Early life stages, growth, and reproduction of spring-spawning ciscoes (Coregonus artedii) in Lac des Écorces, Quebec

Abstract

The biological characteristics of an allopatric population of spring-spawning ciscoes, an extremely rare ecotype, were studied at Lac des Écorces (southwestern Quebec). Environmental conditions during the early life stages are marginal for the species; the eggs are deposited in the deeper section (>20 m) of the lake and the first larva was caught on 30 July. Epilimnetic temperatures were then near the upper lethal threshold for fall cisco larvae. Lac des Écorces ciscoes are very small at the end of their 1st year of life (mean total length 58 mm). They more than double in length during their 2nd year (mean total length 161 mm). Growth thereafter, longevity, fecundity, and egg diameter are within the observed ranges for the species. Spawning occurs from mid-May to early June. Males and females spawn for the first time at age 3. The best predictor of fecundity is liver weight. Gametogenesis occurs under environmental conditions different from those encountered by fall-spawning salmonids. Seasonal changes in the gonadosomatic and hepatosomatic indexes are discussed in terms of temperature, photoperiod, and hormonal influences.