The external appearance of the perch is simple enough. The dorsal side of the fish consists of an upper maxilla and lower mandible for the mouth, a pair of nostrils, and two lidless eyes. On the posterior sides are the operculum, which are used to protect the gills. Also there is the lateral line system, which is sensitive to vibrations in the water.
Perch have a pair of pectoral and pelvic fins. On the anterior end of the fish, there are two dorsal fins. The first one is spiny and the second is soft. There is also an anal fin, which is also considered spiny, and a caudal fin. Also there is a cloacal opening right behind the anal fin. All perciform fish share the perch's general morphology.
Most authorities recognize three species of perch:
The European perch (Perca fluviatilis) is found in Europe and Asia. It is usually dark green with red fins. The European perch has been successfully introduced in New Zealand and Australia where it is known as the redfin perch or English perch.
The Balkhash perch (Perca schrenkii) is found in Kazakhstan, (in Lake Balkhash and Lake Alakol), Uzbekistan, and China. It is very similar to the European perch, and grows to a comparable size.
The Yellow perch (Perca flavescens), smaller and paler than the European perch, is found in the United States and Canada.
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