An Alternative Paradigm for the Conservation of Fish Habitat Based on Vulnerability, Risk, and Availability Applied to the Continental Shelf of the Northwestern Atlantic
Abstract. A conservation paradigm is proposed based on the premise that the priority for habitat protection is directly related to habitat vulnerability and risk and inversely related to habitat availability. This paradigm is applied to three regions of continental shelf in the northwestern Atlantic: southern New England, Georges Bank, and the mid-Atlantic. Habitat is interpreted to include the physical substrate and the fauna and flora associated with that substrate. The vulnerability of a habitat to the effects of fishing is a measure of the potential reduction in ecological services that may result from the disturbance of the habitat due to the passage of fishing gear over the seabed. Sand substrates are considered less vulnerable to the effects of fishing than are gravel or mud substrates due to the lack of emergent fauna and infauna in the sand substrate. Risk of fishing disturbance, based on 11 years of fishing effort data for mobile fishing gears within each area, is assessed by estimating the area impacted by each gear type annually relative to the area of a statistical unit. The relative availability of each habitat type within each region was estimated from the sediment distribution data. In the southern New England region, the less vulnerable sand habitat is dominant, and the more vulnerable and spatially limited mud habitat is found only in a small depression on the outer shelf. Mean fishing disturbance (risk) is nearly equal in the two habitats. Therefore, some protection is suggested for the mud habitat due to its more limited availability and vulnerability. On Georges Bank, areas of vulnerable and spatially limited gravel habitat are at risk due to intense fishing. Therefore, these habitats should have the highest priority for protection. The less vulnerable sand habitat dominant on Georges Bank is less impacted by fishing gear and, therefore, has a lower priority for protection. In the mid-Atlantic region, the less vulnerable sand habitat is again dominant, and the more vulnerable and spatially limited mud habitat is on the slope. Mean fishing disturbance (risk) is very high in both habitats as compared to the other two areas. Therefore, some protection of the more vulnerable mud habitat in this region is suggested as well. The proposed paradigm, although easily implemented with relatively limited data, does not address the heterogeneity in the habitat due to the large areas represented by limited physical data nor the effects of multiple encounters between the fishing gear and habitat. The methodology does provide a rational approach to prioritizing large-scale habitat protection that is consistent with our ability to enforce habitat closures.