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.
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.
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.