The pygmy whitefish, scientific name Prosopium coulterii is a freshwater whitefish of the genus Prosopium within the family Salmonidae. Found within the mountain streams and lakes in western North America, it additionally has remoted populations in Lake Superior and in Ekityki Lake, Chukchi Peninsula.
Pygmy whitefish Description
The pygmy whitefish is a small herring-like fish with a long and cylindrical body by comparability to different whitefishes. Silvery in colour, it has a brownish back and a whitish stomach.
Black spots on the aspect referred to as “parr marks”, that are current on younger trout or “parrs”, are current on the young of this species, and on adults in some Alaskan populations.
Commonly starting from three to 15.3 centimetres (1.2 to 6.0 in) in size, it’s usually 12 centimetres (4.7 in) long and reaches the most size of 28 centimetres (11 in).
It is recognized by its small measurement, and its massive eye, which has a greater size than its blunt snout. Its dorsal fin and pectoral fin are normally clear, and its tail is evident with a faint darkish spot. Its anal fin and pelvic fin are plain whitish.
It has massive scales with solely 56–70 on its lateral line, fewer gill rakers, all traits that point out a level of differentiation from the opposite Prosopium fishes.
Because of this, it’s thought of an early offshoot (basal) species in its genus, and it’s the most trout-like member of a genus thought of probably the most trout-like and primitive whitefish group.
Pygmy whitefish Distribution
The pygmy whitefish is discovered principally within the northern Rocky Mountains, with three different disjunct populations. One is in Lake Superior, one other is in southwestern Alaska, and the third is within the Ekityki Lake, Chukchi Peninsula, Russia.
The pygmy whitefish’s vary most likely was steady till the late Pleistocene. In the Rocky Mountains it’s present in chilly and speedy streams, and in cool lakes at depths of over 6 metres (20 ft). In Lake Superior, it’s present in cooler water, at depths of 18 to 89 metres (59 to 292 ft).
Pygmy whitefish Ecology
In Lake Superior, the pygmy whitefish spawns throughout November and December at depths of 31 to 46 metres (102 to 151 ft). Females lay a mean of 362 orange eggs, with a diameter of two.57 millimetres (0.101 in).
Elsewhere, the pygmy whitefish migrates upstream to spawn, normally spawning in November or December in gravelly streams. Pygmy whitefish feed totally on the aquatic larvae of bugs, and crustaceans.
In Lake Superior, the amphipod Pontoporeia and varied different crustaceans, principally ostracods, type 77 % of the pygmy whitefish’s diet. The burbot, kingfishers, and terns, and pikes have been recorded preying on the pygmy whitefish.
Pygmy whitefish Habitat
Pygmy Whitefish usually inhabits chilly, deep, boreal and montane lakes of low productiveness. It is normally discovered at depths better than 30 m, however, has been positioned at depths <5 m and as nice as 168 m.
Pygmy Whitefish is most frequently encountered at water temperatures under 10°C and oxygen concentrations above 5 mg/l. Pygmy Whitefish can be recorded from average to fast-moving, clear or silted, montane rivers the place it occupies depths of 0.5 to 1 m in nearshore eddies alongside the sting of the sooner mainstream stream.
Pygmy whitefish Biology
Pygmy Whitefish tends to be comparatively short-lived with life expectations ranging between three and 10 years (median 7 years). It typically matures at a younger age and small measurement.
Males mature at 1 to three years of age and 58 to 130 mm total size (TL), whereas females mature at 2 to Four years of age and 61 to 228 mm TL.
Spawning happens yearly between September and December, however, can happen as late as January when water temperatures are between 2 and 5°C. Eggs are broadcast over coarse gravel in shallow water in rivers or alongside lake shorelines at night time.
Egg production scales with body size; particular person females may produce between about 100 to 1,000 eggs. Pygmy Whitefish is a generalist carnivore usually feeding on a wide range of benthic invertebrates. In some populations, Pygmy Whitefish could forage on zooplankton within the pelagic zone.
Population size and traits
The small measurement of the Pygmy Whitefish and the nice depths at which it’s discovered usually makes its seize by way of standard fishing strategies troublesome.
Consequently, little information exists on its inhabitant’s measurement of traits throughout the vary and inhabitants estimates usually don’t exist. Nonetheless, it has been estimated that about 2,000 individuals reside inside Alberta (vary in the estimate, 700 to 3,000).
Annual trawl surveys carried out in Lake Superior point out that Pygmy Whitefish densities have ranged from 1.5 to 135 fish per surveyed hectare since 1963. Systematic trawling surveys recommend that the Lake Superior inhabitants have declined over the past three generations (16 yrs).
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Threats and limiting elements
The Pygmy Whitefish is a cold-water stenotherm, usually preferring water temperatures < 10 °C and dissolved oxygen ranges > 5 mg/l; due to this fact, the distribution of this species is probably going restricted, partly, by a basic lack of tolerance to circumstances the place these parameters are exceeded.
Degradation of habitat together with water high quality related to forestry, hydroelectric, oil, fuel and mining improvement, agriculture, and urbanization pose the best potential anthropogenic threats to Pygmy Whitefish, though few particular threats have been recognized.
Stocking with non-native fishes negatively impacts Pygmy Whitefish populations, significantly in smaller closed-basin lakes the place refugia from predation could also be restricted.
Fishes with limited dispersal capability and stenothermic tolerances, comparable to Pygmy Whitefish, could possibly be on the best threat of extinction following the lack of coldwater habitats from global warming. Learn more about dragon fish.