Defining Triggers for Temporary Area Closures to Protect Right Whales from Entanglements: Issues and Options

摘要

The remaining population of the North Atlantic right whale (Eubalaena glacialis) is small, critically endangered, and appeared to be declining in the 1990s. Human-related mortality from ship collisions and fishing gear entanglements is known to be a major factor in this failure to recover. Among measures being considered by NOAA Fisheries to reduce or eliminate entanglement mortality are temporary area closures, in which a specified area would be closed to fishing when aggregations of right whales are observed there. A key issue concerns the number or density of right whales that must be observed to initiate or 'trigger' such a closure. Here, existing data on right whale occurrence and distribution are analyzed to evaluate criteria for triggering temporary area closures. Specific criteria are then applied to existing aerial survey data sets to assess the effectiveness of the closures, as well as the frequency with which closures would have been enacted in past years had triggers been in place.