Feeding in troubled waters: a comparative diet analysis of pink (Oncorhynchus gorbuscha) and chum (O. keta) salmon during their first months at sea in the Broughton Archipelago, British Columbia

摘要

Closely related species divide shared resources to reduce interspecific competition and to allow for coexistence when resources are limiting. Upon ocean entry, juvenile pink and chum salmon coexist in mixed schools and feed on similar prey. The diet of juvenile pink and chum salmon during their first two months at sea in the coastal waters of the Broughton Archipelago, British Columbia, was described for 2003 and 2006. Full stomach rankings suggested a lack of prey limitation in both years. Stomach content analysis revealed a greater diet separation among pink and chum in 2003 than in 2006. Species specific prey preferences were observed. Electivity comparisons of prey consumed with prey available in the plankton indicated selective feeding in both species. Considering the importance of diet in the survival of juvenile salmon and ultimately in adult recruitment, an understanding of prey conditions provides insight into salmon population trends in the region.