Featured Image Credit: bbc.com
By: Kira Krall
Recently, orca whales in Northern Norway have made an incredible comeback. They vanished 70 years ago from Kvaløya (“whale island” in English) and have been steadily seen each season in the last five years. The island’s long and narrow inlets called fjords also host humpback whales, sperm whales, and many species of dolphins despite the disturbing whale-less trend of Europe’s cetaceans.
Europe’s killer whales, in particular, have almost disappeared. One theory is that the PCB levels in these populations of orcas are preventing them from having calves that survive to adulthood. This study found that PCBs are persistent in European waters despite their widespread European ban in the 1970s. One resident killer whale pod in British waters has not had a calf since 1990 because of this chemically-induced infertility. The eight surviving members will likely be the last before this pod goes extinct.
However, Northern Norway’s killer whales are back despite the dramatic downward trend of other European pods. The locals point to the return of herring to Kvaløya’s waters. Norway is famous for its fatty and flavorful herring that migrates seasonally toward Norway’s coast. The country’s northern reaches greet herring in the winter months as the shoals migrate closer, which is right when visitors and locals alike have been watching orcas feast on the delicious fish.
While a fat and full belly increases survivability, marine biologist Fredrick Broms states that another food-related factor is keeping these Norway orca pods thriving. Herring are filter feeders that feast on the plankton that makes up the lowest level of the food chain. Other orca pods eat things like predatory fish and marine mammals, both of which make their lunch of other animals that are also high in the food chain. Through a process called bioaccumulation, these top-predator animals are chock full of PCB. Eating relatively PCB-free herring is saving Norway’s orcas from complete extinction.