Science Advisory Report 2017/039
Identification of Habitat of Special Importance to Fin Whales (Balaenoptera physalus) in Canadian Pacific Waters
- Fin whale populations in the North Pacific were severely depleted as a result of commercial whaling in the 20th century. Whaling catch records (n = 7,605) from BC shore-based whaling stations (1908 to 1967) indicate that most fin whales were killed west of the continental shelf. However, fin whales were also hunted in Hecate Strait, Queen Charlotte Sound, Greater Caamaño Sound and Dixon Entrance.
- Sightings from surveys (2002-2015) indicate that fin whales are encountered off the continental shelf west of Haida Gwaii and Vancouver Island, along the 1000 m isobaths between Cape St James and Cape Scott, but also on the continental shelf in Hecate Strait, Queen Charlotte Sound, Greater Caamaño Sound and Dixon Entrance.
- Geographic variation in fin whale song as well as genetic studies suggests some degree of population structure may exist in the Northeast Pacific. The occurrence of two song types (type 1 and 2), suggest the distribution of at least two population components may overlap BC waters. One component, that produces song type 2, may use coastal waters more often while the other component may be distributed offshore. Only song type 2 has been detected on inshore recorders in BC.
- Although there have been survey efforts in offshore waters of British Columbia most of the effort has occurred in the accessible inshore waters of Hecate Strait and Queen Charlotte Sound and Greater Caamaño Sound. Furthermore, the fin whale satellite telemetry study took place only in Hecate Strait and Greater Caamaño Sound. Consequently, this assessment of important habitat for the fin whale in British Columbia is limited to this inshore region.
- Modelling of sightings and effort from ship surveys (2002-2014) in Hecate Strait and Queen Charlotte Sound revealed an association between fin whale presence and Moresby Trough, a deep-water gully that extends northeast from the shelf break south of Haida Gwaii towards Banks Island on the east side of Hecate Strait. It also showed an association with the heads of submarine canyons near the 1000 m depth contour between Cape Scott and Cape St James, and with areas along the mainland coast, particularly Greater Caamaño Sound.
- The significance of habitat in Hecate Strait and Queen Charlotte Sound is underscored by previous fin whale distribution models that identified similar areas, based on whaling data (1949-1967) and line-transect surveys (2004-2008).
- Based on mark-recapture analysis of photo-identifications, an estimated 405 fin whales (CV = 6%, 95% CI: 363-469) were present in Hecate Strait and Queen Charlotte Sound during the photo-identification period of 2009 to 2014. An abundance estimate for the same region, based on line-transect survey data from an earlier time period (2004-2008), yielded a similar estimate (mean: 329; 95% C.I. 274-395).
- There are no fin whale abundance estimates for offshore regions of British Columbia.
- Fin whales tagged in Greater Caamaño Sound and in Hecate Strait remained in the region during the period of their tag transmission. Analyses of whale movement recorded by the tags indicated periods of area-restricted movement, that may represent foraging behaviour, lasted for days or weeks but were interspersed with periods of directed movement indicative of travel within Hecate Strait, Queen Charlotte Sound, and Greater Caamaño Sound.
- Analyses of dive data indicated that in Greater Caamaño Sound, fin whales exhibited a strong consistent diurnal pattern with longer, deeper dives during the day than at night. This pattern suggested the animals were foraging on diel vertically migrating zooplankton that occur in dense patches at depth during the day.
- Acoustic monitoring revealed that fin whale calling activity in Hecate Strait and Queen Charlotte Sound was greater than in the offshore areas that were monitored (2009 to 2015).
- Timing of peak periods of singing by males at Hecate Strait sites (November to January) was slightly later seasonally than at other sites. This suggests the possibility of a seasonal movement of fin whales into the Hecate Strait and Queen Charlotte Sound in late fall and winter, which would coincide with the breeding season of this species in the North Pacific.
- Details of fin whale catches in the BC historical whaling records indicate that 75% of births would have occurred between mid-November and mid-March, with a peak in January. Combined with high levels of calling, this suggests that courtship and mating, and calving, could be occurring in Hecate Strait and Queen Charlotte Sound.
- Sightings of fin whales with dependent calves (2006 to 2015), indicates that some fin whales also rear young while in Hecate Strait, Queen Charlotte Sound and Greater Caamaño Sound.
- Given the evidence provided above and using the bounding box approach, an area encompassing Greater Caamaño Sound and part of Hecate Strait and Queen Charlotte Sound was identified as important foraging, breeding, mating and rearing habitat for fin whales.
- Important features and attributes of this area include sufficient quantity and quality of prey, sufficient physical space to freely maneuver, water of sufficient quality so as to not result in loss of habitat function, and an acoustic environment that does not interfere with communication, or navigation, or impede use of important habitat by fin whales or their prey.
- Anthropogenic activities that are likely to result in loss of function of this important habitat include those that would result in reduced prey availability or accessibility, acoustic disturbance, environmental contamination, and physical disturbance
- Climate change may also affect habitat functions by altering prey availability and physical properties of the ocean. Anthropogenic activities and their effects on habitat functions need to be managed in the context of this ongoing issue.
- The area identified in this study likely constitutes only part of the habitat in British Columbia important to fin whales. There is a need to expand research efforts into offshore waters to determine the use and importance of offshore habitats by fin whales.
This Science Advisory Report is from the February 23-26, 2016 National Marine Mammal Peer Review Committee (NMMPRC): Part II. Additional publications from this meeting will be posted on the Fisheries and Oceans Canada (DFO) Science Advisory Schedule as they become available.
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