Research Document - 2010/019

Pathway of effects of escaped aquaculture organisms or their reproductive material on natural ecosystems in Canada

By R.A. Leggatt, P.T. O’Reilly, P.J. Blanchfield, C.W. McKindsey, and R.H. Devlin

Abstract

The purpose of this document is to provide an overview of the pathways of effects of escaped aquaculture fish (specifically finfish and bivalves) on natural ecosystems in Canada. Escape, survival, dispersal and reproduction of aquaculture organisms have been noted in many areas in Canada, although the scale of escapes in Canada is not known. In general, escaped fish have poor survival, foraging, and reproductive capacity relative to wild conspecifics. However, substantial evidence indicates escaped Atlantic salmon can affect wild conspecifics through juvenile competition resulting in decreased productivity of wild juveniles, and through hybridization resulting in partial transfer of culture phenotypes to wild populations. However, the potential for escaped fish to affect wild populations through predation, marine competition, reproductive interference, and disease transfer pathways has been poorly studied. As well, a high degree of uncertainty exists for other escape species (e.g., marine finfish, other salmonids) due to insufficient evidence and uncertainty regarding extrapolation of existing information from other species and ecosystems. For shellfish, information from outside of Canada suggests that release of farmed bivalves can cause ecological disruptions where they are non-native. Effects are expected to be very context-specific and can be influenced by health of the receiving environment, geography, species and strain types, climate, life-stages released, among others. Overall, there is significant potential for escaped aquaculture organisms to impact natural ecosystems in Canada and this potential can be influenced by numerous environmental and genetic factors. However, the effects escaped fish may have on overall community dynamics or ecosystem function are not yet known.

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