The profiles of occupancy by fish fauna of four shallow coastal habitats at a limited regional scale in the south-western Mediterranean

The diversity of the ichthyofauna and the seasonal variations of its assemblages were studied in four different habitats on a limited geographical scale of the eastern coast of Algeria: one downright marine site (The Caroube beach) and three transitional waters, two estuaries (Boukhmira and Mafragh) and one lagoon (Mellah). From monthly samples taken between January and December 2016 using a 3 mm mesh beach seine (L = 14 m, H = 2 m), a total of 13240 fish was caught: 4148 individuals (43 species, 13 families) at The Caroube beach, 1452 (20 species, 11 families) in Boukhmira Wadi, 1218 (15 species, 10 families) in Mafragh estuary and 6422 (14 species, 8 families) in Mellah lagoon. Shannon–Wiener​ (H’) index showed a relatively high specific diversity at the Caroube beach in spring (H’ = 3.87) with a Pielou equitability index J’ = 0.77, while the lowest diversity was noted in spring at Mellah lagoon (H’ = 0.49) with J’ = 0.15. All localities showed a seasonal variation in fish abundance and in specific diversity, as well as in the distribution of the ecological and trophic guilds. The analysis of the seasonal hierarchical clusters differentiated the marine site from the transitional waters (lagoon and estuaries). This site is also characterized by an autumnal ichthyofauna different from that of other seasons. At the combined spatial and temporal scales, canonical correspondence analysis (CCA) revealed the requirements of the species with respect to the considered abiotic parameters (temperature, salinity, oxygen, bottom nature) and showed that the nature of the bottom is the most important factor affecting the distribution and the abundance of fish. •The composition and structure of ichthyofauna was studied in four different habitats (one marine site, one Lagoon, two estuaries) in eastern Algeria.•According to the composition of their ichthyofauna, transitional waters separate from coastal marine waters.•The ecosystems showed seasonal variation in fish abundance and specific diversity, as well as in the distribution of the ecological and trophic guilds.•Occupancy dynamics of the four habitats and the seasonal changes in the structure of ichthyological assemblages in each of them are under the influence of environmental factors.•The nature of the bottom is the most important factor affecting the distribution and the abundance of different species of fish in each of the 4 sites.