Hydroacoustical Survey of Near-Surface Distribution, Abundance and Biomass of Small Pelagic Fish in the Gulf of California

Abstract

Abstract: Near-surface distribution (10–40 m depth), abundance, and biomass of small pelagic fish were estimated using an echo sounder (EY-60, 120 kHz) during January 2007 in central and northern areas of the Gulf of California. Small pelagic fish distribution was spatially correlated with simultaneous, continuous, high-resolution measurements of 4 m depth temperature, salinity, turbidity, chlorophyll a, and dissolved oxygen concentration to characterize water and habitat conditions. Small pelagic fish shoals were concentrated in five areas of northern and central parts of the gulf, along the coast of Sonora, and south of Isla Tiburon. About 62% of small pelagic fish abundance and 57% of the biomass was echo-detected during the night, when small pelagic fish tend to assemble near the surface. Fish abundance in these areas (11,210 km2) was estimated at 6.16 ×109 individuals. Echo-integrated median biomass was 2.6 ×105t. Projecting this biomass to the surveyed area (80,102 km2), median biomass of multispeci...