Commercial hunting for right whales in the eastern North Pacific was initiated by Europeans and Americans in the 1830s; by about 1900, the subpopulation had been reduced to a fraction of its original abundance, as evidenced by the comparatively low number of 20th century sightings (Brownell et al. 2001). Although legally protected by the IWC since 1946 (and by an earlier agreement in 1935), illegal hunting continued into the 1960s with the Soviet catches of 372 animals in the eastern North Pacific (Doroshenko 2000, Brownell et al. 2001).
There is currently no evidence of human-related mortality or injury, but the very low observer effort and remoteness of the right whale’s habitats probably means that most deaths and injuries pass unrecorded.
The eastern North Pacific subpopulation is subject to anthropogenic threats such as entanglements in fishing gear, disturbance by vessels and other noise, collisions, and possibly petroleum-related and other contaminants.
As compared with the intensively studied North Atlantic right whale, the more offshore and remote distribution of eastern North Pacific right whales may be an advantage in terms of less intensive exposure to human impacts, but the disadvantage is that impacts that do occur are less likely to be detected and their consequences are harder to ascertain and evaluate.
Small populations numbering less than a few hundred individuals can have a number of interacting effects that accelerate overall risk (Gilpin and Soule, 1986). Among those effects are demographic stochasticity, inbreeding depression and density depensation (Allee effects). Although direct data are lacking for marine mammals at low density, the expectation is that these threats could be serious because cetaceans are social animals with low reproductive output.
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