Research Document - 2016/070

Seasonal variation in the composition of fishes caught during trawl-based surveys of Little Bear Creek, Ontario

By Scott M. Reid, Anita LeBaron, and Jason Barnucz

Abstract

Little Bear Creek, a tributary of Lake St. Clair, is classified as an agricultural drain and has been identified for maintenance. The creek supports six fish species at risk including Pugnose Shiner, Lake Chubsucker, Grass Pickerel, Blackstripe Topminnow, Spotted Sucker, and Pugnose Minnow. Project staging, fish exclusion methods, and timing windows for in-water works have been proposed as mitigation to minimize drainage work impacts. To assess whether the proposed timing window would minimize the risk of direct mortality to fish species at risk, a trawl-based fish survey was completed over three different time periods (summer, fall and early winter) in 2015. A total of 3,715 individuals representing 32 species were collected from 30 trawling sites. Overall, the most abundant species were Bluegill, Brook Silverside, Ghost Shiner and Gizzard Shad. Of the six fish species at risk known from Little Bear Creek, only the endangered Pugnose Shiner was captured. Two invasive species were also detected, Round Goby and Tubenose Goby. There were large among-season differences in the abundance and composition of Little Bear Creek fishes. The greatest number and diversity of fishes were captured during fall trawling. Ninety percent of all Pugnose Shiner were collected in the fall. The largest fall to winter declines in distribution and abundance were associated with bass, crappie and sunfish species. Compared to the fall, fewer Little Bear Creek fishes are expected to be affected by maintenance activities during the winter.  While the timing window is outside spawning and egg incubation periods, it is not likely to avoid the early-rearing period for Pugnose Shiner or direct impacts to young-of-the-year fish species at risk.

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