Mechanisms regulating growth and food consumption of walleyes and yellow perch in Saginaw Bay, Lake Huron.

I investigated bioenergetics of growth and food consumption of walleyes and yellow perch in Saginaw Bay, Lake Huron, using data from a 1986-1988 fisheries survey and historical data on yellow perch and benthic invertebrates. I performed the most comprehensive corroboration study to date on two yellow perch energetic models. The Karas-Thoresson energetic model adequately defined yellow perch energetics, and was used to estimate prey consumption by the yellow perch population. I tested the hypothesis that extirpation of large benthic prey created poor feeding conditions for yellow perch. During 1986-1988, large benthic prey were absent and yellow perch were stunted. They grew slowly, experienced a size bottleneck, and natural mortality was severe. Most yellow perch consumed chironomid larvae, and piscivory was rare. Comparison of present population characteristics with historical data suggested that stunting resulted from extirpation of large benthic prey, particularly nymphs of the burrowing mayfly Hexagenia limbata. In the presence of Hexagenia, yellow perch growth was moderate to fast depending on population size, size bottlenecks were not present, and fish reached large size despite fishing mortality. Declines in yellow perch growth coincided closely with extirpation of Hexagenia, which appeared to be a preferred prey. Eutrophication of Saginaw Bay appears to have created poor feeding conditions for yellow perch because of reductions in size structure of the benthic community. I also evaluated piscivory by walleyes and yellow perch by comparing estimates of prey consumption with production. The large yellow perch population consumed over twice the prey fish biomass eaten by walleyes. Predation mortality was substantial for all common prey fish except yellow perch. Diet overlap between walleyes and perch was often high. Walleye predation was not an important source of mortality for yellow perch, but yellow perch were important to walleyes as prey. Fast walleye growth appeared to depend on clupeid availability, and piscivory by the two species could rapidly alter the prey fish community during years when clupeids experienced year class failure.PhDNatural Resources and EnvironmentUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/104198/1/9501027.pdfDescription of 9501027.pdf : Restricted to UM users only