Atlantic Horse Mackerel

Photo: Erik Schlögl · CC BY-NC

Horse mackerel aggregate at Los Gigantes Wall in schools that can number in the thousands, their coordinated schooling behaviour creating an ever-shifting silver curtain between diver and open water as the school responds to the presence of predators — primarily the amberjack and occasional bluefin tuna that patrol the blue water adjacent to the wall. As planktivores and small-fish predators in the mid-water column, horse mackerel play a critical energy transfer role in the upwelling ecosystem off Tenerife's northwest coast, concentrating the productivity of the plankton bloom into a prey package that supports the full suite of large pelagic predators in the surrounding ocean. Their schooling density at this site is exceptional even by Canarian standards, a consequence of the wall's structural complexity providing refuge from the open water while the adjacent upwelling delivers the food supply they depend on.