The Beloved Blackfin Icefish
The blackfin icefish (Chaenocephalus aceratus), also known as the Scotia Sea icefish, is a species of fish found in the Southern Ocean, around the Antarctic shelf. They typically reside along the bottom of the ocean closer to the sore, at depths no greater than 770 m (0.47 mi). These waters stay at around -2 °C (28 °F) all year.
Male blackfish are slightly smaller than female blackfish; the former reaches 34–40 cm (13-15 in) in length while the latter reaches 48–49 cm (18-19 in). The blackfin icefish is noted for its unique appearance. It is a scaleless fish, with a white or grey body sporting darker strikes all down its sides.
Part of this color comes from their blood, which lacks hemoglobin and is translucent in color. The icefish family are the only vertebrates in the world that lack hemoglobin. This lack severely reduces the oxygen carrying capacity of their blood; as a trade-off their blood is thinner to reduce viscosity and carries 'anti-freeze' proteins which allow the fish to survive below-freezing waters.
Spawning typically takes place in the autumn or winter. Females may only reproduce every other year due to the high energy costs of egg production. Male C. aceratus dig shallow depressions in the sand, and females lay clutches of up to 10,000 eggs. These eggs can take anywhere from 2-6 months to hatch, and during this time the males do most if not all of the guarding of the nest. After hatching, juveniles may take anywhere from 5-7 years to become fully mature.
The diet of Scotia Sea icefish consists primarily of krill, mackerel icefish, and crustaceans. Juveniles typically consume more krill than fish, and are more often found swimming in the water column, while adults stay along the ocean floor and ambush their prey. It is unknown whether they have any natural predators.
Conservation status: The IUCN considers the blackfin icefish as Vulnerable. Its primary threats are fatalities from fishing by-catch and climate change, which is increasing the temperature of its natural habitat.
Photos
Uwe Kils
Thomas Desvignes
Bill Baker
