| My research encompasses several aspects of fisheries management, ranging from the use of historical databases to help guide monitoring programs to a field study examining the effects of natural and anthropogenic factors on largemouth bass nest success. A common feature of my research is the use of mixed models and generalized linear mixed models to partition variance in ecological response variables and to account for hierarchical data structures. Because the use of mixed models is not commonly employed in fisheries research, where hierarchical data structures are common, my first chapter is an instructional paper on the advantages of using mixed models versus general linear models and how to implement mixed model analyses in a common statistical package, SAS. My other chapters use mixed models to address specific questions and hypotheses. For my second chapter, the specific research question was: are the ecoregion and watershed frameworks for lake classification useful approaches for grouping lakes with regards to fish growth rates (i.e., can mean fish length at age be partitioned by ecoregions and watersheds)? For the ecoregions analysis, I also examined if within-ecoregion variability could be explained by local water quality and lake morphometry characteristics. Variance in mean length at age between ecoregions for all species was not significant, and between-watershed variance estimates were only significant in 3 out of 14 analyses, indicating that ecoregions and watersheds were ineffective in partitioning variability in mean length at age. The results suggest that managers should not rely solely on ecoregions or watersheds for grouping lakes with similar growth rates. For my third chapter, I examined if habitat alteration and spring angling could explain variability in largemouth bass nest success. In 2004, we monitored nest distribution and success and quantified local nest habitat features, lakewide angler effort, and lakeshore development in five Michigan lakes to determine the extent to which habitat alteration and/or fishing limit the number of successful nests. Surprisingly, local habitat characteristics were not important determinants of the probability of a nest producing swim-up fry (P > 0.05). At the whole-lake scale, however, nest success was negatively related to dwelling density, with the probability of a nest producing swim-up fry declining from 0.77 in the lowest dwelling density lake to 0.45 in the highest dwelling density lake (P = 0.018). These results demonstrate that knowledge of the magnitude of anthropogenic effects and the spatial scale at which they operate is integral for black bass management. (Abstract shortened by UMI.)... |
