How Many Fish Do The Orcas Need?

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The single most important thing that needs to be done in order to ensure that the orca families of J, K, and L pods continue to thrive in our inland waterways is to provide them with adequate food. And for these whales, that means salmon, and lots of it. Whale biologists have been sounding this alarm for years:

Linking killer whale survival and prey abundance: food limitation in the oceans’ apex predator?
John K. B. Ford, Graeme M. Ellis, Peter F. Olesiuk, and Kenneth C. Balcomb

“Here we show, using 25 years of demographic data from two populations of fish-eating killer whales in the northeastern Pacific Ocean, that population trends are driven largely by changes in survival, and that survival rates are strongly correlated with the availability of their principal prey species, Chinook salmon (Oncorhynchus tshawytscha). Our results suggest that, although these killer whales may consume a variety of fish species, they are highly specialized and dependent on this single salmonid species to an extent that it is a limiting factor in their population dynamics. Other ecologically specialized killer whale populations may be similarly constrained to a narrow range of prey species by culturally inherited foraging strategies, and thus are limited in their ability to adapt rapidly to changing prey availability.”

Estimates vary, and there are some variations in culture between our southern resident orcas and their cousins to the north, but decades of research shows that both populations prefer Chinook salmon, followed by Chum and Coho. Sockeye and Pink salmon are not often consumed even when present in large numbers.
This preference is so strong that it may drive the whales to follow the preferred salmon to a new location, or the orcas may actually starve if sufficient fish can’t be found, and/or new hunting strategies in a new location can’t be learned in time.

The crucial question then is: how many Chinook salmon do our southern resident orcas need to flourish in their home waters? What will it take to ensure that little J-45 and the other calves grow up to have offspring of their own, and that our own children and grandchildren have the opportunity to enjoy the presence of these magnificent whales? What if this orca population is driven to extinction right about the time we learn how crucial their role is in the ecology of the inland waters, or how these intelligent animals communicate with each other?

No one wants that to happen, and scientists and government agencies have pretty much got the “peddle to the metal” in trying to get the situation fixed. The problem, of course is that there can be a huge disconnect between how quickly the government moves on issues versus the immediacy of the problems they are trying to address.

Adding complexity to the situation is that as yet scientists can’t provide definitive answers to the questions that government officials pose – no one knows for sure how many Chinook salmon the whales need to thrive (more on this topic soon), or where the whales go and exactly what they eat when they are not in their summer inland range. So everybody takes their best guess, then budget constraints and special interest groups push for the adoption of the smaller figures, which range from 221,000 to 1.76 million Chinooks for the whales each year.

But… wild salmon is a favorite diet item for people too. Its health benefits are legend, it is tasty, and salmon is as much a part of Pacific Northwest culture as are the iconic orcas. It only makes sense to err on the side of caution and to use the higher estimates when deciding what actions need to be put in place to restore the salmon populations, and quickly.

Next, some clues as to why the orcas have such a strong preference for Chinook salmon, and a closer look at the status of those salmon populations-

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