EFFECTS OF LOW-HEAD BARRIERS ON FISH SPECIES RICHNESS IN STREAMS WITHIN THE LAURENTIAN GREAT LAKES BASIN

The parasitic sea lamprey, Petromyzon, marinus, is an exotic invader and a serious economic concern in the Laurentian Great Lakes. It causes significant economic losses by attacks on a variety of fishes, including those of commercial and recreational value. A variety of potential control procedures have been suggested or attempted to deal with this species in the Great Lakes. Low-head barriers are being installed as an alternative to chemical control of sea lamprey in tributary streams around the lakes (Great Lakes Fishery Commission 1992). We assessed historical data from federal, provincial and state agencies to investigate whether the placement of low-head sea lamprey barriers has had an effect on stream fish communities within the Laurentian Great Lakes basin (McLaughlin et al. 2001). Previous field surveys and experimental studies on selected Great Lakes streams had suggested that sea lamprey barriers could impede instream movements of non-target fishes (Porto et al. 1999). This lead us to predict that the construction of low- head barriers would block upstream movement of nontarget fishes, and hence cause a reduction in species diversit