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Recovery Strategy for the Basking Shark (Cetorhinus maximus) in Canadian Pacific Waters

7. Critical Habitat Identification

Under SARA S. 2(1), critical habitat is defined as “the habitat that is necessary for the survival or recovery of a listed wildlife species and that is identified as the species’ critical habitat in the recovery strategy or in an action plan for the species”. Further, habitat in respect of aquatic species is defined as “spawning grounds and nursery, rearing, food supply, migration and any other areas on which aquatic species depend directly or indirectly in order to carry out their life processes, or areas where aquatic species formerly occurred and have the potential to be reintroduced”.

SARA S. 41(1)(c) requires the recovery strategy to include the identification of critical habitat, stating “an identification of the species’ critical habitat is, to the extent possible, based on the best available information, including the information provided by COSEWIC, and examples of activities likely to result in its destruction.”

7.1 Identification of the Species’ Critical Habitat

Adequate information does not exist to identify critical habitat at this time. Habitat requirements have not been investigated for Basking Sharks in Canadian Pacific waters, and no specific locations have been identified for reproduction, pupping or rearing; although other migratory shark species are known to mate in northern areas and pup in southern areas (McFarlane et al. 2009). Further, critical habitat has not been defined for this population’s southern range (e.g., the U.S. and Mexico). In other areas of the world where dedicated research and science has been ongoing for this species, such as the United Kingdom, habitat features for reproduction have not been identified. There are historical areas in Canadian Pacific waters that were regularly visited by large numbers of Basking Sharks (e.g., Barkley Sound, Clayoquot Sound, and Rivers Inlet); however, the importance of these areas for feeding and mating is unknown. Historical data does not exist to confirm if these areas were the only areas used by Basking Sharks, or if rather these observations were due to human use of these areas and/or natural variability in productivity of these areas. Therefore, it is unknown if a recovered stock will return to these areas.  Some habitat characteristics that attract particular life stages such as high seasonal food availability are known, but these features vary over temporal and spatial scales (McFarlane et al. 2009). For example, Basking Sharks tend to aggregate in the transition zones of coastal shelves where there is enhanced zooplankton abundance (Sims et al. 2006). Further, zooplankton abundance (the preferred prey) and community structure have been observed to vary on decadal-scales, as seen in the prolonged period of relative low copepod abundance in some areas of the northeast Pacific from 1989-1997 (King, 2005).  Studies have not yet been conducted to identify habitat in Canadian waters required by the Pacific population of Basking Shark to achieve and sustain a viable population. It is therefore not possible to identify the habitat currently occupied by the species, the habitat necessary for the survival or recovery of the species, the activities that are likely to result in the destruction of such habitat, or the extent needed to maintain the current population size or support population recovery. 

As set out in SARA, if information is inadequate to identify critical habitat within the recovery strategy, a schedule of studies must be prepared. This schedule, once implemented, will yield new information that could contribute to the identification of the species’ critical habitat in the future. The schedule of studies identified for the Pacific population of Basking Shark is included below (Table 4). Upon completion of these projects, it is hoped that the results will provide information allowing Fisheries and Oceans Canada and Parks Canada to identify critical habitat for this species. It is important to note that it may take decades to address the issue of critical habitat, given the long lived nature of the species, lack of documented recent sightings in Canada, and the associated long-term scope of the recovery strategy.

7.2 Schedule of Studies to Identify Critical Habitat

In order to identify critical habitat and habitat that is important to the recovery of the Pacific population of Basking Shark, research is needed both in Canadian waters and in other parts of the species’ range. Table 4 outlines the studies required to identify critical habitat. Because of the long-term nature of this recovery strategy, the timelines represent benchmarks at which evaluations of progress towards the identification of critical habitat will be undertaken.

It is recognized that defining critical habitat will be challenging given the relative scarcity of sightings, and the dynamic nature of the marine environment, potentially leading to shifts in habitat use on inter-annual and inter-decadal time scales. Large aggregations of Basking Sharks have historically been identified in Barkley Sound, Clayoquot Sound, and Rivers Inlet; however, historic and current sightings have also been noted in other regions of Canadian Pacific waters. As Basking Sharks require oceanographic conditions that concentrate prey, and have a preference for surface temperatures between 9 and 16ºC (Sims et al. 2003), the necessary conditions may change over relatively small spatial and temporal scales (Sims and Quayle 1998). Studies will primarily be focused on the areas of historic aggregations noted above, but this focus may be modified as new sightings information is collected. Further, the studies will be carried out to coincide with the timing of the Basking Sharks’ seasonal migration into Canadian Pacific waters (May through September).

Table 4: Schedule of Studies to Identify Critical Habitat

Description of ActivityOutcome/RationaleTimeline
1. Maintain and promote the Basking Shark sightings network.
Develop the Basking Shark Sightings Database (2010).  Maintain and promote the Basking Shark Sightings Network.Determine extent of species’ distribution and potential habitat in Canadian Pacific waters.2010-2015
2. Basking Shark Tagging Program
Opportunistic satellite tagging of Basking Sharks in Canadian Pacific waters.Confirm location(s) of Basking Shark presence in Canadian Pacific waters; determine seasonal distribution, movement, abundance and residency of species.2010-2015
3. Opportunistic sampling program
Biological sampling from live sightings and mortalities.Species distribution, population structure, sex, biophysical features, stomach contents, habitat use by life stage.2010-2015
4. Overflights
Use of real time satellite imagery to identify high plankton blooms for targeted overflights (May-September).Biophysical features and species distribution.2010-2015
5. Definition of Critical Habitat
Determine and characterize occupied high-use habitat and define potential critical habitat regions with similar characteristics.Define high use occupied habitat.To be determined 10

9 Activities will be evaluated in 2015. Studies will be adapted and/or recommitted to periodically.
10 This study is essential to the identification of critical habitat; however, initiation and completion is contingent upon the completion and results of the previously listed studies.