Gulf Islands National Park Reserve of Canada
As a follow up to restoration work on Lyall Creek, Parks Canada continues monitoring juvenile fish at stations ranging from just above the estuary to the extent of summer water flows just below the rockfall. Using electrofishing techniques, we can observe the number and diversity of fish through time. We measure and weigh the fish and then return them to the creek unharmed. In 2008, we completed our fourth year of surveys. Although this is a short time frame for a monitoring program the story, that our data provides, continues to unfold.
Fish monitoring using electrofishing techniques.
© Parks Canada / 2005
Lyall Creek supports chum and coho salmon, and cutthroat trout. Each of these species uses the stream in different ways. Chum arrive in the fall to lay their eggs. Once the new generation hatches in late winter, they leave almost immediately. Chum are not reliant on summer water flows nor are they susceptible to warm summer water temperatures. Other than accessing the creek, their big challenges are in the marine environment.
Coho follow a similar pattern for spawning but the next generation of fish spends about 18 months in the creek. Juvenile fish hide out in the deeper pools and under logs and bank while they put on some growth before migrating out to sea. Coho rely on high quality summer water conditions and require lots of cover to evade predators like small mammals and birds.
The coastal cutthroat trout are sea-run, meaning they spend at least some of their time in the marine environment to feed. Unlike the salmon species, cutthroat are repeat spawners and can return in their home streams over many years. They are present in the creek throughout the year.
The data from 2005-2008 is interesting. Coho numbers are variable (fish detected in some years and not in others) and they are restricted to the lower creek. In 2005, we detected coho up as far as the old dam. In 2007, we observed similar densities in the lower reaches but higher densities and range expansion to just upstream of the bakery. In 2006 and 2008, coho were essentially undetected in sampling. Based on fish observed in the fall from year to year, the small population of coho (generally no more than 15-20 adult fish) seems to have improved since the restoration work was completed and the fish now have free access to the creek. Adult coho are cryptic and very difficult to observe in the creek so it is unclear if their numbers are stable or if spotty juvenile numbers are related to other in-stream survival issues.
Park staff collecting fish data.
© Parks Canada / 2005
Unlike the chum and coho, reasonable numbers of cutthroat trout were seen in the creek prior to restoration work. They are found in all areas that we survey. Restoration work has removed barriers for all species so increased competition for spawning habitat, and predation of cutthroat by the more aggressive juvenile coho are likely to result in a decline of trout as a new equilibrium is established.
We do our sampling in the late summer so chum salmon are not present. Using opportunistic counts of adults in the fall we can document chum salmon and we are working to standardize these surveys with our partners at Department of Fisheries and Oceans and our local creek champions Rick Jones and Mike Jack. Prior to restoration efforts, there were no chum salmon above the road. The number of adult chum salmon observed now averages around 100 fish but reached a peak of 500 fish in 2001. Numbers seem to have declined in recent years but we are hopeful that the chum population remains healthy.
We hope to continue our monitoring for many more years and in doing so should continue to gain a better understanding of the Lyall Creek ecosystem. For more information, contact Todd Golumbia, park ecologist at 250-654-4011.