Calanus Finmarchicus

Calanus finmarchicus is a species of calanoid copepod, a small crustacean that ranks among the most abundant zooplankton in the North Atlantic Ocean. It forms a critical link in the regional food web, serving as a primary food source for herring, cod larvae, and several species of baleen whale, including the endangered North Atlantic right whale. The species undergoes a marked seasonal migration, descending to deep water each autumn to enter a dormant state known as diapause and rising back toward the surface each spring to feed on blooming phytoplankton. During its active feeding season it builds up substantial fat reserves, and these stored lipids make it an unusually energy rich prey item relative to its small size. Its population size and the timing of its seasonal migration are closely tied to ocean temperature and current patterns, making it sensitive to changes in regional ocean conditions. Because so many commercially and ecologically important species depend on it directly or indirectly, shifts in its abundance are closely watched as an indicator of the health of the wider North Atlantic ecosystem.