Structure and stability of the midsummer fish communities in Chequamegon Bay, Lake Superior, 1973-1996

We analyzed the structure and stability of the summer fish communities of C hequamegon Bay, Lake Superior, during 1973-1996 from data collected with bo ttom trawls at 39 stations. Fifty-three taxa were collected during the stud y, but we found that relative abundances for 20 taxa described most of the internal variability of the data for all taxa. Abundance data for the 20 sp ecies showed that two communities existed in the bay; one inhabited shallow water (less than or equal to 3.0 m) whereas the other inhabited deeper wat er (>3.0 m). No temporal patterns of change were found in the structure of the shallow-water community, whose variation was best described by abundanc es of 12 taxa. The deepwater community, whose variation was best described by eight taxa, underwent three periods of stability; 1973-1978, 1979-1988, and 1989-1996. We conclude that the shallow-water community was stable thro ughout the 24 years studied. Dynamics of the deepwater community were great ly affected by changes in stocking rates of lake trout Salvelinus namaycush and splake (hybrid of brook trout S. fontinalis X lake trout) and by rehab ilitation of populations of lake herring Coregonus artedi and lake whitefis h C. clupeaformis information on the existence, structure, stability, and h abitats of fish communities in the bay will be useful for assessing changes in those communities that result from further changes in the bay or lake e cosystems.