Made-to-measure for aquaculture
The African sharptooth catfish Clarias gariepinus is a hardy fish of modest needs that is not particular about its diet. Moreover it is an accessorial air-breathing fish that is sometimes to be found living in groups in the most confined spaces at great densities. Its protein- and omega-3-rich fillet tastes good, is healthy and can be processed in many different ways. All this makes C. gariepinus an ideal candidate for aquaculture and it is produced in considerable quantities worldwide.
This article was featured in EUROFISH Magazine 5/2019.
Farmed fish with a long history and an uncertain future
The common carp (Cyprinus carpio) is not only one of the best-known but also one of the most frequently produced freshwater food fishes. Nearly 4.2 million tonnes of this species were reared in carp ponds or in polyculture in 2014, plus a further 150,000 tonnes from fishing. Carp were already popular as food fish in the ancient world, and in Central Europe centuries-old carp fishing ponds are today part of the cultural landscape.
The original distribution area of common carp is in the warm temperate regions of South East Europe and Asia from the Black Sea, through Asia Minor and China, to Japan. The Romans introduced the species to Central Europe about 2,000 years ago and today it is to be found all over Europe, with the exception of Scandinavia. Within this extensive area, however, the species structure is widely controversial. Some taxonomists distinguish four subspecies whose core centres are thought to be found from the Danube River basin to the Ural Mountain range, in the Aral Sea, in the Amur River basin to southern China, and in the waters of North Vietnam. Other experts differentiate only two subspecies – C. c. carpio and C. c. haematopterus, while a third group sees rather a uniform species status. Morphological methods alone hardly enable any satisfactory distinction for, with regard to its body shape, the common carp is one of the most variable freshwater fish species.
Their fillets are used for fish burgers, fish fingers, as well as different surimi products. Alaska pollock can be utilized for different purposes and at relatively affordable cost. Their stocks constitute the largest and the most economically important ground fish resources in the North Pacific Ocean. They are both, well managed and fished on sustainable basis. Yet depletion of their stocks occurs primarily due to natural causes. On that score, a dramatic role is played by the climate change.
Although the walleye pollock (Theragra chalcogramma) known also as the Alaska pollock is a close relative of Atlantic cod, saithe and haddock, intensive fishing started only 50 years ago. Before that, interest in this species was surprisingly low which could possibly be explained by its relatively small body Despite a record length of 91 cm, the length of individuals caught in the net seldom exceeds 50 cm while the weight barely reaches 500 to 600 g. The brownish or greenish coloured, beautifully spotted fish live in large schools at a depth of between 30 and 500 m. In terms of biomass, the stocks of Alaska pollock belong to the largest and most important stocks of food fish due to three main reasons. First, they grow relatively quickly reaching 30 to 40 cm length already at the age of three or four years. From this point onwards, they can spawn virtually every year thus contributing to the survival of the species. It is universally assumed that Alaska pollock lives a maximum 14 to 15 years. Second, their fertility rate is really high. The exact number of eggs depends upon a number of factors including the age, the size and the nutritional status of females, however on average it ranges from 100,000 to 1.2 million. The third reason for the high importance of Alaska pollock is the wide spectrum of feed they use. Although carnivorous they can consume plankton-eating krill or young herrings available in copious amounts in the North Pacific. In the Bering Sea, Alaska pollock accounts for almost 60% of the total fish biomass, while in the Gulf of Alaska and Aleutian Islands they constitute about one fifth of the total fish biomass.
When people talk about halibut in Europe they usually mean Reinhardtius hippoglossoides: Greenland halibut or black halibut. The name halibut is derived from haly (holy) and butt (flat fish) due to its popularity on Catholic holy days.
The species’ geographic range extends along the Norwegian coast as far as the cold North Atlantic waters off Greenland, Iceland and Spitzbergen. It is thus to be found in the same habitat as the Atlantic halibut Hippoglossus hippoglossus, a relatively close relation that is considered to be the “real” halibut in a lot of other countries. Although the two species are similar in appearance and behaviour closer examination reveals a number of noteworthy differences.
Meagre (Argyrosomus regius), also called croaker, has been highly valued as a consumption fish since ancient times. The catch volume from the fishery cannot satisfy demand. Production of the species in aquaculture began in France and Italy at the end of the 1990s and in the meantime nearly 20,000 tonnes are supplied annually. Meagre is still considered a niche product but its potential is by no means exhausted yet.
It would be lying to describe meagre as a particularly striking or attractive fish. Its body shape with its two dorsal fins is perch-like, its sides and belly are pale to silvery white, its back and fins brownish or grey-black. The only spot of colour is to be found on the inside of its mouth cavity which in live fishes has a yellow or orange shimmer. What makes this fish so popular is its firm meat that renders it suitable for frying, baking or grilling but also for steaming, smoking or even marinating raw. It has a strong aroma and does not spoil easily because due to its moderate fat content it is less susceptible to oxidation.
Arctic charr (Salvelinus alpinus), also called mountain trout or salmon trout, is a member of the salmon family (Salmonidae). It is a coldwater species that occurs in Arctic, sub-Arctic and Alpine waters as well as in northern coastal waters. Like salmon, Arctic charr enters the upper reaches of rivers to breed. Some populations inhabit freshwater permanently, others migrate to the sea and only return to the rivers for reproduction.
Plaice is one of the commercially most important target species that are fished in the North Atlantic. What makes this flatfish equally significant for both fishermen and fish lovers is not only its excellent meat quality but also the available biomass. Following the low in the 1990s plaice stocks have in the meantime recovered significantly. Nearly 150,000 tonnes are currently caught per year under the ongoing management plan.
Northern shrimp or Coldwater shrimp (Pandalus borealis) which is found all around the Arctic is the most frequent and economically important species of the decapod genus Pandalus. The firm, tender flesh of this coldwater shrimp is deemed particularly tasty. Despite its relatively small size it has been targeted by the fishing industry since the early 20th century. However, the stocks have been declining for several years, probably as a result of global climate change.
The common squid (Loligo vulgaris) and other cephalopod species are of economic significance, especially in southern Europe. Landings from the fishing sector are decreasing, however. For one thing, because the size of the squid populations is strongly influenced by environmental factors, and for another probably because squid are too intensively fished. There is no effective fisheries management, although this would be urgently needed.
The ice-cold northern seas are not only the home of king crab (Paralithodes camtschaticus), but also of queen crab, also known as snow crab (Chionoecetes opilio). The snow white meat of the long spiderlike legs has an intense, slightly salty yet delicate flavour. The queen crab fishery is sustainable, and annual landings add up to well over 110,000 tonnes.