Fish distribution in three dimensions around the Block Island Wind Farm as observed with conventional and volumetric echosounders

Objective

Offshore wind development is expected to expand rapidly along the East Coast of the United States within the next 10 years and will impact the biology and ecology of the flora and fauna as well as human activities, such as commercial and recreational fishing. The Block Island Wind Farm is a five-turbine, 30-MW wind array located about 6 km off the coast of Rhode Island and has been in operation since 2016.

Methods

We conducted a 4-day acoustical and biological survey of the area during daylight hours to gain insight on the spatial distribution of fish species in and around the turbines. We utilized a hull-mounted, downward-looking Simrad 38-/200-kHz ES70 and a pole-mounted iXblue SeapiX steerable Mills Cross, 150-kHz, 1.6° resolution multibeam echosounder oriented downward to map the two- and three-dimensional distributions using spiral and straight-line transect patterns. We collected fish by using hook and line to verify the sources of acoustic backscatter and to measure length, sex, and diet.

Result

Black Sea Bass Centropristis striata were the most commonly caught species and appeared to be the primary constituents of the fish aggregations that were mapped by the acoustic systems. We found increased levels of acoustic backscatter within 200 m of the turbine structures, suggesting that they were attractive structures.

Conclusion

These levels were not greater than backscatter levels in the surrounding area, suggesting that the proximate effect of the wind array was spatially limited.