THE GROWTH OF YOUNG PIKE IN SMALL FINNISH LAKES WITH DIFFERENT ACIDITY-RELATED WATER PROPERTIES AND FISH SPECIES COMPOSITION

Pike growth was generally slower in small Finnish lakes than has been reported from large lakes or brackish coastal waters. Growth was unrel ated to pH, alkalinity, GOD, or conductivity of the water, but length of 1-2-year-old pike correlated positively with water colour (i.e. hum ic content), nitrogen content, and phosphorus content. These water pro perties also correlated with each other. Growth of 1-2-year-old pike w as negatively correlated with lake area in lakes smaller than 20 ha. I n lakes with a strong roach population or without ruffe the 0 group pi ke grew faster than in lakes without roach or with ruffe. The growth o f pike aged 1-4 years in two very acid and practically fishless lakes did not differ clearly from the rest of the lakes, although the pike w ere forced to forage for abundant acid resistant invertebrates like dr agonfly nymphs (Odonata) or Asellus aquaticus. The results of this wor k support earlier studies where the growth rate above all depends on w ater temperature and food availability. Acidity was not shown to affec t the growth rate of pike. (C) 1995 The Fisheries Society of the Briti sh Isles