About Sander lucioperca (Linnaeus, 1758)
The zander (Sander lucioperca) is the largest member of the Percidae fish family. It typically has a long, muscular body that resembles the Northern pike (Esox lucius), which is why it also has the alternative English common name pikeperch. The upper body is green-brown, and this colour extends to the sides as dark vertical bars, a pattern similar to that of the European perch (Perca fluviatilis), while the lower body is creamy-white. The caudal fin is dark, and the pectoral, pelvic and anal fins are paler off-white. Rows of black spots mark the membranes between the spines and rays of the dorsal and caudal fins; these spots are largest and clearest on the first dorsal fin. Juvenile zander are silvery in colour, and darken as they mature. They have powerful jaws with many sharp teeth, including two long canines at the front of each jaw. They also have large, bulbous eyes that become opaque when the fish lives in especially turbid conditions, an adaptation to low light. There is a single flat spine on the operculum. Like other members of the perch family, the zander has a split dorsal fin: the first dorsal fin has 13–20 spines and 18–24 soft rays, while the anal fin has 2–3 spines and 10–14 soft rays. The caudal fin is long and forked. The maximum published standard length for zander is 100 centimetres (39 in), though most individuals reach around 50 centimetres (20 in). This species can weigh up to 15 kg (33 lb), though typical caught specimens are much smaller. The IGFA All-Tackle world record zander, caught in Lago Maggiore, Switzerland in June 2016, weighed 11.48 kg (25.3 lb). Zander have an average length of 40–80 cm (15.5–31.5 in) and a maximum recorded length of 120 cm (47 in).
Zander are very widely distributed across Eurasia, occurring in the drainages of the Caspian, Baltic, Black, Aral, North and Aegean Sea basins, with their northern distribution boundary in Finland. They have been introduced to Great Britain, southern Europe, continental Europe west of the Elbe, Ebro, Tagus and Jucar drainages, as well as to Anatolia, North Africa, Siberia, Kyrgyzstan, and Kazakhstan. In the UK, zander were first introduced in 1878 by Francis Russell, 9th Duke of Bedford, to lakes on his Woburn Abbey estate, and were soon introduced into the Great Ouse Relief Channel in The Fens. British Waterways listed zander among a "dirty dozen" non-native species most likely to harm native wildlife along Great Britain's rivers. Their successful establishment is due to multiple factors, including their strong adaptation to the slow-flowing, sparsely vegetated, murky waters that make up many British lowland rivers. Unlike pike, which typically dominate the predatory fish niche in clear water, zander thrive in water with low visibility. However, zander require high levels of oxygen and quickly disappear from eutrophic areas. Zander were stocked in Spiritwood Lake, North Dakota in 1989 and have persisted there ever since. Ecologists believe that if zander become established in the Great Lakes, they will compete with game fish such as the closely related walleye or yellow perch for food and habitat, so the Government of Ontario preemptively classifies zander as a future invasive species. In the Netherlands, native zander can be found in many major waterways, including the Waal, Hollands Diep, other Rhine distributaries or estuaries, and are particularly common in Amsterdam's canals.
Zander inhabit freshwater bodies, especially large rivers and eutrophic lakes. They can tolerate brackish water and will use coastal lakes and estuaries. Individuals living in brackish water habitats migrate upriver, as far as 250 kilometres (160 miles), to spawn.
Zander spawn over gravel in flowing water. Males defend a territory where they dig shallow depressions in sand or gravel that are roughly 50 centimetres (20 in) across and 5–10 centimetres (2.0–3.9 in) deep. They will also nest among exposed plant roots, where eggs are laid. Nests are normally found at depths of 1 to 3 metres (39 to 118 in) in turbid water. Spawning occurs in pairs, at night and daybreak. During spawning, the female stays stationary above the male's nest, while the male swims rapidly around her, keeping around 1 metre (3.3 ft) away from the nesting depression. The male then orients himself perpendicular to the substrate, and the pair swim swiftly around together, releasing eggs and sperm. The female leaves after releasing her eggs. The male remains at the nest to defend it, fanning the eggs with his pectoral fins. Each female lays all of her eggs at once, and only spawns once per year. Zander larvae are attracted to light; after leaving the nest they feed on zooplankton and small pelagic animals. The normal spawning season is April and May, though spawning can occasionally occur from late February through to July, with the actual period depending on latitude and altitude. Spawning only begins once water temperatures reach 10–14 °C (50–57 °F).
Zander is considered one of the most valuable food fish native to Europe. It is prized for its light, firm yet tender meat with few bones and a delicate flavour. Although it is not generally bred for food, its adaptability makes zander fisheries quite sustainable. In some regions, release of young zander is restricted, because natural stocks already provide enough supply for markets, and increasing the population of this large predator would negatively impact its prey populations. Zander is especially well-suited for producing fish fillets, but can also be served whole, baked, smoked or cooked. In some culinary circles, zander is more highly appreciated than salmon. Even the offal can be cooked to make consommé. In 2004, it was revealed that some restaurants in the Minneapolis-St. Paul area of Minnesota were serving imported zander instead of the closely related North American walleye, Minnesota's state fish and a popular regional food. While zander and walleye are almost indistinguishable in taste, selling the European fish under the name "walleye" was an illegal practice, and an investigation by the U.S. Food and Drug Administration followed. In Ohio, many restaurants were caught using juvenile zander fillets weighing 40 to 80 grams in place of Lake Erie yellow perch. Shortages of yellow perch combined with sharply rising prices led wholesalers and restaurants to use juvenile zander for popular "pike perch fillets". In Finland, law regulates the minimum size of zander that can be harvested for consumption as a conservation measure. In July 2009, a rare incident occurred where a zander bit bathers swimming in the Swiss section of Lake Maggiore, sending two people to the emergency room; the most severe bite created a wound around 10 centimetres long. Local police later caught the 70-centimetre, 8-kilogram fish, cooked it, and offered it to tourists to make up for the disturbance it caused. As the largest member of the perch family, zander is a popular game fish in the United Kingdom. However, its status as a non-native invasive species means strict legal restrictions apply: any zander caught by anglers in the UK cannot be returned to the water, and must be destroyed.
