Assessing the effect of persistent organic pollutants on reproductive activity in common dolphins and harbour porpoises

Abstract

As top predators, marine mammals can provide information on the accumulation of anthropogenic toxins which present the greatest risk to consumers. We assessed the impacts of persistent organic pollutants (POPs) on two cetacean species that feed on commercially important fi sh species in the eastern North Atlantic; the common dolphin (Delphinus delphis) and the harbour porpoise (Phocoena phocoena). In order to evaluate the possible long-term effects of POPs on the continued viability of these populations, we investigated their effects on reproductive activity in females, using ovarian scars as an index of reproductive activity. In harbour porpoises, high POP burdens tended to be associated with lower ovarian scar number, possibly indicating that high contaminant levels were inhibiting ovulation, or some females may go through a number of infertile ovulations prior to a successful pregnancy, birth, and survival of their fi rst offspring during early lactation. In contrast, initial results identifi ed that the common dolphins with contaminant burdens above a threshold level for adverse health effects in marine mammals (17 g g -1 total PCBs lipid) were resting mature females, with