New Zealand hatchetfish

Educational value

• The deep-sea hatchetfish all belong to the fish family Sternoptychidae. They are generally small, up to 10 cm long, and have a characteristically short, deep body shape. The name 'hatchetfish' refers to their slender compressed bodies and sharply keeled abdomen, which gives some species a resemblance to a hatchet. They are darkly coloured on the back and silvery on the sides.
• The deep-sea hatchetfish migrate upwards during the night to feed on prey in the more productive upper regions of the ocean. Towards dawn, when predators can more easily detect them, they descend again to the ocean's depths. They generally feed on plankton and nekton, such as small crustaceans.
• The deep-sea hatchetfish are adapted to live at depth where food and mates are scarce. Their eyes are very efficient in the low light of the ocean depths, assisting them to navigate, avoid predation and find mates. They also have a good sense of smell, which is used by the males to follow the scent trails produced by females, increasing their chances of reproduction.
• A remarkable adaptation for life at depth in the ocean is bioluminescence, a light produced by a chemical reaction in the specialised organs of many marine organisms. Bioluminescence is used by many deep-sea fish, including hatchetfish, and invertebrates, such as bacteria, jellyfish, krill and squid. In the deep ocean bioluminescence helps to confuse predators, attract mates and find prey.
• The light-producing organs of hatchetfish are on the abdomen and sides of the body, and the light is projected downwards at an intensity matching the light above. This counter-illumination is designed to camouflage its profile from predators below. Bioluminescence patterns of hatchetfish differ for each species, and therefore are also believed to have a role in mate location and identification.
• The New Zealand hatchetfish, also called the Kiwi hatchetfish, is restricted to the continental shelf, continental slope and deep-sea ridges and rises of the Tasman Sea between Australia and New Zealand. This species swims in the water just above the sea floor. It moves upwards at night to feed, and then returns to the safety of the sea floor by day. This species reaches a maximum length of about 8.2 cm.

Year level

2; 3; 4; 5; 6; 7; 8; 9; 10; 11; 12

Topics Bioluminescence Fishes