Long-term changes in the spiny dogfish (Squalus acanthias) trophic role in the southwestern Atlantic

Abstract

We used a comprehensive dataset on the diet of Squalus acanthias in the Southwestern Atlantic Ocean (35° S - 55° S) to test the hypothesis that fishery caused a decrease in the trophic level of this species (fishing down process). Of 3644 stomachs examined between the years 1985 and 2010, 2214 (60.77%) contained prey items. Generalized Linear Models were used to evaluate the support in our data for five explanatory variables (sex, predator?s total length, season, region and decade) that may explain the consumption of given prey. The frequency of fish, mainly M. hubbsi and benthos in the stomachs decreased through time, whereas the squid Illex argentinus and jellyfishes exhibited positive trends. The trophic level of S. acanthias declined from 1980?s to 1990?s due to the high consumption of prey items at lower trophic levels. On the other hand, the consumption of argentine anchovy (Engraulis anchoita), an underexploited species, did not revealed changes through time.