Search

For fishes that migrate to specific locations to spawn within large aggregations at predictable times, fishery independent surveys of the abundance, distribution, and population structure of adult fish at spawning aggregation sites can provide valuable data for fisheries monitoring and assessments. We tested the feasibility of using high resolution, split-beam sonar to estimate the distribution, abundance, and group sizes of Barred Sand Bass (Paralabrax nebulifer) at their primary spawning aggregation site off Huntington Beach, California, in July 2010 and July 2012. We established an in-situ target strength distribution for Barred Sand Bass using tethered fish, collected hydroacoustic data opportunistically over the entire spawning grounds, and validated acoustic data with concurrent video surveys and rod and reel sampling of fishes present within the survey area. The modal target strength of Barred Sand Bass was determined to be -35 dB and was distinct from other fish species present. Groups of Barred Sand Bass averaged 30 individuals in abundance and ranged from 2 to 1,711 individuals, with the vast majority of the groups containing less than 10 individuals. Groups of Barred Sand Bass were most abundant in the water column between 5 and 10 m below the surface over bottoms depths of 20 to 30 m, resulting in a negative relationship between group size and depth. Due to the sand bottom habitat of the spawning site, the tendency for fish to aggregate to spawn in the water column during predictable periods, and the low diversity of other fish species present at the spawning site during the peak spawning months, hydroacoustic surveys of primary spawning aggregation sites represent an efficient, practical method for regional population monitoring and fishery assessments of Barred Sand Bass.