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COSEWIC Assessment and Status Report on the Basking Shark (Pacific population) in Canada

Distribution

Global Range

Basking sharks are found circumglobally in temperate coastal shelf waters but are characterized by localized occurrences (Figure 2), occurring off the coast of fifty countries (Froese and Pauly 2005). In the North Atlantic, basking sharks are observed in waters off countries as far south and east as Senegal, through to Europe (including the Mediterranean Sea), Norway, Sweden, Russia, westward to Iceland, Canada (Newfoundland, Nova Scotia, New Brunswick), along the eastern seaboard of the United States and into the Gulf of Mexico. In the North Pacific, they are observed as far south and west as Japan, through to China, along the Aleutian Islands, Alaska, British Columbia, along the western seaboard of the United States and Mexico (Baja California and northern Gulf of California) (Compagno 2001). Basking sharks have not been observed in equatorial waters.


Figure 2: Global Distribution of Basking Sharks

Figure 2: Global distribution of basking sharks.

Dark grey areas represent known basking shark distribution and light grey areas represent possible distribution based on temperature preferences. Map source: Compagno 2001.


Canadian Range

The current distribution of basking shark in Canada’s Pacific waters is largely unknown. There have only been six reliable sightings on the Pacific coast since 1994 (two confirmed live sightings and four reported as bycatch) (Figure 3). Historical records dating back to the late 1700s have been used to identify several discrete bays and inlets where basking sharks were once regularly found (Table 1; Wallace and Gisborne 2006). Large aggregations of basking sharks were found repeatedly in three areas: (1) Rivers Inlet/Queen Charlotte Sound; (2) Clayoquot Sound; and (3) Barkley Sound (Figure 3). Unconfirmed or smaller groups have been observed historically in numerous other locations in the Strait of Georgia (Cape Lazo, Texada Island and Saanich Inlet) and off the southern banks of Vancouver Island (Table 1).


Figure 3: Known Occurrences of Basking Sharks off British Columbia Between 1996 and 2004 from Trawl Catches

Figure 3: Known occurrences of basking sharks off British Columbia between 1996 and 2004 from trawl catches.

(the PacHarTrawl database, n=4, circles denote individual weights) and opportunistic visual surface sightings (N = 2; stars). Location names (Queen Charlotte Sound, Rivers Inlet, Clayoquot Sound, and Barkley Sound) refer to areas with large historical aggregations of basking sharks.

Over the time period of three generations (66-99 years), basking sharks have all but disappeared from all areas where they were historically abundant. This disappearance cannot be attributed to a reduction in search effort. The three areas identified as historically most important are still used intensively by mariners. Moreover, the coastline of BC is increasingly well-travelled by tourism operators and recreational users. Being large and conspicuous at the surface, basking shark would certainly have been reported in other areas if the distribution of basking shark had merely shifted. The historical extent of occurrence in Pacific Canada includes the area of the continental shelf at depths <200m, an area of 80 000 km2. The current extent of occurrence is unknown but much reduced.

Table 1: Historical Sightings of Basking Sharks in British Columbia and Adjacent Waters Listed Alphabetically by Location
LocationYear# Sharks/CommentsSource
Alberni Canal1921Stopped vesselPort Alberni News, August 31, 1921
Astoria, Oregon19431- 2000 lb liverThe Fisherman, August 24, 1943, p. 2
Ballenas Island (light station)1956 Colonist, June 5, 1956 p. 13
Barkley Sound (many locations)1943-1969Many sharksMany sources (see Appendix 1)
Beaver Creek Wharf, North of Nanaimo1893“another lot of sharks”Colonist, July 30, 1916
Bowen Island19581Sun, August 29, 1958, p. 29
Brentwood Bay1952 Times Colonist, July 5, 1952, p. 11;
Brentwood Bay1956 Colonist, June 5, 1956, p. 13
Cape LazoLate 1990s1 (unconfirmed)Mark Saunders, Pacific Biological Station
Clayoquot Sound1973-1992 Summarized in Darling and Keogh (1994)
Cortes Island (Bliss Landing)19421-1600 lb liver -dogfish netThe Fisherman, September 8, 1942, p. 3
Eagle Crest, Van. Island1956 Colonist, June 5, 1956, p. 13
Esquimalt Harbour19591 (23’ long)Times, July 17, 1959, p. 27
Fitzhugh and QC sounds1955 Province, August 13, 1955, p. 20 (Mag. Sec.)
Gibsons (small island at the south end of Bowen Island)19581 (27’10”)Sun, September 11, 1958, p. 21
La Perouse Banks1935numerous sharksDepartment of Fisheries, File# 62-3-1, letter correspondence written April 15, 1935. 
La Perouse Banks1944 Province, June 16, 1944, p. 5
Ladysmith1952 Colonist, June 28, 1952, p. 13
Mistaken Island1956 Colonist, June 5, 1956, p. 13
Namu (see Rivers Inlet)1940-1948 Various
Neah Bay1868 Swan, James G. 1868. The Indians of Cape Flattery. p. 29
North Saanich (Cole Bay)19591 (not confirmed)Colonist, June 19, 1959, p. 21
Oak Bay1958Not confirmedTimes, August 5, 1958, p. 15
Pachena Bay195631 or 34 (single largest kill-April)Vancouver Sun, May 16, 1956
Parksville (Rathtrevor Beach)19481 (skeleton)Vancouver Sun, December 18, 1948, p. 23 (confirmed by J.L. Hart at PBS). 
Parksville (Rathtrevor Beach)1956 Colonist, June 5, 1956, p. 13
Parksville (Arbutus Point)19431 (18’ long)Fisheries Research Board of Canada Progress Report 56, p. 15 (1943)
Port Alberni19521 (15’ 2000 lb)Times Colonist, July 9, 1952, p. 9
Prince Rupert (Island Point)1937 / 19381The West Coast Fisherman, October 1990, p. 44-45
Qualicum1892;~100Colonist, July 30, 1916
Qualicum1946; Colonist, Nov. 8, 1946, p. 16
Qualicum1955;1Colonist, May 31, 1955, p. 24
Qualicum19561Colonist, June 5, 1956, p. 13
Queen Charlotte Sound (most likely Rivers Inlet area)1891plentifulNatural History Society of BC. 1891. The Economic Fishes of British Columbia. Vol. 1 No. 1 p. 20-33
Queen Charlotte Sound (most likely Rivers Inlet area)1897 Gosnell, R.E. 1897. Year book of BC
Rivers Inlet1915100s of sharks reportedProvince, July 15, 1915, p. 3
Rivers Inlet1940-1948 Numerous newspapers and fishing magazines (see Appendix 1)
Saanich Inlet --Tod Inlet1956
1 hit, 4 observed 1 (16.5’, 2500 lbs)Times, April 20, 1956, p. 6

Saanich Inlet --Tod Inlet1956 Colonist, August 9, 1956, p. 1
Saanich Inlet --Tod Inlet1957 Times, November 28, 1957, p. 23
Texada Island194712Province, June 7, 1947, p. 5
Uchucklesit Harbour (Barkley Sound)19488Times, July 17, 1948, p. 6
Ucluelet1946 West Coast Advocate, July 18 1946, p. 14
Ucluelet (4 miles offshore)1955 Colonist, September 9, 1955, p. 13