Seasonal Gray Whales in the Pacific Northwest: An Assessment of Optimum Sustainable Population Level for the Pacific Coast Feeding Group.

摘要

A single population stock of gray whales referred to as the eastern North Pacific (ENP) stock is presently recognized in U.S. waters (Carretta et al. 2013). A small group of gray whales, known as the Pacific Coast Feeding Group, or PCFG spends the summer and autumn along the Pacific coast of North America, where they overlap with the Makah Tribes Usual and Accustomed (U&A) fishing grounds off the coast of Washington. In 2005, the Makah requested that NOAA/NMFS waive the MMPA take moratorium and adopt regulations that would authorize the tribe to hunt ENP gray whales within their U&A. As part of its review of this proposed hunt, NMFS continues to evaluate information relevant to ENP stock structure and status, including the population dynamics of the PCFG. Assessing whether the PCFG is currently at Optimum Sustainable Population (OSP) (i.e., not depleted) was the objective of the analysis described in this report. The assessment is based on modifications to an existing population dynamics model used by the International Whaling Commission (IWC) to conduct projections of gray whale abundance. The model is deterministic, age- and sex-structured, and consists of two groups (the north group and the PCFG), which are assumed to be separate for purposes of the analysis, but with possible immigration between them. Parameter estimation is based on Bayesian methods.