Growth Rates and Growth Efficiencies in Larvae and Juveniles of Rutilus rutilus and Other Cyprinid Species: Effects of Temperature and Food in the Laboratory and in the Field

Growth rates were determined in four 0+ class populations of roach (Rutilus rutilus): two from warm backwaters of the Danube and two from cold-water lakes. Larval growth was also determined in the laboratory for R. rutilus, Leuciscus cephalus, and Alburnus alburnus at 15, 20, and 25 °C. Q10 values of growth rates were low (1.29–1.67) between 20 and 25 °C but were high (3.9) between 15 and 20 °C. Net growth efficiency of the larvae of R. rutilus ranged from 68.6 to 71.9% at 15 °C and from 72.3 to 73.5% at 20 °C. A comparison of temperature-corrected relative growth rates in the four populations of roach revealed significant differences between the two warmwater and the two cold-water populations. Growth of warmwater populations was fastest right after hatching and then declined in a fairly regular way. Growth of cold-water populations was slow after hatching but increased later. These differences reflect interactions between temperature and food availability in the two types of water bodies. The sudden increase in growth rate in the population from the coldest lake can be correlated with a change in gut contents which in turn reflects the improved ability of the juvenile fish for catching Zooplankton.