August 17, 2017

Investigating a Wild Cutthroat Trout Fishery in Vancouver Island’s Comox Lake

Vancouver Island is home to some of the most heavily fished, all-wild cutthroat trout lakes in B.C. Combined, the 15 large lakes on the island that support these cutthroat populations provide up to 60,000 angler-days a year, which represent almost 25% of all the island’s angling effort in freshwater lake systems. All cutthroat populations in these systems are maintained entirely through natural reproduction, and are not enhanced in any way with hatchery fish.

What makes these fish populations particularly attractive to anglers is that for 11 of these lakes, the cutthroat co-exist with sockeye salmon or kokanee. In such situations, cutthroat can take full advantage of a piscivorous (fish-eating) lifestyle and therefore reach impressive body weights of 2.27 kilograms (five pounds) or more. It appears that, at least in the province’s systems that have been examined (many coastal lakes on B.C.’s mainland have never been sampled), the occurrence of large-bodied, non-anadromous cutthroat trout is rare. Each lake represents a genetically unique population that has adapted over time to the combination of local features (like fish community, spawning and feeding habitats, and temperature regime) that are unique to that lake. Given this combination of rarity and genetic distinctness, fisheries managers must keep conservation uppermost when considering options.

The challenge for fisheries managers is to ensure that these special lakes continue to provide quality fishing. Very little was known about wild cutthroat populations in Vancouver Island’s large lakes beyond what previous angler surveys and limited sampling have told us. Managers know these populations exist, and anglers continue to catch large fish. However, they don’t know much about how these fish spend their lives, the extent to which they move around, or how vulnerable they may be to fishing pressure. These are all critical pieces of information needed to ensure that regulations are appropriate, and harvest levels sustainable.

Vancouver Island Large Lakes (> 1,000 ha) containing wild coastal cutthroat trout: Alice, Buttle, Comox, Cowichan, Elsie, Great Central, Henderson, Huaskin, Kennedy, Lower Campbell, Nimpkish, Sproat, Upper Campbell, Victoria, Woss

Comox Lake supports one of the island’s highest-use lake fisheries, driven mainly by the capture of big cutthroat trout. When anglers voiced concerns about declining catch rate and fish size, managers responded by implementing more conservative regulations in 2013 in hopes of protecting the cutthroat population. However, this change was implemented based on anecdotal evidence only; the actual status of the cutthroat population remains unknown, as does the effectiveness of these new regulations.

In 2016, the Freshwater Fisheries Society of BC funded a pilot project in Comox Lake to determine if a tag-reward program could be used to evaluate the status of its cutthroat trout population. It would also determine the effectiveness of the new fisheries regulations.

Cutthroat trout need to be a minimum of 25 centimetres (10 inches) in length for tagging. Provincial biologists needed to find a way to capture, unharmed, a large number of cutthroat trout over this length. If targets were met, fish could be tagged and returned to the lake in hopes that anglers catching tagged fish would report them. In this way, several informational gaps (like catch rates, fish movement, distribution, growth, maturity and mortality) could be addressed. The success of the recapture component is highly dependent upon angler participation.

The pilot project proved successful in establishing a method to capture fish in large lakes for tagging. Over five days of trapping in 2016, 91 cutthroat were captured, and 58 of these fish received "reward" tags. Since then, the angling public has reported four of these tags as recaptures. 

Given the success of this pilot study, the Freshwater Fisheries Society funded the two-year, $50,000 project. A more comprehensive assessment of the trout population was undertaken in the fall of 2016 and spring of 2017, with 33 and 63 tags deployed respectively. This included an intensive effort over five weeks to capture and tag fish during the spring spawning period, as well as place three electronic tag-detection stations in key spawning tributaries to monitor the movement of tagged fish entering and leaving these systems. Relocation information from the tag-detection stations, recaptures by provincial biologists, and angler-reports of tagged fish will be used together to determine the total mortality rate for the population, and the component that is related to fishing (known as exploitation rate). This information can then be used to assess the balance between population gains (reproduction, growth, and survival) and losses (mortality).

The result is that fisheries managers can evaluate the appropriateness of existing fisheries regulations and alternative regulatory options. Fisheries regulations that are too liberal could result in over-exploitation and a poor-quality fishery (low fish size and/or catch rates), which could even jeopardize the sustainability of the stock. On the other hand, regulations that are too conservative may reduce anglers’ opportunities to catch fish. The hope is that the knowledge gained for Comox Lake can help make better management decisions, and be transferred to other cutthroat fisheries in large lakes on Vancouver Island.

The Society would like to acknowledge the local angling community, including the Courtney and District Fish and Game Protective Association, who have been fully on board since the project’s inception, and have participated in fish captures and reporting.

To learn more about this Freshwater Fisheries Society of BC funded project, contact Brendan Anderson, BC Ministry of Forests, Lands and Natural Resource Operations at:

This 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.

Author: Sue Pollard, Freshwater Fisheries Society of BC
Photo Credit: Mike McMculloch, BC Ministry of Forest, Lands and Natural Resource Operations