Determination of fish diversity in the rocky habitat around mersin boğsak island (northeast mediterranean) by visual census method

This study was conducted in the rocky habitat of Boğsak Island in Mersin Bay in November, March and July, representing the fall, spring and summer months of 2022-2023, by scuba diving between 0-18 m depth for approximately 40 hours. The Go-Pro Hero 12 black camera was used in the study. In the study, the structure of the fish community of the rocky bottom habitat of Boğsak Island in Mersin Bay was determined, and the seasonal availability, abundance, feeding status, and distribution of local and non-native fish species were determined. Sampling was carried out using the underwater visual counting method, and surveys were made along a linear line. Shannon-Weiner Diversity Index (H'), Homogeneity and Relative Diversity Index Evennes (J) and Species Richness Index Margalef Rhichnes (D) were used to determine the species diversity. The distance of the relationship between the data was determined with N-MDS, one of the multidimensional scaling analyses. The Euclidean formula was used to determine the distances of coordinates in the scaling. Principal component analysis was used to classify species based on the number of individuals. A total of 29 fish species, including 28 bony fish species belonging to 15 families and 1 cartilaginous Gymnura altavela (Linnaeus, 1758), were identified in the study area. The richest family in terms of species diversity was Sparidae (6), followed by Mullidae (3), Serranidae (3), Tetraodontidae (2), Soleidae (2), Labridae (2) and other families with 1 species each. Of the fish species identified throughout the year in the study area, 52% were Atlantic, 37% were Indo-Pacific and 11% were cosmopolitan. It was found that 41% of the fish species were invertivores, 22% carnivores (feeding on fish and invertebrates), 18% omnivores, 11% planktivores, 4% herbivores and 4% piscivores. Torquigener flavimaculosus in summer, Cheilodipterus novemstriatus in spring, and Chromis chromis in fall were the most abundant species. According to the Shannon diversity index (H'), the highest species diversity was found in the fall (H'=2,956), followed by spring (H'=2,501) and summer (H'=2,458). Homogeneity and relative diversity index Evennes (J) was determined as J=0.642 in spring, J=0.531 in summer and J=0.800 in fall. The species richness index Margalef Rhichnes (D) was highest in autumn (d=4.804), then in summer (d=3.917) and lowest in spring (d=3.632). This is the first study to investigate the structure of rocky habitat fish communities in the northeastern Mediterranean, which shows a dynamic structure in terms of biodiversity, and is expected to contribute to researchers working in this field.