Food habits of the Pacific angel shark Squatina californica in the southern Gulf of California, Mexico

The food habits of the Pacific angel shark, Squatina californica, was studied in analyzing the stomach contents of specimens monthly caught between September 2000 and March 2003 in the southern Gulf of California, Mexico. The data were analyzed according to length, season, years, and sex. A total of 414 stomachs were examined, of which 190 (46%) contained food and 224 (54%) were empty. The relative importance index (IRI) was calculated to measure the trophic preference. According to this index, the most important prey species are: the jack Decapterus macrosoma (47.5%), the daisy midshipman Porichthys analis (15.9%), the inotted lizardfish Synodus evermanni (8.0%), the soldierfish Myripristis leiognathus (7.2%), and the crustacean Sicyonia penicillata (8.0%). The Levin's standardized index (Bi) shows that the niche breadth is relatively narrow (Bi = 0.31), which means that the angel shark is a selective predator with a preference for demersal fishes. The Morisita-Horn index (Cλ) indicates niche trophic overlaps in diet between juveniles and adults (Cλ = 0.82) and between sexes (Cλ = 0.96).