Reducing organic contamination of shallow areas in brackish lagoons during rearing fish in cages in polyculture

Purpose. The development of the technology of the controlled rearing of marine fish remains one of the priority strategic trends of development of national mariculture. A study of the possibility of using polyculture for cage culture has a particular interest. Joint cultivation of several species of fish in the same cage, as practice of fish farming has demonstrated, does not have a tangible positive effect. At the same time, the use of cages of special design can provide significant additional fish products through the use of additional aquaculture objects. The ecological state of water areas, where the cages are located, is of great importance. High fish stocking density and the use of artificial feeds can serve as a source of powerful biogenic and organic pollution, which is especially important for shallow water areas with weak water exchange. The purpose of the study is to develop the methods for joint fish production in cage mariculture capable to provide high fish production and to weaken organic pollution of shallow water areas where cage farms are located. Methodology. The studies were conducted in 1999 and 2004. Cages of special design (internal 10 m3 and external 18.75 m3) installed in the brackish Shabolat Lagoon were used for rearing, steelhead trout, haarder, grass goby and round goby in polyculture. The standard aquaculture research methods were used. For express-analysis of environment hydrochemical parameters in cage location area the following devices were used: "ECOTEST-2000 T" (О2, NO2, NO3, NH4, CO2, phosphates, pH); termooksimetr "АJА-101М" (Т; О2); "pH meter-150 M); Refractometer "ATAGO-100" (salinity and water density). Findings. The results of marine fish cultivation in cages in polyculture in the shallow Shabolat lagoon are presented. It has been shown that joint cultivation of salmon, mullet and gobies in specially designed cages in shallow marine lagoons allows using artificial and natural feeds more fully and provides a high yield of commercial fish that results in significant additional products with a decrease in pollution level of the water area where the cages are installed. Originality. An original method for rearing marine fish in polyculture in specially designed cages has been developed. The perspective of culturing salmon, mullet and gobies in the polyculture has been demonstrated experimentally. The proposed technology ensures high efficiency of cage mariculture, allows getting additional production through the use of additional facilities and a reduction in the level of organic pollution in shallow water areas where cage farms are located. Practical value. The results of the study can be used to create cage mariculture farms in shallow seaside lagoons. Creating marine fish polyculture in specially designed cages will increase the efficiency of cultivation, reduce feed costs and reduce pollution in shallow water areas.