Importance of carrying capacity for sustainable trout culture: the case of “bagci balik”

Trout is a fish species that is produced widely all over the world and it has an important place
\nin the aquaculture industry. For the sustainable development of the trout culture, it is need to
\ndetermine how much fish can be stocked per unit volume (carrying capacity). Over-stocking
\ncould threaten fish welfare and sustainable use of environmental resources. Estimating of
\ncarrying capacity is necessary both to minimize these adverse impacts on fish and
\nenvironment, and in terms of sustainable use of water resources. In this study, carrying
\ncapacity of a commercial land based trout farm in Koycegiz (Mugla/TURKEY) was
\ninvestigated. Two methods were used to calculate carrying capacity and compared with each
\nother: “Oxygen requirement based carrying capacity” and “Metabolic waste based carrying
\ncapacity”. The mean values of studied water quality parameters that used in calculations were
\nmeasured as; 14.12 ± 0.72 °C for temperature, 7.78 ±0.20 for pH, 10.1 ± 0.93 mg/l for
\noxygen, 3,05 ± 0,84 m3 s-1 for flow rate. The annual production capacity was calculated
\nwith these measured parameters. By the observed data, the carrying capacities of the farm
\nwere found respectively with based on oxygen requirement as 538.42 ± 196.22 tonnes; and
\nbased on metabolic waste as 1113.4 ± 463.7 tonnes per years. According to the results that
\nobtained from the study, there was significant difference between two carrying capacity
\nestimation methods. However when the oxygen levels of the water were examined, in some
\nmonths the negative values, that could adversely affect the life and growth of the trouts, were
\nobserved. Fort this reason, to reduce the limiting effect of the oxygen and reach maximum
\ncarrying capacity; it is needed to be integrated oxygenation or aeration systems into the
\nproduction ponds. On the other hand, for the sustainable use of the environmental sources in
\nthe facilities engaged in production according to the metabolic waste based carrying capacity,
\nit is important to use advanced water filtration systems.
\nKeywords: Carrying capacity, land-based trout culture, water quality.