Predatory fishes affect trophic cascades and apparent competition in temperate reefs.
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.
Frid
Alejandro
A
Vancouver Aquarium, Vancouver, British Columbia, Canada. alejandro_frid@alumni.sfu.ca
Marliave
Jeff
J
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