Benthic Habitats and the Effects of Fishing

Symposium Abstract: The Effectiveness of Marine Protected Areas on Fish and Benthic Fauna:The Georges Bank Closed Area II Example

F. Almeida, P. Valentine, R. Reid, L. Arlen, P. Auster, J. Cross, V. Guida, J. Lindholm, J. Link, D. Packer, J. Vitaliano, and A. Paulson

doi: https://doi.org/10.47886/9781888569605.ch80

In late 1994, a substantial portion of eastern Georges Bank was closed to commercial fishing (Closed Area II) to assist with stock rebuilding. After about five years of closure, the southern portion of CAII (south of 41°30′), exhibited a substantial increase in biomass and density of sea scallops, Placopecten magellanicus, and was reopened to the scallop fishery. Before the industry was allowed entry into this area, we conducted a survey to monitor the recovery of benthic habitat and fauna inside CAII. Sampling sites were selected in a paired station design for an inside/outside comparison; a grid design was used to monitor the remainder of the inside area. At each station, we conducted video transects, collected still photos, CTD casts, and sediment samples for physical and chemical analysis. A Smith-McIntyre bottom sampler was then used to sample the benthic community, followed by an otter trawl. Trawl catches were sorted to species and all fish and invertebrates were weighed, enumerated, and measured. Stomach contents, maturity observations, and age structures were collected for selected species at each station. Our results suggest limited differences between the inside/outside paired stations for species composition, community diversity, species richness, and trophic ecology. Fish abundance and biomass was also similar inside and outside the area; however, most individuals of a species were larger inside than outside. The lack of other major differences is likely a result of the fact that the seabed in the southern portion of CAII is a relatively high-energy sand habitat of low to moderate complexity and has a relatively low vulnerability to trawling and dredging. Other parts of closed areas on the northeast shelf may exhibit stronger gradients for the same metrics due to the presence of higher complexity gravel habitats and increased vulnerability to bottom tending fishing gear. The subtle differences in the size structure of fish species we observed in CAII may have significant implications for the population dynamics of commercially valuable species.