Larval distribution and connectivity of the endemic Sciaenidae species in the Upper Gulf of California

Because the endemic Sciaenidae species (commonly known as drum or croakers) are important to the fishing industry in the Upper Gulf of California, their larval distribution and connectivity was analyzed in relation to hydrographic conditions during spawning periods (March, June and September). Totoaba macdonaldi, Micropogonias megalops, Menticirrhus nasus and Cynoscion othonopterus larvae were morphologically and genetically identified. Genetic analysis reveals for the first time the presence of Isopisthus remifer, which had not previously been morphologically identified. The most relevant hydrographic structure in the region was the permanent stratification front (φ = 10 J/m³) originated by the convergence of mixed water of the Northern Gulf (∼20 m depth) and stratified water coming from the adjacent oceanic water (∼200 m). Whereas T. macdonaldi larvae were only collected in the shallowest area in March, the other species were found mostly along the front in June and September. Connectivity matrixes showed high particle retention along the front (>80%) coinciding with the larval distribution. Results indicate that the stratification front might favor larval survival and prevent their advection toward the ocean. This type of retention likely enhances endemism, not only of these species but also of others coastal demersal species.