April 3, 2018

Preserving a Premier Steelhead Fishery on the Dean River: What Biologists Need to Know

The Dean River, a glacier-fed system nestled in the remote mountains that line B.C.’s spectacular mid-coast, is a bucket-list destination for many a dedicated steelhead angler. The Dean’s steelhead are available to anglers immediately upon leaving saltwater and are in superb condition during the prime warm-weather season from June to October. A daunting canyon in the lower river and natural selection likely have much to do with the revered size and fighting power of these fish. For this ultimate fishing experience to continue, fisheries biologists need to know the status of the Dean’s steelhead population.

In the past, steelhead returned to the Dean like clockwork. Anglers were satisfied, and catch rates seemed solid. The River Guardians on the Dean have gathered “catch-and-effort” data from steelhead anglers for over three decades. Until the mid-1990s, the river’s adult returns were consistently high, and these data were adequate as an index to track the abundance of fish over time. However, in recent years, conditions have shifted, and adult returns have become increasingly variable.

Fig. 1. Roderick Haig-Brown's Western Steelhead Bee is a legendary dry fly for west coast rivers like the Dean.

Angler surveys are influenced by factors like changes in fishing regulations and socio-economic factors. Additionally, a phenomenon called “hyperstability” – inflated abundance estimates and an overly optimistic view of status despite low fish abundance – can affect how angler catch data are interpreted. How does hyperstability happen? Less experienced anglers tend to move to another system when they are no longer catching fish, while experienced anglers remain and continue to be successful. Reported catch values still seem to indicate stable populations.

It was time to recalibrate what we thought we knew from the adult data with juvenile steelhead numbers. In 2015, the Province, supported with funds from the Freshwater Fisheries Society of BC, initiated a five-year quantitative study to assess the status of the Dean River’s juvenile steelhead population. The Province is keen to relate the River Guardian catch information on adult steelhead with independently collected data on juvenile fish to ensure the angling data continue to reflect the true status of this exceptional steelhead run.

This work has its logistical challenges, since weather is notoriously unpredictable, and frequent autumn floods can often hinder access and safe sampling. The Dean is also a large stream, with a width of 75 metres near tidewater. Luckily, juvenile steelhead (fry and parr) gravitate to boulder-dominated, fast-water habitats in the main stem for refuge and preferred feeding locations, of which there are an abundance to appraise.

This project is now entering its third year, with juvenile steelhead densities monitored at 16 key locations. The Province also benefits from juvenile surveys conducted prior to 2015 which can be related over a range in adult abundance and creel data. Multiple years of juvenile data will determine the relationship with adult catch data to establish reliable conservation reference points.

For a high-profile steelhead population like the Dean’s, dependable conservation measures linked to known rearing capacity are critical for the protection of the fishery. Netting steelhead fry and parr isn’t quite as thrilling as playing a bright summer-run chromer, but knowing that enough juveniles exist to produce a healthy run of those highly prized adults is pretty satisfying for the biologists tasked with managing these fish.

This series has been established as a way to inform freshwater anglers in B.C. about projects 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.

Author: Sue Pollard, Freshwater Fisheries Society of BC
Photo Credit: Doug Pollard, Lee Williston; BC Ministry of Forests, Lands, Natural Resource Operations and Rural Development & Joe Mckeen; 2016-2017 Dean River Guardian