Trophic relationships of the long-finned squid loligo Sanpaulensis on the southern Brazilian shelf

Abstract

The diet and predators of Loligo sanpaulensis (Cephalopoda: Loliginidae) on the southern Brazilian shelf were studied by examining the stomach contents of 668 long-finned squid (12–184 mm mantle length) caught by bottom trawl and the stomach contents of 47 potential predators, including stranded penguins and marine mammals as well as fish and cephalopods caught with diverse fishing gears in the region. Of 313 long-finned squid stomachs containing food, fish occurred in 36.4% of stomachs, crustaceans in 23.3% and cephalopods in 6.4%. Identified prey included demersal fish, shrimps and conspecifics. Loligo sanpaulensis was preyed on by 31 of the 47 potential predatory species examined. The frequency of occurrence (FO) was high (>20%) in the stomach contents of La Plata dolphins Pontoporia blainvillei, penguins Spheniscus magellanicus, fur seals Arctocephalus spp., the benthic shark Mustelus canis and the benthic finfish Astroscopus sexpinosus and Percophis brasiliensis. It was less important (5–20% FO) for the benthic and demersal fish Helicolenus lahillei, Paralichthys isosceles, P. patagonicus, Merluccius hubbsi and Urophycis mystacea, and of minor importance (2–5% FO) in the diet of the finfish Trichiurus lepturus, Cynoscion guatucupa, Macrodon ancylodon, Pagrus pagrus and Pomatomus saltatrix. Loligo sanpaulensis seems to be a link in the pelagic and benthic foodwebs of the southern Brazilian shelf, because it is preyed on by such high-level predators as marine mammals and penguins, and by several of the most abundant fish found in the region.