Southern Resident Killer Whales – What’s Going On?

Southern Resident Killer Whales (SRKW) have been in the news a lot lately (well the scientific and environmental news). A pregnant female washed up dead on a beach in British Colombia at the beginning of December and even more tragically was pregnant at the time which, has brought them further into the public eye.

All the SRKW belong to one clan – or “extended family” – therefore they are all related. This clan – J Clan – is made up of three pods – J, K , and L – with 77 individuals of which, only 12 are reproductive females. Four individuals of the population were lost this year which is a big blow for this small clan.

The populations is struggling to recover their numbers back to a viable level and in this post I will discuss why.

Prey Availability

Chinook Salmon. Photo: NOAA.

Chinook Salmon. Photo: NOAA.

SRKW favour Chinook Salmon almost exclusively feeding on it. The problem is that Chinook salmon are struggling to spawn and their numbers are also dwindling due to unsuitable habitats to spawn in. This means that SRKW are facing a depleted prey source and nutritional stress.

Nutritional stress has been shown to affect Glucocorticoids (cortisol) and thyroid hormone in killer whales. Glucocorticoids affect glucose metabolism for a quick response to an immediate threat over a short time frame (indicator of a short term stress), while thyroid hormone lowers metabolism to conserve energy stores over a longer time frame (indicator of long term/sustained stress).

Chinook salmon decline has been caused by activities such as logging and road construction have reduced the habitat condition degrading, fragmenting and eliminating key areas. To turn around their decline river habitats need to be restored to encourage spawning of salmon. This includes the removal/modification of dams on streams and the improvement of water quality and flow.

This issue can be fixed and would be a positive for both the killer whales and local fishermen.

Historic Capture

SRKW captured in 1964 - UBC professor Pat McGeer administers penicillin to Moby Doll at Burrard Dry Dock in North Vancouver in July 1964.  Photo Supplied, Vince Penfold. Via www.nsnews.com

SRKW captured in 1964 – UBC professor Pat McGeer administers penicillin to Moby Doll at Burrard Dry Dock in North Vancouver in July 1964. Photo Supplied, Vince Penfold. Via www.nsnews.com

In the middle of the last century the SRKW populations took a large hit when many members and sometimes whole families were removed in the live-capture industry.
Individuals/groups were removed to be put on display. With the removal of whole family groups the structure and populations numbers were severely disrupted. The SRKW were the most affected populations with 36 whales collected and at least 11 dying. There is nothing we can do now to correct this however there is a ban on the removal of all individuals in North America.

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The Vanishing Vaquita

The worlds smallest cetacean (reaching lengths of only 4-5 ft.) and limited to a small home range in Baja, California is in dire straits. The vaquita (Phocoena sinus) is a notoriously shy and difficult to study therefore underwater acoustic technology has been utilised by the International Committee for the Recovery of the Vaquita to monitor their latest numbers. This study revealed their numbers have dwindled below 100 with an estimate 97 individuals of which only about 25 are reproductive females.

The Vaquita within their protected area. Photo: Paula Olson (NOAA Contractor) taken under permit (Oficio No. DR/488/08)

What is the cause of their decline?

Illegal gillnets fisheries put this species as risk of by-catch and with there numbers so small even the loss of one individuals has detrimental effects on the population as a whole.

The totoaba (Totoaba macdonaldi), a marine fish also indigenous to the region, is the target of the gillnet fisheries. At up to 6 feet in length they are a smilier size to the vaquita. The totoaba is a valued catch as its swim bladder is highly prized in Traditional Chinese Medicine (TCM), meaning that an individual catch can go for thousands of dollars. The high price it fetches at market means that regulations to ban commercials gill net fisheries in key vaquita habitat have been compromised. I think this quote from Lorenzo Rojas-Bracho (Coordinator of Marine Mammal Research and Conservation at the National Institute of Ecology, in Ensenda, Baja California, Mexico) really hits the nail on the head in regards to why fishers are finding it hard to resist fishing for totoaba:

“It’s like trying to control traffic while someone’s throwing money from the Empire State Building,”

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