Seawater was taken from 70 m depth in the Trondheim fjord and
was passed through a sand filter (20 μm) and a bio-filter unit for recolonisation
of bacteria prior to use. Fertilised eggs of Atlantic cod
(G.morhua) fromMarine Breed (Sunndalsøra, Norway) were disinfected
(glutaraldehyde; 400 ppm, exposure for 6 min, Salvesen et al., 1997)
before distribution to the larval rearing tanks. In each experiment,
six tanks were stocked with cod eggs (40 eggs L−1) 2 days prior to
hatching (Table 2). The microalga I. galbana was added to larval
tanks before eggs and live feed and a slow exchange of waterwas initiated
at 3 dph. Tankswere equippedwith skimmers. The bottom precipitate
was removed three times a week and dead larvae were counted. A. tonsa
nauplii concentrations in the fish tanks were kept at 5 ind ml−1 and rotifers
at 5–7 ind ml−1. Live feed organisms and microalgae were
added to the tanks three times daily, and the live feed concentration
was then adjusted to the specified concentrations.