Fish assemblages of the Marchica lagoon (Mediterranean, Morocco): Spatial patterns and environmental drivers

The fish assemblages in the Marchica lagoon were studied in June 2015, by purse seine netting, according to a systematic sampling design of 32 stations covering the whole lagoon area. The fish community was analysed both in terms of its taxonomic and functional structure, and the spatial patterns in the community distribution analysed in relation to environmental gradients in the lagoon. A total of 25,674 individuals, belonging to 43 fish species and 20 families were recorded, consisting of 20 marine migrant, 12 marine straggler and 11 lagoon residents species. Numerically, the fish assemblage was largely dominated by pelagic marine planktivore species. A spatial gradient in the bentho-demersal component of the fish assemblage structure was observed, with more marine species occurring near sea inlet and more resident species in the lagoon inner margins. No clear spatial structure was identified for the pelagic fish component, which was homogeneously distributed within the lagoon. Depth was the most important abiotic factor affecting the abundance distribution of both bentho-demersal and pelagic species, along with other factors such as vegetation cover, pH, temperature, dissolved oxygen, salinity and suspended matter. To maintain high biodiversity and sustainable fishing in the lagoon, management measures based on the protection of shallow habitats are recommended.