Sei: A whale of the past?

Jun 3, 2013

Will we ever see the return of the sei whale (Balaenoptera borealis) to BC?  The name now seems foreign to most whale watchers, naturalists, and scientists on our coast. Even the most seasoned mariners in BC are apt to say they’ve never heard of a sei, let alone seen one in recent history.  This wasn’t always the case– sei whales may even have once been one of the most abundant baleen whales off our coast.  So what happened?

Sei (pronounced ‘say’) is an anglicized version of “sejhval”, which was the common name given by Norwegian whalers because the species arrival in Scandinavian waters coincided with the “seje”, or pollock. Sleek, streamlined and measuring upwards of 15m in the North Pacific, sei whales are one of the fastest whales in the world, often bursting at speeds upwards of 50 km/hr.   Sei whales, like blue, fin, and minke whales, are balaenopterids– baleen whales with heavily pleated throats.  The pleats are perfectly suited to gulp large amounts of zooplankton and small schooling fish.

As with many of the great whale species, the decimation of sei whale populations in the Pacific is directly related to commercial whaling.  Sei whales were targeted primarily after 1950, when other larger or easier to catch whale populations were already depleted.  On our coast, at least 4,002 sei whales were taken by coastal whaling stations in British Columbia between 1908 and 1967, with the majority taken after 1955 (Gregr 2000).  While whaling ceased on British Columbia in 1967, it continued in the greater North Pacific until 1976.  A total of 62,550 sei whales were taken in the North Pacific, with peak catch of 25,000 animals annually in the late 1960s (IWC).

While other heavily persecuted large whales appear to be making a comeback (see here, here, and here),   sei whales continue to be notably absent from our coast.  Despite ten years of dedicated ship surveys by Fisheries and Oceans Canada, none have been recorded during those efforts.  In the BC Cetacean Sightings Network database, there are only a handful of reports rated as ‘certain’.  In the United States, NOAA (the American equivalent of DFO) estimates that the eastern north Pacific stock (California-Oregon-Washington) may only be 35-55 animals.  However, a lack of information means that accurate estimates for our area are not currently available.  Regardless, it appears that the reduction caused by whaling was severe enough or recent enough (or both) to impede the type of  recovery seen in other species.

The lack of current information on sei whales may not just be a function of their low numbers, but also because they are easy to misidentify and they are typically found far from shore.  Sei whales closely resemble fin whales or even Bryde’s whales (although they are found further south) and are of similar size to both species.  Additionally, sei whales once occupied deep, open water habitats and did not regularly appear in shallow, coastal waters.  With less observer effort offshore, rare sei whale occurrences may go unrecorded.

So how would you know if you’ve seen a sei whale?  Seis, like most balaenopterid species are seasonal visitors, and in the past were seen primarily in the summer months (June-August).  While they may overlap in size with fin whales, sei whales do not have the asymmetrical white right jaw and ventral side that is diagnostic for fin whales.  Even though Bryde’s whales are not found in BC, the two whales can be differentiated by the number of ridges round running down the rostrum- Sei’s have one, while Bryde’s have three.  Other features include:

Colour: dark to bluish grey, often with many grey to white scars (from cookie cutter sharks and other parasites)

Dorsal fin: 1/4 to 2/3 metre high, strongly curved towards the back, situated less than 2/3 from the front of the body

Blow: up to 3 metres in height

Tail fluke: seldom arch tail high or expose flukes

For now, we can only hope the damage done by commercial whaling throughout the North Pacific may one day be reversed and we will again see sei whales off British Columbia.  Modern day threats such as prey depletion, ship strikes, and chemical and noise pollution may present further impediments to recovery.  Learn more about these and what you can do here. A new Action Plan for Blue, Fin, and Sei whales is currently being developed by Fisheries and Oceans Canada to help address the recovery of these species. Remember, if you think you’ve spotted a sei whale, take photos, record details, and report it to wildwhales.org

References and resources:

-Gregr, E.J., J. Calambokidis, L. Convey, J.K.B. Ford, R.I. Perry, L. Spaven, M. Zacharias. 2005. Proposed Recovery Strategy for Blue, Fin, and Sei Whales (Balaenoptera musculus, B. physalus, and B. borealis) in Pacific Canadian waters. Nanaimo: Fisheries and Oceans Canada. vi + 54 pp. (link)

-National Marine Fisheries Service. 2011. Final Recovery Plan for the Sei Whale (Balaenoptera borealis). National Marine Fisheries Service, Office of Protected Resources, Silver Spring, MD. 108 pp. (link)

-COSEWIC 2003. COSEWIC assessment and status report on the sei whale Balaenoptera borealis in Canada. Committee on the Status of Endangered Wildlife in Canada. Ottawa. vii + 27 pp. (link)

NOAA sei whale page

-An analysis of historic (1908-1967) whaling records from British Columbia, Canada. Gregr, E.J. 2000. MSc thesis, University of British Columbia, Vancouver, BC. 104 pages  (link)

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