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

NICOLÁS SUÁREZ; MIRIAM POLLICELLI; PABLO YORIO; TATIANA KASINSKY

Puerto Madryn

Congreso; Xth INTERNATIONAL CONFERENCE ON MARINE BIOINVASIONS; 2018

The introduction of alien species is one of the main threats to biological diversity, as it can result in changes in trophic 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 since throughout a large coastal sector. The Green Crab is a threat to coastal biodiversity due to its predatory habits on mollusks, crustaceans and other invertebrates, which could lead to negative effects on predators that depend on them, such as birds. In addition, the Green Crab is preyed upon by several bird species, so the 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 generalist feeding habits, takes advantage of this novel food source, and (2) if so, quantify the relative contribution of the Green Crab to the diet composition of breeding Kelp Gull. Diet assessment was based on regurgitated pellets (n = 157) and stomach content samples of adults and chicks (n = 36) obtained during different stages of the breeding cycle in 2016 at the Isla Vernaci Este colony in the Patagonia Austral Marine Park, Golfo San Jorge. Results based on regurgitated pellet analysis showed a wide trophic spectrum, based mainly on fish. Frequency of occurrence of the Green Crab variedbetween 6.5 and 43.9% depending on the breeding 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 are regularly consumed by breeding Kelp Gulls, particularly during the incubation stage, and will contribute to the understanding of the role of this invasive species in the ecology of upper trophic level predators of coastal Patagonia. of the role of this invasive species in the ecology of upper trophic level predators of coastal Patagonia.