Effectiveness of mandatory vessel speed limits for protecting North Atlantic right whales

Abstract

To reduce right whale Eubalaena glacialis deaths caused by ship collisions along the US East Coast, a rule was implemented on 8 December 2008 requiring all vessels ≥65 feet (19.8 m) to travel 10 knots (18.5 km h-1) or less in 10 seasonal management areas (SMAs). To evaluate the effectiveness of this rule, we plotted the locations of all right whale and humpback whale Megaptera novaeangliae carcasses attributed to ship-strikes since December 1990 in US waters to determine their proximity to SMAs. In the 18 yr pre-rule period, 13 of 15 (87%) right whales and 12 of 26 (46%) humpback whales killed by ships were found inside later SMA boundaries or within 45 nmi (83 km) of their perimeters during later active dates. In the first 5 yr after the rule became effective, no ship-struck right whales were found inside or within 45 nmi of any active SMA. This was nearly twice as long as the longest pre-rule period with discovery of a ship-struck carcass in those areas during effective time periods. Based on the 18 yr pre-rule period, bootstrap resampling analyses revealed that the probability of finding no ship-struck whales in or near SMAs during the first 5 yr post-rule period would be a statistically significant reduction in such deaths (p = 0.031). The results suggest the rule has been effective at reducing right whale deaths. We suggest enlarging SMAs to include additional parts of the right whale migratory corridor.