7143 - Laserfiche WebLink

Home Browse Search

. populations of adult northern pike in a set of lakes by enhancing the quality "and quantity of spawning habitat (Williams and Jacob 1971). Young northern pike eventually disperse from spawning areas, but pike of all ages continue to frequent shallow areas with vegetation. Small pike are especially dependent on this habitat. Growth and food conversion efficiency of young pike kept in tanks with no vegetation were erratic; pike kept in ponds with no vegetation resided in-any areas that provided cover (Johnson 1960). The minimum size of northern pike captured in gill nets in Lac La Ronge was positively associated with depth, but the maximum size was not, indicating that large pike use a wider range of depths than do small pike (Koshinsky 1979). Nine tagged northern pike (1.6 to 4.1 kg) in an eutrophic Alberta lake generally remained in areas with submerged and emergent aquatic vegetation, in water shallower than 4 m, and within 300 m of shore (Diana et al. 1977). Northern pike in a Michigan lake, that were tagged at spawning time and subsequently recaptured by anglers, were caught almost exclusively in weed beds (Carbine and Applegate 1948). Ninety. percent of the pike captured in a gill netting survey of Great Slave Lake in northern Canada were caught within 400 m of shore, and very few were taken at depths greater than 10 m (Rawson 1951). Fisheries surveys in lakes of the Churchill River basin in northern Saskatchewan also indicated that pike mostly inhabit water shallower than 10 m, although they occur at least as deep as 27 m (Dean 1975; Liaw and O'Connor 1975; Koshinsky 1979). Depth per se does not appear to be the factor determining depth distribu- tion of northern pike. Depth distribution appears to be in response to dif- ferences in temperature, dissolved oxygen, vegetation, and food. .Northern pike rarely venture below the thermocline (Reighard 1915; Pearse 1922; Rawson 1951). In Douglas Lake, Michigan, a well-defined thermocline typically forms at a depth of 12.2 to 13.7 m; 13.7 m was the maximum depth at which northern pike were captured (Reighard 1915). The other northern pike collected in this study were caught at depths 5 7.9 m, which coincides with the lower (lakeward) depth limit of aquatic vegetation. Eleven of these 21 pike were caught at depths between 7.6 and 7.9 m, perhaps indicating that pike prefer the interface between vegetation and open water (Reighard 1915). Underwater observations of northern pike in an Alberta lake also indicated an attraction to this boundary zone (Chapman and MacKay, in prep.). The edges of vegetated areas would provide good cover for feeding activities. Northern pike are a coolwater species (Casselman 1978). Their occurrence over a broad latitudinal belt, circa 40 to 70° N in North America (Karvelis 1964), however, demonstrates their adaptability to a variety of thermal regimes. For example, the average maximum summer temperature in the limnetic zone of Great Bear Lake (Northwest Territories) is 5 to 7° C, and the ice free season usually lasts less than 19 weeks (Johnson 1966b). Temperatures may reach 16° C, at least briefly, in protected bays, where most northern ,pike occur (Miller 1947). Lake Mendota, in southern Wisconsin, typically warms to about 24° C, with an ice free season of 36 to 40 weeks (Juday 1940). 4 J