Age- and sex-related changes in organochlorine compound levels in fin whales ( Balaenoptera physalus) from the eastern North Atlantic

Abstract

Patterns of variation in organochlorine burdens with age and sex in cetaceans are poorly understood and differ between species. This paper presents the results of a survey on fin whales in this respect. Blubber from 166 individuals of known age and sex was analyzed for DDTs and PCBs. In young whales, pollutant burdens in specimens from the two sexes were indistinguishable but, from the onset of sexual maturity, concentrations of all organochlorines increased with age and body size in males and decreased in females. The relationships were not linear and in both cases tended to reach a plateau. The decrease observed in female blubber concentrations is attributed to reproductive transfer, mainly through lactation, and occurs throughout all the female's life span, suggesting absence of reproductive senescence in this species. Relative abundance of degraded forms of pollutants increased with age in males and decreased in females. The tDDT/PCB ratio was negatively correlated with age in males and positively correlated in females. Different PCB congeners showed dissimilar trends. All these dissimilarities between sexes in the pattern of accumulation of the different forms of organochlorines are associated with differential activation of microsomal enzymes and with dissimilar transfer rates during reproduction in females. Because of these differences, pollutant burdens in males are characterized by higher levels of pollutants and by higher DDE/tDDT and tDDT/PCB ratios than those for females.