SALMON WATERSHEDS LAB
Ecology & Conservation of Aquatic Systems
Jonathan Moore and Team
March 04, 2019
By Karl Seitz
It’s 2:37am, the dead of night, and we are loading our little skiff to make our 5km river run from the lodge to the weir camp. We’re taking this midnight ride, not because we enjoy navigating the river in darkness, but because this is the only time today when there will be enough water to get our boat up the estuary without dragging it along the river bottom. On the Koeye River estuary our activities are dictated by the tides which, more often than not, means we are forced to work outside of “normal” business hours. But it’s not just us researchers that are governed by the ebb and flow of the ocean; the tides lord over everything here, from the massive schools of sand lance that swarm the shallows of the bay to the lone stickleback stuck in a marsh puddle waiting for the waters to rise and set him free. With all the gear loaded, we push off from shore and begin to glide across the still black water of the bay. The night is clear and the moon almost full, no need for headlamps so out they go.
Down here at the river’s mouth, the surf beats against the rocks and sand, insatiably grinding away at the land and dragging it into the sea. The water here stays salty and its temperature remains relatively stable throughout the day. Most of the fish we catch here during sampling fit neatly into the ‘marine’ category and the rocks along the shoreline are encased in a living crust of barnacles, mussels, and limpets. This all starts to change as we move just a few hundred meters upstream.
Tears leak from my eyes and streak across my cheeks as we cruise over the eelgrass beds at full throttle. A few hours ago, the boat’s propeller would have become impossibly tangled with this submarine grass, but now there is at least a meter of water above even the longest blade. These underwater meadows act as nursery grounds for many species and are a prime spot for catching juvenile salmon in the springtime as they migrate out to sea. The waters here are more variable than down in the bay and residents must be able to cope with these ever-changing conditions. This is especially true for the gunnels and spotted snailfish who like to live amongst the rocks along the shoreline and mudflats which become exposed to the air on low tides. They truly become fish out of water!
The boat rocks a bit as we hit the swirling currents of the narrow canyon between the eelgrass beds and the marshland of the middle estuary. In the bow of the boat, Jared, the project's field technician from the Heiltsuk First Nation, flicks on his headlamp to keep an eye out for bits of floating debris which are common in this area. Almost immediately, I must swerve hard to narrowly avoid smashing into a deadhead log drifting with the rising waters. Once through the canyon, the landscape opens into a series of mudflats and meadow marshes straddled by nice, wide river channels; a smooth sailing area, so again it’s lights out.
The fish living here in the middle estuary are fascinating to me. The underwater area can decrease by more than 75% from high tide to low tide, the salinity can go from fully saltwater to fully freshwater twice per day, and temperatures can fluctuate wildly during the summer months. The amount of stress one must endure to live in such an environment must be enormous, but this place has to confer some sort of advantage to its residents because there is certainly no shortage of fish. Our seine nets are filled with three-spine sticklebacks, shiner perch, and coho salmon fry every time we sample in these reaches. Some of our biggest catches are in areas that may only be underwater for a couple of hours per day! Fish here must be closely following the water’s edge, accessing new habitat areas as they are engulfed by the rising tides while also ensuring they are not left high and dry when the waters recede. Always on the move and endlessly riding the tides would seem to be a peculiar behaviour for coho fry, who hold and defend territories when living in streams and rivers. What makes these estuary residents act so differently from their upstream cousins? I guess I’ll have to figure that out.
I could muse over the activities of these marsh fishes for hours, but I need to start paying closer attention to my boat driving as we move into the upper estuary. The water here stays mostly fresh no matter the tide, but it’s depth can change by a meter or more and the tide height tonight is just barely above the level we need to motor the whole way up. Where we are right now can be particularly tricky, as the river flow, with the help of redd-digging pink salmon, has caused the bottom to have a rolling, wave-like structure that seems to attract my boat’s propeller. Time to slow down, turn on my headlamp, and check our depth before we hit a-CRACK! SCRAAAAAAPE………...…‘sigh’……rock.
The bay. Photograph by Karl Seitz
Eelgrass beds. Photograph by Karl Seitz
Upper estuary. Photograph by Karl Seitz
The bay. Photograph by Karl Seitz