Fishing-induced shifts in a Pacific ocean fish assemblage

The US Pacific Coast has been largely free of fishery collapses that have occurred elsewhere, but the situation appears to be changing. Here, we show results from the first systematic study of demersal fishes along the US Pacific Coast. Using data from a quarter-century long, fishery-independent, coast-wide trawl survey, we document fundamental shifts in the demersal fish assemblage along the US west coast. Average fish size, across a diversity of species, has declined 45% in 21 years. There have been major shifts in the constituent species of the assemblage, with some species achieving annual population growth rates (i.e. λ) of > 1.1, while others have declined with λ’s of < 0.90. λ appears to be function of life history and habitat interacting with historical fishing pressure. The results of our analyses are disquieting as they raise the possibility that fishing-induced phase shifts in fish communities may affect the recovery of fishes, even after the implementation of severe fishing restrictions. Introduction With the exception of the collapse of the sardine fishery in 1950’s, the West Coast of the United States has been largely free of the spectacular collapses of marine fishes that have occurred elsewhere. However, this envious position appears to be changing (Parker et al. 2000) . Indeed, concern over a number of rockfishes (Sebastes spp.) along the US Pacific coast has resulted in the implementation of large-scale fishery closures along the U.S. Pacific continental shelf, with an expected annual cost to coastal communities of about $60 million (PFMC 2003). Although it is clear that many groundfish species along the US Pacific Coast are in trouble, there is generally a lack of