Stomach contents of 204 individuals of the common stingray, Dasyatis pastinaca, caught in the seas surrounding Sardinia (central-western Mediterranean), were analysed to assess the feeding ecology and the ontogenetic shifts in the diet. Specimens, 138 to 377 mm in DW, were collected from 2008 to 2010, during experimental trawl surveys (MEDITS and GRUND) conducted at depths between 27 and 56 m. Of all stomachs analysed, 20 were empty (%Cv = 9.8). In the remaining 184, 7 major prey taxa were found: Crustacea, Osteichthyes, Chondrichthyes, Mollusca, Polychaeta, Echinodermata and Cephalochordata. The low Levin’s index value (Bi = 0.04) indicated a strong stenophagous feeding behavior. Crustaceans (%IRItot = 91.6) were the most common preys. The diet was completed by Osteichthyes (%IRItot = 4.38) and Polychaetes (%IRItot = 3.99), while the other preys were occasional. Mysids, and particularly Gastrosaccus sanctus (%IRI = 58,9) were of fundamental importance among Crustaceans. Trophic level value (TROPH = 3.30 ± 0.43 s.e.) reflected the high relevance of these preys. The ontogenetic analysis of the diet, conducted on three size groups (89 immature, 96 subadults and 19 adults), revealed some differences in the feeding habits. During growth individuals seemed to replace small Crustaceans, as Mysids, with bigger and more mobile preys, as Decapod Crustaceans in subadults and Osteichthyes in adults. However, no statistical differences were found among diets. These ontogenetic shifts were, in fact, too slight to avoid competition, as revealed also by the high values of the Morisita’s index (CH = 0.99 between immature and subadults).
Diet of common stingray, Dasyatis pastinaca, a shallow water Elasmobranch in the Sardinian waters (Central-Western Mediterranean)
MULAS, ANTONELLO;BELLODI, ANDREA;PORCU, CRISTINA;
2012-01-01
Abstract
Stomach contents of 204 individuals of the common stingray, Dasyatis pastinaca, caught in the seas surrounding Sardinia (central-western Mediterranean), were analysed to assess the feeding ecology and the ontogenetic shifts in the diet. Specimens, 138 to 377 mm in DW, were collected from 2008 to 2010, during experimental trawl surveys (MEDITS and GRUND) conducted at depths between 27 and 56 m. Of all stomachs analysed, 20 were empty (%Cv = 9.8). In the remaining 184, 7 major prey taxa were found: Crustacea, Osteichthyes, Chondrichthyes, Mollusca, Polychaeta, Echinodermata and Cephalochordata. The low Levin’s index value (Bi = 0.04) indicated a strong stenophagous feeding behavior. Crustaceans (%IRItot = 91.6) were the most common preys. The diet was completed by Osteichthyes (%IRItot = 4.38) and Polychaetes (%IRItot = 3.99), while the other preys were occasional. Mysids, and particularly Gastrosaccus sanctus (%IRI = 58,9) were of fundamental importance among Crustaceans. Trophic level value (TROPH = 3.30 ± 0.43 s.e.) reflected the high relevance of these preys. The ontogenetic analysis of the diet, conducted on three size groups (89 immature, 96 subadults and 19 adults), revealed some differences in the feeding habits. During growth individuals seemed to replace small Crustaceans, as Mysids, with bigger and more mobile preys, as Decapod Crustaceans in subadults and Osteichthyes in adults. However, no statistical differences were found among diets. These ontogenetic shifts were, in fact, too slight to avoid competition, as revealed also by the high values of the Morisita’s index (CH = 0.99 between immature and subadults).
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