Southern Residents Moving Out?
Southern Resident Killer Whale J16. Photo taken with zoom lens and heavily cropped. SpringTide Archive Photo.
  • August 13, 2019

The Southern Resident Killer Whales are spending less time in the Salish Sea… Is it no longer a favourite place?

The evidence is clear. Usually the Southern Resident Killer Whales will spend a good portion of the summer months doing a tour of the inland waters of the Salish Sea. Scientific research and years of observation show how important the Salish Sea is for Southern Resident Killer Whales to socialize, create new babies, and feast on salmon. That’s because their favourite food source, Chinook Salmon, has historically run up the many rivers that meet the ocean in the Salish Sea. Unfortunately, what we are seeing now is a decline in the number of days the Southern Residents spend in the Salish Sea. There is something going on, are the waters of the Salish Sea not as alluring as they once were?

Salmon abundance is in decline. Specifically, terminal run size, a measure of the number of salmon in the sea, has been declining. A graph published by the Orca Behaviour Institute illustrates the trend. The red line shows the declining number of salmon returning each year. Most interestingly, the decline in the number of days Southern Residents spend in the Salish Sea closely matches the declining salmon trend. The blue line shows the declining number of days the Southern Residents are spending in the Salish Sea.

Graph
Graph shows the yearly decline in days the Southern Resident Killer Whales spend in the Salish Sea. The decline in Chinook Salmon terminal run size declined over the same period. Graph courtesy of Orca Behaviour Institute.

We already know how much the Southern Residents rely on Chinook salmon from diet analysis (Ford and Ellis, 2006). The Orca Behaviour Institute graph shows that the reliance on Chinook Salmon affects whale behaviour. Southern Residents are adapting their behaviour. As the terminal run size decreases, the number of whale days also decreases. Southern Residents are searching for food elsewhere, abandoning the area that was once their core habitat in the summer months (Center for Whale Research). The question is, are they finding food elsewhere?

resident orcas
L pod calf L123 “Lazuli” breaching next to mom L103 “Lapis”. SpringTide Archive photo.

In the past, Southern Resident Killer Whales have used the Salish Sea as a home base in the summer months. It is considered their “core summer habitat” (Centre for Whale Research). Part of what makes the Salish Sea so critical is its role in connecting ecosystems. Particularly the Salish Sea, being an inland sea, connects land and ocean ecosystems. The interface between land and sea is important because there are so many rivers and streams connecting the sea to the land. The connection between the ocean and land via rivers is important in two ways:

First, the interface between salty ocean and freshwater streams and lakes is important. Salmon depend on access to both. Salmon are an anadromous species, meaning they spend part of their lives in saltwater ocean, migrating upstream to reproduce in freshwater. When the young fish have hatched and fed enough on river bugs, they then go into the ocean where they grow up and feed on the open ocean plankton. Once mature and ready to reproduce the salmon return to the rivers where they were born. They congregate at the entries to these rivers, making the Salish Sea a hub for salmon during the spawning season.

Second, the rivers that flow into the Salish Sea are a conveyor belt connecting land ecosystems to ocean ecosystems. Land ecosystems are a source of nutrients. Decaying material and minerals from the highest mountain tops make their way down rivers. The nutrients and minerals first contact the ocean in the Salish Sea. Those nutrients support abundant marine life that feeds many coastal animals like eagles, racoons, river otters, and even coastal wolves. These animals pull their food out of the ocean and return those nutrients to the land by leaving scat and scraps of food. The scat and food scraps decay returning nutrients back to the land-based ecosystems as fertilizer. The influx of nutrients from the land supports the salmon populations that Southern Residents depend on by providing the small invertebrates and fish that the adult salmon eat.

We can see why the Salish Sea would be a hotbed for salmon and the larger marine mammals that prey on those salmon. Because the fresh water and salt water interface is where the salmon meet up and the nutrients brought down by the rivers support the food at sea that the salmon need to grow strong. The concentration of river systems entering the Salish Sea makes it a hub where salmon to congregate before they spawn, a good place if you are hungry killer whale looking for a large salmon to munch on.

Map of the Salish Sea
Map of the Salish Sea & Surrounding Basin, Stefan Freelan, WWU, 2009

A salmon run is the name for the group of salmon returning to the rivers to spawn each year. A good run will have a lot of salmon returning. Salmon runs are low for many reasons. In some places changes to the river structure make it impossible for salmon to swim upstream and spawn (loss of pools and slower moving water, hydroelectric dams and other man made alterations). In addition, climate change can cause severe drought and higher temperatures. A stream with little water because of low snowfall and low rainfall, will heat quickly under warmer air temperatures. Young salmon may not survive in the warm or non-existent streams. Finally, pollutants can contaminate habitat and may be lethal for salmon, particularly when they are young. By the time young salmon get to the ocean there may be so few of them, they experience greater pressure from their predators. Killer whales, humans fishing, seals, sea lions, and other fish are all competing for the same salmon resource. There are not enough fish to go around. Therefore, the solution is to increase the number of fish.

Southern Resident Killer Whale
Male Southern Resident Killer Whale. SpringTide Archive Photo.

Where are the whales now?

As of July 1 2019, J17 Princess Angeline, K25 Scoter, & L84 Nyssa are presumed dead (Centre for Whale Research media release). The Southern Resident population is now down to 73. Repeated sightings of the pods have shown these individuals were missing from their family groups. Researchers have documented extreme weight loss in Southern Resident Killer Whales, and Southern Resident Killer Whales have had high mortality in years with low Chinook salmon abundance (Ford and others 2009).

The rest of the three Southern Resident Killer Whale pods were spotted off the coast of California in late March. They were further North near Tofino in July along with a new calf was spotted. In early August, multiple sources reported them to be at the entrance to The Strait of Juan de Fuca at an important spot: Swiftsure Bank (Orca Network.org).

Swiftsure bank is a shallow area near the deep underwater canyon the runs into the strait of Juan the Fuca. Shallow spots like that create upwelling currents, bringing nutrients up from the ocean depths. The nutrients increase the amount of food in the waters, food that salmon like. For Southern Residents, Swiftsure is a critical area that probably gives them access to many fish runs. The salmon feeding over the bank are making their way in towards the river mouths that funnel into the Salish Sea’s protected waters. The Southern Residents are hopefully finding better food out there, a good enough reason for them staying away.

What can we do?

Ocean.org highlights three ways that we can help ensure there are enough fish for the Southern Resident Killer Whales.

  1. Eat sustainable seafood. Seafood caught or harvested in a way that supports long-term health of our ocean ecosystems is sustainable. Use the Oceanwise program and the Sea Choice guide to make the best choices when eating seafood.

  2. Follow fishing regulations at all times.

  3. Support local salmon conservation by donating or volunteer with a local organization. The wildlife conservation fee we collect from our guests goes directly to support the South Vancouver Island Anglers Coalition.

 

To Conclude, it is the lack of prey species abundance which is the single largest threat facing the Southern Resident Killer Whales. Without enough Chinook salmon in our waters, it doesn’t matter what else we do. On the other hand, the Biggs Killer Whales, or Transient Killer Whales, are thriving both in number and in size. The reason is abundant prey species availability. Additionally, Humpback Whales have returned in record numbers, the reason why: abundant prey species availability. We’re calling it the Humpback Comeback! Whale Watching has never been better in these waters surrounding Victoria BC. That’s why we call this the Whale Watching Capital of the world.

Written by Stefania, Marine Biologist

Literature Cited:

Ford, J.K.B., G.M. Ellis. 2006. Selective foraging by fish-eating killer whales (Orcinus orca) in British Columbia. Marine Ecology Progress Series 316:185-199. 

Ford, J.K.B., G.M. Ellis, P.F. Olesiuk, K.C. Balcomb.  2009. Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator?  Biology Letters. 6(1): 139–142.

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