Plantings of Atlantic salmon fry were made in the Duffin Creek system in order to determine the survival and distribution of salmon under a variety of stream conditions. Population studies estimated that the three general June plantings resulted in an average survival of 12.7 per cent until the autumn of the first year, 9.2 per cent until the autumn of the second year. High summer temperatures were lethal to the salmon in certain parts of the creek system. Over the balance of the planted part, the greatest mortality occurred soon after plantings when heavy predation by other species of fish occurred. The extent of predation was determined largely by the amount of shelter available to the fry. Suitable shelter for the young salmon was limited generally to gravelly riffle areas where the degree of bottom sedimentation determined the amount of shelter offered. Other stream conditions were of minor or no importance in salmon survival. Further losses of salmon were low once the young salmon had become established in the creek system.

No abstract

Studies were made during 1964 and 1965 on the reproductive biology of the carp in selected marsh areas of Lake St. Lawrence. Male and female carp matured at ages III and IV, and IV and V, respectively. The sex ratio of males to females was 1.8:1. Spawning occurred from 18 May to 26 June in 1964, from 16 May to 1 August in 1965. Spawning did not occur below 17 C, reached an optimum activity at 19 to 23 C, decreased above 26 C, and ceased at 28 C. Major environmental factors affecting spawning and survival of eggs were water temperature and water level. Spot poisoning of marsh areas in September 1965 revealed a substantial survival of young‐of‐the‐year carp hatched at various times during May, June, and July.

No abstract

Fingerling and yeariing trott (Salmo goirdner'i Richardson) responded differently rvhen exposed to a series of artificial daylight illuminations. Fingerling trout show-ed no apparent response to the overhead cover, being randomly distributed at all light intensities. Yearling trout, except in total darkness, exhibit a positive response to the overhead cover, but their pattern of behaviour differed with the light intensity and the positioning of the cover. lReceived for publication December 7,1965. 983 J. Frsn. RBs. Bo. Crxrn,r., 23(i),1966. Printed in Canada. J. Fish. Res. Bd. Can. Downloaded from www.nrcresearchpress.com by McMaster University on 11/18/14 For personal use only.