Muddy Boots is our internal blog where our staff members share experiences getting their boots muddy with on-the-ground conservation research! You can find our contributions to external blogs and Op Eds here.
By Jacob Seguin
Lake sturgeon used to be so plentiful in the Great Lakes that steamboats crossing the waters would burn their dried carcasses in their boilers to supplement their coal supplies. Then, because of caviar’s sudden popularity, lake sturgeon were fished out of much of the Great Lakes watersheds in a matter of decades – less than the lifespan of an individual fish. When the fish you are catching only spawns once every four to six years, and even then only maybe 1% of their eggs survive, and those 1% take 20-25 years to reach breeding age themselves, the population is bound to plummet when harvesting pressures grow. While we now better understand these long survival odds, we still have a lot to learn about this ancient fish.
Fast forward to today. Now we have the benefit of not just hindsight, but new technology to help us better understand the behaviour and threats to sturgeon survival. Today, we’re deploying advanced fish tracking technology in the watersheds of Hudson’s Bay, which represent sturgeon’s last stronghold of intact habitat in Ontario. Fortunately for the fish, Ontario’s far north is one of the few places left in North America where their passage upriver is rarely blocked by dams or other human-made obstructions, with five major intact watersheds supporting lake sturgeon in the region. Here sturgeon travel hundreds of kilometers upstream to spawn, meaning it is not easy to follow their movements.
Since 2016, WCS Canada has been participating in a joint lake sturgeon research project with Moose Cree First Nation: tracking sturgeon health, habitat use, and behaviour in the Moose River basin. This includes the Lower Mattagami River, with its four hydroelectric dams, and the North French River, which flows unimpeded as it has for centuries. We catch sturgeon in nets and make a small incisions to insert smooth transmitters the size of an AA battery into the fish’s body cavity. We then suture the cuts closed and release the fish (Figure 1). These implants transmit data remotely to receivers rather than storing it, which means there’s no need to re-capture the sturgeon to gather the information we need. The transmitter can remain in the sturgeon without harming them, so we don’t need to bother them again!
Figure 1: A lake sturgeon being given an acoustic transmitter, a type of biologger that will teach us how this fish uses its habitat over time, and in relation to disturbances like hydroelectric facilities. Photo credit: Alex Litvinov
This June, I was lucky enough to join the WSC Canada and Moose Cree First Nation team in time to tag nine lake sturgeon in a section of river between two hydroelectric generating stations on the Lower Mattagami River. We deployed receivers, anchored to the river bottom with heavy pieces of granite. These receivers will listen for the messages that each implanted fish is sending. Whenever a sturgeon swims by, the recorder captures the sturgeon’s identity and the time and date, so we know what fish was where and when. Twice a year we visit all our receivers to change their batteries, check their seals and download the stored data.
With this work done, we now have fish teaching us about how they use different types of river habitat: segments of river in between dams, above dams, below dams, and in intact (dam-free) rivers. This means we can make a full set of comparisons of how fish are moving and behaving in these different river segments and understand how dams may alter sturgeon behaviour (Figure 2).