Spatial-temporal patterns of fish and macroinvertebrate communities in sandy beach surf zones: Short and medium-term variations

The aim of this study was to identify the patterns of short and medium term variations in fish and macroinvertebrate communities in five sandy beach surf zones on the Cádiz coast (southwest Spain). Sampling was done monthly (December 2016 to November 2017) with a beach seine net with a 5 m long purse-bag at its center. A total of 48 different species were identified, of which fish and crustaceans were the most abundant groups. General patterns indicated that warm periods showed higher levels of abundance and species richness than colder periods, and the community's biomass increased at sunset as opposed to sunrise, however, this was not the case for species richness or abundance. The type of beach, on the other hand, had no significant effects. The analysis of abundance by taxa indicated that the most significant responses to the beach, season, time of day, and moon-phase predictors were by the species Trachinotus ovatus, Haplostylus normani, and Crangon crangon. In addition, water temperature together with wave height were the most determining factors affecting the abundance of the most dominant species in the community. Furthermore, our research suggests that sandy beach surf zones are used as a nursery by fish species and that these environments are where short and mid-term spatial-temporal variations of the community's structure occur.