More hatchery salmon cannot help endangered killer whales

In December 2023, the Raincoast Conservation Foundation, along with six other conservation groups that work on salmon and killer whales, submitted an amicus brief to the U.S. 9th circuit court (PDF). Later in 2024, the 9^th circuit court will make a decision on how to proceed on the matter of harvesting Chinook salmon in the Southeast Alaska troll fishery.

While we are not a litigant in the court case that was launched by the US based Wild Fish Conservancy against the US National Marine Fisheries Service, submitting an amicus brief allows us to provide information and perspective on a matter in front of the court. Our interest in this case is the effect that fisheries in Alaska have on endangered Southern Resident killer whales.

One specific consideration the court is examining is whether the increased production of hatchery Chinook from Puget Sound constitutes a ‘remedy’ to the problem of Alaska’s troll fishery removing tens of thousands of Chinook salmon destined for BC and the Pacific Northwest that are prey for hungry Southern Residents.

In the brief, we argue that the Puget Sound hatchery program does little to solve the prey problem for these whales.

The prey problem

Southern Resident killer whales consume Chinook salmon as their primary prey. Depending on the season, between 50% to almost 100% of the Southern Residents’ diet is composed of Chinook. Research done almost 20 years ago by Dr. John Ford and his team at Fisheries and Oceans Canada provided compelling evidence that the abundance of Chinook salmon is strongly linked with birth rates and mortality in these salmon-eating killer whales. For example, when Chinook abundance was high, birth rates and survival increased. When Chinook abundance dropped, mortality increased. In essence, Chinook abundance was key to the health of these whales. Research, then and now, further shows that it’s not just any Chinook that Southern Residents eat. The whales select for big, old Chinook; generally 4 years or more of age, and larger than 74 cm.

If you follow the salmon news, and listen to fishermen, it will be no surprise to hear that Chinook size is not what it used to be. While declines in Chinook size have made recent news, size declines discussed today are actually in addition to those documented in the 1970s, 1950s and the 1920s. In some cases, weights of Chinook observed in the 1970s were up to half the average weights from the 1920s, with dominant age classes dropping as much as two years. Chinook in the Salish Sea, for example, were once as old as 7 yrs of age. These fish would have been huge, larger than 1 metre in length. The same is true of 6 yr olds.  Today, the oldest fish are typically 5 years of age and they make up only 2-3% of the Chinook swimming in the Salish Sea, so even the 5 year olds have become rare.

This leads to the second problem: Chinook aren’t just smaller once they become adults, they are becoming adults at younger ages. 

So for a whale trying to find and consume big, old Chinook, there are 1) fewer of them, and 2) more are at the low end of the size criteria. Bigger Chinook (30 + lbs) have become rare, and killer whales need to expend more energy to get their caloric needs from smaller fish. Data from the US National Marine Fisheries Service indicates that 4 and 5 year old Chinook make up less than 10% of the Chinook in the Salish Sea.

The problem with hatcheries 

Today, tens of millions, to hundreds of millions, of Chinook are produced in hatcheries and sent into the ocean annually. While these fish can be used for catch assessment purposes, and in some cases conservation, they are overwhelmingly produced for harvest in commercial and sport fisheries. More recently, the US government has argued that producing Chinook in hatcheries helps killer whales. 

But is there evidence that increased production of hatchery Chinook in Puget Sound and elsewhere has aided the recovery of Southern Resident killer whales? 

While it might seem logical that producing hatchery salmon would alleviate pressure on wild salmon and assist whales with food supply, this has not proven to be the case. Over the many decades that hatcheries have operated, they have failed to restore the abundance, older ages, larger sizes, the broad range of migration times, and diversity of wild Chinook salmon that existed at the turn of the 20th century, and that Southern Residents evolved to rely on. 

Today, the average age of returning hatchery fish in the Columbia River is below the age of four, having declined from 4.13 years in the 1970s to 3.75 years. In Puget Sound, the average age of a returning hatchery fish is now just under 3 years old with an average length of 62 cm. This is a decline from 73 cm in the 1970s (see figure 1 and table 1 below). 

More importantly, in the 1970s, 63% of hatchery-produced Chinook returning to Puget Sound rivers and hatcheries were large enough to meet the size preference (generally upwards of 74 cm) of Southern Residents. So more than half of the hatchery fish coming back to spawn would have been suitable prey for the whales.

Today, less than 20% of these spawners are above 74 cm.  This means most hatchery Chinook coming out of Puget Sound are now too small to be desired by Southern Residents, even during spawning migration when the absolute largest fish are present.  Because Puget Sound Chinook can spend many seasons rearing in the Salish Sea before they head to spawn, these smaller immature fish (generally 1-3 years old) can make up most of the Chinook abundance. 

Recovery of Southern Residents requires more than just numbers of Chinook. Recovery requires restoring big, old Chinook. This is possible, but it is not the goal of large production hatcheries, nor fisheries management. Hatcheries are mainly focused on producing fish for the economic and social objectives of fisheries harvest, and fisheries harvest is not focussed on ensuring wildlife receive enough to eat.

Stay tuned for future articles on how we might solve the problem of small fish.  In solving this problem, we could recover prey for Southern Resident killer whales,  rebuild the historic sizes of Chinook salmon, and ensure that local communities have access to sustainable harvests.

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