Research Document - 2009/110

Quantifying the fluvial habitat needed for the re-introduction of Atlantic Salmon (Salmo salar) in Lake Ontario

By R.G. Randall

Abstract

For extirpated Atlantic Salmon (Salmo salar) in Ontario, fluvial habitat for spawning and early growth would be required to re-introduce the Lake Ontario population. Based on a review of habitat suitability, the Ontario Ministry of Natural Resources identified three tributaries for restoration, Credit River, Duffins Creek and Cobourg Creek, all of which supported salmon historically. Based on a drainage area of 87,100 ha, the conservation targets for the Credit River were estimated to be 8.61 X 10⁶ eggs and 3,631 female spawning salmon (1 lake winter; average 1.8 kg), assuming a conservation egg deposition target of 2.4 eggs/m². Conservation targets (number of female spawners) for the other two tributaries would be less. All accessible rearing habitat in the rivers could be essential for survival for three reasons: 1) allowable harm assessment indicated that population viability is sensitive to juvenile mortality; 2) only 3 of the original 27 rivers inhabited by salmon are targeted for restoration; and 3) identification of the whole river as important habitat is consistent with the proposed approach for inner Bay of Fundy salmon. Methods are proposed for identifying the amount of fluvial habitat needed if an adult population recovery target is identified on a lake basis rather than a tributary basis. Identification of important habitat in Lake Ontario proper could be deferred until more is known about migration routes and feeding areas. Residences (as defined in SARA) may apply to Atlantic Salmon for redds (egg incubation), but a Fisheries and Oceans Canada policy on residences is still pending. Based on known reproducing populations of other Salmoninae in Lake Ontario, suitable habitat for Atlantic Salmon is likely available, and re-introduction of this extirpated species is ecologically feasible.

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