Survival of Salmon Released from Test-fishing Vessels


The Skeena River is one of the largest watersheds flowing entirely within British Columbia, and is home to all five Pacific salmon species, including multiple populations of steelhead. Skeena River steelhead, coho and Chinook support a major recreational industry for both British Columbians and visitors from around the world. Yet many of the salmon and trout populations face intense harvest exploitation during the summer while returning to their spawning grounds.  In recent years, lower numbers of salmon returning to the river has been causing concern, with the prospective causes being tied to the commercial fishery or to climate change issues.

Since 1955 the Canadian Department of Fisheries & Ocean (DFO) has conducted annual gillnet test fishery to provide abundance index of salmon and steelhead entering the Skeena River at Tyee after passing through the commercial fisheries (Area 4). In 1994 collaboration between DFO and the British Columbia Ministry of Environment was initiated to protect the steelhead stocks in the Skeena River.

In 2006, the Tyee test fishery identified an unexpectedly large sockeye run while steelhead numbers appeared relatively low. A commercial sockeye opening subsequently exposed co-migrating Skeena steelhead to fishing pressure. This decision caused immense public debate and led to a demand for an independent science review panel to examine Skeena River salmon and steelhead management strategies. A component of the review identified a number of critical issues and several recommendations made; one of them was the need for a telemetry study of steelhead removed from the water in the Area 4 fisheries.

Location of Skeena and Bulkley River array, 2008. Distances are measured in river kilometer from the Skeena River mouth. Bathymetric and topographic data curtsey of the Department of Natural Resources Canada. All rights reserved.

As part of Kintama’s 2008 Skeena River study, returning steelhead salmon caught in gillnets at the Tyee test fishery were tagged and released with acoustic tags and their survival up-river measured. Only 56% of the released steelhead were detected on the acoustic sub-array (first receiver was located 109 km upriver). Apparent survival estimates followed a smooth exponential decline with distance (apparent survival/km = 0.992) and there was no evidence of immediate post-release mortality related to the capture and tagging process.  Apparent survival to the last sub-array in the Skeena River was 35% and four individuals were detected as far as 325 km up in the Bulkley River.  Survival estimates are called “apparent survival” because it was not possible to distinguish mortality from emigration into river tributaries or over wintering in the mainstem.

Cumulative apparent survival values for returning wild Skeena River steelhead released at both Tyee Test Fishery and the Moricetown Canyon sites.

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Skeena and Bulkley River 2009


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