Salmon egg subsidies and interference competition among stream fishes


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Authors: Bailey, CJ; Andersson, LC; Arbeider, M; Bradford, K; Moore, JW
Year: 2019
Journal: Environ. Biol. Fishes 102: 915-926   Article Link (DOI)
Title: Salmon egg subsidies and interference competition among stream fishes
Abstract: Resource availability may modulate interference interactions among competitors. For example, competition among stream fishes for drifting eggs from salmon (Oncorhynchus spp.) spawning events may be influenced by the availability of this energy-rich food source. This study used camera-based techniques to evaluate the effect of varied prey availability (i.e., pink salmon (O. gorbuscha) eggs) on rates of interference competition within natural stream fish communities at 10 sites. Aggressive interactions were quantified across different levels of egg additions, ranging from 6 to 3575 O. gorbuscha eggs, at 10 sites on the Keogh River, British Columbia, Canada. There were fewer aggressive interactions among salmonids (O. kisutch, O. mykiss, and O. clarkii clarkii) when there were more available eggs. Aggressive interaction rates were species-dependent; for example, the number of aggressive acts relative to null expectations based on abundances were highest in juvenile coho (O. kisutch) towards conspecifics. For some interactions, size of fish appeared to be a key factor as well. Thus, higher densities of spawning salmon in streams may provide sufficient prey resources in the form of eggs to temporarily decrease interference competition among stream fishes.
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