DHA and EPA levels in a piscivorous fish changed by preying upon stocked salmon fry

DHA and EPA levels in a piscivorous fish changed by preying upon stocked salmon fry

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Abstract Increases in prey population size can affect the physiology and ecology of upper-trophic ilootpaperie level organisms.This phenomenon is known as a bottom-up effect.For example, the increased abundance of prey resources can trigger physiological (internal) changes in predators, such as improvements in nutritional status.

However, these physiological aspects of bottom-up effects have not been considered.In this study, we tested the hypothesis that white-spotted charr Salvelinus leucomaenis, a salmonid fish, increases body stores of omega-3 fatty acids, especially docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA), by preying upon stocked hatchery-reared masu salmon Oncorhynchus masou fry in streams.The dynamics of fatty acid contents in charr inhabiting salmon-stocked and unstocked streams clearly support this hypothesis: fatty acid contents (DHA, EPA, and here total fatty acid) increased after stocking in stocked streams, but not in unstocked streams.

In addition, DHA increased with increasing body size of white-spotted charr and vice versa for EPA.The impacts of human activities, such as fish stocking, on freshwater ecosystems are a matter of serious concern for conservation.Future attempts to gain a comprehensive understanding of the impacts of fish stocking should consider not only community ecology but also physiology.