Degree of Threat: Substantial, imminent threat
Comments: Initial large decline due primarily to hunting that occurred through the mid-1930s. Lack of population recovery has been attributed to mortality caused by collisions with ships and entanglement in fishing gear, degradation of feeding habitat (e.g., through effects of pollution on zooplankton), human disturbance (ships) (Right Whale Recovery Team 1990). Fujiwara and Caswell's (2001) analysis points to mortality of adult females caused by collisions as the primary factor in the decline. In fact, they suggest that reducing the death rate by only two adult females per year would reverse the decline. MtDNA data, in conjunction with behavioral and population data that indicate that the North Atlantic population may be suffering from reduced fertility, fecundity, and juvenile survivorship, support the hypothesis that inbreeding depression is also a cause of the lack of recovery (Schaeff et al. 1997). However, the data analysis and modelling of Fujiwara and Caswell (2001) does not support this hypothesis.