Special Brief (1st section) Right Whales: A Look Back on the Summer of 2017

2017-11-07

Stéphane Plourde

During the summer of 2017, a dozen North Atlantic right whale carcasses were found in the Gulf of St. Lawrence, mainly between the Gaspé Peninsula and the Magdalen Islands. Usually, two to four dead individuals are found in this population each year across its range.

This unprecedented event is cause for concern, given that the right whale is listed as an endangered species under Canada's Species at Risk Act. There are only around 500 right whale individuals left in the world. And the threats to its recovery are numerous: collision with ships, entanglement in fishing gear, underwater noise and difficulty accessing its food, zooplankton.

Actions undertaken
Numerous deaths recorded this summer prompted Fisheries and Oceans Canada (DFO), the Canadian Coast Guard and Transport Canada to undertake a series of actions designed to put an end to this situation. The measures focused primarily on fisheries and shipping. The first action was to partially close the snow crab fishery in the southern Gulf of St. Lawrence. Other fisheries have also been limited, delayed or closed for the same reason. Moreover, since August, vessels 20 metres or more have been subject to a speed restriction of 10 knots when travelling in a specific region defined based on an analysis of areas frequented by the right whale. To ensure compliance with this restriction, Transport Canada and Fisheries and Oceans Canada conduct aerial surveillance of the restricted area. The Marine Communications and Traffic Services (MCTS) centres of the Canadian Coast Guard are also involved in vessel monitoring efforts (see the article Canadian Coast Guard MCTS centres also involved in protecting the right whale).

At the same time, other science-based actions were carried out to identify the possible causes of the whale deaths. DFO conducted toxicity analyses of zooplankton samples collected in the affected area in June to see if the whales might have been affected by a toxic algae bloom. An ocean modelling team also assessed the potential for collisions between vessels and whales at the time and location of their deaths.

Change of feeding sites
The high mortality rate might also be associated with a recent change in distribution of the right whale population. In the spring, they migrate north to feed on energy-rich zooplankton (mainly copepods of the genus Calanus). Two of the known feeding habitats are in Canadian waters: the Grand Manan (Bay of Fundy) and Roseway (Scotian Shelf) basins. However, right whales have abandoned these two habitats since 2014, presumably as a result of a sharp decrease in the availability of Calanus. Since Calanus is generally abundant in the Gulf, this region might represent an alternative to commonly frequented habitats.

Necropsies
Six necropsies were performed on carcasses recovered this summer to explore the potential causes of death. A report written by the Canadian Wildlife Health Cooperative as part of a partnership between the Marine Animal Response Society and DFO was released on October 5, 2017. Based on the specimens studied, the report confirms that the most likely causes of death for these whales are collisions with vessels and entanglement in fishing gear.

Species protection and recovery
Over the coming months, the Government of Canada will meet with representatives of the fishing and shipping industries, Aboriginal communities, whale experts and scientists, as well as the US National Oceanographic and Atmospheric Administration (NOAA). The goal is to plan the measures to be put in place next summer to protect right whales from any other hazard.

Furthermore, as part of its right whale recovery program, Fisheries and Oceans Canada has been supporting a research program in the Gulf of St. Lawrence for the past five years. This includes:

an increased observation effort on the Department's sampling platforms;
large-scale spatial data analysis of zooplankton to identify new feeding habitats;
the development of coupled biology-physics models on the transport of Calanus;
a network of hydrophones allowing high-resolution temporal monitoring of the presence of right whales based on their vocalizations at specific sites.

The information collected under this program could identify new feeding habitats and support actions to restore the right whale population in the Gulf of St. Lawrence.