Rearing Larvae of Different Strains of Coregonus lavaretus under Cold Water Conditions: Comparison of a Special Cold-Water Line with a Standard Agglomerated Microdiet

We studied the performance of a commercial, agglomerated larval microdiet in terms of survival, growth and feed acceptance and compared a dedicated “cold water line†of the product to the standard product involving a Baltic and an Alpine strain of whitefish. Experiments were conducted under cold water conditions < 8 °C (average 5.1 °C) for 60 days after hatching. Replicate tanks of 400 and 200 liter volume received filtered lake water disinfected with ozone and UV light and were stocked with 15 larvae per liter. Daily rations of 4% body weight were manually delivered in six portions every two hours and group samples were taken weekly to determine length, weight and feed acceptance. Dead larvae were removed and counted daily. Before our experiment was influenced by an outbreak of an unknown disease during the last two weeks, we observed similar growth, survival and feed acceptance for each of the feed types with low variability within each of the two strains. Strains showed characteristic differences in growth and survival related to lower feed acceptance during the first four weeks of the Alpine strain. We concluded that the specific cold water line of the commercial microdiet did not provide any advantage compared to the standard product under low temperature conditions. However, differential performance might exist under different temperature regimes.