Antarctic silverfish

While widely distributed around the Antarctic, the species appears to have largely disappeared from the western side of the northern Antarctic Peninsula, based on a 2010 research cruise funded by the National Science Foundation under the US Antarctic Program.^[4] Due to climate change, the rising water temperatures in the Antarctic Peninsula cause this decline in Antarctic Silverfish abundance by interfering with psychological adaptations and spawning behaviors in ice.^[5]  Additionally, Antarctic Silverfish mortality rates spike after only a 5°C increase in water temperature, due to the presence of antifreeze glycoproteins in their blood, a common adaptation of Nototheniidae to survive in freezing waters.^[5][6]

The Antarctic silverfish was first formally described in 1902 by the Belgian-born British zoologist George Albert Boulenger with the type locality given as Victoria Land in Antarctica.^[9] It is the only species in the monotypic genus Pleuagramma which was also described by Boulenger.^[10] Some authorities place this taxon in the subfamily Pleuragrammatinae,^[11] but the 5th edition of Fishes of the World does not include subfamilies in the Nototheniidae.^[12] The genus name is a compound of pleuro meaning "side" with a which means "without" and gramma meaning "line", an allusion to the absence of a lateral line.^[13]

Antarctic silverfish usually grow to about 15 cm (5.9 in) in length, with a maximum of 25 cm (9.8 in). The maximum reported weight of this species is 200 g. Antarctic silverfish have a maximum reported age of 20 years. When alive, they are pink with a silver tint, but turn silver only after death. All the fins are pale. The dorsal side is slightly darker.^[2] This Antarctic marine fish is one of several in the region that produce antifreeze glycopeptides as an adaptation against the extreme cold of Antarctic waters.^[14]

Female Antarctic Silverfish release their eggs into sea ice along the Antarctic Peninsula to await fertilization.^[15] Antarctic Silverfish migrate in schools to seek out areas of high sea ice abundance; this forage determines spawning season.^[5] It usually occurs between the late winter months and early spring,^[15]  and larvae hatching occurs around November-December.^[16]  Each life stage of the Antarctic Silverfish occurs at different levels of the water columns, moving deeper as they mature.^[16]  An exception is the move closer to surface level between the larval stage and metamorphosis occurring at 2-3 years old. The postlarvae, 8–17 mm (0.31–0.67 in) in size, feed on eggs of calanoids (Calanoida), sea snails Limacina and tintinnids (Tintinnida).^[17]  Juveniles feed on copepods (Copepoda), mostly on Oncaea curvata and can be found at depths of 50 to 400 m (160–1,310 ft),^[2][17] while adults can be found at depths 0–728 m (0–2,388 ft).^[2] As their size increases, so does the size of their prey items. The age of sexual maturation of the Antarctic Silverfish is 6+ years, adults being the most abundant over the Ross Ice Shelf.^[16]