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Population Dynamics of Burbot in the Eastern Basin of Lake Erie
Between 1987 and 2003, burbot Lota lota abundance in eastern Lake Erie significantly increased, especially in Ontario waters. We considered four hypotheses to explain this increase: (1) reduced competition; (2) increased abundance of the two main prey species; (3) reduced interference with burbot reproduction by alewife Alosa pseudoharengus ; and (4) reduced predation by sea lamprey Petromyzon marinus on burbot. Our results suggested that the recovery of the burbot population of Lake Erie was driven by effective sea lamprey control. We then examined time series for burbot abundance or biomass in the remaining four Great Lakes, extending as far back as the early 1970s to present time, characterized the long-term trends, and attempted to explain these temporal trends. Recovery of the burbot population occurred in lakes Michigan and Huron during the 1980s. Control of sea lampreys also appeared to be a requirement for recovery of burbot populations in these two lakes. Declines in alewife abundance appeared to be a second requirement for burbot recovery in Lakes Michigan and Huron. Although sea lampreys have been controlled in Lake Ontario, alewives are probably still too high in abundance to permit burbot recovery. Burbot abundance in Lake Superior has probably remained relatively low and stable since 1930. We estimated growth and mortality parameters for Lake Erie burbot by aging 2,793 burbot caught in annual surveys of eastern Lake Erie from 1994-2003. The results suggest that recent survival and growth of Lake Erie burbot is greater than it was in 1946 and greater than the other North American populations contrasted. Further, the results support a hypothesis that a healthy population of adult lake trout can serve as a buffer species that reduces predation of burbot by sea lampreys when sea lamprey populations increase. Finally, we present results from sensory panels on fried burbot meat that had been frozen and stored for 5 months with three methods: (1) dipping meat in liquid nitrogen, followed by storage at –80 ° C; (2) direct freezing and storage at –80 ° C; and (3) direct freezing and storage at –18 ° C. Fried samples that had been directly frozen and stored at -80 ° C were scored by panelists as most tender, most juicy, and most desirable overall. Panelists also scored fried samples that had been directly frozen and stored at -80 ° C as less fishy tasting than samples frozen at -18 ° C. Although direct freezing of burbot meat at -80 ° C yielded more preferred cooked samples, prepared products (e.g., canned chowder) from frozen burbot meat may be better suited for commercial sale than frozen fillets.