After being hunted to near extinction in the Salish Sea, humpback whale populations have rebounded significantly. While this is a great win for conservation efforts, the return of humpbacks comes with risks, such as boat strikes and entanglements in what is now a busy urban waterway.
Authors: Chad Nordstrom and Caitlin Birdsall, Coastal Ocean Research Institute, an Ocean Wise initiative
Reviewer: Lance Barrett-Lennard, Coastal Ocean Research Institute, an Ocean Wise initiative
Banner Photo Credit: Ocean Wise
North Pacific humpback whales (Megaptera novaeangliae) are returning to the Salish Sea 100 years after being extirpated by commercial whaling, and well after humpbacks began re-occupying large tracts of British Columbia’s coast. At least 100 humpbacks were hunted and killed in the mid-1800s from the Strait of Georgia and Queen Charlotte Strait and later, between 1908 and 1967, at least 5,618 humpbacks were harvested and processed by the five main whaling stations along the coast. Humpback whales are now returning to near historic numbers coast-wide, with the Salish Sea being one of the last areas to be re-occupied. Using this area as a case study for documenting a humpback comeback allows us to highlight the efforts of coastal citizens, who have been critical in recording this recovery in what is now a major urban waterway.
Why is it important?
The return of large rorquals (the family of baleen whales characterized by heavily pleated throats) to the Salish Sea will have widespread ecological impacts. Humpbacks require large volumes of prey and it’s estimated the population in B.C. could consume as much as 250,000 to 320,000 tonnes of feed (euphasids, or krill, and forage fish such as herring and sardines). Commercial fish species such as salmon and hake, as well as marine mammals such as dolphins, porpoises, seals, and sea lions in the region may be impacted, as humpbacks will compete directly with them for the same prey resources. Humpbacks are also susceptible to boat strikes and entanglements involving marine debris or commercial fishing gear, which could be problematic given high volumes of commercial and recreational boat traffic in the Salish Sea. An increase in the number of whales, paired with an increasing number of vessels, is a recipe for more frequent whale-boat collisions and/or entanglements.
What is the current status?
North Pacific Humpback whales have recovered substantially from commercial whaling and have reoccupied large tracts of former feeding grounds on the west coast of North America. A notable area where humpbacks were conspicuously absent during their return to British Columbia over the past 30 years was the inner Salish Sea – the inland waters of the Strait of Georgia extending south to Puget Sound (Figure 1A) – where a small and possibly resident population of humpbacks was extirpated by 1909. The highly urbanized area is home to a large number of citizen scientists who regularly report their sightings of whales, dolphins, porpoises, and sea turtles to the B.C. Cetacean Sightings Network (see the Citizen Science and Participation article under the Sense of Place and Wellbeing Theme) and their reports have documented the return of humpbacks to the inner Salish Sea.
The B.C. Cetacean Sightings Network (BCCSN) currently curates more than 29,500 humpback whale sightings collected coast wide over 35 years (1981– 2016), with 10.3 percent or 3,052 of those reports originating from the study area (Figure 1B). By limiting reports to those graded as reliable or certain, the BCCSN began consistently receiving 50 or more humpback sightings per year from the inner Salish by 2003-2004 (Figure 2). This was approximately 15 years after similar numbers of sightings were made regularly along the west side of Vancouver Island, a known high-density area in B.C. By 2013, humpbacks were the most frequently reported cetacean in the province and 19 percent of humpback sightings were located in the inner Salish Sea.
In order to account for uneven observer effort and increasing awareness of the Sightings Network over time, the data were analyzed using an effort-corrected Geographic Information System (GIS) model. The coast-wide model confirmed the delayed but notable increase of whales in the area: humpbacks were considered entirely absent from the inner Salish Sea prior to 2004 (Figure 3A) and sighting density per unit effort increased to a maximum of 0.11 per square kilometre when modelling data from 2004 through 2016 (Figure 3B). This value represents roughly 20 percent of the maximum sighting density per unit effort predicted for major hotspots along the west side of Vancouver Island and is notable given that the model accounts for the large observer base in the inner Salish Sea.
What can you do?
Individual and Organization Actions:
- Report your cetacean and sea turtle sightings, including humpbacks, from anywhere in British Columbia to the B.C. Cetacean Sightings Network online or via WhaleReport – the free smartphone application available for iOS and Android devices.
- Follow the Be Whale Wise guidelines if you encounter any cetaceans while on the water.
- Slow down and stay vigilant in areas of known humpback whale activity to avoid collisions from unpredictable humpback surfacing.
- Recycle and properly dispose of garbage to prevent marine debris that can be harmful if ingested, or cause entanglement. Ensure workplaces are equipped with proper disposal options.
Report incidents of entangled whales immediately to the BC Marine Mammal Incident reporting line: 1 800 465 4336.
- Contribute photos of humpback whale tail flukes for photo identification catalogues to [email protected] or [email protected].
Government Actions and Policy:
- Consider humpback nutritional requirements when regulating the commercial catch of B.C. euphasids, particularly in the Strait of Georgia.
- Implement and enforce slow-down zones for large vessel traffic in areas of high overlap between humpback and vessel densities. Studies have shown that travel below 10 knots greatly decreased the likelihood of fatal vessel strikes.
- Continue to support and facilitate growth of the Marine Mammal Response Network to ensure timely and safe incident responses coast-wide.
- Provide large vessel captains and pilots with cetacean resources that include distribution of species, and how to safely transit when whales are in the area (e.g., The Mariner’s Guide to Whales, Dolphins and Porpoises of B.C.).
- Legislate mandatory safe-distance for vessels from cetaceans (e.g., using Be Whale Wise Guidelines).