Temporal and spatial distribution of pelagic larval fishes of Dauphin Lake, Manitoba
Rowes, Kenneth Dale
The distribution of larval fish was investigated in Dauphin Lake (51o 17'N, 99o 48'W) 283 km northwest of Winnipeg, Manitoba from May - August, 1984 and 1985. Larvae were sampled using dual fine mesh conical nets with non-porous mouth-reducing cones. Tweive species of larval fish were found, of which four species dominated in 1984: Notropis atherinoides, Perca flavescens, Etheostoma nigrum, and Percopsis omiscomaycus. Percina caprodes replaced P. omiscomaycus in 1985. Species composition varied, with. P. omiscomaycus dominating in late May and early June, P. flavescens and E. nigrum in late June and early July, and N. atherinoides mid July to early August. CPUE was greatest in the clay-silt habitat associated with rivers and lowest in the sandy and cobble habitats. Habitat type and temperature were major environmental factors influencing species distribution. Abundance of fish increased in close proximity to river mouths in early spring, and in mid-water during mid-summer. The hypothesis that the timing of appearance of pelagic larval fish jn Dauphin Lake is temperature controlled was supported. I found that (a) the time of appearance of larvae in early spring reflected the cold water (<15.0oC) spawning preference of benthic spawners using near-shore spawning grounds before and during ice breakup; (b) the timing of occurrence of larvae in early summer was attributed to the cool water (16.0-20.0oC) spawning preference of other benthic species; (c) the timing of occurrence of larvae in mid-summer reflected pelagic warm water (21.0-23oC) spawners. The hypothesis that the spatial distribution of the major species of larval fish is attributed to habitat type and in-lake environmental variables such as lake mixing and water currents was also supported by species abundances in each location during each sample period.