Growth and diet of introduced coregonid fish Coregonus peled (Gmelin) and Coregonus lavaretus (L.) in two Belgian reservoir lakes

Introduced Coregonus lavaretus L. and Coregonus peled Gmelin populations in the Robertville and Bütgenbach Reservoir lakes (Belgium) were studied in order to assess their adaptation to their new habitat. We considered the evolution of abundance, biomass, size distribution structure, growth parameters and diet. Maximal temperature values are acceptable for C. peled but slightly too high for an optimal development of C. lavaretus. In order to remain in their acceptable range for dissolved oxygen, the coregonids must stay in surface water during stratification, although water temperature is largely above their optimum in these water layers. Length frequency diagrams established for C. peled in both lakes show only older cohorts, which indicate that there is no natural reproduction. Slope coefficients for C. peled in both lakes indicate an allometric growth (b