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 unrelated to pH, alkalinity, COD, or conductivity of the water, but length of 1–2-year-old pike correlated positively with water colour (i.e. humic content), nitrogen content, and phosphorus content. These water properties also correlated with each other. Growth of 1–2-year-old pike was negatively correlated with lake area in lakes smaller than 20 ha.
In lakes with a strong roach population or without ruffe the 0 group pike grew faster than in lakes without roach or with ruffe. The growth of 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 were forced to forage for abundant acid resistant invertebrates like dragonfly nymphs (Odonata) or Asellus aquatlcus .
The results of this work support earlier studies where the growth rate above all depends on water temperature and food availability. Acidity was not shown to affect the growth rate of pike.