Larval fish drift in the Valley River, Manitoba: influence of abiotic and biotic factors, and relationships with future year-class strengths

Authors:
  • TJThomas A. Johnston
    Thomas A. Johnston
  • MGMarc N. Gaboury
    Marc N. Gaboury
  • RJRichard A. Janusz
    Richard A. Janusz
  • LJLaureen R. Janusz
    Laureen R. Janusz
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Abstract
We examined patterns in the spring drift of larval fishes in the Valley River, Manitoba. White sucker (Catostomus commersoni) and walleye (Stizostedion vitreum) were the most common species. The median date of larval drift for walleye was significantly earlier than for all other species. Capture rates of all species were significantly greater during the night than during the day. Larval abundance was positively related to river discharge in the 35 d preceding the median date of larval drift. Larval abundance was also positively related to mature female biomass in Dauphin Lake for walleye, but not for white sucker. Year-class strength of a cohort (catch per unit effort of 3- or 4-year-old fish) in Dauphin Lake was positively related to total larval drift of the same cohort (3 or 4 years earlier) in the Valley River for walleye, but not for white sucker. Our results suggest that the year-class strength of Dauphin Lake walleye is determined very early in the life history and that factors which enhance the natural production of walleye larvae will enhance walleye recruitment.

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