Documenting giant bluefin tuna off the west coast of Canada - Part 1
Fisheries records show bluefin in California but not as far north as Vancouver Island
This essay in my ‘Discoveries’ series involves a scientific study of mine that was almost 20 years in the making. I’ve chosen it as my first Substack topic because Pacific bluefin tuna have recently been in the news. After more than a decade of worry about its long-term survival, an updated NOAA assessment released in June 2024 showed the species has made a remarkable recovery well ahead of schedule.1
My story involves one of my most satisfying scientific investigations – documenting the 5,000-year pursuit of giant bluefin tuna off the Northwest Coast of North America that mysteriously ended before the 20th century began. Bones of these enormous fish are routinely found in archaeological sites on western Vancouver Island and Aboriginal elders have stories, passed down through generations, of Nuu-chah-nulth hunters landing giant tuna with gear normally reserved for harpooning grey and humpback whales.
This was not an Aboriginal tuna fishery: giant tuna caught off the B.C. coast measured 6-8 feet long and were a formidable prey that required the most substantial hunting gear available.
The tale starts early in my career, over the winter of 1977-1978, when I was working at the Royal British Columbia Museum in Victoria. My job was to identify animal bones excavated from an archaeological site called Shoemaker Bay. The site was located on the west coast of Vancouver Island, near the present-day community of Port Alberni, which sits at the head of a huge fjord far inland from Barkley Sound.
In amongst one tray of bones was a vertebra that clearly came from a fish but was as large as a similar backbone element from a 1,200 pound sea lion. I could tell it was a bone from a fish because, among other clues, the vertebra was concave at each end, while those from a sea lion bone are virtually flat.
The museum had a collection of modern animal skeletons that I used to identify ancient bones from fish, birds, reptiles, amphibian, and mammals from the Eastern Pacific and Western Canada region. It included the bones of sea mammals like seals and dolphins, as well as land-dwelling animals like bears, deer, and beaver. The ancient animal bones I worked with were almost always isolated elements — a femur here, a vertebra there — that were often broken as well.
A lot of pattern recognition is required to identify a bone or bone fragment down to the genus and species it came from. In general, the bigger the animal, the larger the fragment needs to be to recognize with certainty what animal it represents.
In this instance, I had a complete bone. I found I could match the shape to a vertebra of an albacore tuna, whose scientific name is Thunnus alalunga. My bone was obviously a tuna — just not this kind of tuna! I needed one many times larger than the albacore in the collection.
Albacore do occur in the Eastern North Pacific but are relatively small fish that reach at most about 3 feet in length (~100 cm) and are only caught about 200 miles offshore. I not only needed a much larger tuna, but one that could be caught far closer to shore. That’s because ancient Nuu-chah-nulth people only had canoes made from hollowed-out cedar trees that couldn’t have safely navigated the open ocean.
By looking at the description of all the tuna species known to live in the Pacific, I guessed that this huge fish bone must have come from a bluefin tuna. And not just a bluefin, but a ‘giant’ bluefin near its maximum size.
The problem was that no giant Pacific bluefin had ever been definitely recorded in British Columbia waters, even though they had been caught occasionally off southern California since the 1800s.
‘Giant’ bluefin tuna are adult fish more than 4 years old and can reach a length of almost 10 feet (~ 3 m) in the Pacific and about 13 feet or more in the Atlantic (~4 m). The largest Atlantic bluefin can top the scales at about 2000 lbs (910 kg) but the heftiest Pacific giants weigh roughly half that much (1123 lbs/555 kgs).
The large size and torpedo shape of bluefin make them one of the fastest and strongest fish in the ocean.
When I started my investigation in the late 1970s, Atlantic and Pacific bluefin tuna were considered different geographic forms of the same species, otherwise known as subspecies. This meant that we had Thunnus thynnus orientalis in the Pacific and Thunnus thynnus thynnus in the Atlantic.
Oddly, I found nothing in the literature to explain why Atlantic bluefin were consistently able to reach such a remarkably larger size than the Pacific subspecies. However, it seemed to me that to consistently grow so much larger, the Atlantic subspecies must have a noticeably discrete growth pattern from the Pacific form, perhaps during early development, which in other animals creates enough distinctive features to get them classified as different species.
Eventually, that’s the conclusion other researchers have reached. Sometime around 2001, these two forms officially became classified as distinct species based on a new comprehensive analysis of their morphological and genetic differences, giving us Thunnus orientalis in the Pacific and Thunnus thynnus in the Atlantic.2
Since the 1950s, there has been increasing commercial demand for giant bluefin in response to the popularity in Japan for raw tuna used in sushi and sashimi. In 2021, the IUCN Red Book listed the Pacific species as ‘near threatened’ and the Atlantic form as ‘least concern.” In 2016, the lawsuit-happy Center for Biological Diversity tried to force the US to list Pacific bluefin as ‘threatened’ under the Endangered Species Act – claiming that 90% of the world catch of bluefin was under two years old and less than 3 ft. long – but a NOAA assessment report in 2017 rejected their petition.
Getting back to my ancient tuna bones, by the end of 1979, I had found 17 whole or fragments of vertebrae from similar sized fish in the Shoemake Bay assemblage. The fact that no very large individuals of any tuna species had ever been recorded in the Eastern Pacific this far north pushed me to be conservative in my identification: I tentatively recorded the specimens as bluefin with a note on the exceptional size and inconclusive identification, and left it at that.3
However, I soon found out that these weren’t the only ancient giant tuna bones that had been found on Vancouver Island. An astonishing 87 whole or fragmented elements from the head and backbone of very large tuna — not just vertebrae — had been reported from an archaeological site at an ancient village called Yuquot at the entrance to Nootka Sound that had been excavated in the 1960s. The descriptions of these bones suggested they were too large to be albacore.4
Remarkably, those Nootka Sound tuna remains date from about the late 1800s to about 5,000 years ago, suggesting an impressively long and continuous record of giant bluefin presence off Vancouver Island.
A year or so later, I found four similarly-large tuna vertebrae while identifying the bones from another Vancouver Island shell midden. This site was further north from the first one but located on the open coast, in a prominent bay called Hesquiat Harbour.
It seemed to me that this record of so many prehistoric giant bluefin specimens must be biologically significant, so I wrote to someone at the Inter-American Tropical Tuna Commission in California about the finds.
I never received a reply.
By then, it was late 1980 and I was pregnant. My curiosity about these bones was temporarily sidelined by the birth of the first of my two children and the subsequent attention they required.
But by 1991, I was working full time and the tuna issue popped up again. A colleague was working on bones from an ancient archaeological site in Haida Gwaii (formerly the Queen Charlotte Islands) — even further north along the B.C. coast than where the other tuna vertebrae had been found — and showed me a series of five vertebrae, found in their natural, articulated position, from a tuna as large as the ones I had identified from the two Vancouver Island sites in the late 1970s. Talking with other colleagues, I heard of several more vertebrae from very large tuna that had since been found up and down the B.C. coast.
I lost patience dealing with local biologists who told me these bones couldn’t possibly be from giant bluefin simply because there were no modern records. With the permission of the Haida Gwaii archaeologists, I packed up those five articulated vertebrae and sent them to Dr. Bruce Collette, the world’s most distinguished tuna expert, who worked at the Smithsonian (US National Museum of Natural History) in Washington D.C.
While I waited for a response, I talked to museum colleague Richard Inglis from the Ethnology Department about the giant tuna phenomenon. Richard had been helping several Nuu-chah-nulth elders from Nootka Sound record stories about their traditional ways of life, and he agreed to ask them about tuna during his next round of interviews.
I was determined to figure out the details of this phenomenon. And while most of my anthropology and archaeology colleagues were most interested in how and why ancient First Nations people were catching such large fish, I was interested in the big biological question hanging in the air.
If these were indeed giant bluefin, what the hell were they doing so far north in the Eastern Pacific for 5,000 years, and perhaps as recently as the late 1800s, when no one had seen them there since?
To be continued…
International Scientific Committee for Tuna and Tuna-like Species in the North-Pacific Ocean. (2024). Stock assessment of Pacific bluefin tuna in the Pacific Ocean in 2024. download pdf here.
Collette, B.B. 1999. Mackerels, molecules, and morphology. In: B. Seret and J.-Y. Sire (eds), Proceeding of the 5th Indo-Pacific Fish Conference, pp. 149-164. Noumea. [cited in Collette et al. 2021b]
Collette, B.B., Boustany, A., Fox, W., Graves, J., Juan Jorda, M. & Restrepo, V. 2021b. Thunnus thynnus. The IUCN Red List of Threatened Species 2021: e.T21860A46913402. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T21860A46913402.en. Accessed on 27 February 2024. https://www.iucnredlist.org/species/21860/46913402
Collette, B.B., Boustany, A., Fox, W., Graves, J., Juan Jorda, M. & Restrepo, V. 2021a. Thunnus orientalis. The IUCN Red List of Threatened Species 2021: e.T170341A170087840. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T170341A170087840.en. Accessed on 27 February 2024. https://www.iucnredlist.org/species/170341/170087840
Calvert, S.G, and Crockford, S.J. (1982). Appendix IV. In A.D. McMillan and D.E. St. Claire (eds.) Alberni Prehistory: Archaeological and Ethnographic Investigations on Western Vancouver Island, Theytus Books, Penticton, p.174-219. Download pdf here.
McMillan, A.D. (1979). Archaeological evidence for aboriginal tuna fishing on western Vancouver Island. Syesis 12, 117-119.