Reproduction, early life history, and characteristics of the spawning grounds of the lake sturgeon (Acipenser fulvescens) in Des Prairies and L'Assomption rivers, near Montréal, Quebec

Spawning, early life history, and physical characteristics of lake sturgeon (Acipenser fulvescens) spawning grounds were compared between two rivers located in the Montréal region. The spawning grounds in Des Prairies River were enlarged in 1985, during the reconstruction of the Des Prairies power plant spillway. The L'Assomption River spawning ground has not been physically altered by human activities. In 1989, spawning occurred between May 14 and 27 in Des Prairies River (water temperature 11.6–15.4 °C) and between May 15 and 22 in L'Assomption River (water temperature 11–21.5 °C). On a given date, embryos were slightly more developed in L'Assomption River, where hatching began 3 days earlier than in Des Prairies River (26 vs. 29 May). The great similarity in the spawning and early development sequence suggests that spawners utilizing these two rivers cannot be differentiated on the basis of these biological characters. In 1990, larval emigration from the Des Prairies River spawning ground began on May 29, 11 days after peak spawning. The larvae drifted to the St. Lawrence River in June (peak on 16 June), at a mean length of approximately 20 mm. In both rivers the proportion of stations with eggs present tends to decrease as depth and current velocity increase. Egg deposition occurs on a wide variety of substrate types, ranging from fine- to medium-sized gravel to boulders. Although utilization varies with prevailing hydrological conditions, in 1990 the artificial spawning bed in Des Prairies River showed a high proportion of stations with eggs present.