feeding grounds towards the north, but there is almost no mixing between the east and west Atlantic stocks. Another common coastal species, the chub mackerel (Scomber japonicus), is absent from the Atlantic Ocean but is widespread across both hemispheres in the Pacific, where its migration patterns are somewhat similar to those of Atlantic mackerel. In the northern hemisphere, chub mackerel migrate northwards in the summer to feeding grounds, and southwards in the winter when they spawn in relatively shallow waters. In the southern hemisphere the migrations are reversed. After spawning, some stocks migrate down the continental slope to deeper water and spend the rest of the winter in relative inactivity. The Chilean jack mackerel (Trachurus murphyi), the most intensively harvested mackerel-like species, is found in the south Pacific from West Australia to the coasts of Chile and Peru. A cousin species, the Pacific jack mackerel (Trachurus symmetricus), is found in the north Pacific. The Chilean jack mackerel occurs along the coasts in upwelling areas, but also migrates across the open ocean. Its abundance can fluctuate markedly as ocean conditions change, and is particularly affected by the El Niño. Three species of jack mackerels are found in coastal waters around New Zealand: the Australasian, Chilean, and Pacific jack mackerels. They are mainly captured using purse seine nets, and are managed as a single stock that includes multiple species. Some mackerel species migrate vertically. Adult snake mackerel conduct a diel vertical migration, staying in deeper water during the day and rising to the surface at night to feed. The young and juveniles also migrate vertically, but in the opposite direction, staying near the surface during the day and moving deeper at night. This species feeds on squid, pelagic crustaceans, lanternfishes, flying fishes, sauries, and other mackerel. It is, in turn, preyed upon by tuna and marlin. Lifecycle Mackerel are prolific broadcast spawners, and must breed near the surface of the water because the eggs of the females float. Individual females lay between 300,000 and 1,500,000 eggs. Their eggs and larvae are pelagic, that is, they float free in the open sea. The larvae and juvenile mackerel feed on zooplankton. As adults, they have sharp teeth, and hunt small crustaceans such as copepods, forage fish, shrimp, and squid. In turn, they are hunted by larger pelagic animals such as tuna, billfish, sea lions, sharks, and pelicans. Off Madagascar, spinner sharks follow migrating schools