This note reports on the age and size at maturity, sex ratios, spar,vning season, and fecundity of white perch, Roccus americanus, inhabiting the Bay of Quinte area of Lake Ontario. Scott and Christie (1963) believed the white perch invaded Lake Ontario about 1950 via the Osrvego River system in upper New York State. Since then, it has become very abundant in the Bay of Quinte area and in the last few years it has usurped the dominant position in the fish fauna of the Bay formerly held by the yellow perch, Perca f.aaescens. It is now fished commercially and may be of some sporting interest. During the last 10 years, the staff of the Ontario Department of Lands and Forests Fisheries Station at Glenora have been collecting information on the biology of the r'vhite perch in the Bay of Quinte. Their data and our own observations show the species matures at an early age, breeds annually for a number of years, and has a very high fecundity. Its reproductive capacity must be considered in attempting to explain the almost explosive increase in its numbers during the last decade.Mater'ials and, noeLhods.-Details of 3502 rvhite perch sampled during test fishing between 1957 and 1966 were available to provide information on sex ratios and age and size at maturity. Collections were made twice monthly wherever possible.In addition, during the spring of. 1967,50 gravid females were collected near the dock of the Fisheries Station at Glenora using Windermere traps. Iiach trap was 4 ft long and 2 ftin diam, u,'ith an opening on one sicle tapering to 4 inches, and a door on the other side from which fish could be removed. 'lhe traps were made of 2r-inch r,vire gauze or ]-inch nylon mesh. Only ripe females which were not suspected of partial spar,vning u.ere selected. These were easy to recognize as with very little pressure on the abdomen, ambercoloured eggs were extruded which stuck together and had a very thick jellylike consistency. The females selected ranged f.rom I23 to 281 mm fork length, weighed 36.3-485.3 g, and were I* to VIII* years of age as determined from the scales. The fork length, weight, and place and date of collection \,-ere recorded and scales u'ere taken from the left side of the body, from an area above the lateral line and betu.een the soft and spinous dorsal fin. Then each fish was opened and the complete ovaries carefully removed. The ovaries were preserved in Davidson's Solution A for 24 hr and then transfered to Davidson's Solution B until the eggs were counted (after Henderson, 1963).Examination revealed the ovaries contained eggs of three obviously different sizes, distributed uniformly throughout the organ. As the fish were about to spar,vn r,vhen collected, only the large eggs l,vould have been shed and only these were included in the counts.
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