Many species of freshwater
game fish more or less resemble perch, but belong to different genera. In fact, the exclusively saltwater-dwelling
red drum (which belong to a different order
Acanthuriformes) 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.
Species
Most authorities recognize three species within the perch genus:
The
European perch (P. fluviatilis) is primarily found in
Europe, but a few can also be found in
South Africa, and even as far east on the
Southern hemisphere as
Australia.[3] 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 in
New Zealand and
Australia, 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).
The
Balkhash perch (P. schrenkii) is found in
Kazakhstan, (in
Lake Balkhash and
Lake Alakol),
Uzbekistan, and
China. 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 the
Nuru and
Chu 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).[4]
The
yellow perch (P. flavescens), smaller and paler than the European perch (but otherwise nearly identical), is found in
North 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).
Anatomy
External anatomy
Perch have a long and round body shape which allows for fast swimming in the water. True perch have "rough" or
ctenoid scales. Perch have paired
pectoral and
pelvic fins, and two
dorsal fins, the first one spiny and the second soft. These two fins can be separate or joined.[6] The head consists of the
skull (formed from loosely connected bones),
eyes,
mouth,
operculum,
gills, and a pair of
nostrils (which has no connection to the oral cavity). They have small brush-like teeth across their
jaws 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 have
gill rakers inside the mouth.[7]
External anatomy can be used to determine the
sex of perch in multiple ways. Perch have two posterior openings located on their abdomen, the
anal and
urogenital. 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]
Internal anatomy
The
esophagus is a flexible tube that goes from the mouth to the stomach. The
stomach is connected to the intestine via the
pyloric sphincter.[7] The
intestines of perch consist of the
small intestine and
large intestine; the intestines have many
pyloric caeca and a
spiral value, the small intestine consists of a part called the
duodenum. The
spleen is located after the stomach and before the spiral value. The spleen is connected to the
circulatory system, not part of the
digestive tract. The
liver is composed of three lobes: one small lobe (includes the gall bladder) and two large lobes. Perch have long and narrow
kidneys that contain clusters of
nephrons which empty into the
mesonephric duct.[9] They have a two-chambered
heart consisting of four compartments: the
sinus venous, one
atrium, one
ventricle, and
conus.[10] Perch have a
swim bladder that helps control
buoyancy or floating within the water, the swim bladder is only found in bony fish. In perch, the duct connecting the swim bladder to the
pharynx is closed so air is unable to pass through from the mouth, these fish are called
physoclists. Specifically in perch, the gas bladder can vary from 12% to 25% of
oxygen and 1.4% to 2.9% of
carbon dioxide gas.[11] Perch
reproductive organs include either a pair of
testes (sperm-producing) or a pair of
ovaries (egg-producing).[9]
Habitats
Perch are classified as
carnivores, choosing waters where smaller fish,
shellfish, zooplankton, and insect
larvae are abundant.[13][14] The 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 the
Great Lake region, in particular
Lake Erie. These fish inhabit bodies of water where vegetation and debris is readily accessible.[15][16][17] In the spring when the perch chooses to
spawn, they use vegetation to conceal their eggs from predators.[18]
Fishing
Perch are a popular
sport 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, including
float fishing, lure fishing, and
legering. 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 lb 11+1⁄2 oz),[19] and in America 2.83 kg (6 lb 4 oz).
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.