Fish assemblages of a shallow Mediterranean lagoon (Nador, Morocco): An analysis based on species and functional guilds

Abstract

Background. Due to their location between the continent and the sea and their shallow depths, lagoons play an important ecological role in coastal ecosystems by providing a selection of habitat types for many species, functioning as nursery areas and feeding grounds for marine opportunistic fishes. The fish fauna of the Nador Lagoon (NE Morocco), as in the majority of southern Mediterranean lagoons, has been insufficiently studied, even though the lagoon itself supports important commercial fisheries. The presently reported study investigated the spatial and seasonal uses of shallow habitats for fish fauna in the Nador Lagoon. Materials and methods. Sampling was done using a beach seine net at six stations covering almost entire lagoon and representing habitats differing in many parameters such as the distance from the inlet, bottom sediment characteristics, presence of macroalgae, etc. The fish abundance was standardized as catch per unit effort (CPUE) and the fish community was analysed both in terms of its taxonomic and functional composition (by making use of both ecological and dietary preference guilds). Results. A total of 2872 individuals, representing 15 species from 12 families, was collected during the four seasons. Only six species were always present in all seasons. Fish abundance peaked in spring and the species diversity was higher in spring and summer. The fish assemblage was largely dominated in terms of ecological guild by the resident and benthivorous species. Spatial and seasonal fish assemblages differed both in terms of fish abundance and diversity and also in terms of functional guilds composition. In autumn, the fish assemblage was dominated by the marine juvenile migrants whereas in winter, spring, and summer, resident species were the most abundant. Conclusion. The combination of taxonomic and functional characteristics of the fish assemblages, determined in the presently reported study, may contribute to a better understanding of the ecological networks of the Nador Lagoon, thus providing useful data for its conservation and management.