Reproduction et force des classes d'âge du Grand Brochet (Esox lucius L.) dans le Haut-Richelieu et la baie Missisquoi

Abstract

Captures of northern pike on the spawning grounds and measures of egg deposition showed that from 1975 to 1978 spawning occurred in April, after the onset of spring high waters and the warming of the water above 5–6 °C. Maximal egg deposition occurs on abandoned meadows, pastures, and shrub–grass areas, in water 60 cm or less. In the Bleury Stream area, these substrates lie mostly between elevations 30 and 30,5 m. Water temperature influences the length of the spawning and incubation periods. Spawning, egg incubation, and growth of the young to a mean length of 20 mm require approximately 40 days. From 1970 to 1977, two strong year classes (1973 and 1976) were produced; they were both followed by a weak year class. Air temperatures in June, summer water levels (June–September), and also the strength of the preceding year class, had a determining effect on year class strength.

Spatially explicit model predicting the spawning habitat and early stage mortality of Northern pike (Esox lucius) in a large system: the St. Lawrence River between 1960 and 2000

“…We determined that an average of 4 weeks after the spawning date is necessary for the eggs to incubate and the larvae to reach 20 mm in length. At this size, young larvae are capable of swimming and can thus avoid being trapped in vegetation during dewatering (Fortin et al, 1982). Five PMI reference scenarios were computed, corresponding to the five dewatering situations of -0.14, -0.28, -0.50, -1.00 and -3.00 m at Sorel, for each of the eight reference discharge scenarios, the four regions and all of the St. Lawrence River.…”

“…These authors classified and ranked the key habitat requirements for pike spawning and embryonic-larval development: vegetation type and density, water level, warming exposure, river connectivity and substrate type. In the present study, we selected three key variables to characterize pike spawning habitat, relative to their importance in the literature (e.g., Machniak, 1975;Nelson, 1978;Inskip, 1982;Fortin et al, 1982;Craig & Kipling, 1983;Verret & Savignac, 1985;Massé et al, 1991;Anderson, 1992;Casselman & Lewis, 1996;Farrell et al, 1996Farrell et al, , 2001Farrell et al, , 2006 and to the spatial modelling capacities (Table 1). First, the most important variable refers to the wetland type, with a specific reference to pike avoidance of Typha sp.…”

“…Because water level influences the spawning chronology of Northern pike (Fabricius & Gustafson, 1958), the model was built using field data recorded in Rivière aux Pins during a period of high flows in the St. Lawrence (1975Lawrence ( -1977, when the access to spawning sites did not delay spawning (Massé et al, 1991). The model was validated using field data recorded between 1974 and 2003 in the St. Lawrence River and the nearby Richelieu River (Fortin et al, 1982;Dumont & Fortin, 1977;Massé et al, 1991;Mingelbier et al, 2005). A simple linear regression was used to establish the relationship between predicted spawning date and observed values.…”

“…High spring discharge connects the riverbed with the floodplain and allows access to spawning areas (Fortin et al, 1982;Brodeur et al, 2004). Generally, Northern pike spawn in sheltered, shallow water areas over inundated vegetation of wetlands or shorelines (Casselman & Lewis, 1996).…”

“…Pike recruitment is positively influenced by the abundance and quality of the spawning habitat, a high water temperature, and a high water level maintained for several weeks after egg deposition (Johnson, 1957;Casselman & Lewis, 1996). Sudden dewatering in the spring, during the first life stages, can potentially lead to high mortality when the embryos and larvae are dewatered (Dumont & Fortin, 1977;Fortin et al, 1982). Modelling reproduction habitat forces a consideration of potential mortality events occurring at different life stages.…”