Presentation Abstract

The Discovery Islands region is a major salmon migration corridor. Open net-pen salmon farms in the Discovery Islands and the Broughton Archipelago are a potential source of sea lice infestation and disease transfer to wild salmon, but the real risks and impacts remain unquantified. In 2017, 306 wild Chilko Lake sockeye smolts were captured and acoustic- tagged as they migrated from the lake. To investigate exposure time near salmon farms during their migration through the Discovery Islands region, we deployed acoustic receivers in Okisollo Channel, Hoskyn Channel, and two minor passes. Two of these acoustic receivers were placed within fish farm tenures. We calculated both travel time past individual farms and through the channels based on the time difference between first and last detections of individual fish; all of the farms in the Hoskyn and Okisollo Channel were fallowed in 2017 so exposure times presented here are baseline estimates. Seventy percent of tagged sockeye smolts used a migration route through the Discovery Islands that contained salmon farms. The median detection time near individual farms was low, ~4.5 minutes. Migration time through Hoskyn and Okisollo channels combined (7 salmon farm tenures; 25 km) averaged 31 hours, and 6 hours between the eastern and western receiver sub-arrays in Okisollo Channel (3 tenures; 4 km). Because DFO’s models of fish farm effluent concentrations near salmon farms indicate that a plume of particles is distributed over several dozen km, our travel time estimates can be used to calculate potential exposure times. In future, travel times can be assessed at operational farms and combined with models of effluent concentration to better assess the risk of wild salmon exposure to fish farms.

Session Title

The Salish Sea Marine Survival Project: Understanding Salmon Survival

Keywords

Sockeye salmon, Telemetry, Salmon farms, Salmon migration

Conference Track

SSE11: Species and Food Webs

Conference Name

Salish Sea Ecosystem Conference (Seattle, WA : 2018)

Document Type

Event

SSEC Identifier

SSE11-670

Start Date

5-4-2018 2:15 PM

End Date

5-4-2018 2:30 PM

Type of Presentation

Oral

Contributing Repository

Digital content made available by University Archives, Heritage Resources, Western Libraries, Western Washington University.

Geographic Coverage

Salish Sea (B.C. and Wash.)

Rights

This resource is displayed for educational purposes only and may be subject to U.S. and international copyright laws. For more information about rights or obtaining copies of this resource, please contact University Archives, Heritage Resources, Western Libraries, Western Washington University, Bellingham, WA 98225-9103, USA (360-650-7534; heritage.resources@wwu.edu) and refer to the collection name and identifier. Any materials cited must be attributed to the Salish Sea Ecosystem Conference Records, University Archives, Heritage Resources, Western Libraries, Western Washington University.

Type

text

Language

English

Format

application/pdf

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Apr 5th, 2:15 PM Apr 5th, 2:30 PM

Exposure time of juvenile sockeye salmon to Discovery Islands salmon farms

The Discovery Islands region is a major salmon migration corridor. Open net-pen salmon farms in the Discovery Islands and the Broughton Archipelago are a potential source of sea lice infestation and disease transfer to wild salmon, but the real risks and impacts remain unquantified. In 2017, 306 wild Chilko Lake sockeye smolts were captured and acoustic- tagged as they migrated from the lake. To investigate exposure time near salmon farms during their migration through the Discovery Islands region, we deployed acoustic receivers in Okisollo Channel, Hoskyn Channel, and two minor passes. Two of these acoustic receivers were placed within fish farm tenures. We calculated both travel time past individual farms and through the channels based on the time difference between first and last detections of individual fish; all of the farms in the Hoskyn and Okisollo Channel were fallowed in 2017 so exposure times presented here are baseline estimates. Seventy percent of tagged sockeye smolts used a migration route through the Discovery Islands that contained salmon farms. The median detection time near individual farms was low, ~4.5 minutes. Migration time through Hoskyn and Okisollo channels combined (7 salmon farm tenures; 25 km) averaged 31 hours, and 6 hours between the eastern and western receiver sub-arrays in Okisollo Channel (3 tenures; 4 km). Because DFO’s models of fish farm effluent concentrations near salmon farms indicate that a plume of particles is distributed over several dozen km, our travel time estimates can be used to calculate potential exposure times. In future, travel times can be assessed at operational farms and combined with models of effluent concentration to better assess the risk of wild salmon exposure to fish farms.