title: Predatory fishes affect trophic cascades and apparent competition in temperate reefs.
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.
authors.affiliation: Vancouver Aquarium, Vancouver, British Columbia, Canada. alejandro_frid@alumni.sfu.ca
authors.forename: Alejandro
authors.initials: A
authors.lastname: Frid
authors.forename: Jeff
authors.initials: J
authors.lastname: Marliave
mesh_terms: D000818:Animals; D037421:Anthozoa; D001955:British Columbia; D033364:Decapoda / Q000502:physiology; D003710:Demography; D017753:Ecosystem; D005399:Fishes / Q000502:physiology*; D020387:Food Chain; D008954:Models, Biological; D011156:Population Density; D011235:Predatory Behavior / Q000502:physiology*; D013997:Time Factors