Scales were used for the determination of age with back-calculation of length. The oldest fish was VII + years old. Back-calculation did not exhibit Lee's phenomenon. The most rapid growth occurred in summer at water temperatures over 25" C. The growth in weight was c. 331 g year-' after IV vears of life. Growth was well described by von Bertalanffy . 1 2 2 (1-0'*5)]. The length-weight relationship followed the cube law (6 = 3.0601) K , ranged from 0.74 to 1.18 with a mean value of 1.0. Spawning occurred in January, fecundity was 74 509 with a mean of 1 157 eggs g-' body weight. Mean diameter of eggs was 1071 (pm). A developed ovary had ova of two sizes, immature oocytes and mature ova. The fish is a carnivorous feeder.

This study is concerned with the age and growth of perch (PercaJEuviatilis L.) in two contrasting Scottish lochs-the Dubh Lochan and Loch Lomond. Age and back-calculated growth were determined from annual rings in the opercular bones, and during the 2-year project 470 perch from the Dubh Lochan and 796 from Loch Loinond were examined. Growth in length in the two lochs, though similar for the first 2 years, differed thereafter, the average length at 8 years in the Dubh Lochan being less than 15 cm, that in Loch 1-omond more than 23 cm at the same age. In neither locality did the growth of perch follow the Von Bertalanffy growth formula. Reasons for differential growth rates are discussed and comparisons made with the growth of perch in other waters in Europe and North America.

No abstract