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Salmonids Migrate Up Seymour River Five Years After Slide

Seymour Slide: 2019 Sees First Success for Returning Sea-Run Salmonids After Five Years of Hard Work

The Seymour is one of only two Burrard Inlet streams to support both a summer and winter run of steelhead. Its location makes it popular for anglers and non-anglers alike. However, anglers familiar with Vancouver’s North Shore will undoubtedly recall the devastating rockslide that dumped 50,000 cubic metres of boulders and rubble into the Seymour River on December 7, 2014. The Seymour system already suffers from the various challenges of an urban stream, as well as having been dammed since the 1920s to provide a clean drinking water supply. Many thought this latest catastrophe could be the final nail in the coffin for its salmon and steelhead runs.

Prior to the slide, salmon and steelhead returned to the river annually. This has been in large part due to the committed efforts of the Seymour Salmonid Society, which maintains the on-site hatchery that produces coho, summer and winter steelhead, chum, and pink salmon juveniles for release each year. With no fishway at the dam, adult fish are not able to migrate beyond it without assistance. This group is also coordinating efforts to get fish above the dam to the upper watershed, where significant stretches of spawning and rearing habitat exist.

Until the rockslide, coho and steelhead (both summer and winter) were able to access portions of the river below the dam to spawn. In 2015, though, a tagging study confirmed that no adult salmon or steelhead could move upstream beyond the slide. Given the rockslide’s location, spawning options for coho and steelhead were so severely restricted that, if mitigation weren’t undertaken, these populations would likely become unviable over the next couple of generations.

As the chinook population has always been very small, and since chum and pink salmon are generally limited to spawning locations below the rockslide, the impacts to these species are considerably less. Unfortunately, to reduce the blockage’s impacts on all salmonids, the entire river has been closed to fishing since the slide occurred. Restoration of fish passage was determined essential to maintain the ecological integrity of this river as a priority salmonid-bearing system in the Lower Mainland.

Starting in 2016, multiple partners, including the Freshwater Fisheries Society of BC, contributed significant funds to the Seymour Salmonid Society to coordinate the restoration of the salmonid migratory channel at the rockslide’s location for both adults moving upstream, and juveniles moving downstream. This has been no small feat. Removal of debris had to be done in a controlled way to retain bank stability, and to ensure that debris removal in one section did not subsequently create barriers downstream. Water flow levels also had to be considered, since passage through the slide area is easier for fish during certain flow conditions.

So far, rock drilling and controlled blasting have taken place annually during summertime low flows to reduce the river gradient at critical locations, and to fill in large spaces in order to provide a usable channel for fish. Once these activities are completed, hydraulic engineers must wait until after the next springtime freshet (when material is mobilized by large volumes of water) to assess their effectiveness in terms of channel formation.

These are positive signs that efforts to restore passage through the Seymour rockslide are working. In 2020, more rock breaking and moving work is planned during the summer low flows.

The Society is pleased to have contributed funds to this multi-partner initiative over the past four years.  We would also like to acknowledge the tireless work of the Seymour Salmonid Society in coordinating efforts to have salmon and steelhead once again move naturally upstream beyond the rockslide.


Large male coho caught in the Seymour River. | Brian Ha, Capilano Hatchery.

For further information please contact:

Mike Willcox (Ministry of Forests, Lands, Natural Resource Operations and Rural Development)
Reece Fowler (Seymour Salmonid Society)

Interactive Map: Watch the Seymour Steelhead Ocean Migration 

Kintama Research Services has conducted marine tagging work to better understand ocean migration and survival of juvenile salmonids. Interested readers can study an interactive map of 229 Seymour summer-run steelhead that were acoustically tagged in 2015, from the time of release starting May 19, to September 14 when no further movement past receivers was detected.

This blog series has been established as a way to inform freshwater anglers in B.C. about projects, such as this one, that their angling licence dollars support. In 2015, the Freshwater Fisheries Society of BC began receiving 100% (up from 70%) of all freshwater angling licence fees. With this additional funding, the Society committed to broadening the scope of its activities to include joint initiatives with the Provincial Government to support projects that benefit freshwater recreational fishing around B.C.