The green crab (Carcinus maenas) as a novel food source for the opportunistic kelp gull (Larus dominicanus) in Patagonia, Argentina.

POLLICELLI, MIRIAM; KASINSKY, TATIANA; SUÁREZ, NICOLÁS; YORIO, PABLO

Congreso; Xth International Conference on Marine Bioinvasions; 2018

The introduction of alien species is one ofthe main threats to biological diversity, as it can result in changes introphic webs and functioning of coastal and marine systems. The Green Crab  (Carcinus maenas)  is  and invasive  species,  which was  first  recorded in  the  coasts of Patagonia, Argentina, between 1999 and 2000, and has expanded sincethroughout a large coastal sector. The Green Crab is a threat to coastalbiodiversity due to its predatory habits on mollusks,  crustaceans  and other  invertebrates,  which could  lead  to negative  effects  on predators that depend on them, such asbirds. In addition, the Green Crab is preyed upon by several bird species, sothe invasion of this exotic crab may result in direct positive effects on upper  trophic level  predators.  Our goals  were  to (1)  determine  if the  Kelp  Gull (Larus dominicanus), a widely distributed species with generalistfeeding habits, takes advantage of this novel food source, and (2) if so, quantifythe relative contribution of the Green Crab to the diet composition of breedingKelp Gull. Diet assessment was based on regurgitated pellets (n = 157) andstomach content samples of adults and chicks (n = 36) obtained during differentstages of the breeding cycle in 2016 at the Isla Vernaci Este colony in thePatagonia Austral Marine Park, Golfo San Jorge. Results based on regurgitatedpellet analysis showed a wide trophic spectrum, based mainly on fish. Frequencyof occurrence of the Green Crab varied between 6.5 and 43.9% depending on thebreeding stage, with the highest representation during  the Kelp  Gull  incubation stage.  Green  Crabs were  not  recorded in  adult  or chick stomach content samples. Results show that Green Crabs areregularly consumed by breeding Kelp Gulls, particularly during the incubationstage, and will contribute to the understanding of the role of this invasivespecies in the ecology of upper trophic level predators of coastal Patagonia.