Impact of Scallop Harvesting on Eelgrass (Zostera marina) Meadows: Implications for Management

Abstract

Eelgrass (Zostera marina), an important component of estuarine areas from Nova Scotia to North Carolina, is the primary habitat for the economically important bay scallop (Argopecten irradians). The bay scallop fishery in North Caxolina is extensive yet precarious in its dependence on seagrass systems. A balance between habitat integrity and scallop harvest is necessary to sustain the fishery. In this study, we examined the effect of scallop dredging on eelgrass meadows. When the eelgrass was in its vegetative stage, 15 and 30 dredgings were carried out in a hard sand substrate and a soft mud substrate and the results compared to an area of no dredging. Impact was assessed by analyzing the effects of scallop harvesting on eelgrass foliar dry weight and on the number of shoots. The hard bottom had significantly greater overall biomass of eelgrass (P < 0.01, ANOVA) than the soft bottom but fewer differences were apparent for eelgrass shoot density (P < 0.10). Increased dredging led to significantly reduced levels of eelgrass biomass and shoot number (P < 0.01) on both hard and soft bottoms. Harvesting of bay scallops in North Carolina occurs at a time of seasonally low eelgrass foliar biomass, peak abundance of commercially harvestable scallops, and settlement of post-larval scallops that require eelgrass leaves for attachment. Onr data demonstrated potentially negative impacts on the scallop fishery that would result from harvest-related damage to existing eelgrass meadows.