The present paper is meant to analyse some of the ecological factors involved in the sympatric occurrence of brown trout and brook trout in a stream in southeastern Newfoundland.Brook trout were found in the least favourable niches in the pools or in areas of shallow rapids.No sea-run brook trout were encountered, possibly as a result of selection against alleles determining downstream migration.The brook trout population, which was only found in part of the river is probably maintained by involuntary stocking from small tributaries, which are inaccessible to ascending fish.Downstream from the area of sympatry, brook trout are absent possibly because of heavy pollution and upstream (in the absence of restocking from brooks) because of domination and predation by brown trout and differential catchability by anglers.No food segregation between the two species was apparent in the area of sympatric occurrence, which should favour the larger and sometimes piscivorous brown trout.Food selectivity was low for both species and no species specific trends could be detected.Samples of stomach contents from areas where the species were allopatric displayed that food composition varies obviously with the relative abundance of the food objects.
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O. L. Nyman (1970) studied this question.