On-Feeding and Juvenile Production of Coregonid Species with Formulated Dry Feeds: Effects on Fish Viability and Digestive Enzymes

The present study describes a successful method for on-feeding and fingerling production of C. atterensis and C. marena using solely formulated dry feeds. Also the development and differentiation of the digestive system in relation to different feed types was investigated. The tested commercially available starter feeds were not suitable for on-feeding of larvae of the two species. Only self-formulated starter feeds containing zooplankton or Artemia in defined quantities and organic acids as preservatives resulted in survival rates and growth rates similar to the live zooplankton control. For successful fingerling production resulting in survival rates and growth rates similar to a live feed control not only a suitable starter feed was necessary, but also specific feeding regimes where starter feed was replaced with intermediate feed and then with commercial feed in defined chronological sequences. Trypsin, chymotrypsin, lipase, phospholipase A, and acid and alkaline phosphatase occurred in the digestive tract of larvae of C. atterensis and C. marena. At the onset of exogenous feeding the digestive system of C. atterensis was less developed than the digestive system of C. marena. In both species the activities of the investigated digestive enzymes depended strongly on the administered feed types. Inadequate feeds significantly decreased activities of the assayed digestive enzymes.