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- Valued Component Features
- Narwhal research in ASTIS
Valued Component Features
Rationale for Selection
Narwhals were selected as a focus for this study primarily on the basis of the overlap between their known range and the High Arctic study area. Narwhals are also an important species to Nunavutmuit for subsistence, cultural and economic reasons. Over a five year period from 1996 to 2001, for example, the total annual mean number of harvested narwhals was approximately 734 (Priest and Usher 2004).Their skin and underlying fat (muktuk) is consumed and the tusks are sold and are quite valuable (DFO 1998b, a).
Throughout the Arctic, narwhals prefer deep or offshore waters (Hay and Mansfield 1989). During winter, Canadian narwhals can be predictably found in the winter pack ice of Davis Strait and Baffin Bay along the continental slope. These areas contain ecological parameters that make this habitat favorable including high gradients in bottom temperatures, predictable open water (< 5%) and relatively high densities of Greenland halibut (Laidre, et al. 2004). During the winter, intense benthic feeding occurs in contrast to lower feeding activity during the summer, and therefore may be considered the most important habitat for narwhals (Laidre and Heide-Jorgensen 2005).
Critical physical and biotic habitat factors for narwhals include dense annual pack-ice, shear zone/leads, shelf break, deep ocean basins, estuaries/lagoons/fjords. Important areas to narwhals include open-water and the interface between open-water and pack-ice. Narwhals are also known to use loose annual pack-ice (Laidre, et al. 2008). Areas not categorized as important, or used, by narwhals include shore-fast ice, multi-year pack ice, polynyas, shallow water/continental shelf, pack ice and continental shelf interactions and polynya and shallow-water interactions (Laidre, et al. 2008).
Threats to narwhals include ice entrapment, predation by killer whales and polar bears, disease and parasites, climate change, environmental contaminants, offshore oil and gas activities, shipping, hunting and commercial fisheries (COSEWIC 2004b; Huntington in press).
Susceptibility to Oil and Gas Activities
Environmental contamination could disrupt biological functions, offshore oil and gas exploration may deter animals from preferred habitat, migration routes and increase the risk of oil spills, shipping may also disrupt migration patterns, hunting could deplete stock sizes and commercial fisheries may alter food webs by reducing available prey (Huntington in press).
Increased land development along the coast may cause negative effects on narwhals. Potential increases in shipping and offshore oil and gas development may induce temporary or long term changes in habitat, distribution and migration (Richard 2001; Huntington in press).
Increased vessel traffic and offshore oil development may also negatively affect the narwhal populations through habitat displacement and/or ship strikes (though strikes are less likely with fast moving whales such as the narwhal). Behavioural studies of narwhal reaction suggest narwhals "freeze"(seek shallow water and remain immobile) when approached by vessels (Finley and Evans 1983; COSEWIC 2004c). As well, some Inuit hunters suggest that narwhals are sensitive to and avoid noise from industrial machines and explosions (COSEWIC 2004c).
Potential Effects of Climate Change
Due to their strong association with ice, climate change may induce changes in habitat, migration pattern and predation rates. Changes in primary productivity may alter the location of prey and may cause the occupation of new feeding areas (Moore and Huntington 2008). Narwhals follow ice edges during migration and changes in the timing of ice break-up and freezing may alter their seasonal migratory cycle (Moore and Huntington 2008). Changes in extent and duration of sea-ice has resulted in increased killer whale presence in Nunavut (Laidre, et al. 2006). Due to their predation on narwhals, it is likely that if this trend continues, more narwhals will be killed by killer whales. Such climate changes could also decrease shelter habitat, thus elevating predation risk by killer whales, polar bears, hunters and exposing them to a rough ocean environment of Baffin Bay (Moore and Huntington 2008).
According to Laidre, et al. (2008), narwhals appear to be one of the three most sensitive Arctic marine mammal species most sensitive to climate change (primarily based on their reliance on sea ice and specialized feeding).
Sensitivity rankings for narwhal habitat in the High Arctic study area were developed using two primary types of information: i) known and likely range/distribution of this species (as determined from available literature sources [e.g., COSEWIC status reports]; and ii) ecological sensitivity described recently by Laidre, et al. 2008. Hence, application of the ecological sensitivity components included by Laidre, et al. 2008 may not always be consistent with known locations of narwhal habitat. For example, COSEWIC (2004) states that narwhals are likely found as far north and west (within the Canadian high Arctic region) as ice conditions permit. Thirty year median ice charts, produced by the Canadian Ice Service, were used in applying the ecological sensitivities (as described by Laidre, et al. 2008, and others) and known ice distribution. Lastly, a maximum sensitivity approach was used in differentiating between narwhal habitat types. In other words, if an area could be considered as having two different sensitivity rankings (for one or more months), only the highest sensitivity ranking was mapped. Two sensitivity maps for narwhals in the High Arctic study area were developed: Figure 4.4 for winter and Figure 4.5 for summer.
High Sensitivity (5)
Areas identified as highly sensitive for toothed whales includes areas designated as critical for narwhals and a spatially limited area (< 100 km2) during the summer months that provides specific ecological function essential to narwhals. In the winter months this rating was also given to that provide core overwintering habitat or where very large concentrations of narwhals are known to occur.
Highly sensitive summer or winter narwhal habitat was not identified within the high Arctic study area.
Moderate/High Sensitivity (4)
Areas with moderate to high sensitivity in the summer includes habitat with loose or dense annual pack ice, shear-zone/leads, fjords, shelf-break, or deep ocean basins. In winter, areas where large concentrations of narwhal are known to occur are considered moderately to highly sensitive.
Moderate to highly sensitive summer narwhal habitat was identified primarily for those regions of loose pack ice in July – September. These regions include waters near King Christian Island and Penny Strait; as well as south of Prince Patrick and Melville Island (though narwhals have not been observed in these last two western regions). No moderate to highly sensitive narwhal habitat was identified in the High Arctic study area.
Moderate Sensitivity (3)
Moderate sensitivity during the summer months was given to areas of open water, shelf-break, and the ice-edge (pack ice next to open water). This rating would also apply to areas that contain moderate to large numbers of narwhals. Moderate sensitivity during the winter months was given to areas that contain low to moderate sized concentrations of narwhal, deep water, the shear zone, or leads and polynyas. Moderately sensitive narwhal summer habitat was described primarily to capture the ice edge (pack ice next to open water) region of Queens Channel north of Cornwallis Island. Narwhal have been sighted in this region. According to 30 year median ice charts, leads in November are likely to be present in Penny Strait, Queens Channel, Austin Channel and Cardigan Strait as identified in Figure 4.4, hence some narwhals may use this moderately sensitive habitat in relation to their fall/winter migration out of the Canadian Arctic archipelago.
Low/Moderate Sensitivity (2)
Multiyear pack ice in summer and open-water habitat (>20 km from pack ice or land-fast ice or ice edge) in winter is considered low to moderately sensitive habitat for narwhal. This sensitivity rating also applies to areas with low densities of toothed whales and areas of multiyear pack ice in winter.
Much of the southern region of the High Arctic study area contains multi-year ice and hence is considered as low to moderately sensitive habitat. No records of narwhal in this region were located however 30 year median ice charts suggest summer open water habitat is common and therefore narwhals may occur in the areas identified in Figure 4.5. Winter narwhal habitat of low/moderate sensitivity was not identified in the High Arctic study area.
Low Sensitivity (1)
Low sensitivity habitat includes areas where no narwhal habitat is identified, offshore (> 100km) regions in the open water (summer) season, deep water (non-shelf break), and open-water habitat or winter regions of consistent very dense ice concentration and land-fast ice.
Multi-year pack ice and 100% ice concentrations are expected to be more common and consistent in the northern region of the High Arctic study area; hence narwhal presence during this summer here is less likely. In the winter, the majority of the High Arctic study contains dense concentrations of ice and narwhal habitat sensitivity here was ranked as low.
The most effective available mitigation tool to avoid potential effects to marine mammals is planning which can notably assist in avoiding sensitive spatial and seasonal narwhal habitat. Unfortunately, in the Canadian Arctic, knowledge on sensitive, and biologically important habitat, is at a very coarse level (commensurate with few, and often older, studies). Implementation of dedicated surveys for these animals prior to potential contact with industry will assist proponents and government to more confidently plan and approve project implementation. Other common, minimum standard, mitigations regarding seismic testing are outlined in the Canadian Statement of Practice with respect to the Mitigation of Seismic Sound in the Marine Environment (DFO 2010, internet site). This document outlines such measures as the use of dedicated Marine Mammal Observers aboard related vessels, designation of a marine mammal exclusion zone around active seismic arrays, soft-starts (ramp-ups) and use of Passive Acoustic Monitoring. Vessel speed restrictions and minimum aircraft altitude restrictions are also common best practices with regard to minimizing the potential for mammal – vessel strikes and disturbance.
ReferencesSee references used for Narwhal information.
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