Effect of feeding strategy on digestive tract morphology and physiology of lake whitefish (Coregonus lavaretus)

The common whitefish (Coregonus lavaretus) plays an increasingly important role in European and North American aquaculture industry. At the same time a considerable decrease in whitefish abundance in natural waters is observed. Therefore, it is necessary to develop methods of whitefish rearing not only for commercial but also reintroduction purposes. Fish feeding with natural food (Anemia sp. nauplii) is much more expensive compared to the use of commercial feeds, and thus the attempts to develop optimal feeding strategies have been undertaken to obtain most satisfactory rearing effects at the lowest costs. The aim of the present study was to establish the best moment of commercial feed introduction (Otohime B1) and to evaluate the effects of various feeding strategies on morphological and physiological development of digestive tract in whitefish larvae. This was done using histological analysis of the digestive tract and measurements of digestive enzyme activity. The lowest mortality occurred in the group fed exclusively Anemia sp., while the highest was recorded in the group fed Otohime B1 diet exclusively. Histological analyses revealed no significant pathological alterations in the digestive tract, in all experimental groups. The analysis of digestive enzyme activity revealed the fastest development of gastric glands in fish fed only natural food, however, the intestinal epithelium developed at a similar rate in all groups. The results indicate that the initial feeding of larvae with natural food is not necessary in common whitefish pre-rearing when using the commercial feed Otohime Bl, but the highest larval growth was observed in the group which was initially fed Artemia nauplii for one week before the transition to Otohime B1.