Reproductive parameters of the North Atlantic right whale

Abstract

North Atlantic right whale reproduction was assessed for the period 1980 through 1998. At the end of this period, we estimated there werebetween 299 and 437 right whales alive, including 70 mature females. Using maximum and minimum population estimates for the entireperiod, mean values for gross annual reproductive rate were 0.36 and 0.49 respectively, and the mean value for calves per mature femaleper year was 0.25. There is a significant decreasing trend in calves per mature female per year over the entire study period. The mean ageat first calving is 9.53 years. The mean number of cows recruited annually since 1985 is 3.8. Mean annual calving intervals have increasedsignificantly during the study period from 3.67 years (1980-1992) to over 5 years (1993-1998). Although the North Atlantic population isaffected by significant anthropogenic mortality, diminishing reproductive rates are probably also responsible for the plight of thisspecies.