Summary


Habitat and development

The Pikeperch belongs to the Percidae family within the order of the Perciformes. The species lives in inland and coastal waters, originally in Scandinavia, the Baltic states, the Black, the Caspian and the Aral Seas, and in the mouths of the Elbe (North Sea) and the Maritz (Aegean Sea). Today, due to artificial introduction, this species is also common in the waters of Western Europe, North Africa, and even of China, the Azores, and of the United States, however with ecological consequences in some of these countries.

The Pikeperch can adapt to temperatures between 0 and 27 centigrades; the preferred temperature is above 20 centigrades. At lower temperatures the species becomes stationary and prefers lower and calmer water layers.

In nature, Pikeperch cover a daily average distance between 0.3 and 6.3 km. Adult females reach swimming speed up to one and a half times their body length per second. Generally Pikeperch dwell in depth between 0 and 5 m (a maximum of 31 m is reported), during the day at lower water layers, presumably to shelter from predators. Juveniles appear at the surface at dusk, return to the depth by dawn.

Pikeperch can live in fresh and in brackish water, tolerating salinities between 0 and over 10 per mill. Juveniles tend to trek downstream, whereas adults after spawning in spring migrate to the coast from where they return to the river in autumn. 

Photo: Steffen Zienert
 

Growth and reproduction

Pikeperch on average reach total length between 50 and 70 cm and weight of 2 to 5 kg. Maxima achieved are age up to 14 years, total length up to 130 cm, and weight up to 18 kg. Males become mature at the age of 1.5 to 2 years, females at 2 to 3 years. They spawn in spring (February to May) following a long and complex mating behaviour. 

The male creates a nest at 1 to 3 m depth, in the sand or gravel or between protruding rootage, measuring about 50 cm in diameter and 5 to 10 cm in depth. Then he vertically shakes head and circles over the nest, cleaning it to signal the female where to place the eggs. Then he lets her access the nest, chases her away, lets her access again, repeatedly with increasing frequency. When she is near the nest, she encircles it in the form of alying “8”, head upward, while he shakes head. Finally both encircle the nest together, sometimes in zig-zag moves, female head up, male head down and body colour intensifying. Moves slowing down, they circle side by side over the nest for hours or even days. When her genitals swell, she moves in mounting position. Shortly before spawning, he encircles her in downward or almost vertical position and shakes head quickly. The female produces 140,000 to 255,000 eggs per kilogramme body weight. After spawning, the male cleans the nest again in order to provide for oxygen.

Photo: Jiri Bohdal

 

Way of life

Pikeperch are ambush predators, living over fine mud-free substrates of sand, stones or rocky sheets, but also in the open water. Juveniles feed on small crustaceans, insects, and small fish; adults prey on bigger fish. Cannibalism can occasionally occur.

As choice experiments reveal, Pikeperch prefer regions of low light intensity and grow faster under such condition. The visual perception of Pikeperch is adapted to this niche. No studies are available on other senses of Pikeperch, including sensation of pain, and again no studies on communication between individuals, on learning and other cognitive abilities like playing, or on the strategies to cope with negative stimuli – knowledge that would be important to improve the welfare of this increasingly farmed species.

In nature, Pikeperch predominantly hunt at dusk and dawn, but also at night and by day. The preferred time of hunting varies individually as well as seasonally. Pikeperch do not school, they hunt in small groups. Besides occasional cannibalism, there are no findings on territorial or aggressive behaviour.

 

 

The development of Pikeperch farming

Farming of Pikeperch started in the nineteenth century in Central and Eastern Europe where the species was inserted into carp earthen ponds. The volume of production at the time was however negligible. In the early 1900s, brood of Pikeperch was gained from natural spawning in earthen ponds to rebuild the stocks in nature. Since the second half of the twentieth century, Pikeperch were farmed in ponds also in Western Europe. Pond farming of this species is carried out in an extensive way still today, and Pikeperch produced this way are reared as supplement to other species reared in such ponds.

Only since the early 2000s, Pikeperch in Western Europe have been farmed also in Recirculation Aquaculture Systems (RAS). In the first decade of the current century only ten Pikeperch RAS were established, but intensive breeding and fattening of this species is increasing, also by means of smaller RAS modules which get installed in unused livestock buildings.

Today, Pikeperch are mainly farmed in the Czech Republic, Hungary, Poland, Romania, Ukraine, Denmark, the Netherlands, and Tunisia. However, still nine times more Pikeperch stem from fishing than from farming.

 

In classical pond farming Pikeperch are kept among other species.
Photo: The Strussnig pond in Moosburg, Carinthia (Johann Jaritz / Wikimedia Commons)
 

Major problems of common Pikeperch farming

Farming of Pikeperch is increasing despite the fact that – as explained above – many aspects of the species’ biology are still not understood. The low FishEthoScore is mainly due to the big gap of knowledge on the following issues:

Mainly unexplored are questions on how to satisfy natural needs under farming conditions, above all the need of home range, depth range, and substrate, and what to provide against stress under farming conditions. Moreover, the complex mating behaviour is impaired in an artificial environment; as a matter of fact, farmed Pikeperch reproduce only by natural spawning, however mainly induced by manipulation of photoperiod and temperature.

In addition, farming conditions prohibit the natural migration behaviour, force individuals to school foreign to the species’ social behaviour, and lead to various deformations in more than 10 percent of the animals concerned (however, the number of deformations in nature is unknown). Finally, as in all predator species, feeding so far depends on fish meal and fish oil which preponderantly still stem from specialised forage fisheries on small species like anchovies and sardines by which, in an agonising way, much more fishes die than the Pikeperch finally harvested in the farm.

There is potential for the improvement of the welfare of farmed Pikeperch. Extensive farming in ponds and low stocking densities are simple measures for higher fish welfare and less stress. Under intensive farming conditions in tanks, the enrichment of the environment could add to more fish welfare. The need for space could at least be met in the vertical dimension. Considering the species’ circadian rhythm and its preferred time of day for activity and rest will add to welfare. Finally, the partial or even full replacement of feed components from forage fisheries would reduce the impairment of wild fish welfare.

Further research is needed, both on the senses and the natural behaviour of the species and on the effects of farming conditions, in order to provide more purposeful recommendations to improve farmed fish welfare.

For the time being, labels (i.e. seals of approval) are not helpful for clients who care for the welfare of farmed fish. The guidelines of organic labels are the ones most inclined to grant animal welfare, yet they define no tangible instructions. All other labels address animal health at best, but do not acknowledge all-encompassing aspects of animal welfare. That is to say that even fishes farmed under labels like organic, ASC, or Friend of the Sea, often live under the conditions of intensive animal husbandry. However there is some hope as several labels are currently studying the feasibility of integrating fish welfare into their certification schemes. 

If we want to change the disregard for animal welfare, we need more of two things: ethological research and pressure from concerned consumers who want to eat respectfully-farmed fish.