The Alaska Blackfish

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Alaska Blackfish
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Image of animal

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General Information;

Type: Fish
Diet: Omnivore
Size: 7 inches
Weight: 10 ibls
Conservation status: Not applicable
Scientific Classification: Kingdom: Animalia, Phylum: Chordata, Class: Actinopterygii, Order: Esociformes, Family: Umbridae, Genus: Dallia
Size relative to a 6-ft (2-m) man: Not applicable
Alaska Blackfish Range


The hardiness of the Alaska blackfish is of mythical proportions, including tales of reviving fish after they are frozen solid. The fish survive the cold winters by moving to a depth of 7–8 metres (23–26 ft) when the surface becomes solid ice. Large gills protected by gill covers help them to survive the winters where the water temperatures drop to 0 °C (32 °F).
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Physical Features;
Alaska blackfish are small, seldom longer than 8 inches (200 mm), although individuals up to 13 inches (330 mm) have been found. They are distinguishable from other fish by their large paddle-like pectoral (lower front) fins and tail, tiny ventral (lower middle) fins, backward placement of their dorsal (upper) and anal fins, and rather broad, flat heads. Their color is dark green or brownish on the upper sides and pale below, with irregular blotchy areas on their side. Mature males can be distinguished from females by the presence of a reddish fringe along the dorsal, caudal (tail), and anal fins. Also, in mature males the tips of the ventral fins extend well beyond the front of the anal fin, whereas in females they do not.
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Mental Features;
Spawning occurs from May to August, with the possibility of individual fish spawning several times and females releasing only a portion of their eggs each time. Depending on her size, a female may release a total of 40 to 300 eggs at intervals throughout the entire spawning period. The eggs adhere to the heavy vegetation and hatch in a short time (about nine days at 54°F). The young are tiny at hatching (about 6 mm), and, depending on water temperature, live off their yolk sacs for about ten days. The Alaska blackfish are unique because they have a modified esophagus capable of gas absorption, meaning they can exist off atmospheric oxygen. The existence of an air-breathing fish in arctic regions at first seems unlikely as most oxygen problems in the water would be expected to occur in winter-a time when air breathing would not appear to be of any advantage because of the ice cover.
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Diet;
Aquatic insects and other small invertebrates are the principal foods of most blackfish. However, in Bristol Bay the larger blackfish are cannibalistic and feed on their own kind; they also eat small, young-of-the-year northern pike.
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Threats towards this animal;
The Alaska blackfish is distributed throughout eastern Siberia and most of western Alaska. Alaska blackfish inhabit lowland weed-choked ponds, lakes, and sloughs of the Togiak National Wildlife Refuge. They typically live in the densely vegetated areas of lowland swamps, ponds, rivers, and lakes.
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Credits (c);

Images:
http://www.donerickson.com/alaska/fish/blackfish1.jpg

Information:
http://en.wikipedia.org/wiki/Alaska_Blackfish
http://togiak.fws.gov/blackfish.htm
http://www.adfg.alaska.gov/static/education/wns/alaska_blackfish.pdf
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