Atlantic cod eggs (Gadus morhua) received from Nofima marinenational breeding station, Havbruksstasjonen i Tromsø AS, at 7.0◦Cwere disinfected in seawater containing glutaraldehyde (500 ppt)(Salvesen and Vadstein, 1995). The eggs were kept dark in anincubator tank. At −2 days post hatching (dph) the eggs were trans-ferred from the incubator to rearing tanks of 100 L with a densityof 100 eggs L−1. At 0 dph 90% of the larvae were hatched. The tem-perature in the rearing tank water was 6.5◦C, salinity was 37 ppt at1 dph, but was gradually reduced to 34 ppt at 4 dph, and 30 ppt at9 dph. Elevated levels were again measured towards the end of theexperiment