Cultus Lake: A Treasure to Protect

 Cultus Lake is a nursery lake ecosystem, used by the endemic, endangered Cultus Lake Sockeye Salmon to spawn and rear juveniles prior to outmigration to the Pacific Ocean (COSEWIC 2003). Including Sockeye Salmon, the fish community of Cultus Lake is comprised of 19 native species. Other species of salmonids include Chinook (O. tshawytscha), Coho (O. kisutch), Chum (O. keta), Pink (O. gorbuscha), Cutthroat Trout (O. clarki clarki), Rainbow Trout (O. mykiss), and Dolly Varden (Salvelinus malma). Cyprinids found in Cultus Lake include Northern Pikeminnow (Ptychocheilus oregonensis), Redside Shiner (Richardsonius balteatus), , Longnose Dace (Rhinichthys cataractae), and Peamouth (Mylocheilus caurinus). Largescale Sucker (Catostomus macrocheilus) are also present, as are Threespine Stickleback (Gasterosteus aculeatus). Cultus Lake hosts three sculpin taxa, including the Prickly Sculpin (Cottus asper), Coastrange Sculpin (C. aleuticus), and the endemic Cultus Pygmy Sculpin (C. aleuticus; Coastrange Sculpin, Cultus Population). The Cultus Pygmy Sculpin is currently listed under Schedule 1 of SARA as threatened, due to its limited range and local freshwater habitat threats, and is currently being considered by the Minister for up-listing to Endangered status given the known anthropogenic degradation of same (Minister of Environment and Climate Change Canada 2020). Two species of Lamprey, the Western Brook Lamprey (Lampetra richardsoni) and the River Lamprey (L. ayresi) can also be found in the lake. A White Sturgeon (Acipenser transmontanus), has also been caught in the lake, though they are not thought to naturally inhabit the system continuously.   Fish species to add, Smallmouth Bass, Pumpkin Seed, and Starry Flounder (non-invasive)/ 

Cultus Sockeye: A Unique Legacy Unlike other sockeye salmon, the Cultus sockeye spawns exclusively in the lake and does so later than any of its Fraser River counterparts. This extraordinary adaptation means their eggs develop faster, and the fry dive deep immediately, escaping predators.

Since the 1920s, Cultus sockeye has been studied extensively, making it one of the most well-documented salmon populations in the world. In 2002, the Committee on the Status of Endangered Wildlife in Canada (COSEWIC) classified it as "endangered."

Click here to see the up-to-date fish counts.

Watch this eagle fish on the lake! 

Invasive Threats Non-native species have wreaked havoc on British Columbia's freshwater ecosystems. The illegal introduction of Small Mouth Bass (SMB) in 2018, a voracious predator, poses a dire threat to native species like the Cultus pygmy sculpin and sockeye salmon. DFO is suggesting the near shore fish community has drastically decreased in both number and species composition. Predation by invasive Smallmouth Bass is suspected but other factors such as unusually warm lake temperatures may also contribute.

Learn more about SMB here. 

You can also watch a video produced by the Fraser Valley Invasive Species Society here.  

Invasive Flora The Cultus watershed is plagued by invasive plant species, from Japanese knotweed to yellow flag iris. These plants threaten biodiversity and disrupt the ecosystem, infrastructure, and landscaping. 

Aquatic invaders like Eurasian Watermilfoil have taken over the lake’s shoreline, degrading fish habitats and hindering recreational activities. Efforts to mitigate these plants often backfire, as each fragment can spawn new colonies. Boaters and anglers play a crucial role in preventing their spread.

Understanding Eutrophication Cultus Lake faces the early stages of cultural eutrophication—excessive nutrient levels causing dense plant and algae growth. This disrupts the lake's delicate balance, threatening aquatic life.

Historical data reveals that Cultus Lake once thrived with low nutrient levels and oxygen-rich waters, perfect for the sockeye salmon. However, since the 1950s, human activities have altered this balance. Local agriculture, septic fields, and airborne deposits have increased nitrogen and phosphorus levels, exacerbated by climate change.

Reversal Is Possible Research by Dr. Dan Selbie and others indicates that early symptoms of eutrophication can be reversed. The fight to restore Cultus Lake’s pristine condition continues.

Monitoring Lake Health CLASS volunteers regularly measure water turbidity, temperature, and oxygen levels, reporting to BC’s Ministry of Environment. Compare Cultus Lake’s data with other BC lakes here.

Engaging the Community Working with the local school, the students also monitor the lake’s health using Water Rangers kits. View their findings here.

Air Quality CLASS and FVRD have installed air monitoring devices around the lake. Check real-time data here.

Our Mission Since 2007, CLASS has been dedicated to preserving Cultus Lake’s health for future generations. By integrating scientific research and traditional knowledge, we strive to understand and mitigate threats to this vital ecosystem.

Join us in our monthly meetings and subscribe to our newsletter to stay informed and contribute to our mission of safeguarding Cultus Lake. Together, we can ensure its legacy endures.

Explore more about Cultus Lake and how you can help protect this natural treasure. Let's keep it thriving for generations to come. 🌊🍃