The world's smallest whale population?

Abstract

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 5 31 (95% CL 23-54), genotyping 5 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 todaythe world's 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.

Estimating North Pacific right whale Eubalaena japonica density using passive acoustic cue counting

“…Here, we only used 3 sensors with non-random placement, and therefore the quality of our estimate of detection probability is dependent on how closely, such an assumption was met in this case. The fact that the estimate obtained is so close to other estimates (Wade et al 2011 estimated an abundance of 28 or 31 whales, depending on the data used) for the population is reassuring. Nonetheless, in future implementations of these methods, special care should be given to sampling design, in particular to the number and location of sensors.…”

“…The eastern stock is thought to be smaller in number, and its current size might be too small to ensure its persistence . This is further supported by recent published work based on markrecapture methods (Wade et al 2011, N = 31 animals, 95% CI 23-54, based on photo ID data, and N = 28, 95% CI 24-42, based on genetic data). Better estimates of population size are fundamental to assess a population's chances of recovery.…”

Too Much Is Never Enough: The Cautionary Tale of Soviet Illegal Whaling

“…The best estimate of total North Pacifi c right whale catches in the North Pacifi c and the Okhotsk Sea is 681, only 11 of which were reported (Ivashchenko and Clapham, 2012). In particular, the Soviets probably removed the bulk of the remaining population in the eastern North Pacifi c: a recent estimate puts the size of this population today at only 30 animals (Wade et al, 2011). The current status of the second recognized population (the western stock, which feeds in the Okhotsk Sea) is unknown, but is thought to number in the hundreds.…”

Assessing the design and power of capture-recapture studies to estimate demographic parameters for the Endangered Oceania humpback whale population

“…However, calf survival has been estimated to be lower: 0.82 (95% CI: 0.48−0.98) for the N orth Pacific (0 to 6 mo; Zerbini et al 2010) and 0.66 (95% CI: 0.52−0.78) in the Gulf of Maine (6 to 18 mo; Robbins 2007). For this reason, the typical method used to reduce the heterogeneity in survival in baleen whale datasets is to exclude dependent calves from the analyses (Wade et al 2011, Constantine et al 2012), and we shall follow this convention.…”

“…Therefore we recommend sampling in a way that allows for the identification of sex, implying a preference for biopsy sampling, which has previously met Assumption 2 of providing permanent marks that are consistently identifiable (Wade et al 2011, Constantine et al 2012). …”