Fish Assemblages Reveal the Environmental Heterogeneity of Shallow Coastal Areas in Monte Hermoso, Argentina.

OSINAGA M.I.; FIORI S. M.; MOLINA J.M.; CARCEDO M.C.; BLASINA G.E.

Conferencia; The 3rd International Electronic Conference on Diversity; 2024

Multidisciplinary Digital Publishing Institute (MDPI) and Diversity (Journal)

Within shallow coastal areas, the waters of open ocean dissipative sandy beaches can bedifferentiated into the surf zone, where wave action generates turbulent conditions, and thesubtidal zone, characterized by higher depth and calmer conditions. These differences inhydrodynamic conditions could provide specific habitats for fish populations. This studyconducted at Monte Hermoso beach, Argentina (38°59’ S, 61°18’ W), analyzed the spatial–temporalvariation in fish assemblage diversity in the surf zone (SZ) and the adjacent shallow subtidal zone(SSZ). Samples were simultaneously collected in both zones during low tide using a 10 mm (knotto-knot) net, dragged for 300 m parallel to the shoreline. In the SZ, hand-towed trawls wereconducted at a depth of 1.2 m, while in the SSZ, samples were collected at a depth of 5 m aboarda vessel at a constant speed of 4 km/h. Overall, 210 individuals belonging to 7 species were caughtin the SZ and 1864 individuals belonging to 27 species in the SSZ. According to the graphicalanalyses based on the Olmstead-Tukey test (discriminant criterion = arithmetic means), Odontesthes argentinensis and Ramnogaster arcuata were dominant in the SZ, while R. arcuata, Cynoscion guatucupa and Anchoa marinii dominated in the SSZ. Richness and Shannon andSimpson’s diversity, evaluated through Hill numbers, were higher in the SSZ during all seasons andshowed no differences in winter. A high dissimilarity value was registered between the zones ( sor= 0.64), and the nestedness component (Bnes = 0.50) was higher than the turnover ( sim = 0.14). This study represents the first record of shallow subtidal fish assemblages in Argentina and revealsthat the wave action in the SZnegatively affects the richness and abundance of the fishassemblage. However, certain species, such as R. arcuata, exhibit remarkable plasticity inadapting to both environments.