Ocean Networks Canada is a fiber optically cabled observatory that powers instruments and returns data from a array of nodes distributed in the Salish Sea and northeast Pacific Ocean. They maintain a number of high definition cameras that return images and real time video from the seafloor in various locations. One of these cameras is deployed at more than 1000 meters depth in Barkley Canyon off the coast of Bamfield and Ucluelet on the west coast of Vancouver Island.
On February 12, 2015 a citizen scientist logged on to the POD 1 camera in Barkley Canyon and saw a most amazing migration of Tanner crabs (Chionoecetes tanneri). Michael, a post-office worker from Minnesota in the United States, saw the following and contacted ONC scientists to report his discovery:
What is the Rush?
Dr. De Leo and other scientists got together to try to unravel why the crabs are on the move.
ONC researchers began pondering what may have caused such a large crab fest. Could the crabs be fleeing an earthquake or underwater landslide? Barkley Canyon is an actively eroding underwater canyon where underwater landslides occur. A closer look at the video reveals that the crabs moved in a single direction, up the canyon toward shallower water depths. This unidirectional movement suggests that this is not a panic response to a sudden event, where the crabs would likely flee in multiple directions, but rather a mass migration.
A quick look at data from ONC instruments in Barkley Canyon shows little change in environmental factors such as bottom temperature, currents and dissolved oxygen during this migration time. So, we can safely conclude that the mass migration was not being triggered by environmental change.
Are the crabs responding to an internal stimulus to move to shallower depths? After viewing the video sequence University of Victoria researcher Verena Tunnicliffe suggested a possible link to the crab’s annual reproductive cycle.
According to Fisheries and Oceans Canada (DFO), in March and April, female Tanner crabs, which live at deeper water depths than males, “move shallower for the purpose of egg release and mating.”
If you are interested in getting involved as a citizen scientist with ONC visit the website and sign up. You never know what you are going to find if you look.