Low-head barrier dams restrict the movements of fishes in two Lake Ontario streams

Publication Date



dams, Great Lakes, sea lamprey, lamprey, barriers, mark-recapture, streams, upstream, species richness

Journal or Book Title

North American Journal of Fisheries Management


The Great Lakes Fishery Commission (GLFC) is considering greater use of low-headbarrier dams on stream tributaries of the Laurentian Great Lakes to control populations of sealampreys (Petromyzon marinus). The impact of these barriers on nontarget fishes is not known. Amark-recapture study on four Lake Ontario streams examined movements of fishes in streamswith (barrier) and without (reference) low-head barriers. A significantly lower proportion of fishesmoved across a real barrier on barrier streams than across a hypothetical barrier on referencestreams (0.15 versus 0.50, respectively). The impact of the barriers on movement was morepronounced in spring and fall than in summer. However, the likelihood of fishes moving versusnot moving between sample segments on either side of a barrier location (but not across thebarrier) did not differ significantly between barrier and reference streams. The upstream(longitudinal) decline in species richness was greater for barrier streams than for referencestreams in each season. At both interspecific and intraspecific levels, mean total lengths of fishtraversing real barriers were significantly greater than the mean total lengths of fish traversinghypothetical barriers. Our findings demonstrate that low-head barriers restrict the movements ofsome fishes and suggest this restriction affects assemblage structure above the barrier.





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