Many species of freshwatergame fish more or less resemble perch, but belong to different genera. In fact, the exclusively saltwater-dwellingred drum (which belongs to a different orderAcanthuriformes) is often referred to as a "red perch", though by definition perch are freshwater species. Though many fish are referred to as perch as a common name, to be considered a true perch, the fish must be of the family Percidae.
Most authorities recognize three species within the perch genus:
TheEuropean perch (P. fluviatilis) is primarily found inEurope, but a few can also be found inSouth Africa, and even as far east on theSouthern hemisphere asAustralia.[2] This species is typically greenish in color with dark vertical bars on its sides with a red or orange coloring in the tips of its fins. The European perch has been successfully introduced inNew Zealand andAustralia, where it is known as the redfin perch or English perch. In Australia, larger specimens have been bred, but the species rarely grows heavier than 2.7 kg (6 lb).
TheBalkhash perch (P. schrenkii) is found inKazakhstan, (inLake Balkhash andLake Alakol),Uzbekistan, andChina. It has a dark gray/black color on its dorsal side, but the ventral areas of the fish are a lighter silver or even sometimes green color. The Balkhash perch also displays the vertical bars on its sides, similar to the European and yellow perches. In the latter half of the 20th century, the Balkhash perch was introduced into the basins of theNuru andChu rivers. The introduction of these fishes to the Nuru and Chu rivers was successful. Because of this success, the population of Balkhash perch in the Balkhash Lake is rarer now. They are similar in size to the yellow and European perches, weighing around 1.5 kg (3 lb 5 oz).[3]
Theyellow perch (P. flavescens), smaller and paler than the European perch (but otherwise nearly identical), is found inNorth America. In northern areas, it is sometimes referred to as the lake perch. This species is prized for its food quality and has often been raised in hatcheries and introduced into areas in which it is not native. These fish typically only reach a size of about 38 cm (15 in) and 1 kg (2 lb 3 oz).
European perch (Perca fluviatilis), exhibiting its green coloration and red tipped fins, as well as the vertical bars on its sides.[4]Skull of the European Perch showing the eye sockets, connective bones, operculum, and gill slits.[5]
Perch have a long and round body shape which allows for fast swimming in the water. True perch have "rough" orctenoid scales. Perch have pairedpectoral andpelvic fins, and twodorsal fins, the first one spiny and the second soft. These two fins can be separate or joined.[6] The head consists of theskull (formed from loosely connected bones),eyes,mouth,operculum,gills, and a pair ofnostrils (which has no connection to the oral cavity). They have small brush-like teeth across theirjaws and on the roof of their mouth. The gills are located under the operculum on both sides of the head and are used to extract oxygen molecules from water and expel carbon dioxide; the gills havegill rakers inside the mouth.[7]
External anatomy can be used to determine thesex of perch in multiple ways. Perch have two posterior openings located on their abdomen, theanal andurogenital. In males, the shape of the urogenital opening is round and larger than the anal opening. In females, the urogenital opening is often a V- or U-shape which is a similar size to the anal opening. Also, males usually have a more brown-red colored urogenital opening compared to females.[8]
Theesophagus is a flexible tube that goes from the mouth to the stomach. Thestomach is connected to the intestine via thepyloric sphincter.[7] Theintestines of perch consist of thesmall intestine andlarge intestine; the intestines have manypyloric caeca and aspiral value, the small intestine consists of a part called theduodenum. Thespleen is located after the stomach and before the spiral value. The spleen is connected to thecirculatory system, not part of thedigestive tract. Theliver is composed of three lobes: one small lobe (includes the gall bladder) and two large lobes. Perch have long and narrowkidneys that contain clusters ofnephrons which empty into themesonephric duct.[9] They have a two-chamberedheart consisting of four compartments: thesinus venous, oneatrium, oneventricle, andconus.[10] Perch have aswim bladder that helps controlbuoyancy or floating within the water, the swim bladder is only found in bony fish. In perch, the duct connecting the swim bladder to thepharynx is closed so air is unable to pass through from the mouth, these fish are calledphysoclists. Specifically in perch, the gas bladder can vary from 12% to 25% ofoxygen and 1.4% to 2.9% ofcarbon dioxide gas.[11] Perchreproductive organs include either a pair oftestes (sperm-producing) or a pair ofovaries (egg-producing).[9]
The above picture is a labeled image of the internal anatomy of the species Perch Perca flavescens. Each letter corresponds to an internal body part, A: gills, B: auricle of the heart, C: ventricle of the heart, D: liver, E: stomach, F: digestive cecum, G: swim bladder, H: intestine, I: testis, and J: urinary bladder.[12]
Perch are classified ascarnivores, choosing waters where smaller fish,shellfish, zooplankton, and insectlarvae are abundant.[13][14] The yellow perch can be found in the central parts of the United States in freshwater ponds, lakes, streams, or rivers. These fish can be found in freshwater all over the world, and are known to inhabit theGreat Lake region, in particularLake Erie. These fish inhabit bodies of water where vegetation and debris is readily accessible.[15][16][17] In the spring when the perch chooses tospawn, they use vegetation to conceal their eggs from predators.[18]
Perch are a popularsport fish species. They are known to put up a fight, and to be good for eating. They can be caught with a variety of methods, includingfloat fishing, lure fishing, andlegering. Fly fishing for perch using patterns that imitate small fry or invertebrates can be successful. The record weight for this fish in Britain is 2.81 kg (6 lb 3 oz), the Netherlands 3.05 kg (6 lb11+1⁄2 oz),[19] and in America 2.83 kg (6 lb 4 oz). The biggest recorded catch in Sweden is 3.15 kg (6lb 15oz) in 1985.
Perch grow to around 50 cm (20 in) and 2.3 kg (5 lb) or more, but the most common size caught are around 30 cm (1 ft) and 450 g (1 lb) or less and anything over 40 cm (16 in) and 900 g (2 lb) is considered a prize catch.
^Weatherley, A. H. (1963-03-01). "A Note on the Head Kidney and Kidney of the Perch Perca Fluviatilis (linnaeus), with Special Reference to the Blood Vascular System".Proceedings of the Zoological Society of London.140 (2):161–167.doi:10.1111/j.1469-7998.1963.tb01859.x.ISSN1469-7998.
^abRomer, Alfred Sherwood (1977).The vertebrate body. Thomas S. Parsons (5th ed.). Philadelphia: Saunders.ISBN0-7216-7668-5.OCLC3003870.
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