Open-net aquaculture/salmon migration

Objective

To assess potential exposure of migrating wild Pacific salmon to sea lice and viral pathogens from former open-net aquaculture operations in the Discovery Islands region of British Columbia.

Context

In 2020, the Department of Fisheries and Oceans (DFO) Canada ordered the closure of all open-net aquaculture operations in the Discovery Islands region following concerns about their impact on wild Pacific salmon.

These concerns stem from:

The lack of physical separation in marine ecosystems (opposed to terrestrial ecosystems).
The spread of sea lice and viral pathogens from former open-net aquaculture sites to migrating wild Pacific salmon populations.

Method

Mapped former open-net aquaculture site locations using OpenStreetMap data.
Modelled wild Pacific salmon migration routes through key channels.
Generated a proximity-based heat map to estimate relative exposure risk to pathogens.

Note: This model is based on distance (localized impact) and does not account for ocean currents, which may have further dispersed pathogens throughout the ecosystem.

Key Insights

Two of the three modelled migration routes passed through areas of moderate-high exposure.
The Okisollo Channel (between Sonora Island and Quadra Island) shows the highest exposure.
The Discovery Passage (between Vancouver Island and Quadra Island) also presented an elevated risk due to aquaculture site density.
Results suggest a widespread potential exposure for wild Pacific salmon moving between the Johnstone Strait and the Strait of Georgia. Moving in-and-out of the Salish Sea Bioregion.

Outcome

This analysis highlights how spatial overlap between aquaculture operations and migration corridors increased exposure risk for wild Pacific salmon, supporting ongoing concerns around ecosystem health and responsible fisheries management.

Data Sources

Salmon migration routes: created by me. Depicts the three main routes salmon will travel along in and out of the Salish Sea Bioregion. With other pathways being a variation of either of the three.

Heat map: generated in QGIS using open-net aquaculture data pre-2020. Depicts proximity to and density of open-net aquaculture operations.

Open-net aquaculture operation sites pre-2020 (depicted with a red dot): OpenStreetMap contributors (landuse = aquaculture), extracted via QuickOSM in QGIS (2026). Data reflects crowd-sourced land use classifications. The data was cleaned to remove aquaculture operations that are not classified as open-net (e.g.: hatcheries).

City: OpenStreetMap contributors (places = city), extracted via QuickOSM in QGIS (2026). Data reflects crowd-sourced land use classifications.

Coastline: OpenStreetMap contributors (water = coastline), extracted via QuickOSM in QGIS (2026). Data reflects crowd-sourced land use classifications.

Salish Sea Bioregion Boundary shapefile: Flower, A (June 2021). Salish Sea Atlas - Western Washington University. Accessed March 2026. Link: https://salish-sea-atlas-data-wwu.hub.arcgis.com/datasets/wwu::salish-sea-bioregion-boundary/about.

Basemap: OpenStreetMap contributors, rendered by CARTO (Positron No Labels). Added manually using XYZ Tiles. Link: https://cartodb-basemaps-a.global.ssl.fastly.net/light_nolabels/{z}/{x}/{y}.png.