Aquaculture & Fisheries

Biography

Biography: Kay Lubke

Abstract

            Today the issue of animal welfare is of increasing importance, especially in farmed fish. Both, consumers and producers, are highly interested in a good welfare status of the fish for ethical, as well as product quality reasons. In this context some management actions applied in aquaculture, e. g. high stocking densities or raising fish in artificial habitats, came under criticism. To evaluate common husbandry actions in aquaculture a non-invasive method for measuring cortisol, the most important stress parameter, in fish holding water was used. A set of investigations was done manly with rainbow trout. In the beginning tests were made to gain information about cortisol release under normal husbandry conditions (reference/basic values). First results indicated a basic release rate of approximately 0.1 ng/(g*h) for smaller trout and even lower values for larger fish sizes. Furthermore, the short term influences of management actions were studied as well as the long term influence of different stocking densities. To determine the welfare in the long term study, further parameters as the general performance of the fish, e. g. growth, food conversion, survival, and the fin condition index was used next to the cortisol release. Here we found that actions like netting and transferring fish to another pond provoked a sharp increase in cortisol release rate, but only for one to two hours. Furthermore, high density does not lead to increased cortisol release or impaired welfare in other parameters, if environmental conditions are managed correctly