Trophic ecology of the brown smooth hound shark "Mustelus henlei" (Gill, 1863) using stable isotopes and stomach content analyses in Bahía Tortugas, Baja California Sur, México

Abstract

Trophic ecology of the brown smooth hound shark Mustelus henlei collected in Bahía Tortugas, Baja California Sur was studied to understand their function in ecosystem and the food web dynamics. Between August and November 2016, samples of one species of cartilaginous fish of the family Triakidae were taken. We used stable isotope and stomach contents analyses to determine the most important prey of this species, as well as the trophic level of this species. Stomach contents and muscle samples of 102 females of M. henlei female were analysed, sampled ranged in size from 55 cm to 114 cm total length (TL), only 7 (7,2%) individuals were immature. A total of 18 prey items were identified, of which 8 were fish, 6 crustaceans, and 2 molluscs. According to the index of (PSIRI) the main prey items for M. henlei was the red crab Pleuroncodes planipes (65.25%), followed by Hemisquilla californiensis (10.08%) and Sardinops sagax (1.38%). Levin’s index indicates that M. henlei may be a specialist feeder in Bahía Tortugas. With stable isotopes of 𝛿13C were values of -17.99‰ approximately, low enriched carbon values, which corresponds to coastal organisms, and average of 16.99‰ of nitrogen isotopic values. Both analysis showed that M. henlei is a selective predator with a specialist behaviour, consumes prey that are abundant in the area, such as crustaceans and fishes.