Taylor, J. C.

Analysis of hydroacoustic data for large reef fish targets in Puerto Rico

2005

NC State University Center for Marine Sciences and Technology

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Final Report

"This report summarizes the findings and outcomes of an in-depth analysis of the 2002 and 2003 Red Hind Hydroacoustic Surveys datasets. Hydroacoustic survey datasets were originally analyzed for the presence, distribution and density of fish aggregations likely representing red hind around Puerto Rico and the surrounding islands. It is well known that numerous species utilize habitats that are considered important locations for reef fish spawning aggregations. Mobile hydroacoustic surveys provide a method to continuously sample along a transect and record the presence and position of underwater targets in three-dimensions. Therefore, the datasets were reanalyzed to isolate, count and determine the spatial location of other large targets that could represent other large reef species of interest. Databases were produced for each years survey. The databases include the date and time of observation and the three-dimensional position (latitude, longitude and depth) of each individual target as well as information on the targets acoustic size (proportional to fish size). Results show that solitary fish targets were in close proximity with identified aggregations as well as in areas where fish aggregations were not previously identified. In general, a greater number of fish targets were found in water column depths between 30-80 m and the majority of the fish targets were observed within 10 m of the bottom. There were, however, several targets that were off the shelf break over deep water (greather than150 m). A greater number of fish were found during the surveys in 2003 in the northern regions of Puerto Rico when compared to the 2002 surveys of the southern regions. Target strength distributions suggest that several solitary targets were slightly larger as a group that the average target size of fishes in the aggregations. Findings from these analyses could be used to identify regions where fish targets are in high densities a help to prioritize regions for future sampling of large reef fish species."

FY2005 CRCP Project ID 1242; Project Title: Hydroacoustic Biomass Assessment of Reef Fish Spawning Aggregations; Principal Investigator: G. Todd Kellison