Anchovies are moving.
As waters off Peru have warmed during El Niño, the country’s climate monitoring commission says anchovies have been pushed deeper and further south. Peru has repeatedly suspended fishing in affected areas as conditions deteriorated. The government describes this as protecting the “resource”.
Resource. They mean millions of individual fishes trying to get away from water that is becoming too hot for them. And where the anchovies go, the fishing industry wants to follow.
Welcome to climate adaptation.
The fishes are already adapting
El Niño is now firmly established across the tropical Pacific. The World Meteorological Organization says there is a near 100% chance that the event will continue through February 2027 and expects a very strong El Niño before the end of this year. Meanwhile, human-driven climate change is loading the dice. Marine heatwaves have approximately doubled in frequency since the 1980s, while becoming longer and more intense. The IPCC says human influence very likely contributed to 84% to 90% of marine heatwaves between 2006 and 2015. These extreme events can expose animals to temperatures beyond their tolerance and cause mass deaths. We are already seeing what that looks like.
During an extreme marine heatwave in the Red Sea, researchers counted 971 dead fishes from 54 species along the Saudi Arabian coast. The deaths coincided with unprecedented rapid warming. It was the largest recorded event of its kind in the Red Sea.
Another study found that marine heatwaves can cause fish biomass to fall by as much as 43.4% among populations already living near the warmest edge of their range. Meanwhile, populations at the cooler edge can suddenly increase as fishes move into new areas. The fishes are effectively redistributing themselves as temperatures change around them.
For the fishing industry, this creates an obvious problem. The fishes are no longer where humans expect them to be. So we get better at following them.
Run. We’ll catch you somewhere else.
Fisheries management is increasingly being told to become “dynamic”. Strip away the jargon and it often means this:
The water gets hotter.
Fishes move.
Humans work out where they moved to.
Fishing moves too.
We have somehow turned animals fleeing hostile environmental conditions into a logistical problem. Peru offers an almost perfect example. Anchovies are shifting deeper as the water warms. These same anchovies are also one of the world’s most important sources of fishmeal and fish oil. The UN Food and Agriculture Organization says Peruvian anchoveta are the primary global source of both. And what do we do with all those fishes? Feed them to other animals. The FAO reports that aquaculture has become the dominant destination for fishmeal and fish oil, driven by the expansion of fish farming. In its 2020 figures, 86% of fishmeal and 73% of fish oil went to aquaculture.
So follow this through. Wild fishes try to escape warming seas. Humans pursue them. Humans kill them. Humans grind them into feed. Humans feed them to other fishes who are trapped in farms and cannot escape warming seas at all.
You could not design a better illustration of how absurd our relationship with other animals has become.
The fishes in farms cannot run
In August 2024, northern Norway experienced one of the most severe marine heatwaves recorded there.
Coastal waters exceeded 18°C in some places, more than 4°C above the long-term average. The heat contributed to an unprecedented outbreak of salmon lice on fish farms and increased salmon deaths. The marine heatwave lasted 21 days. Wild animals at least have some possibility of moving when their environment changes. Farmed fishes are imprisoned inside cages. The water warms around them. Parasites flourish. Disease spreads. They remain where humans put them. And the proposed answers are almost always technical. Better monitoring. Different killing schedules. Disease treatment. Breeding fishes who can tolerate more heat. Anything except asking why we are breeding and confining them in the first place.
The effects of marine heatwaves do not stay neatly inside fish farms or fishing quotas either. When a huge marine heatwave known as the Blob struck the north-east Pacific from 2014 to 2016, the food web was disrupted so badly that around 4 million common murres starved to death in Alaska. Half the population. Four million birds. Scientists described it as the largest documented single-species wildlife die-off in modern history. This is what a rapidly warming ocean looks like. Animals moving. Animals starving. Animals becoming sick. Animals dying. But our response to fishes moving away from lethal conditions is still to ask how fishing can keep up.
We call that adaptation.
For the fishes, it looks a lot more like relentless pursuit.