Investigating the nursery function of the Alboran MPA on the Mediterranean coast of Morocco

Abstract

Coastal habitats provide shelter and food for juvenile fish, ensuring their survival and supporting a range of species that are both commercially and ecologically important. The Alboran Marine Protected Area (MPA) off the Mediterranean coast of Morocco has been identified as a nursery area, although this role has never been the subject of characterisation. This study investigates the nursery function of habitats at six sites, two of which have seasonally flooded rivers with small persistent lagoons (transition systems) actively connected to the sea. Mixed sand-and-gravel beaches and transition systems were surveyed using a beach seine (four hauls) during two consecutive summer periods (June 2019 and July 2020), and a beam trawl was used in July 2020 in order to survey shallow waters at three depths: 3, 5 and 7 m. The use of both fishing methods provided a comprehensive assessment of juvenile fish communities. Different habitats in these coastal areas supported juvenile fish of 31 different species, with higher species richness and densities of young-of-the-year (YOY; first year of life) fish in transition systems despite their limited surface area and depth. Shallow marine waters supported fish species with specific microhabitat requirements despite lower overall YOY fish densities. The Alboran MPA coast has a nursery function, with different habitats acting as nurseries for juveniles of different fish species, creating a seascape of interconnected nursery habitats. As low densities of juvenile fish were a common concern across species and habitats, protecting these nursery habitats through enforcement of their protection regime appears to be a priority.