[ AQUACULTURE ] which many are still unknown and which are difficult to simulate in the hatcheries. Another difficulty is feed, because the tiny larvae accept only dust-fine live feed at first. Taiwan has probably progressed farthest with hatching grouper: two thirds of the fry used for grouper farming there are already said to come from hatcheries. Another worthwhile candidate for aquaculture would be the sablefish (Anoplopoma fimbria), also called black cod. This is one of the most commercially valuable fish species in the North Pacific. The most important market for this fish is Japan where the white, fat-rich, very tasty flesh is particularly popular in sushi and sashimi restaurants. In the past there have been several attempts to produce sablefish in aquaculture but so far none of them have proved really successful, due on the one hand to financial and biological problems and on the other hand to protests and disputes with fishermen who fear for the loss of a lucrative source of income. Research institutions in British Columbia have been working on the possibilities of producing sablefish in aquaculture for over 30 years and have during this time been able to solve a lot of the technological problems involved in farming the fish. Because wild catches have been falling in recent years the state authorities have declared sablefish to be a “priority candidate” for commercial production. Private investors in Canada have repeatedly tried to push sablefish farming ahead. In 2003 a commercial hatchery was set up to improve technology for rearing this fish. The survival rate of eggs and larvae fluctuates strongly from batch to batch, and spinal disorders occur 56
frequently in the fish. Although such fish can survive under aquaculture conditions they are hardly marketable. There are also still numerous problems with hatching but overall it has been possible to improve the process noticeably. Troutlodge Marine already raised several year classes in their hatchery on Hood Canal (Brinnon, Washington) and they now offer sablefish fry almost on a routine basis. The centre of sablefish farming is currently still in British Columbia, however. With the farms in Jervis Inlet and on the west coast of Vancouver Island the potential of this fish species is still by no means exhausted, however.
Different regions demand different species There are also great hopes in about 20 species of the Trachinotus genus which are traded under the name pompano or jack. These fishes are in high demand in North America and Asia on account of their excellent meat quality. Catches from the fishery fluctuate very strongly, but tending towards a downward trend, so that wild catches alone can hardly satisfy demand anymore. This makes the chances rise that pompano farming could be commercially lucrative. The production of Florida pompano (Trachinotus carolinus) would probably be particularly lucrative since this fish is traded at very attractive prices in the USA. Florida pompano fillets cost 35 US$ per kilogram on average. Although attempts have been made again and again since the 1960s and 70s to produce this fish in aquaculture the necessary technology in still in its infancy. The main problems are the poor growth of the species above 200 g, difficult and expensive feeding, and a low survival rate. These
Eurofish Magazine 3 / 2013
problems make it difficult to grow Florida pompanos to sizes over 450 g as they are desired by the market. Trachinotus carolinus is already produced in individual cases but production volume is low and fluctuates very strongly. Perhaps it would be better to grow the fish not in net cages in the open sea but in enclosed recirculation systems. Experiments have already shown that juveniles can grow from 20 g to 450 g in four to five months and to 700 g in eight months – and with a good survival rate of around 95. Production of a further Trachinotus species, T. blochii, whose natural territory extends along the whole of the East African coast from the Red Sea to South Africa, has advanced much further. This Trachinotus species is farmed under the name “Golden Pompano” in considerable quantities particularly in China (Region Xiamen). Mortality problems and health problems in the early phases of the fish's lives have presumably been overcome for the production volume has shot up. Whereas in 2006 production amounted to only a few hundred tonnes, one year later it was more than 15,000 t and in 2010 more than 24,000 t were produced. Interest in this fish which is offered on the market practically all the year round in sizes from 400 to 1,200 g is growing in other Asian countries, too, particularly in Malaysia, India and Singapore. In a lot of countries, and particularly in the Mediterranean region, meagre (Argyrosomus regius) which is also called croaker or corbina is extremely popular. The meat of this fish which can produce easily audible drumming and croaking noises with its swim bladder is very tasty and highly desirable so that the annual catches from the fishery which
are often under 5,000 t cannot satisfy demand. Like nearly all fish species that grow to a relatively large size – meagre can reach a length of 2 m and a weight of 75 kg – the fish grow very fast during the first months, something which is of course a positive feature for aquaculture. A drawback, on the other hand, is the fact that these fish are predators, eating above all herring, sardines and other school fish, and thus requiring protein-rich feed in aquaculture, too. The high market value of the larger fish over 2 kg in particular compensates for the high production costs, however, particularly since meagre is otherwise not a demanding fish and grows well at temperatures of between 16 and 20 °C. In countries like France or Spain meagre have been produced for years in varying quantities. Up to 2007 annual production amounted to around just a few hundred tonnes but rose in 2008 and 2009 to about 4,000 t. Based on this level it then more than tripled to 14,634 t just one year later in 2010. What is amazing is not only the explosive growth in volume but also the country that was behind this production: Egypt, which has for years been considered the biggest fish farming nation in Africa. The FAO statistics named Egypt’s production of meagre in 2008 for the first time at slightly more than 2,000 t, and then in 2010 at 12,246 t. Another meagre species is produced in South Australia: Japanese meagre or suzuki (Argyrosomus japonicus) The main buyer is the USA where the white flesh of this fish which is rich in Omega 3 fatty acids is seen as a reasonably priced alternative for the expensive Chilean seabass (Dissostichus eleginoides). Suzuki costs only half the price of Chilean seabass. mk www.eurofishmagazine.com