Abstract

Very little is known about the distribution, abundance and stock structure of many species of marine mammals inhabiting remote regions of the northern British Columbia coastline, primarily because of the logistical and fiscal constraints associated with surveying this area. Freighter canoes, originally used by aboriginal peoples and Hudson Bay Company trappers and traders to transport people and goods over long distances, can provide a low cost and logistically simple method of surveying these remote waters and studying the marine mammals that inhabit them. Surveys conducted by freighter canoes during August 2003 in the inshore waters of the Hecate Strait region produced 13 separate sightings of 107 individual marine mammals. Seven different species were identified, one mustelid species: river otters (Lutra canadensis); two pinniped species: Steller sea lions (Eumatopias jubatus) and harbour seals (Phoca vitulina richardsii) and 4 cetacean species: harbour porpoises (Phocoena phocoena), Dall’s porpoises (Phocoenoides dalli), killer whales (Orcinus orca) and humpback whales (Megaptera noveaengliae). Sightings generated by freighter canoe survey were compared with opportunistic sightings for the same region generated by volunteers and logged by the British Columbia Cetacean Sightings Network (summer months, 1999 through 2001, n=84, 6 species recorded). These comparisons reveal general distributional patterns for some species and high sighting rates for humpback whales in the southern inshore waters of our study area. These results indicate that the waters of Estevan Sound, Wright Sound and Squally Channel may be a previously unidentified summer feeding ground for humpback whales, a species designated as threatened in the waters of British Columbia by the Committee on the Status of Endangered Wildlife in Canada.

Funding Statement

Introduction

The northern coast of British Columbia (B.C.) is considered a relatively remote region, bordered to the east by the extensive and largely uninhabited Coastal Range mountains and seaward by the open pacific or the waters of Hecate Strait². A combination of plate tectonics, glacial scouring and isotonic changes in sea level due to glacial retreat has fractured the coastline of the Hecate Depression into large numbers of channels, inlets and small to medium sized islands¹. Increased mixing due to strong tidal currents over variable bathymetry and through narrow channels, along with freshwater input from several large rivers that drain into this area (e.g. Skeena River) produce oceanographic conditions (see Thomson 1981 for a review of the physical oceanography of this region) likely make the waters in this region relatively productive habitat for many species of fishes and their marine predators.

Twenty four species of marine mammals (whales, pinnipeds and otters) are known to inhabit the British Columbia coastal zone – on a permanent or seasonal basis (Osborne et al. 1988; Shore 1999) – including both coastal ecotypes of killer whales (Orcinus orca), humpback whales (Megaptera novaengliae), fin whales (Balaenoptera physalus), minke whales (Balaenoptera acutorostrata), grey whales (Eschrichtius robustus), Dall’s porpoises (Phocoenoides dalli), harbour porpoises (Phocoena phocoena), Pacific white-sided dolphins (Lagenorhynchus obscurus), harbour seals (Phoca vitulina) and Steller sea lions (Eumetopias jubatus), yet very little is known about the seasonal distribution, stock structure and abundance of many of these species in the northern portions of the B.C. coastline . Several of these species are listed nationally (by the Committee on the Status of Endangered Wildlife in Canada, or COSEWIC), or internationally (e.g. the World conservation Unions Red List of Endangered Species) as species at risk. For example, humpback whales were depleted through commercial whaling in the North pacific (Gregr et al. 2000) and are currently listed as a threatened species in Pacific waters by COSEWIC (Whitehead 1987 – status reconfirmed in May 2003).

To date, little effort has been directed to surveying the distribution of marine mammals in this region because of its rugged and remote setting, the large costs of transportation to and within the region and the lack of logistical support (e.g. stores, accommodation etc.) present there. However, a good understanding of how and when marine mammals use remote regions of B.C. – including Hecate Strait and adjacent waters – is becoming increasingly important. For example, there is growing interest to develop portions of Hecate Strait for gas and oil production (Anonymous 2003) and such development poses unquantified risks for marine mammals inhabiting the region on a seasonal or permanent basis.

Despite the modern viewpoint of “remoteness” for this region, it has been inhabited and its waterways traversed by many people in both prehistoric and historic times, with almost all transportation of goods and people occurring by sea (see Glavin 2000 for a review of the prehistory and early history of sea travel by humans in the Pacific Northwest). Of particular importance for travel was the freighter canoe, which is a large (7 to 10m) and efficient hull that is sea kindly, capable of carrying a large load, and can get on, and off, an exposed beach under most tidal conditions. Large canoes were at one time the standard form of transport on the B.C. coast, and similar canoes allowed the Hudson’s Bay Company to have trade routes across Canada, using the extensive network of rivers and lakes as highways. They have, until very recently, been the standard form of transport in the Arctic and in Hudson’s Bay. Historically, the cargo manifest for a “4 1/2 fathom” fur trade canoe would list approximately 2 tonnes of cargo plus paddlers and gear (Adney & Chapelle 1964). These canoes offer unique benefits as working boats: they are rugged and relatively cheap to charter, buy, build and repair, they allow extended range of travel in exposed areas where there are few if any anchorages, and are light enough to get off the water when the weather deteriorates. They also allow departure from any road access to start a trip.

This paper presents the results of an initial survey of marine mammal distribution during July 2003 in the inshore waters of a remote section of the Hecate Strait coastline of B.C. using two 7m freighter canoes as experimental survey/research platforms. Furthermore, we supplement our data with sightings generated during 1999 to 2001 in the same region by the British Columbia Cetacean Sighting Network (BCCSN) to provide a basic outline of how cetaceans may utilize this portion of the northern coast of British Columbia during the summer months.

Methods

Survey Area

Surveys were conducted from July 21 through July 28 2003 in portions of Edye Passage, Hecate Strait, Otter Passage, Estevan Sound and Grenville Channel, between Porcher Island in the north and Campania Island in the south. The study area, bounded on the northwest at N 54.21, W 130.91 and at the southwest at N 53.10, W 129.11 is presented in figure 1A

Freighter Canoes

We employed two freighter canoes based on the design of a “4 1/2 fathom North canoe”. The lines are from a pattern of the type built by Cree Indians for carrying cargo for the Hudson’s Bay Company (Adney & Chapelle 1964) but are very similar dimensions to the commercially available freighter canoes of that size that were once available. The construction is of steam bent yellow cedar ribs and planking with a layered Dacron™ fabric cover. Each canoe is 7m long, 1.7m wide, 0.66m deep, 1m at the stem, and weighs 110 kg. Both canoes were powered by small 2 stroke outboard engines (15&20hp) with a top cruising speed of approximately 27km h^-1. Each canoe carried gear, fuel and provisions for 2 to 3 people. Canoes were rolled up and down campsite shorelines using 2 or 4 lightweight pneumatic tires (Roleez Wheels, Inc. 3890 Industrial Way Benicia, CA 94510, USA) on cedar/aluminum axels.

Survey Methods

Surveys were conducted during daylight hours in sea states of Beaufort 2 or less. Global Positioning System (GPS) devices (Garmin eTrex, Garmin International Inc. 1200 E. 151st Street Olathe, KS 66062) were used to record the movement of boats and the position of marine mammals sighted during scans. One or two observers in each canoe continually scanned waters while underway, scanning for a maximum of 3 hours interspersed with short breaks. At least one experienced observer (familiar with common species of B.C. marine mammals) was present in each canoe. Average cruising speed for surveys was 17 km h^-1. Details of survey effort and locations of shore stations are presented in Figure 1B. Marine mammals were identified to species using a combination of blow characteristics, morphometric features, behavioural clues and pigmentation patterns. On some occasions boat tracks deviated from survey tracks towards sighted marine mammals (complying with current marine mammal viewing regulations) to insure proper identification and to record obvious surface behaviours. On two occasions marine mammals were sighted from shore camps and their positions estimated using marine charts for the area. All sightings used in this analysis were confirmed by the crew of both canoes.

Survey Data Treatment

Effort data and marine mammal sightings were incorporated into a Geographic Information Systems (GIS) database for display in the ArcMap software package (ESRI, 380 New York Street Redlands, CA 92373-8100) and projected with a British Columbia specific Albers Equal Area Conic projection. Coastline data (1:20 000 scale) for the region were obtained from British Columbia’s Ministry of Sustainable Resource Management TRIM Watershed Atlas (available on the web at http://srmwww.gov.bc.ca/gis/arcftp.html).

British Columbia Cetacean Sightings Network Data

In 1999, the BCCSN was established to collect and compile reports of whales, dolphins and porpoises submitted by the public. Data are reported to the network via regular mail, email, a web-based interface, or logbooks kept by active mariners. The BCCSN database was queried for all cetacean sightings during May through September located between 52.5 N and 54.5 N. These data represent sightings recorded by lighthouse keepers, crew on commercial and recreational vessels, researchers, whale watch tour operators and other professional and amateur naturalist sightings during the years 1999 to 2001. These data were imported into ArcMap and projected as described above.

Results

Survey effort and platform performance

During the 7 days of appropriate survey weather, a total of 387km were surveyed representing approximately 22 hrs of sighting effort. The freighter canoes performed well for a small survey platform, with seated observers roughly 0.75 m above the waterline. Both canoes were stable enough to have one observer standing in the canoe during surveys (1.5m above waterline). The rugged coastline offered few options for accessing the shore for camping; however 6 camps were made on sand or pebble beaches that were acceptable for landing by canoe. Canoes were easily unloaded and rolled above the high water line at each campsite.

Freighter canoe surveys for marine mammals

Thirteen separate sightings of 107 individual marine mammals were recorded. Seven different species of marine mammals were identified, one mustelid species: river otters (Lutra canadensis); two pinniped species: Steller sea lions (Eumatopias jubatus) and harbour seals (Phoca vitulina richardsii) and four cetacean species: harbour porpoises (Phocoena phocoena), Dall’s porpoise (Phocoenoides dalli), killer whales (Orcinus orca) and humpback whales (Megaptera noveaengliae). A summary of sighting data for freighter canoe surveys is presented in Table 1. Sighting rates for marine mammals were generally low (Table 1), with the exception of humpbacks in the southern portion of our study area; when analysed separately, sighting rates for humpbacks in the southern region were 2.1 individuals per hour. Group sizes for pinnipeds sighted ranged from 5 to 35 individuals while groups sizes of cetaceans sighted were smaller, ranging from 1 to 5 individuals. Sightings of Steller sea lions were restricted to the offshore portions of our survey – in the vicinity of Bonilla Island – while harbour seal sightings were restricted to the inshore, sheltered sections of our survey area. Pinnipeds were hauled out on rocks when initially sighted, although some were subsequently spotted in nearby waters. We identified both male and female Steller sea lions (based on sexual dimorphism in body morphology – see Reeves et al. 2002) and pups. Porpoises (Dall’s and harbour) were seen in the northern and southern sections of the study area, within or at the entrance of restricted channels or sounds. One sighting of harbour porpoises consisted of a single mother/calf pair. Humpback whale sightings were restricted to the southern portion of our study area, within Estevan Sound, Wright Sound and Squally Channel. Humpbacks were initially sighted by blows or by surface active behaviours including breaching, tail and flipper slapping. On one occasion in Otter Passage, a humpback whale defecated approximately 200m from the canoes, just before a terminal dive. Whale feces were not collected. A single sighting of killer whales occurred within the northern portion of the study area and consisted of two individuals, one adult male and one adult female. The locations and group sizes for all marine mammal sightings during freighter canoe surveys are presented in Figure 1B.

British Columbia Cetacean Sightings Network Data

Database queries resulted in 84 reports of approximately 244 individual cetaceans for the study area. These sightings were comprised of 6 species of cetaceans: Dall’s porpoise, harbour porpoise, Pacific white-sided dolphins, killer whales, humpback whales and minke whales. Humpback whales were the most frequently reported cetacean, and all reportss but one were restricted to southern waters of our survey area. Many humpback reports occurred to the west of our study area, in Douglas Channel. Dall’s porpoises, harbour porpoises and killer whales were reported thoughout the study area, but most sightings occur enclosed sounds or bays and within restricted passages. As with humpbacks, there were many killer whale reports west of our survey region, in the restricted waters of Douglas Channel. One group of pacific white-sided dolphins was sighted within our study area (along the eastern shore of Banks Island) and one minke whale was sighted near Bonilla Island in Hecate Strait. A summary of species sighted and group size is presented in Table 2 and locations and group sizes of all sightings are presented in Figure 2.

Discussion

Freighter canoes as research/survey platforms.

Very few systematic surveys for marine mammals in this area exist, a notable exception being a long term aerial survey study of harbour seals on the B.C. coastline (Olesiuk 1999). We found that freighter canoes performed well as working boats for accessing remote regions and for conducting simple surveys for marine mammals in an efficient and cost effective manner. We accessed shore camps throughout the survey route which other forms of transportation could not (e.g. rigid powerboats) and our surveys covered an area much larger than most human powered craft (e.g. kayaks) could in the same time frame. Both canoes exhibited excess room for gear, and we could easily carry portable oceanographic equipment (e.g. Falmouth Scientific’s “Mini –CTD” conductivity temperature depth probe and winch) and equip canoes with depth sounders for collecting bathymetric and prey presence/absence data. These canoes are stable enough in the water to be useful platforms for photo-identification work or for biopsy cruises where a solid platform is required for researchers to stand and orient towards study animals. Freighter canoes represent a low-tech and innovative solution to the lack of infrastructure and financial support available for conducting marine mammal surveys.

There are also many shortcomings to using freighter canoes as research vessels. Clearly these watercraft do not represent an optimal platform for conducting proper line transect surveys to generate true density estimates for marine mammals (see Buckland et al. 1993 for details on line transect sampling procedures), and our surveys were not intended to generate such numbers. One problem for surveys is, for example, the observer’s height above waterline (0.5 to 1.5m, depending if sitting or standing). This is not high enough to see smaller marine mammals (e.g. both porpoise species) at any great distance from the trackline. Considering this, the strip width sampled by freighter canoe is small and future canoe surveys designed to estimate the abundance of animals in these areas will require greater at-sea time. Also, small survey platforms may also elicit significant amounts of responsive movement from nearby marine mammals. For example, some species are attracted to small boats (e.g. Dall’s porpoise – see Hobbs & Lerczak 1993) while others avoid them (e.g. harbour porpoises – see Polacheck & Thorpe 1990) both of which can greatly effect encounter rates and, subsequently abundance estimates derived from such surveys (Palka & Hammond 2001). Our surveys were also not designed specifically to study pinnipeds. We also likely missed many haulouts, especially when tracklines were not adjacent to shorelines or islands. Future surveys for seals or sea lions in such craft could focus effort closer to shore to enumerate and study pinnipeds. Since much of our survey effort was restricted to calm, enclosed waters, we feel it was unlikely that many groups of larger whales went undetected during periods where observers were on effort. While freighter canoes are sea-worthy boats capable of handling rough conditions, they are best suited as research vessels to inshore, protected waters.

Marine mammals and the northern B.C.coastline

Of the 24 species of marine mammals known to inhabit B.C. waters, we sighted 7 species during our experimental surveys. Although our sighting rates for most species were relatively low, the sighting rates for humpbacks were quite high in the southern portion of our study area when analysed separately. While limited, our survey results represent some of the first directed marine mammal survey data for this region, and confirm the distributions of some species derived from opportunistic data collected by the B.C. Cetacean Sightings Network. These results are important because they contribute to our knowledge of several marine mammal species at risk in B.C. waters. The Hecate Strait region is also a recent focus of interest for offshore gas and oil production (Anonymous 2003). Considering this, our results can help develop an understanding of the importance of these areas to marine mammals and are useful for assessing the risk posed by such development on their populations in local and adjacent waters. For example, at least one species sighted in our surveys (humpback whales) are sensitive to seismic surveys associated with oil and gas development (Richardson et al. 1995).

We sighted a group of 12 rivers otters in Lowe Inlet north off Grenville Channel. All otters were spotted simultaneously moving down towards the water along the edge of a waterfall at the head of the bay (Locally known as Verney Falls). While not technically classified as a marine mammal, river otters in B.C. often use nearshore oceanic waters for foraging (Osborne et al. 1988) and these animals were likely foraging on an abundant salmon run present in the inlet. They are commonly seen throughout coastal B.C., and little is understood about movement patterns or breeding. The best estimate for abundance is between 15,000 and 30,000 individuals for the entire B.C. coast (Mos et al. 2003).

Our sightings of Steller sea lions were restricted to the eastern edge of Hecate Strait, near Bonilla Island. This finding is similar to data presented by Bigg (1988) which indicated that a large breeding colony of Steller’s sea lions was located at Danger Rocks, south and west of our sighting location. The most recent status assessment for Steller sea lions in Canada (Bigg 1988) suggest that their numbers are stable or growing in B.C. waters and our sighting may represent spill over from population growth at the rookery at Danger Rocks, or may simply be a transient or previously unrecorded rookery. Harbour seals were among the most numerous marine mammals sighted during our surveys, and their numbers also appear to be increasing in B.C. waters (Baird 2001; Olesiuk 1999). Olesiuk (1999) appears to be the only survey for pinnipeds in the northern coastline of B.C. and the survey region for seal haulouts in that study was restricted to waters proximate to the mouth of the Skeena River, and therefore did not cover portions of the region in our survey.

Harbour porpoises were sighted within or at the entrance of restricted channels or sounds during our surveys, in particular in Edye Passage, and off the Terror point, a southern headland of Banks Island (Figure 1). These results are similar to porpoise sightings from the B.C. Cetacean Sightings Network database, where porpoises were sighted in a narrow passage north of Pitt Island, and near Digby Island, Kaien Island and Ridley Island (Figure 2).

Strong tidal flow past small islands, headlands and over variable bathymetry produces a variety of fine scale upwellings and fronts (Geyer 1993; Mann & Lazier 1996; Signell & Geyer 1991). In the Bay of Fundy, these types of oceanographic conditions are known to attract large numbers of harbour porpoises, presumably because they facilitate foraging by predictably aggregating or attracting large volumes of prey (Gaskin 1983; Smith et al. 1984). Similar conditions occur in the Haro Strait region in southern B.C./northern Washington State (Farmer et al. 1995), where porpoise are also frequently sighted (Calambokidis et al. 1993) and in the Broughten Archipelago where porpoises are frequently seen (Olesiuk et al. 2002). The convoluted inshore waters of the Hecate Strait region also experience large tidal flows (Thomson 1981) and both Dall’s and harbour porpoises may aggregate in narrow channels or near headlands that produce similar oceanographic features to facilitate foraging efforts. Very little is known about harbour porpoise abundance and distribution in northern B.C. waters, although the most recent abundance estimate for porpoises in southeast Alaska (which are considered the same population for management purposes – see Rosel et al. 1995), from Dixon Entrance to Cape Suckling and out to the 1,800m (1,000 fathom) depth contour is 3,550 individuals.

While little is known about the reproductive schedule and seasonality of harbour porpoises in B.C. waters, our sighting of a mother-calf pair of harbour porpoises is consistent with the life history of porpoises in U.S Pacific waters. Porpoises in mid-California reach sexual maturity after three to four years and tend to produce a single calf every two years – in contrast with porpoises in eastern Canadian/U.S. waters which produce a single calf yearly (Read & Hohn 1995) – and usually give birth in May/June (Bjorge & Tolley 2002). Considering this, our sighting likely represented a young of the year calf and a mother of at least 3 years in age. There is some evidence that porpoises in the Bay of Fundy and elsewhere in the North Atlantic use areas with sheltered bays amongst islands as nursery areas (Gaskin & Watson 1985; Sonntag et al. 1999), and much of the region in our survey region may offer similar opportunities to raise calves.

Killer whales were only sighted once during our surveys, in the northern portion of our study area in the eastern end of Edye Passage (Figure 1). We could not positively identify the ecoytype of these whales, but they may have been transient killer whales due to their observed behaviour. For example, the animals were few in number, were traveling quickly along the contour of the shoreline, surfacing infrequently and disappeared from view rapidly, all typical observations for transient killer whales conducting near-shore foraging (Ford & Ellis 1999). Our study region is within the documented range of transient killer whales (Ford & Ellis 1999). Killer whales are a frequently reported species in the BCCSN database, most likely because they are familiar, large, strikingly pigmented and therefore easy to identify at sea. Our single sighting of two animals, and the BCCSN records used in the present analysis, indicate that almost all inshore waters of our study area is likely killer whale habitat. Details on matriline affiliations/ecotype were not recorded for any of the BCCSN sightings used in this analysis.

The cetaceans most frequently sighted during our surveys were humpback whales. Humpback whales in B.C. waters were hunted commercially by Canadian whalers and were also subject to hunting by coastal aboriginal peoples. In 1967, Canada ceased commercial whaling operations in the Pacific, and it appears that humpback whales had been depleted or extirpated in B.C. waters much earlier (Gregr et al. 2000). More recently however, humpbacks appear to be re-colonizing B.C. waters, with greater numbers of sightings off the northwestern shore of Graham Island in the Queen Charlottes, and in Johnstone Strait and adjacent waters (Personal Communication, Nicola Dedeluk, Straitwatch Program. Johnstone Strait Killer Whale Interpretive Centre Society, P.O. Box 2-3, Telegraph Cove, BC Canada V0N 3J0). Our surveys indicate that Estevan Sound, Wright Sound and Squally Channel may be important summer feeding habitat for humpbacks, and reports logged by the BCCSN also reveal the same pattern, with large numbers of sightings occurring in the same areas, along with large numbers of sightings in Whale Sound and farther up into the restricted waters of Douglas Channel (Figure 2). Humpbacks, like killer whales, are familiar and easy to identify at sea and this is most likely a contributing factor to the large number of sightings logged by the BCCSN.

Our results are consistent with predictions of critical habitat for humpbacks (based on spatial modeling of oceanographic variables and commercial whaling catch data) which indicate that humpbacks should have a tendency to use coastal waters during summer months, presumably for foraging (Gregr & Trites 2001). Our results are also consistent with previous commercial whaling observations of humpbacks in enclosed coastal waters of B.C. (Webb 1988) and in the coastal waters of southeast Alaska (Calambokidis et al. 2001). It is possible that a distinct sub-population of humpbacks once occurred in B.C. waters (Gregr et al. 2000) and there are some indications that humpbacks recently seen in northern B.C. may result from dispersal from feeding aggregations in waters of southeast Alaska (Gregr et al. 2000). The stock structure of humpbacks sighted during our surveys is unknown, but further research could confirm if they represent dispersed animals from other feeding aggregations or, more unlikely, the remnant of an unstudied distinct B.C. sub-population. Humpbacks feed on euphausiids and small schooling fish throughout their range (Reeves et al. 2002). Although we did not collect whale feces for analysis, the rich pink colour of feces indicated that this whale had recently been feeding on euphausiids.

Conclusions and limitations of data

The results of our surveys indicate that freighter canoes are a useful platform for low-cost research on marine mammals in remote locations. Our data, along with comparisons with data generated by the BCCSN, indicate that the inshore waters of the Hecate Strait region support a diverse community of marine mammals. While our data are limited, they do allow us insight into how marine mammals use portions of the northern B.C. coastline and represent the first directed effort to study most of these species in this remote region. As well, these data suggest that a previously unidentified summer feeding aggregation of humpback whales occurs in the waters of Estevan Sound, Wright Sound and Squally Channel.

Clearly these data are preliminary and do not represent estimates of the numbers or ranges of marine mammals using our study area. Much of the BCCSN data is not correctable for effort and was not collected by trained observers. This introduces an unknown level of uncertainty about encounter rates, sighting probability, species identification and estimations of group size, especially for cryptic species like harbour porpoises. For example, the majority of BCCSN harbour porpoise sightings occurred in waters just outside Prince Rupert harbour (Figure 2), where boat traffic (and, subsequently, volunteer sighting effort) is relatively large. It is likely that this concentration of effort results in greater encounter rates with porpoises and therefore more frequent sightings and identifications. This relationship, however, may not be true for easy to identify species such as killer whales and humpback whales. Recent analyses of the quality of volunteer and untrained observer data for terrestrial and marine mammal conservation studies suggest that such data are generally valid and useful for a variety of analyses (Fore et al. 2001; Newman et al. 2003; Tregenza et al. 1997) . While the reliability of volunteer data logged by the BCCSN has not been verified previously, the similarity between our relatively high sighting rates for humpbacks in the southern portion of the study area and the large number of humpback sightings generated by volunteers suggests that the BCCSN data may represent good approximations of the distributions of easy to identify marine mammals in the coastal waters of British Columbia, even where effort may be low.

Acknowledgements