Salmon egg subsidies and interference competition among stream fishes
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Salmon egg subsidies and interference competition among stream fishes C. J. Bailey & L. C. Andersson & M. Arbeider & K. Bradford & J. W. Moore
Received: 6 June 2018 / Accepted: 24 March 2019 / Published online: 13 April 2019 # Springer Nature B.V. 2019
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 speciesdependent; 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
C. J. Bailey and L. C. Andersson contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s10641-019-00880-9) contains supplementary material, which is available to authorized users. C. J. Bailey (*) : L. C. Andersson : M. Arbeider : K. Bradford : J. W. Moore Earth to Ocean Research Group, Department of Biological Sciences, Simon Fraser University, 8888 University Dr., Burnaby, BC V5A 1S6, Canada e-mail: [email protected]
salmon in streams may provide sufficient prey resources in the form of eggs to temporarily decrease interference competition among stream fishes. Keywords Aggression . Fish community . Resource superabundance . Competitive interactions . Oncorhynchus sp
Introduction Competition for resources can create strong density dependence in stream salmonids (Grant and Kramer 1990) and ultimately set the carrying capacity of their populations (Ayllón et al. 2012). Heightened competition can increase the rates of mortality, decrease growth rates, and displace salmonids from their territories (Imre et al. 2004; Young 2004). For example, intraspecific competition expressed as territoriality amongst stream salmonids has been used to predict the abundance and composition of a multicohort brown trout Salmo trutta (Linnaeus, 1758) population (Ayllón et al. 2012). However, the rate of competitive interactions among stream fishes may be modulated by changing food availability as proposed by three competing hypotheses. i) Higher food availability could increase occurrences of interference competition because the costs of competition are outweighed by higher benefits (Keenleyside and Yamam
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