Brenda K. Rone

The world's smallest whale population?

The North Pacific right whale (Eubalaena japonica) was heavily exploited by both nineteenth century whaling and recent (1960s) illegal Soviet catches. Today, the species remains extremely rare especially in the eastern North Pacific. Here, we use photographic and genotype data to calculate the first mark–recapture estimates of abundance for right whales in the Bering Sea and Aleutian Islands. The estimates were very similar: photographic = 31 (95% CL 23–54), genotyping = 28 (95% CL 24–42). We also estimated the population contains eight females (95% CL 7–18) and 20 males (95% CL 17–37). Although these estimates may relate to a Bering Sea subpopulation, other data suggest that the total eastern North Pacific population is unlikely to be much larger. Its precarious status today—the worlds smallest whale population for which an abundance estimate exists—is a direct consequence of uncontrolled and illegal whaling, and highlights the past failure of international management to prevent such abuses.

Alaska marine mammal stock assessments, 2009

NOTE – March 2008: In areas outside of Alaska, studies have shown that stock structure is more fine-scale than is reflected in the Alaska Stock Assessment Reports. At this time, no data are available to reflect stock structure for harbor porpoise in Alaska. However, based on comparisons with other regions, smaller stocks are likely. Should new information on harbor porpoise stocks become available, the harbor porpoise Stock Assessment Reports will be updated.

From clicks to counts: Applying line-transect methods to passive acoustic monitoring of sperm whales in the Gulf of Alaska

A visual and acoustic line-transect survey of marine mammals was conducted in the central Gulf of Alaska (GoA) during the summer of 2013. The survey area was divided into four sub-strata to reflect four distinct habitats; “inshore,” “slope,” “offshore,” and “seamount.” Passive acoustic monitoring was conducted using a towed-hydrophone array system. One of the main objectives of the acoustic survey was to obtain an acoustic-based density estimate for sperm whales. A total of 241 acoustic encounters of sperm whales during 6,304 km of effort were obtained compared to 19 visual encounters during 4,155 km of effort. Line-transect analytical methods were used to estimate the abundance of sperm whales. To estimate the detection function, target motion analysis was used to obtain perpendicular distances to individual sperm whales. An acoustic-based density and abundance estimate was obtained for each stratum (N = 78; CV = 0.36 offshore; N = 16; CV = 0.55 seamount; N = 121; and CV = 0.18 slope) and for the entire ...