Abstract.Arctic charr,Salvelinus alpinus(L.), from the same full‐sib family were reared under two different densities for 97days at 10°C. In one treatment density was adjusted every 2 weeks by means of a tank enclosure to a density of 50kg/m3. In the other treatment the density was allowed to increase as fish biomass increased to 50kg/m3. Density had no significant effect on the variation observed in individual fish weights over the course of the growth trial. Density had a significant effect on the relationship between fish weight and specific growth rate. The increasing density treatment had an overall higher mean specific growth rate of 0·1%/