Compensation in individual growth rates and its influence on lake trout population dynamics in the Michigan waters of Lake Superior

Abstract

The role of compensatory mechanisms in the population dynamics of lake trout in the Michigan waters of Lake Superior was explored during three time periods: the pre‐sea lamprey period, prior to 1950 when lake trout were at a relatively high abundance and the fishery was the primary source of lake trout mortality; the sea lamprey dominant period, from 1951 to 1961 when lake trout were at a very low abundance due to sea lamprey predation and overexploitation; and currently, from 1985 to 1993 when wild lake trout abundance was at a moderate level. The role of compensatory changes in growth and fecundity rates of lake trout in the Michigan waters of Lake Superior was evaluated using a life table approach. Individual growth and fecundity rates were calculated and compared between time periods. These rates were used to determine age‐specific fecundity which, along with age‐specific survival, were incorporated into a Leslie projection matrix to calculate the finite rate of population increase (λ). Individual growth rates and age‐specific fecundity rates changed in response to the different levels of lake trout abundance during each of the study periods. Lake trout during the sea lamprey dominant period, which experienced the lowest abundance and highest mortality levels, exhibited the fastest individual growth rates and the highest age‐specific fecundity. These high rates contributed to the relatively large compensatory scope exhibited by lake trout during the sea lamprey dominant period as compared to lake trout during the pre‐sea lamprey or the current periods which are associated with higher levels of abundance.