Evaluation of practical and natural diets for juvenile lake herring

Juvenile lake herring Coregonus artedi were cultured over a 5-week period in a laboratory experiment to evaluate the effects of two practical diets (dry and moist formulated feeds) and two natural diets (nauplii and decapsulated cysts of brine shrimp Artemia sp.) on hatchery production attributes. Although all fish had similar initial sizes, the final mean lengths and weights of fish fed dry formulated (82.2 mm and 4.5 g) and moist formulated (85.3 mm and 5.1 g) diets were significantly greater than those fed Artemia nauplii (66.9 mm and 2.2 g) and decapsulated cysts (59.4 mm and 1.5 g). Specific growth rates also differed among feed treatments, with lake herring that were fed formulated diets having greater mean daily percent increases in length and weight than fish fed natural diets. The mean Fulton condition factors of fish fed dry (0.78) and moist formulated diets (0.81) were significantly greater than those offish fed Artemia nauplii (0.72) and decapsulated cysts (0.68). Greater weight gain (%) and feed efficiency were also observed in fish fed practical diets than in those fed natural diets. Mean final whole-body lipid content was greatest for lake herring fed the moist formulated diet (10.9%), followed by fish fed the dry formulated diet (8.1%), those fed Artemia nauplii (4.5%), and those fed decapsulated cysts (3.2%). Survival was high for all fish (range, 91-100%) and did not differ significantly among treatments. Based on these results, we recommend using moist formulated diets to rear juvenile lake herring in intensive culture environments.