Hot, Hungry Seas Raised the Odds of a Disastrous Fish Catch by Up to 80%

Fishing has always had bad years. Storms, poor spawning, a wrong guess about where the fish have gone.

But a new global study suggests some bad years are becoming more predictable. They tend to follow the ocean’s own extremes.

When the sea was unusually hot and unusually short of food at the same time, the odds of a disastrous catch rose sharply.

It’s a warning for coastal communities, and for anyone who eats seafood.

What is a marine heatwave?

A marine heatwave is a stretch of unusually warm water in the ocean, well above what’s normal for that place and time of year.

Like heatwaves on land, they’ve become more frequent and more intense. The new study notes they are disrupting marine life and fisheries around the world.

The researchers looked at a related idea: extreme years. They classed a year as extremely hot when the average ocean temperature in a region was in the top 10% of its record.

They also looked at a second kind of extreme that gets far less attention. That’s an extremely low year for net primary production, the growth of tiny ocean plants at the base of the food web.

When that growth collapses, there’s simply less food to go round. Fish and their prey both feel it.

The study: 27 years of catches

Who did it

The study was led by William Cheung at the University of British Columbia, with colleagues at the University of Bern in Switzerland. It was published in Nature Communications in September 2026.

What they analysed

The team combined reconstructed fisheries catch data from 1993 to 2019 with ocean temperature and productivity data.

For each species in each region, they asked a simple question. Was a terrible catch year more likely after hot or low-productivity years?

What the study found

Heat alone raised the risk

Extreme heat on its own increased the odds of a very poor catch. The biggest effect came when hot years arrived back to back.

Two consecutive extremely hot years raised the odds of an extreme low catch by about 40%, compared with normal years.

Two extremes together were worse

The worst combinations paired heat with a collapse in ocean productivity.

A hot year followed by a year with record-low productivity was the worst. It raised the odds of an extreme low catch by up to about 80%.

The authors explain why. Heat harms the growth and breeding of fish, especially young ones.

Low productivity then limits their food.

The damage can show up a year or more later, when the affected fish would have entered the catch.

Some fish and places were hit hardest

Tropical and subtropical regions were especially exposed. The authors note that species important for food security and conservation were disproportionately affected.

The future looks worse

The team projected what might happen as the climate keeps warming, assuming fisheries don’t adapt.

In vulnerable regions, the share of fish stocks hit by extreme low catches rises from about 11% in the early 1990s. By the middle of this century, it reaches almost 16%.

That rise looked similar under both low- and high-emission scenarios up to 2060. The projections assume the past relationships keep holding.

Why the result needs caution

Catches are not fish numbers

The study measured catches, not how many fish are actually in the sea. Catches also depend on fishing effort, prices, rules and markets.

The authors say their models don’t fully capture overfishing, shifting fish ranges, falling oxygen levels or food-web changes.

Links, not proof

This is an observational analysis. It shows that bad catch years tend to follow extreme ocean years, but it can’t prove the extremes alone caused them.

Messy data in some places

Catch records are reconstructed, and they’re less certain in data-poor regions. The study also gives two slightly different counts of its time series, which is a minor but real inconsistency.

What earlier research found

Warming has already cut fisheries

A 2019 study in Science looked at 235 fish populations of 124 species. It estimated that warming reduced their maximum sustainable yield by 4.1% between 1930 and 2010.

Some regions lost far more, between 15% and 35%.

Heat extremes add to the damage

A 2021 modelling study in Science Advances, also led by Cheung, projected what happens during an extreme hot year. On average, 77% of exploited species in that region would decline in biomass.

The maximum catch potential would drop by 6%, on top of long-term climate effects.

A more mixed picture for bottom fish

The new paper also cites a recent meta-analysis that found marine heatwaves had “muted and variable impacts” on fish living near the seabed. So not every species responds the same way.

How it fits together

Models predicted that ocean extremes would hurt fisheries. This study adds real-world catch data showing those effects, especially when heat and food shortages strike together.

How much should you trust this?

Promising. It’s a large, global analysis with nearly three decades of data. But it relies on catch records and shows associations, not direct cause.

What makes it convincing

• It covers 1,246 species across 254 regions over 27 years.
• The results held when the team used bottom-water temperatures instead of surface ones.
• Earlier models predicted similar effects.
• The authors declared no competing interests.

What makes me cautious

• Catches reflect fishing and markets as well as fish numbers.
• Fishing effort data weren’t available for every fishery.
• Catch records are uncertain in some regions.
• The projections assume past patterns continue.

What this means for you

• Expect more volatile seafood supplies. Prices and availability of some fish may swing more in extreme years.
• Spare a thought for fishing communities. The hardest-hit places are often lower-income coastal regions.
• Choose sustainable seafood. Well-managed fisheries are better placed to cope with bad years.
• Support early warnings. The authors call for better monitoring and fisheries rules that respond to climate extremes.

In this short video from the National Oceanography Centre, you can see what marine heatwaves are and why our seas are warming:

What we still don’t know

1. Do fish numbers fall as much as catches? Survey data on fish biomass would help answer this.
2. How much does overfishing add? The two pressures likely interact.
3. Can good management reduce the risk? Adaptation could change the projections.
4. Why are some species more sensitive? Shifts in habitat and food webs may explain it.
5. What about shorter heatwaves? The study looked at whole-year extremes, not brief spikes.

My take: watch the double hits

What I like about this study is its scale. It turns scattered stories of collapsing fisheries into a global pattern.

I’m less convinced by the precise projections. They rest on the assumption that the past will repeat, and fisheries can adapt.

Still, the core lesson is clear and useful. The ocean’s worst years for fishing tend to come when two extremes hit at once.

Planning for those double hits could protect food and jobs for millions of people.