Glass eye perch

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Glass eye perch
Sander vitreus.jpg

Glass eye perch ( Sander vitreus )

Systematics
Perch relatives (Percomorphaceae)
Order : Perch-like (Perciformes)
Subordination : Percoidei
Family : Real perch (Percidae)
Genre : Sander
Type : Glass eye perch
Scientific name
Sander vitreus
( Mitchill , 1818)

The walleye ( Sander vitreus ) even American Zander called, is a perch and belongs to the family of Real perch for species Sander . It was discovered and named in 1818 by Samuel Latham Mitchill .

description

Appearance, dimensions and morphology

The glass eye perch is a relatively large, elongated fish with a body length of around 75 to 107 centimeters. The almost cylindrical body reaches 7 to 11.3 kilograms in weight. Its name comes from the sometimes "glassy" (also Latin vitreus ) appearing look, to which the American fish name wall-eye refers, which refers to an alleged clouding of the cornea - while both are actually based on a light-reflecting layer behind the retina , which improves twilight vision.

In the head and back area it shows an olive - to yellowish - brown coloration, with the sides being a little lighter. The first dorsal fin is the only one with a dark spot in the area of ​​the rear base, whereas the second dorsal fin has several rows of small spots. The anal and pelvic fins are usually transparent, while the underside of the head is white to yellowish. The very distinctive snout has developed and strong dog teeth in the jaw and on the palatine bones . The upper jaw is slightly protruding and extended to below the middle of the eye , the rear edge of the jaw extends below the rear edge of the eye. The lower and upper jaws are slightly curved at the tip. The glass eye perch has eight low gill spines per arch, a total of 13–17 dorsal spines, 18–22 dorsal soft rays, two anal spines, 11–14 anal soft rays, 44–48 dorsal vertebrae , 13–16 pectoral fin rays and 7 (or 8) Branchiostegal - rays. There are no tubercles on the spawning dress . While the cheeks have a thin scale , the anterior gill covers are broadly sawn. The forked caudal fin is widely separated from the dorsal fin. The full sideline is straight.

Way of life

The glass eye perch can be found in shallow waters and in bays of large lakes in spring and autumn, where it can often be found in rocky areas. In summer, on the other hand, it looks for cooler and deeper areas, and then retreats to deeper waters during the day. The preferred water temperature is an average of 23 degrees Celsius .
As a predator that feeds mainly on fish , the glass eye perch mostly searches for food in the early morning and evening, but it can also be active throughout the day, especially in murky waters. However, it avoids intense light, so that the most active hunting times take place at dusk and when it is cloudy. The glass eye bass reaches a possible age of around eight to ten years, but there are also documented cases of 29 years of age.

Subspecies

  • Sander vitreus glaucus ( Hubbs , 1926), extinct
  • Sander vitreus vitreus ( Mitchill , 1818)

distribution

The glass eye perch is found in large parts of North America . It can also be found in the St. Lawrence River , in the Arctic , in the Mississippi River , in the catchment area from Québec to the Northwest Territories in Canada and in the south to Alabama and Arkansas .

nutrition

At night, the glass eye perch feeds primarily on insects and smaller fish, including small perch, trout and pike and the freshwater drummer . When insects and fish become scarce, it alternatively feeds on crustaceans , snails , amphibians , leeches and small mammals . As a young fish, it feeds mainly on plankton and aquatic insects.

Reproduction

Males reach sexual maturity between two and four years of age, while females reach sexual maturity between three and six years of age. The spawning season takes place in the months from February to April at water temperatures of 8.9 to 12.8 degrees Celsius. Shallow lakes or flooded vegetation areas with ample gravel subsoil serve as spawning grounds. Regularly carried out, the spawning in the evening in small groups, wherein the male or the female initiates the spawning process, by applying pressure against the partner laterally continuous. On the surface of the water, eggs and sperm are secreted at the same time. The female can release up to 612,000 eggs, each about 801 millimeters long, during spawning time. The number increases per year up to an age of at least ten years, whereas the male spawns over a longer period of time. After fertilization , the eggs sink to the bottom and stick to the bottom with the help of the sticky outer membrane . The fish larvae initially feed on small crustaceans when the respective yolk sac has been completely used up, but sometimes also eat their siblings ( cannibalism ). The change in diet to fish and invertebrates only occurs when they are 34 to 80 millimeters in size . The population usually doubles between 4.5 and 14 years.

Fish farming

Although the eyeglass is not widely reared for consumption , the fishing industry does raise eyeglasses on farms . In the USA, a court ruling prohibited the marketing of imported fillets of European pikeperch ( Sander lucioperca ) as wall-eye, although no difference in taste can be noticed.

literature

Web links

Commons : Eyeglasses ( Sander vitreus )  - Collection of images, videos and audio files