Examination of Factors Contributing to the Decline of the Yellow Perch Population and Fishery in Les Cheneaux Islands, Lake Huron, with Emphasis on the Role of Double-crested Cormorants

Abstract

Double-crested cormorants increased exponentially in the Les Cheneaux Islands area during the 1980s and 1990s. The yellow perch fishery and population declined by the late 1990s and finally collapsed in 2000. Previous research confirmed that cormorants fed seasonally on perch. This analysis sought to use creel survey data and data from an annual gillnet collection to characterize the perch fishery and population during this time so as to explore if declines were a result of declining recruitment or increased mortality or both. Regression analysis explored six possible independent variables to account for yellow perch trends. Yellow perch abundance and its fishery declined throughout the Les Cheneaux Islands. Mean age declined which was consistent with a high mortality rate explanation. Yellow perch recruitment, as indicated by gillnet catch rate of age-2 perch, continued during this time including one very strong year class. Total annual mortality rates determined by the cohort method were as high as 85% during much of this time and increased over the time series. Cormorant abundance accounted for a total of five significant relationships with the yellow perch data, more than any other independent variable. From this, it is apparent that cormorant predation is at least one factor affecting the perch population and fishery and may be the most influential force, among those examined, during this time series.