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Space and food utilization by salmonids in marsh habitats of the Fraser River estuary Dunford, William Errington

Abstract

The temporal utilization of space and food by juvenile Pacific salmon was studied in selected marsh habitats of the Fraser River Estuary. Two types of marginal habitat were examined- slough habitat (exposed to main current) and channel habitat (backwaters). Chum salmon fry (Oncorhynchus keta) and chinook salmon fry (0. tshawytscha) were the most abundant species present in both habitats, with peak densities occurring in late April. Chum and chinook exploited many similar food sources, and the size of prey selected was examined to show a size segregation of the diet. Chum tended to select a. greater proportion of smaller, planktonic prey, while chinook ingested a greater proportion of larger, benthic prey. The divergence in types of prey and prey size selected was greatest during maximum density in late April and early May. The density of chinook was greater than chum, except in early April. Few chum were taken, after early June, while chinook were present until late July, showing a steady increase in length throughout the season. It is suggested, that chinook may reside in the estuarine marsh habitats temporarily each spring and summer. The chum fry utilize the habitats for feeding, during migration, but disperse to marine habitats in a shorter time period than chinook.

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