THE EFFECTS OF WELL BOAT TRANSPORT ON STRESS RESPONSES UNDER DIFFERENT DENSITIES OF RAINBOW TROUT (ONCORHYNCHUS MYKISS, WALBAUM 1792)
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THE EFFECTS OF WELL BOAT TRANSPORT ON STRESS RESPONSES UNDER DIFFERENT DENSITIES OF RAINBOW TROUT (ONCORHYNCHUS MYKISS, WALBAUM 1792)
Yunita Maimunah
Fakultas Perikanan dan Ilmu Kelautan Universitas Brawijaya Malang
The transport of harvested fish has been recognized to bring stress effect on fish. In this study the stress effects mainly assessed by monitoring the chemical blood characteristics in each transport sequences which were loading, transporting and unloading. The objectives of this paper were to test the new well boat design from MMC Tendos AS, Norway, with circulatory tanks and suction pumps would show such effects, and further to compare the transport densities of fish and the effects of unloading by pumping in terms of stress response. The Rainbow trout (Oncorhynchus mykiss, Walbaum 1792) were transported in two biomass densities, 18 % volume (low density) and 26 % volume (high density). The results showed that the low density fish recovered faster from the induced handling stress encountered at crowding with respect to HCO3-, glucose, and lactate levels. However, it was observed a significant reduction in oxygen consumption in the high density tank during transport. This was probably due to a slight sedation effect from the metabolic CO2 accumulation in the transport tank. After unloading, significantly elevated levels of pCO2 and lactate, and significantly lower potassium and blood pH were observed in the low density group compared to the high density group, and also when compared to data obtained for both groups under transport. The results thus clearly demonstrated that most stress was induced by handling under crowding and pumping on loading and unloading, whereas the transport may benefit from increased fish density up to at least 26 volume %.
Keywords: Blood, rainbow trout, stress, transportation, well-boat