Research Document 2024/033

Atlantic Sturgeon (Acipenser oxyrinchus) of the Saint John River, New Brunswick: Spawning Population Characteristics and Migration Timing

By Themelis, D. and Bradford, R.G.

Abstract

Several measures are used to manage the commercial fishery for Atlantic Sturgeon in the Saint John River (SJR), including a closure during June to protect spawning adults. The degree of overlap between the June closure and the timing of Sturgeon spawning was examined using commercial catch data, experimental fishing during June in 2016, the migration timing of acoustically tagged Sturgeon, and the degree of gonad maturation in females caught and harvested or released by the fishery. Spawning began in June in some years and was underway by early July in all years, based on the appearance of spent females during commercial fishing between July 2 and July 8, and during experimental fishing in June. Using the patterns observed in daily catch rates and sex ratios during commercial and experimental fishing in 2016, it can be predicted that Sturgeon first arrive in the area of the commercial fishery in May, with abundance peaking in early June. Females were a little later than males in arriving and may not have been sufficiently ripe to be harvested before June 1. Residence time in the river for females was variable, with some spawning and leaving relatively quickly post-spawning, while others spawned later or spent variable amounts of time in the river after spawning. Ripe Sturgeon were present in the river in some years until mid-August. The closure does not prevent the fishery from accessing ripe females; female Sturgeon are still ripening in July and frequenting the area where the fishery occurs. The closure directs fishing activity to a time when spent females are at greater risk of interception within the commercial fishery.

Research Document 2024/033 (PDF, 585 KB)

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