Symposium Abstract: Effects of Fishing on the Mid-Atlantic Tilefish Habitat: Restructuring a Structured Habitat
V. G. Guida, P. C. Valentine, and F. Almeida
The tilefish habitat on the New Jersey continental shelf and uppermost slope near Hudson Canyon is a little studied, heavily trawled region (~800 km2) with unusual sediments and topography and substantial fisheries habitat value. During October 2001, we conducted an investigation to map the distribution of habitat types, macrofaunal associations and trawling disturbance at depths of 100-300 m. Side scan sonar was used for mapping and locating stations for video transects, using the SEABOSS drift camera vehicle, and for sediment grab sampling. Otter trawl tows were made to assess abundances and confirm the identities of organisms seen on video. Surficial sediments consisting of sand-clay mixtures, underlain by consolidated clay and producing high side scan backscatter, occurred at depths exceeding 111 m. The combination of sidescan sonar and visual observations revealed the structural complexity of the habitat. Low relief structures included hummocks, biogenic depressions, trawl marks, tilefish burrows, small burrows (1-6 cm diameter), and linear strings of cobbles and boulders. Trawl mark frequencies ranged from 100% coverage to complete absence. Benthic megafauna seen in videos at all stations (sea pens: Virgularia sp., sea stars: Astropecten americanus, cerianthid anemones, brachyuran crabs) showed no pattern with respect to trawl disturbance. Fish, e.g. spotted hake (Urophycis regius), were commonly seen in depressions. Areas with trawl marks had fewer depressions, small burrows, hummocks, and fewer fish than comparable ones without such marks, suggesting a negative impact on habitat value by bottom trawls. The cobble/boulder habitat supported the greatest density and diversity of fishes.