interactions between Walleyes and Four Fish Species with Implications for Walleye Stocking

Abstract We used a number of different data sets and four criteria to evaluate evidence of competition and predation between walleye Sander vitreus and northern pike Esox lucius, muskellunge E. masquinongy, smallmouth bass Micropterus dolomieu, and largemouth bass M. salmoides in northern Wisconsin lakes. The four criteria were as follows: (1) indices of population abundance were inversely related, (2) two species had shared resources or one species preyed on the other, (3) competition or predation was strong enough to produce a measurable effect, and (4) experimental manipulations produced results consistent with the hypothesis of competition or predation. Using these criteria, we identified which species interact most strongly with walleyes, determined the most likely mechanism for interaction (predation, competition, or both), and characterized the effects of walleye stocking on these species. Largemouth bass was the only species that strongly interacted with walleyes: (1) indices of largemouth bass an...

The role of density dependence in growth patterns of ceded territory walleye populations of northern Wisconsin: Effects of changing management regimes

Abstract We assessed density-related changes in growth of walleye Sander vitreus in the ceded territory of northern Wisconsin from 1977 to 1999. We used asymptotic length (L ∞), growth rate near t 0 (ω), and body condition as measures of walleye growth to determine the relationship between growth and density. Among lakes, there was weak evidence of density-dependent growth: Adult density explained only 0–6% of the variability in the growth metrics. Within lakes, growth was density dependent, L ∞, ω, and body condition of walleyes changing with density for 69, 28, and 62% of the populations examined, respectively. Our results suggest that walleye growth was density dependent within individual lakes. However, growth was not coherently density dependent among lakes, which was possibly due to inherent differences in the productivity, surface area, forage base, landscape position, species composition, and management regime of lakes in the ceded territory. Densities of adult walleyes averaged 8.3 fish/ha and di...

A Comparison of Regulatory and Voluntary Release of Muskellunge and Walleyes in Northern Wisconsin

Abstract Voluntary release of fish can play an important role in the management of recreational fisheries. I investigated how the release rate, defined as the proportion of all fish caught that are released, may be affected by minimum length regulations and changes in angler behavior over time for walleye Stizostedion vitreum and muskellunge Esox masquinongy fisheries in northern Wisconsin. Release rates estimated from creel surveys were compared among years over a 10-year period and between different minimum length regulations. The release rate for walleyes varied significantly between different minimum length regulations but did not vary among years. The muskellunge release rate increased significantly over time but did not vary between different minimum length regulations. The magnitude of the difference in release rate between the two substantially different length regulations in the walleye fishery (9.0%) was similar to the increase in the release rate over time in the muskellunge fishery (7.5%). The...

Positive Effects of Agricultural Land Use Changes on Coldwater Fish Communities in Southwest Wisconsin Streams

Abstract The Conservation Reserve Program (CRP) is a federal program that encourages the planting of cool- or warm-season grass cover on highly erodible croplands and along stream corridors. We sought to determine whether fish community structure in coldwater streams was associated with CRP and other agricultural land use changes in southwestern Wisconsin. We compared coldwater fish index of biotic integrity (IBI) scores and species richness in streams located in areas of relatively high (21.3% of land area; high-CRP area) versus relatively low (12.1% of land area; low-CRP area) CRP participation. All of the streams were sampled in the 1970s before implementation of the CRP and again at the same locations after implementation, from 2000 to 2005. Pre-CRP fish communities were characterized by a relatively high diversity of eurythermal species and low coldwater IBI scores. We found significant increases in coldwater IBI scores over time in streams within the high-CRP area relative to streams within the low-...

Evaluation of a 15-Inch Minimum Length Limitfor Walleye Angling in Northern Wisconsin

Abstract In 1990 the Wisconsin Department of Natural Resources implemented a 15-in (1 in = 2.56 cm) minimum length limit for walleyes Stizostedion vitreum on waters throughout the state, excluding some lakes where walleyes demonstrated slow growth or high mercury contamination. To determine if management goals for the regulation had been met, we examined the effects on lakes with self-sustaining walleye populations in the ceded territory of Wisconsin, specifically effects on population structure, exploitation, and angler catch and harvest. We compared creel survey data from up to 19 lakes sampled before and after the regulation had been implemented, including lakes affected by (N = 13) and exempted (N = 6) from the 15-in regulation. We also compared postregulation (1990–1998) creel and biological data from up to 76 lakes that were both affected and exempted. Effects of tribal harvest, which occurred on all of these 76 lakes but was not subject to the same length limit, were also examined using postregulat...

Determining Optimal Stocking Rates Using a Stock-Recruitment Model: An Example Using Walleye in Northern Wisconsin

Abstract We propose that stock–recruitment models can be used to estimate optimal stocking rates. Data to estimate the optimal stocking rates can be obtained in a relatively short amount of time by sampling similar populations over a few years. Whether the goal of stocking is endangered species recovery or supplementation of recreational fisheries, accurately determining the optimal stocking rate is of ecological and financial importance. As an example, we applied this approach using a Ricker stock–recruitment model to walleye Sander vitreus stocking in northern Wisconsin lakes. Using June stocking data and fall age-0 survey data for 39 lakes over a 14-year time period, we found that the stocking rate resulting in the greatest number of age-0 walleyes was 60 age-0 walleyes/ha. Similarly, using June stocking data and fall age-1 survey data in 18 lakes over a 9-year time period we found that the stocking rate resulting in the greatest number of age-1 walleyes was 75 age-0 walleyes/ha. About 16% of the varia...

Evaluation of a Modified Bag Limit for Walleyes in Wisconsin: Effects of Decreased Angler Effort and Lake Selection

Abstract We evaluated a modified daily bag limit for walleyes Sander vitreus to determine whether management goals were achieved. The modified bag limit consisted of no minimum length limit but allowed a daily harvest of only one walleye longer than 356 mm. The Wisconsin Department of Natural Resources implemented the single-fish, 356-mm regulation in 1997 on a number of lakes in northern Wisconsin that were previously subject to a 381-mm minimum length limit. The intent of the regulation was to increase the harvest of smaller walleyes in order to increase growth, spawning stock abundance, and harvest rate in lakes characterized by high densities of slow-growing walleyes. We examined the effects of the regulation in light of variables associated with walleye populations, the walleye fishery, and tribal harvest. All lakes included in our evaluation are located within the ceded territory of northern Wisconsin, where tribal harvest of walleyes, which is regulated differently than angler harvest, occurs annua...

Influence of Walleye Stocking on Angler Effort in Wisconsin

We compared relationships between angler effort and population densities of four species of fish in lakes with stocked and self-sustaining walleye populations in Wisconsin to determine the effect of walleye stocking on angler effort. The origin of walleye populations affected angler effort directed at walleyes in lakes with a daily bag limit of two, but not with daily bag limits of three or five. For lakes with a bag limit of two, angler effort was related to walleye density in lakes with self-sustaining walleye populations but not in stocked lakes. For lakes with a bag limit of three, angler effort did not differ between lakes with stocked and self-sustaining populations. For lakes with a bag limit of five, angler effort was not related to walleye density. Walleye stocking reduced the amount of effort directed at largemouth bass, but had no effect on effort directed at smallmouth bass or muskellunge. We thank the WDNR fisheries biologists, technicians, and creel clerks who collected the data included in this investigation. In particular, we thank Mike coshun and Jamison Wendel. We also thank the Great Lakes Indian Fish and wildlife Commission for providing data. Patrick Schmalz and Sarah Carter Fayram provided helpful comments on an earlier draft of this manuscript. Steve Hewett, Mile Staggs, Dennis Schenborn, Jay Beder, Stefan Schnitzer, and John Janssen helped facilitate the completion of this project. Partial funding for this project was provided by the Federal Aid in Sport Fish Restoration program.

Effects of Stream Order and Ecoregion on Variability in Coldwater Fish Index of Biotic Integrity Scores within Streams in Wisconsin

ABSTRACT Most indices of biotic integrity (IBIs) are designed to represent the biological condition of individual sampling locations in a river or stream. Characterizing the biological condition of an entire stream is often of interest and requires data from multiple sites. The representativeness of these data depends on the variability in the scores between sampling locations. We compared the variability in IBI scores using two parameters whose values can be obtained easily—stream size and ecoregion. The variability in IBI scores tended to be greater in smaller Wisconsin streams (first and second order) than in larger ones (third and fourth order) but there was no difference in the variability between ecoregions. Thus, in order to confidently characterize the true mean IBI score for a smaller stream, essentially a census of the entire stream would be required. In order to confidently characterize the mean IBI score of a larger stream, approximately six scores are necessary, which is equivalent to one station per 2 km of stream given the mean length of third and fourth order streams in Wisconsin.

Simulated Equilibrium Walleye Population Density under Static and Dynamic Recreational Angling Effort

Abstract 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 ...