Limnological conditions and growth of trout in three lakes near Rotorua

[First paragraph...]
A small group of lakes near Rotorua has been the subject of research by the Marine Department for a number of ears to determine the rate of growth 0 the resident rainbow trout (Salmo gairdnerii) (Smith 1959) and the effect of increasing these trout populations by artificial stocking with hatchery-reared fingerlings. As a result, fish size in some lakes has been noticeably reduced in recent years. It has been shown elsewhere that the quality of the water in a lake has an important effect upon the fish present (Hasler 1947). Some factors affecting water quality were therefore examined during the summer of 1962 in lakes Okataina, Ngapouri and Okaro. These data are correlated with others relating to those trout present which were over 20 cm. long (smaller fish are caught neither by anglers nor by the gill nets used in research).