Relaciones tróficas del pez ángel (Squatina guggenheim) en el Golfo San Matías, Río Negro, Argentina

The angel shark Squatina guggenheim has been historically caught as bycatch and landed in the Argentine hake Merluccius hubbsi fishery, and since 2013, in the Argentine red shrimp Pleoticus muelleri fishery in the San Matías Gulf (SMG). The aim was to evaluate the feeding habits of the angel shark in the SMG during period 1 (P1, 2005-2010) and period 2 (P2, 2015-2022). Stomach contents of 334 individuals were analyzed, 152 from P1 and 182 from P2. The incidence of prey species in the diet was calculated using frequency of occurrence (%FO), numerical percentage (%N), percentage by weight (%P), the relative importance index IRI, %IRI, and specific %PSIRI. Results from P1 indicate a diet dominated by hake (84.3%IRI). In P2, the diet was mainly hake (42.5%IRI), with an increase in malacostracan invertebrates, including shrimp (22.6%IRI), squat lobster (14.6%IRI), and stomatopods (8.9%IRI). This dietary shift is reflected in the calculated trophic level (TL) through the standardized index of diet composition according to Cortés (1999); in P1, sharks were tertiary predators, with TL = 4.22 in adults and TL = 4.16 in juveniles. Based on prey and their trophic levels, P2 showed TL = 3.77 in adults and TL = 3.81 in juveniles, placing angel sharks as secondary predators. The results highlight the species’ feeding plasticity, shifting its diet according to prey availability and showing a feeding strategy with strong individual specialization during both periods.