Stock Characteristics and Catches of Atlantic Salmon (Salmo salar) in Quebec, and Newfoundland and Labrador in Relation to Environmental Variables

Abstract

More than 500 stocks of anadromous Atlantic salmon (Salmo salar) in a natural vigorous state are estimated to exist in Newfoundland and the Quebec–Labrador peninsula. They represent the end result of 6000–13 000 years of natural selection for local conditions and have been subject to relatively little manipulation. Stock characteristics correlating with environmental variables include an inverse relation between smolt age and mean temperature, and smolt age and growing season, and a positive relation between the length of sea life and river discharge. Variations in precipitation and temperature across the area result in different patterns of river discharge. Winter discharge is critically low in the north and salmon are restricted to larger rivers; low summer discharge on the east coast of Newfoundland and in southern Quebec may limit parr territory and hamper adult upstream migration. Because upstream migrations are delayed in years of low rainfall, causing salmon to remain longer in the area of commercial fisheries, salmon catches are generally higher in years of low rain than in wet years. The negative correlation occurs again in the catches of salmon 1, 2, and 7 years after years of low rainfall, but the reasons for this are obscure. Sea and river temperatures confine migration to a very short interval in Ungava and affect life cycles and maturation patterns. Most males spend over 12 mo in freshwater before spawning. Constraints are relaxed further south until high summer temperatures cause selection for early and late running stocks. There is a need for more systematic compilation of salmon stock data particularly over long enough periods to evaluate the effects of climatic variables and management strategies.Key words: Atlantic salmon, stock characteristics, precipitation and catches, temperature, migration