The Chilean jack mackerel is not a mackerel, but is a jack. Perhaps a more accurate name for this species, therefore, would be the “mackerel jack.” It lives in the productive waters of upwelling zones, where deep nutrient-rich seawater is brought to the surface by the prevalent currents. Chilean jack mackerel feed in these zones and form massive schools that are heavily exploited by commercial fisheries. The fishing nations of the world have captured Chilean jack mackerel in such large numbers in recent years that there are now international treaties in place to manage these fishing activities among multiple countries.
Chilean jack mackerel are filter feeders that eat fish larvae and small, pelagic crustaceans. Though they filter very small prey, they use their relatively large eyes and strong eyesight to increase the density of prey in the water that they filter. This strategy is in stark contrast to that used by the very large bodied filter feeders (like whale sharks and basking sharks, which essentially feed blindly and rely on large volumes of water to obtain sufficient prey.
This species reproduces via broadcast spawning, where several females release their eggs and several males release their sperm into the water column at the same time. This method increases the likelihood that eggs will become fertilized and increases the genetic variability in the population. As it can be very common and form massive schools, the Chilean jack mackerel is an important prey species for large fishes, seabirds, marine mammals, and other predators.
Fisheries targeting Chilean jack mackerel peaked at more than four million metric tonnes during the early 1990s. These fisheries certainly depleted the populations of this species, and now the catch is much smaller (less than 10% of peak numbers). Though some Chilean jack mackerel are marketed for human consumption, much of the catch is processed into fishmeal or oil and fed to livestock. A recent expansion in aquaculture facilities throughout the fjords of southern Chile has increased demand for the fishmeal processed from this species. Farms that raise chinook salmon and other salmon, in particular, utilize Chilean jack mackerel. Unfortunately, this wasteful process costs approximately 5 pounds (or more) of Chilean jack mackerel to raise one pound of salmon. Even though the commercial catch of Chilean jack mackerel is way down from its historic peak, current population trends are unknown, and scientists do not believe that they have sufficient information to determine the conservation status of this species. However, if the fisheries that target the Chilean jack mackerel are not carefully managed, there is little doubt that the species could crash.