Fish Species Dynamics

In recent years, exotic fish species in the upper Great Lakes watershed continue to expand their range and are having substantial negative effects on native fishes.  A particular exotic, the rainbow smelt (Osmerus mordax), is spreading rapidly in the upper Great Lakes region.  Changes in the native fish communities have followed the smelt invasions; this species impacts native fishes directly through predation and indirectly through exploitation competition.

The long-term data sets have been instrumental in allowing researchers at the North-Temperate Lakes (NTL) LTER site to identify the mechanisms of inter-specific interaction, rates of decline and extinctions of native species.

Predation effects of smelt have led to the extinction of native cisco (Coregonus artedi) in Sparkling Lake over the span of approximately a decade (Figure 1 Hrabik et al. 1998).  Also, competitive interactions have reduced a historically dominant yellow perch (Perca flavescens) population in Crystal Lake to a small component of the fish community (Figure 1, Hrabik et al. 1998).  In this example, the long-term records of temperature and fish size allowed estimation of consumption rates of young of the year perch in Crystal Lake.  The resulting analyses showed that young of the year perch were feeding at a much lower rate in years when young of the year smelt were abundant and that the low feeding rate was linked to year class failure and declines in abundance of perch (Figure 8, Hrabik et al. 2001).   The information contained in the long-term records collected by the NTL-LTER site was essential for the identification of mechanisms of negative interaction among exotic smelt and native fish species in northern lakes.  Short-term studies (two- to five-years) would not have been able to identify the shifts in abundance and performance of the native fish community that were the result of invasions of exotic rainbow smelt.

Hrabik, T. R., J. J. Magnuson and A. S. McLain.  Predicting the effects of rainbow smelt on native fishes in small lakes:  evidence from long-term research on two lakes. Canadian Journal of Fisheries and Aquatic Sciences 55(6): 1364-1371.