Gilling in Trap-Net Pots and Use of Catch Data to Predict Lake Whitefish Gilling Rates

Abstract

Gilling of lake trout (Salvelinus namaycush) and lake whitefish (Coregonus clupeaformis) in trapnet pots was investigated for three commercial nets set during the fall of 1980 in northern Lake Huron. Approximately 73% of observed giliing occurred as nets were being lifted. Consequently, high percentages of gilled fish were alive when fishermen harvested their catch. More than two-thirds of the gilled fish were located in side netting, while smaller proportions of gilled fish were found in the back, front, top, and bottom of the pot. A regression model was developed to predict the number of lake whitefish gilled based on total catch. Independent variables for the statistically significant (P < 0.001) model were the number of lake whitefish caught and the square root of the number of lake trout in the pot. Lake whitefish schooling behavior associated with the approach of spawning season was regarded as an important factor in explaining gilling rates. The number of gilled whitefish could be reduced by increasing the frequency of net lifts if it were found to be economically feasible.