Samples of progeny from wild rainbow trout (Salmo gairdneri) homing to four widely separated Great Lakes watersheds, when incubated and reared under similar conditions and acclimated to 15 C, did not differ in tolerance to upper lethal temperatures. The size of the individual fish under test did not affect the resistance time. The similar response of the four samples to upper lethal temperatures complements the conclusions previously reported from phenotypic observations of wild and cultured trout from the same four watersheds.
The reproductive potential of two lake whitefish (Coregonus clupeaformis) populations with dissimilar growth rates was studied and compared. The smaller-sized Pigeon Lake females and the larger-sized Buck Lake females had similar ratios of gonad weight to body weight during the gonad development period, but the Pigeon Lake fish produced fewer but larger eggs. Spawning occurred in both lakes for a period approaching 4 mo in both open water and under ice cover in a wide range of water temperatures. Concentrated spawning occurred in shallow water over a boulder, gravel, and sand surficial lake sediment of both lakes. The incubation of whitefish eggs was retarded under ice cover but accelerated to hatching as the water warmed and the ice left the lakes in the spring. The length of the egg incubation period, not the size of the egg under incubation, governed the size of the hatching lake whitefish.
Divergence in the growth pattern of Pigeon Lake and Buck Lake whiteflsh (Coregonus clupeaformis) began during the winter months in young-of-the-year fish. The growth rate of individuals in the Pigeon Lake whitefish population has declined over the past 12 years whereas individuals in the Buck Lake population have maintained a relatively stable growth pattern. These differences did not appear to be genetically controlled. Increased interspecific and intraspecific competition for the available food supply likely suppressed the growth rate of the Pigeon Lake whitefish population. Reduction of predator numbers in Pigeon Lake by the removal of habitat and increased angling pressure accelerated recruitment to both the white-fish population and other competitive feeding forage fish. A predator–prey relationship conducive to the maintenance of a faster growing lake whitefish population has been maintained in Buck Lake over the same period of time.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.