Title: Effect of live feed on growth and survival of Arctic charr (Salvelinus alpinus) juveniles.

Juveniles of Arctic Charr were raised for 20 days in buckets with a density of 10 juveniles per litre according to 5 diet treatments: artificial food as a control, microworms, artemia, enriched artemia and the combination artemia-microworms. The aim was to measure the effect of these different treatments on growth and survival. The results showed that there was a significant difference of growth performance among treatments. Fish fed on artificial feed had the highest weight 0.079 g ± 0.021 and it significantly differed from other treatments. Fish fed with enriched artemia, microworm and the combination of artemia and microworms achieved similar growth performances. Combining microworms with artemia, the growth performance of Arctic Charr juveniles was better than when fed with microworms only. Overall, the mortality rate was lower than 4%. The highest mortality rate was recorded with the artificial food, 3.4% ± 1.0 while the lowest rate was obtained with enriched artemia 0.6 % ± 0.0. The average weight of the prey used was 1.70 E-06 g ± 1.2 E-07, 1.9E-06 g ± 5.8 E-08 and 5.1 E-07 g ± 8.1 E-08 respectively for nauplii, enriched artemia and microworms. Their size was 0.50 mm ± 0.06, 0.85 mm ± 0.07 and 1.44 mm ± 0.21 respectively for nauplii, enriched artemia and microworms. The weight ratio between the nauplii and microworm is 3.3 g. Microworms could be a good candidate to replace the traditional artemia which is quite expensive, and which, probably due to osmotic stress, does not survive as long in freshwater as the microworms. The duration of this study did not permit the determination of nutritional value yet highlighted the importance of these worms. Its value in unsaturated fatty acid, amino acids and vitamins has not been determined. Future research should test the effect of microworm enrichment on juveniles and determine its adequate density to match tested fish species nutritional needs.