Age and sex distributions in the catches of belugas, Delphinapterus leucas , in West Greenland and in western Russia

Age and sex were determined for belugas or white whales, Delphinapterus leucas, harvested in West Greenland in 1985-86 and 1989-1997. There was a clear segregation of whales in the drive fishery conducted during autumn in Qaanaaq and Upernavik. Primarily immature whales of both sexes together with mature females were taken.

Age was estimated from Growth Layer Groups (GLGs) in sectioned teeth, assuming the currently accepted criteria of 2 GLGs forming annually. The mean and median ages were increasing slightly in both sexes from Upernavik from 1985 through 1994. Both immature and mature whales were taken on the wintering grounds from Disko Bay and south.

Estimation of survival was confounded by the large number of whales where only a minimum age could be assigned because of tooth wear at the crown (i. e. no neonatal Line in the dentine). The apparent survival rates for belugas from West Greenland were estimated as 0.81 and 0.79 for females and males, respectively.

Correction of these estimates for an observed population decline of 4.7% per year revealed true survival rates of 0.85 and 0.82 for females and males, respectively. The estimates of true survival rates are less than those determined for beluga populations in the White and Kara seas and in Alaska for comparable age truncations.

Since the exploitation levels are much Lower in these areas the low apparent survival rate from West Greenland strongly supports the evidence of a population decline. Colour change from grey to white occurs at mean ages of 8.5 yr and 9.1 yr and median lengths of 367 cm and 445 cm in females and males, respectively.