Probability of detecting escaped aquaculture salmon is related to distance between production areas and rivers

PARR-2016-NL-14

Description

Salmon that escaped from sea cage aquaculture facilities have been detected in a large number of rivers in eastern North America with the detection of escapees seemingly related to the distance of the river from the production areas. Morris et al. (2008)^Footnote1 compiled the existing information available to 2007 on aquaculture escapees in rivers of eastern North America but did not provide any quantitative analysis that could be used to link the detection of escapees relative to the distance of the rivers from the production areas. This project proposed to update the compilation of observations from Morris et al. (2008) to 2015 , to review the literature on the behaviour of escaped salmon, and based on these components, to examine a series of models with differing assumptions on behaviour and diffusion, for their ability to generate the empirical observations of escapees in monitored rivers. The objective was to examine models that would provide probability statements of observing an escaped salmon in a river based on the distance of the river from the escape location, the intensity of the escape event, and the river monitoring effort. This knowledge helps to inform siting decisions for new aquaculture sites.

Findings

Propagule pressure² was the model used to produce a cumulative spatial measure of aquaculture production pressure from farm escape salmon on wild salmon. The number of escaped farmed salmon (i.e., propagules) detected at counting facilities was positively correlated with propagule pressure. The amount of farmed salmon genetic impacts on wild salmon was also positively correlated with propagule pressure. The location and size of aquaculture facilities directly affected the magnitude of risk to wild salmon populations from escaped farmed salmon. Features of aquaculture production present a risk to wild salmon populations from escaped farmed salmon and propagule models are a step towards predicting the impact of cage-based Atlantic salmon aquaculture on wild salmon.

Publications

Keyser, F., B.F. Wringe, N.W. Jeffery, J.B. Dempson, S. Duffy, and I.R. Bradbury. 2018. Predicting the impacts of escaped farmed Atlantic Salmon on wild salmon populations. Canadian Journal of Fisheries and Aquatic Sciences. 75:506-512.

Program Name

Program for Aquaculture Regulatory Research (PARR)

Year(s)

2016 to 2017

Principal Investigator

Ian Bradbury
Research Scientist, St. Andrews Biological Station
Email: Ian.Bradbury@dfo-mpo.gc.ca