Potential Gains in Operational Efficiency During Multi-Species Bottom Trawl Surveys Through the Use of Real-Time Multibeam Sonar

The Northeast Fishery Science Center of the National Marine Fisheries Service has been conducting multi-species bottom trawl surveys from Cape Hatteras, NC to the Scotian Shelf since the early 1960’s. During this time, all aspects of survey operations have evolved in some manner and to some degree, including methods used to evaluate sea floor conditions prior to trawling. Early in the history of these surveys, little information regarding bottom conditions was available beyond that afforded by nautical charts. While single beam sonar was available during the 1960’s and 1970’s, the technology of the day provided little detail regarding seafloor conditions. In the more recent past, sonar technology advanced considerably in sensitivity, yet swath limitation of single beam sonar greatly limited utility is surveying. Our primary survey vessel, the FSV Henry B. Bigelow is equipped with a Simrad ME-70 scientific multibeam sonar. This particular sonar was designed for use in characterizing objects in the water column. Simrad developed an add-on bathymetric option that enables sea floor characterization, which we tested over a two year period during standardized bottom trawl surveys. Utilizing commercially available mapping software, we are able to view bathymetry data in real-time during survey operations. This technology allows us to characterize a large swath of survey track in a single pass, develop a tow path and execute trawls in a more efficient manner. Although we have yet to develop the tools required to quantify the gains directly, we believe we have improved survey efficiency in the following areas: reduced time spent surveying in hard bottom areas, reduced damage to survey trawls and time spent repairing gear, and improved access to areas that were not previously available.