The Calanus ConnectionExcerpt from "Bowhead Whales" National Geographic Vol.188, No.2, August 1997 ... OF ALL FINLEY'S OBSERVATIONS of bowheads, perhaps none is quite so fascinating as his analysis of their feeding activity. He calls it the Calanus Connection. The Calanus copepod is a tiny crustacean at the epicenter of the Arctic food web in Baffin Bay. It is bread and butter for the fish that feed the seals that feed the bears. But there are no middlemen, no fish or seals, between the copepod and the bow head. The bowhead with its gaping mouth and filter-feeding baleen has short-circuited the system and, with great efficiency, closed that great mouth directly around the food web's basic link. And what exactly is the Calanus Connection? It is Finley's discovery that the autumn gathering of bowheads at Isabella Bay coincides with a massive migration of copepods. The feasting is initiated when the northerly gales of late summer help propel the copepods out of the fjord into the deeper bowl of Baffin Bay. Those not eaten by bowheads will hibernate while slowly moving north on a deep bay current. As the ice melts in spring, they rise to feed and drift back toward Isabella Bay. But during years affected by the global climatic phenomenon El Nino, Baffin Bay stays colder and thaws later, reducing the Calanus population- and thus the number of bowheads that can feed here. That was the case in 1983, the year Finley saw only two whales.
Finley suspects that the bowheads are attracted to this particular fjord because, in addition to the Calanus Connection, its shoals provide some measure of security against attacks by killer whales. Still, many of the bowheads Finley has observed close-up bear scars from killer whale attacks, and one distinctive individual is missing a third of its tail. Some researchers, including Finley, believe that such predation-on top of a low birthrate-may account for the stock's apparent inability to recoup more than a fraction of its historic numbers.... |
