| Ocean-going vessels and fishing gear represent primary threats to the endangered North Atlantic right whale (Eubalaena glacialis ) and are responsible for the majority of known deaths in this species. Various conservation measures, including vessel-navigation restrictions and modified fishing practices, have been proposed, and some implemented, to reduce mortality in this species. This thesis document quantifies threats and risks to right whales from vessels and fishing gear, primarily in Canadian waters. Vessel-strike and -speed data used to estimate the lethality of vessel strikes show that only below 12 knots (22 km h-1) does the probability of a lethal injury drop below 0.5, and above 15 knots (28 km h-1) the probability approaches 1. Similar data are used to estimate a 60% chance of observing at least one lethal vessel-strike annually. When the estimates are corrected for undetermined and unobserved causes of death, the expected annual number of lethal strikes is estimated at ten. Vessel-strike risk analyses in the Bay of Fundy and Roseway Basin regions contributed to the design and implementation of vessel navigation amendments that were adopted by shipping interests and reduced the risk of lethal vessel-strikes by 62% and 82% in each region respectively. Analyses of right whale entanglement reports and scarring frequency reveal a 0.01 probability of a lethal injury given an entanglement. Analyses of fishing-gear deployments demonstrate that seasonal fishery closures offer an effective means for reducing entanglement risk with seemingly small impact on fishing interests. Exploratory analyses of right whale movements in and around the Gulf of Maine indicate that although right whales are resident in the Bay of Fundy and in Roseway Basin for an average of75 and 136 days respectively, and most movements among the five known whale habitats occur during the August through September period. A composite of the above analyses leads me to conclude that despite recent conservation initiatives, at least one third of the species remain exposed to vessel and fishing-gear threats in Canadian waters. If Canada was to pursue additional conservation initiatives to protect the North Atlantic right whale from possible extinction, my research provides some essential insights. |
