Contribution of polychaetous annelids to the diet of Cheilodactylus bergi (Pisces, Cheilodactylidae) in Argentina

The hawkfish (castañeta) Cheilodactylus bergi Norman, 1937 is distributed in the Atlantic Ocean, from southern Brazil (22°S) to the Gulf of San Jorge in Argentina (47°S), between 50 and 150 m depth, and constitutes a fishing resource of commercial value. Previous studies indicated that polychaetes constitute its main food. The contribution of different families of worms to the diet of hawkfish and the relationships between those taxa and the benthic fauna of the feeding grounds are presented in this paper. A total of 522 specimens of fish was measured, weighed and the gut contents analyzed. Polychaete families, mainly Onuphidae, Lumbrineridae and Eunicidae, were the most important feeding items in specimens from 28 to 51 cm total length, both in percent of frequence (%F) and percent of weight (%W). Occasional presence of Aphroditidae, Arabellidae, Palmyridae, Lysaretidae and Dorvilleidae was recorded. Bibliographic data on faunistic composition of feeding grounds indicate that polychaetes constitute between 12 to 21% of number of taxa of macroinvertebrates. C. bergi feed upon 25–38% of species of polychaetes present in the area. It is concluded that C. bergi feed on polychaetes which are mandibulated, implying mobility over the benthic surface.