Fish Fence

Fish-fence-construction-crew, Seymour River Hatchery
“The floating fish fence was a big project that involved many volunteers, DFO, Metro Vancouver, and both Squamish and Tsleil-Waututh Nations. Everyone contributing in all aspects, from fabrication, installation and now operation of the fence.”
– Brian Smith, Hatchery Manager

As the Society and it’s partners deal with the rock slide on the river, a temporary fish fence has been built. The fence was installed in an attempt to intercept fish migrating upstream. Prior to the fence many fish were migrating to the slide and injuring themselves trying to pass the barrier.

Steelhead with head injuries from repeatedly trying to jump through the rockslide.

Thousands of staff and volunteer hours were spent attempting to net the stranded fish and move them past the rockslide debris. This level of volunteer commitment and labour was unsustainable. The tangle netting and seining was hard on the fish and it was not an effective short term solution. In 2015 fundraising began to allow the Society to build a fish fence. Once funds were secured from Pacific Salmon Foundation and Fisheries and Oceans Canada, construction began. The floating fish fence, the largest in BC, began fishing in August of 2016.

The fence is only operational when the river is at low to medium water levels. In high flow events the design allows for water and debris to go over top of the fence. It is a design strategy that enables the fence to remain in the river year round while sustaining minimal damage during months when water levels are very high.

When water levels permit, fish can only bypass the fence by entering into the large live box with a one-way door. The top of the box can be easily opened by staff. Staff can then net the fish from the trap to a waiting trailer and move them up, beyond the rockslide with minimal stress.

In 2016, from August 6th when the fence began catching fish to the first week of October when water levels rose too high for the fence to be a barrier, 485 fish where trapped. Of the 485 fish, 337 were moved to the upper river, upstream of the slide, to spawn naturally and the remainder were taken to the hatchery to be used as broodstock.

In 2017 the fence was operational between June 19th and October 1st. During that time we trapped and trucked:

Fish Fence
Species Totals
coho 128
Steelhead 36
Pink 140
Total 304

A percentage of those fish were held at the hatchery as broodstock, while the majority were released in the upper river to spawn naturally.

fish fence in late summer at low water

Low water levels in late August meant most fish were holding in the pool below the fence. To access and move these fish weekly seines where undertaken. Between August 30th to November 1st staff and an army of volunteers seined to the maplewood pool 7 times. Results from the seines are as follows:

Trap and Truck Seining Program
Species Broodstock Release Total
pink salmon 334   334
summer steelhead 25 29 54
coho salmon 276 1,777 2,053
chum salmon 67   67
Total 2,508


Seine in Maplewood pool

The fish fence began operation again on May 24, 2018 following a period of low flows that enabled the instream installation works to occur.

A small number of early coho and summer steelhead trapped at the fence were tagged in early summer with radio tags. These fish were monitored weekly to see if they were able to migrate past the rock slide area to spawning grounds in the upper river, none were detected above the slide

The fish fence remained operational in the river until higher flows in late September 2018 that resulted in damage to the in-river anchors and the bladder sleeve. Numbers of returning fish were down from 2017, likely as a result of environmental conditions delaying the migration of salmon into the lower river. The coho and steelhead captured were used in the radio tagging program and released to the river upstream of the fish fence.

The image above shows a coho receiving a gastric radio tag.

Although the fish fence was not successful in trapping many fish in 2018, it did create a useful barrier at low flows. Hatchery staff and volunteers were able to use a seine net in a pool directly downstream of the fish fence to capture and move fish. As part of the river seining activities, a total of 133 coho were moved upstream of the rockslide, while an additional 62 coho, three chum and one steelhead were taken to the hatchery as

The fish fence began operation again on February 20, 2019. The fish fence remained operational in the river until higher flows in mid-October 2019 that resulted in damage to the bladder sleeve. Numbers of returning fish were comparable with last year.

Installing the new bladder in February allowing the fence to be operational once more.

A total of 44 adult salmon captured during the river seine events or as a result of the fish
fence were used in the radio tagging program and released to the river upstream of the fish fence.

This year saw an end to our fish fence (not surprising for crazy 2020). A big storm in February damaged the fence and live box beyond repair (Image below). In March, with the help from the DFO, we removed all the damaged parts of the fence.  

A closer look at the mangled live box.

The day after the storm, when high flows receded, all that was visible was a mangled live box. We later discovered several panels were ripped out.