Investigation of the feeding biology of the mullidae family members at the coasts of the İskenderun bay and Gökçeada

Given their abundance and wide distribution throughout the Mediterranean Sea, members of the family Mullidae are ecologically and economically important components of the Mediterranean ecosystem. In this study, growth parameters and the feeding biology of Mullus barbatus, M. surmuletus, Upeneus moluccensis and U. pori collected between September 2014 and July 2015 were examined. The effect of sex, sampling period, depth and size on feeding have been analyzed, and the role of these parameters in habitat partitioning has been discussed. The samples were obtained around the Gökçeada Island and Iskenderun Bay at 33-396 m depths via trawl fishing. The length-weight and von Bertalanffy growth parameters of the species were calculated, and age readings were carried out by examining Sagittae otoliths. Vacuity index (VI) and fullness index (FI) were calculated as an expression of feeding intensity, and index of relative importance (IRI) was used to calculate the role of each prey group in the stomach content. In addition, the trophic level (TROPH) of each species was estimated and diet overlap between species was assessed with Schoener's index. Crustacea, specifically Decapoda was the main prey group in the stomachs of all species. While Polychaeta was of secondary importance in the feeding of Mullus species (especially in the Iskenderun Bay), it had little significance in the feeding of the Upeneus species. The order Amphipoda (Crustacea) was of prominence in the stomach content of M. surmuletus individuals around the Gökçeada Island and U. pori in the Iskenderun Bay. In general, the effect of sex, sampling period, depth and size on the stomach content composition was found to be significant. Upeneus moluccensis had the highest trophic level (3,50), followed by U. pori (3,45), M. surmuletus (Gökçeada Island: 3,16, Iskenderun Bay: 2,93) and M. barbatus (Gökçeada Island: 3,01, Iskenderun Bay: 3,02). The diet overlap between Mullus species around the Gökçeada was significant. In the Iskenderun Bay, significant diet overlaps were found between M. barbatus – M. surmuletus, M. surmuletus – U. moluccensis, M. surmuletus – U. pori and U. moluccensis – U. pori. The results of this study constitutes a source for feature scientific studies on Mullid species, as well as understanding habitat partitioning between alien and local species and evaluating the benthic invertebrate fauna around the Gökçeada Island and Iskenderun Bay.