Land based "low-waste" Turbot Culture employing industrial salt
During the recent decades, flatfishes are of interest for aquaculture in Europe, especially turbot (Scophthalmus maximus) (Fig. 1), sole (Sole solea) and halibut (Hippoglossus hippoglossus) are candidates for the commercial aquaculture. However, only the aquaculture of turbot makes commercially effective progress, reaching market size after 18 to 24 months. In 1996 3.050 t were cultivated in six European countries, in which Spain (1.800 t) and France (980 t) are leading in the production (FAO). Interestingly, next to the size of the turbot, the correct pigmentation is a decisive factor for consumer's acceptance. The market offers commercial possibilities especially because catches from wild stocks are low (less than 10.000 t per year).
The use of industrial salt in the medium for the aquaculture of turbot
Background of this study is the planning of a possible aquaculture facility construction for the breeding of turbot in Bremerhaven (Germany). The pilot project is realized at AWI in Bremerhaven in cooperation with the Bremerhavener Institute of Food Technology and Bio Process Engineering (BILB). In the river Weser in Bremerhaven only brackish water is available, therefore the water for the cultivation of turbot requires additional salinisation. In this pilot project effects of applying salt from the fish industry is tested. This salt emerges in high amounts through the production of coalfish. The salt may contain toxic substances in small concentrations or higher amounts of microorganisms as well as biogenic amines. The latter result as degradation products from the storage of fish.
The whole system consists of three recirculation systems (Fig. 2), which are equipped with three culture tanks and components for the preparation and cleaning of water. One of the tanks is filled with water from the river Weser and purified with reverse osmosis to increase its salinity. The second tank is run with water from the river Weser and industrial salt. The third tank is filled with clean water including artificial aquarium salt. For each of these culture tanks approximately 20 juvenile fishes are introduced (overall 60 animals per recirculation system).