Mammalian order Cetacea
POPULATION
The methods traditionally used to assess the status of exploited whale populations have been based mainly on data from catches. These included: the use of catch per unit effort (CPUE) as an index of abundance; data on pregnancy rates and age of sexual maturity as measures of productivity; age data to estimate recruitment and mortality; and the capture of marked animals to estimate population size and define separate stocks. Analyses by the International Whaling Commission (IWC) Scientific Committee over the past few years have shown many of these methods to be unreliable both in principle and in practice. Following the moratorium on commercial whaling in 1986, there has been an increase in efforts to survey whale populations directly. Despite the increased research on some of the directly exploited species, quantitative population estimates are still only available for a minority of species. Population estimates of the great whales, where known, are given in Table 1.
Table 1. Current status of the great whales
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