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PEW Global Shark Assessment

2007
Myers, R A, Baum J K, Shepherd T D, Powers S P, Peterson C H. 2007. Cascading Effects of the loss of apex predatory sharks from a coastal ocean. Science. 315 (5820):1846-1850. Abstract


2006

Ward P, R A Myers. 2006. Do habitat models accurately predict the depth distribution of pelagic fishes?. Fisheries Oceanography. 15 (1): 60-66.


2005

Myers R A, B Worm. 2005. Extinction, survival, or recovery of large predatory fishes. Proceedings of the Royal Society B. .

Abstract: Large predatory fishes have long played an important role in marine ecosystems and fisheries. Overexploitation, however, is gradually diminishing this role. Recent estimates indicate that exploitation has
depleted large predatory fish communities worldwide by at least 90% over the past 50-100 years. We demonstrate that these declines are general, independent of methodology, and even higher for sensitive species such as sharks. We also attempt to predict the future prospects of large predatory fishes.

(i) An analysis of maximum reproductive rates predicts the collapse and extinction of sensitive species under current levels of fishing mortality. Sensitive species occur in marine habitats worldwide and have to be considered in most management situations.

(ii) We show that to ensure the survival of sensitive species in the northwest Atlantic fishing mortality has to be reduced by 40-80%.

(iii) We show that rapid recovery of community biomass and diversity usually occurs when fishing mortality is reduced. However, recovery is more variable for single species, often because of the influence of species interactions.

We conclude that management of multi-species fisheries needs to be tailored to the most sensitive, rather than the more robust species. This requires reductions in fishing effort, reduction in bycatch mortality and protection of key areas to initiate recovery of severely depleted communities.

Shepard T D, R A Myers. 2005. Direct and indirect fishery effects on small coastal elasmobranchs in the northern Gulf of Mexico. Ecology Letters. 8: 1095-1104.

Ward P, R A Myers. 2005. Shifts in open-ocean fish communities coinciding with the commencement of commercial fishing. Ecology. In Press.

Abstract: We identify changes in the pelagic fish community of the tropical Pacific Ocean by comparing recent data collected by observers on longline fishing vessels with data from a 1950s scientific survey when industrial fishing commenced. A major shift in size composition and indices of species abundance and community biomass accompanied the start of fishing. The largest and most abundant predators, such as sharks and large tunas, suffered the greatest declines in abundance (21% on average). They also showed striking reductions in mean body mass. For example, the mean mass of blue shark (Prionace glauca) was 52 kg in the 1950s compared to 22 kg in the 1990s. The estimated abundance of this species was 13.4% of that in the 1950s. Overall, the biomass of large predators fell by a factor of ten between the periods. By contrast, several small and formerly rare species increased in abundance, e.g., pelagic stingray (Dasyatis violacea). However, the increases in small species did not balance the reductions in the biomass of large predators. Of three possible explanations for these patterns - fishing, environmental variation, and sampling bias - available evidence indicates fishing to be the most likely cause.

Ward P, R A Myers. 2005. A method for inferring the depth distribution of catchability for pelagic fishes and correcting for variations in the depth of longline fishing gear. Canadian Journal of Fisheries and Aquatic Sciences. 62: 1130-1142.


2004

Baum J K, R A Myers. 2004. Shifting baselines and the decline of pelagic sharks in the Gulf of Mexico. Ecology letters. 7:135-145.

Ward P, R A Myers, W Blanchard. 2004. Fish lost at sea: the effect of soak time and timing on pelagic longline catches. Fishery Bulletin . 102: 179-195.

 

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