Sustainable forage for aquaculture are urgently needed. Mixtures based on insect meal have particularly great potential. The impact of these new feedstuffs on fish is investigated by IGB phD student Martin Tschirner. For this purpose, he compares blood samples from two fish groups whose feed rations contain different protein sources: either fish meal or insect meal. Of particular interest is the proportion of the stress hormone cortisol in the blood. "We assume that insect-fed animals are more stress-resistant and therefore emit less cortisol than their conventionally fed species," explains Tschirner. With the aid of the so-called ELISA method, hormones such as cortisol can be detected in body fluids. First, Tschirner places the sample on a test plate (left) before he can see the cortisol concentration on the computer (right).