Melissa T. Drake

A Comparison of Bluegill Reproductive Strategies and Growth among Lakes with Different Fishing Intensities

Abstract Life history theory suggests that maturation schedules of male bluegill Lepomis macrochirus and the occurrence of alternative male reproductive strategies (i.e., parental or cuckolder) may contribute to the development and duration of undesirable bluegill population size structure (few fish larger than 150 mm). To investigate this relationship, we assessed parental male maturation schedules and relative abundance of cuckolders in six lakes subject to differing levels of fishing effort. Bluegills were collected by electrofishing shortly after the onset of the spawning season. Lakes with lower fishing effort had parental males that were older and larger at maturity than parental males in lakes with high fishing effort. Also, growth of parental males in lakes with low fishing effort was faster at older ages, and growth of immature males was faster than growth of cuckolders. Unlike other lakes, two of the three low-fishing-effort lakes had very few cuckolders. Our results indicate that intense fishin...

Development of a Fish-Based Index of Biotic Integrity for Small Inland Lakes in Central Minnesota

Abstract We developed a fish-based index of biotic integrity (IBI) for a set of Minnesota lakes having similar geophysical and chemical features. Fish data were collected by means of trap nets, gill nets, shoreline seines, and backpack electrofishing. Of 30 evaluated metrics, we identified 16 metrics of three types: species richness, community assemblage, and trophic composition. In contrast to lotic IBIs, where a single sampling gear is usually used, data from all four sampling gears were necessary for IBI development. We selected metrics based on responses to measures of human-induced stress based on watershed land use patterns and human population density. Species richness and community composition metrics describing intolerant or habitat specialist species were most sensitive to differences in human-induced stress. Because these species were found in the nearshore zone of lakes, effective sampling of the nearshore fish community was essential to the development and performance of the IBI. Trap-net- an...

Effects of Simulated Angling Regulations on Stunting in Bluegill Populations

Abstract Stunting in populations of bluegill Lepomis macrochirus is a major management problem in the upper midwestern United States, Traditionally, stunting has been attributed to a lack of food resources. An alternative theory suggests that stunting may result from harvest of the large parental males that inhibit spawning by smaller males, allowing small males to direct energy to reproduction instead of to growth. We used a population model to simulate restrictions on harvest of large males under various conditions of vulnerability to angling, growth rate, and angler effort. Regulations tested were a daily bag of 5 fish and seasonal bags of 50 fish or 50 fish but only 1 trophy specimen (>180 mm total length); a limit of only 1 trophy fish during the spawning season; and a spawning season closure. Growth and angler effort had the greatest effects on size structure in simulated bluegill populations; high growth and low effort led to notable increases in mean fish length. Tested regulations and male vulner...

Validation and Application of a Fish-Based Index of Biotic Integrity for Small Central Minnesota Lakes

Abstract We evaluated the performance of an index of biotic integrity (IBI) based on 16 fish population metrics of three types: species richness, community assemblage, and trophic composition. Two sets of central Minnesota lakes independent from the original set of lakes used to develop the IBI model were used to validate it. One set of lakes (n = 15) had physical features similar to those used to develop the IBI, while the other set (n = 22) averaged 9 m shallower with 28% more littoral area. We used general linear models to test whether the relationships between IBI or individual metric score and indicators of lake quality (trophic state, floristic quality, or surrounding land use) were the same or differed for the original IBI data set and each new data set. Responses were similar among all data sets, lake IBI scores and individual metrics reflecting differences in land use, trophic state, and aquatic habitat. Sensitivity of individual metrics to different measures of stress varied, supporting the need...

Size- and Sex-Specific Capture and Harvest Selectivity of Walleyes from Tagging Studies

AbstractEstimates of size- and sex-specific gear selectivity are important for making informed management decisions. Sex-specific selectivity curves may be needed for two-sex statistical catch-at-age models when information about sex ratios in the catch is unavailable. We used data from three tagging programs in Minnesota and Wisconsin to estimate the size- and sex-specific selectivity of angling and spearing for Walleyes Sander vitreus. We estimated capture selectivity (the relative catchability of each component of the population) and harvest selectivity (the combined effect of capture selectivity and the decision to retain or release a fish from a given component). These components are of interest because (1) the hooking mortality of released fish contributes substantially to total mortality, so that it is important to know how harvest and release vary by size; and (2) capture selectivity is likely similar across lakes, such that data from other lakes may provide information on capture selectivity for ...

Population Dynamics, Trophic Interactions, and Production of Northern Pike in a Shallow Bog Lake and Their Effects on Simulated Regulation Strategies

Abstract Bog lakes provide a unique but common environment for northern pike Esox lucius within the native range of northern pike. The Minnesota Department of Natural Resources intensively removed nearly half of the population of age-2 and older northern pike from a 28.3-ha bog lake. The removal provided a unique opportunity to study the population dynamics, diet, and secondary production of northern pike. These northern pike formed a dense population with moderate growth rates and a relatively high total mortality rate. Estimated density for fish of ages 2 and older was 59.0 fish/ha, growth through age 4 for both sexes was comparable to an international growth standard, total annual mortality was 63%, and natural mortality was a critically large component of the total mortality. Yellow perch Perca flavescens prey sustained much of the growth and secondary production of northern pike. Estimated secondary production was 4.0 kg/ha/year for male northern pike and 4.8 kg/ha/year for females, with the bulk of ...

Estimating Sampling Effort for Biomonitoring of Nearshore Fish Communities in Small Central Minnesota Lakes

Abstract I estimated the sampling effort required to sufficiently describe the species richness and composition of fish inhabiting the nearshore (wadeable) zone of lakes and compared 10 species richness estimators in 56 similarly sized (small) central Minnesota lakes. A systematic sampling design was employed wherein 10 stations were equally spaced around each lake and the first station was selected randomly. Sampling methods consisted of a combination of backpack electrofishing and shoreline seining. Using sample-based rarefaction curves, eight sampling stations produced at least 90% of the sampled species in 96% of the study lakes. Less sampling effort (four to six stations) was needed to describe the composition of the nearshore fish assemblage, as measured by similarity of species composition or species relative abundances in cumulative samples. The effort needed to sufficiently describe nearshore species richness was not related to observed species richness but was negatively correlated with species ...