Rearing of coregonid ( Coregonus schinzi palea Cuv. et Val.) larvae using dry and live food : IV. Proximate and mineral composition of diets and fish

In two trials coregonid larvae were fed either with live food ( Artemia nauplii or zooplankton) or dry, compound diets for several weeks. Artemia nauplii had a low level of Ca (1.86 g/kg dry matter, DM) in comparison to freshwater zooplankton (30.72 g/kg DM), whereas the opposite applied to Na and K levels (21.98 and 14.56 in Artemia and 1.49 and 2.22 g/kg DM in cladocerans, respectively). Dry diets based on single-cell protein (SCP) and freeze-dried pork liver had moderate levels of these elements. A high level of Fe (5.94 g/kg DM) in zooplankton was not reflected in fish body content in comparison to other groups of fish fed with diets containing Fe at 0.2-1.5 g/kg DM. On the contrary, high levels of Cu in the diets (0.1-0.13 g/kg DM) resulted in high Cu levels in the fish body (14–25 mg/kg DM) in comparison to fish fed live food (2.0–7.5 mg/kg DM). Although coregonid larvae and juveniles appeared to tolerate wide variation of macro- and trace elements in the diet, further studies are needed to specify the nutritional effect of minerals in larval diets.