Status of Whale Populations

 

The table below summarizes status using two measures from such stock assessments: Relative Abundance and 20-Year Change. Since many whale populations were severely depleted during the period of commercial whaling, the Scientific Committee usually expresses Relative Abundance as a proportion of the estimated number of whales prior to whaling, but sometimes it is expressed as a proportion of the number the habitat is likely able to support (‘carrying capacity’). With a changing environment, carrying capacity may change, so a reference year is sometimes specified. Usually the pre-exploitation abundance is assumed to have equalled carrying capacity then. Thus, a Relative Abundance value of 0.50 means that models indicate that the whale population is half as numerous now as it was prior to whaling, or as the habitat could now support, depending on which type of reference level is used.

 

The 20-Year Change statistic is based on model estimates of how much the population abundance has changed over the last 20 years. Negative values mean that the stock has declined and positive values mean the population is increasing. A value near zero is not necessarily concerning since a population near carrying capacity will remain stable (near zero growth) but its status would be very good.

More details on how Relative Abundance and 20-Year Change are used is given here. Specific details about each status assessment, including recent survey data and key concerns, are available from the Status Summary and Status Details links below.