Zander is a species of fish closely allied to perch. Zander are often called pike-perch as they resemble the pike with their elongated body and head, and the perch with their spiny dorsal fin. Zander are not, as is commonly believed, a pike and perch hybrid.
The zander is a common and popular game fish in Europe: it is often eaten and may reach 20 kilograms in size. Typical catches, however, are considerably smaller, and most anglers are very happy with fish of 5 kg or so. The zander is not indigenous to the UK, but was introduced into the East Anglian drains (large artificial rivers) in the 20th century, and spread rapidly.
Zander thrive in water with rather low visibility, whereas the pike often dominates the predator fish niche in clear water: pikes use their vision to find prey, while zander "listen" to the water, and are very active at night. However, they need plenty of oxygen and soon disappear from eutrophic areas.