Suckers in the Spotlight
Contributed by Christy Juteau, Conservation Science Director – A Rocha Canada, Brooksdale Environmental Centre
In 2011 the Salish Sucker made a big splash in the news when it was accidentally captured in a land-locked pond in South Surrey. What was an endangered fish doing in a watershed where it was thought to be extirpated (locally extinct)?
Since then surveys by the conservation organization, A Rocha Canada, have found that the Little Campbell River, an urbanizing watershed, is home to a small population of Salish Suckers. This is excellent news for this rare freshwater fish which only exists in 15 watersheds worldwide, all of which drain to the Salish Sea.
The Salish Sucker (Catostomus sp.4) is closely related to the Longnose Sucker (Catostomus catostomus). During the last ice age it became evolutionarily distinct due to geographic isolation. Salish Suckers are part of a particularly interesting group of species known as the “Chehalis fauna”, which persisted and evolved in unglaciated areas of the Chehalis valley (present day NW Washington) during the Pleistocene glaciations until around 12,000 years ago. As the Cordilleran ice sheet retreated north, the Suckers began to discover and inhabit new watersheds. Today the Salish Sucker is threatened by oxygen depletion (anoxia) caused by polluted runoff, increasing temperatures, and reed canary grass, an invasive species which fills in aquatic habitat.
Like many other sucker species, the Salish Sucker hangs out around stream bottoms where it uses its large fleshy-lipped mouth (where suckers get their name!) to forage for benthic macroinvertebrates found in the bottom substrate. This species prefers deep (>70cm) slow-moving pools for rearing habitat and gravel-bottom riffles or groundwater upwellings for spawning. Salish Suckers tend to congregate and stay where these combination of conditions are found. They also tend to travel limited distances (on average 170m), although a few individuals have travelled up to 2km during spawning season (April-July).
A Rocha Canada has partnered with Dr. Mike Pearson to monitor population distribution, map critical habitat and characterize threats within the Little Campbell River watershed. Part of this has been to map both dissolved oxygen levels and invasive riparian vegetation. Since the discovery of Salish Suckers in the Little Campbell in 2011, initial population survey results were small. From 2011-2016, biologists set 624 traps in approximately 50km of potentially suitable habitat and only 39 Salish Sucker individuals were captured. In 2017, biologists were encouraged with greater results. A mark-recapture survey was initiated in two reaches where Salish Suckers captures were consistent over the past six years. Through these mark-recapture surveys, 80 individuals were marked over the two week survey period. Population estimates were found to be approximately 33 in Campbell Valley Regional Park and 238 upstream of the Langley Municipal Natural Park.
While recent results are encouraging, the situation remains grave for this beautiful fish. Our studies show the Little Campbell River continues to support a small population of this species. But like the other watersheds where this species remains, development pressures continue to be a threat as does anoxia from high nutrient runoff and invasive reed canary grass exacerbate the hypoxic conditions of the groundwater-fed, slow-moving deep pools that Salish Suckers rely on. Continued monitoring, habitat enhancement and landowner engagement are critical threads to enable this species to thrive.
Find out more about A Rocha’s important work on the Little Campbell River here.
Image Credits: Joel Sartori, the National Geographic Photo Ark project