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Biol Lett. Aug 23, 2010; 6(4): 533–536.
Published online Feb 24, 2010. doi:  10.1098/rsbl.2010.0034
PMCID: PMC2936221
Predatory fishes affect trophic cascades and apparent competition in temperate reefs
Alejandro Frid* and Jeff Marliave
Vancouver Aquarium, Vancouver, British Columbia, Canada
*Author for correspondence (alejandro_frid/at/alumni.sfu.ca).
Received January 13, 2010; Accepted February 3, 2010.
Abstract
We provide evidence for a trophic cascade involving apex predators and mesopredators of marine temperate reefs, lingcod and rockfish, respectively. We measured spatio-temporal variation in the relative abundance of lingcod, subadult rockfish and two shrimp groups eaten by rockfish (Pandalus sp. and three smaller-bodied genera aggregated). Lingcod had an indirect positive effect on shrimps, as mediated by the direct negative effects of lingcod on rockfish and of rockfish on shrimps. These top-down effects on shrimps, however, were stronger for Pandalus than for small-bodied shrimps. Further, abundances of Pandalus and small-bodied shrimps were negatively correlated and the latter had a stronger positive effect on rockfish, suggesting that rockfish mediated asymmetrical apparent competition between shrimps. Our results indicate mechanisms by which predatory fishes may influence the structure of marine communities.
Keywords: asymmetric apparent competition, marine predators, rockfish, trophic cascade
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