The growth of whitefish in relation to water quality and fish species composition

Water quality in 16 Finnish lakes did not affect directly densely gill-rake red whitefish growth, except possibly in an acid (pH 4.9) lake, Iso Lehmala mpi, where acidity may have retarded the growth of whitefish. The density o f roach affected whitefish growth in the second year of life: highest growt h rates were in lakes without a roach population and lowest growth rates in lakes having strong roach populations. Competition by vendace also retarde d the growth of young whitefish. The efficient mass removal of roach from a t eutrophic lake was considered to have increased the growth rate of young whitefish. It is suggested that an examination of the fish species composit ion and relative abundance, as well as the growth of whitefish, can be used as an aid in predicting the success of stocking with whitefish. (C) 1999 T he Fisheries Society of the British Isles.