1. What El Niño Does to the Ocean Along the Equator
Normally, trade winds blow west along the equator and push warm surface water from South America toward Asia. Cold, nutrient-rich water rises from the deep to take its place. That rising is called upwelling [1].
During El Niño, the trade winds weaken, and warm water spreads back east toward the coast of the Americas. NOAA, the U.S. ocean and weather agency, counts El Niño conditions as present in the ocean when the three-month average sea temperature in a monitored patch of the central Pacific is at least 0.5 °C (0.9 °F) above normal [2]. Events come every two to seven years, on average, and usually last nine to 12 months [1].
The name comes from South American fishermen, who first noticed unusually warm water in the 1600s. They called it El Niño de Navidad, “the Christmas boy,” because it usually peaks around December [1]. So fishing is where this story began.
2. Why Weaker Upwelling Means Less Food for Fish
Here is the main answer to the question in the title. The cold water that rises along the coast carries nutrients, and nutrients feed tiny drifting plants called phytoplankton. When El Niño weakens or stops upwelling, there are fewer phytoplankton, which affects fish that eat them and then everything that eats those fish [1].
Warm water can also pull fish in new directions. Tropical species such as albacore tuna can show up in places that are usually too cold [1]. So the same warming can mean less food in one place and fish moving to other places. The next two sections show both.
3. Why Peru Called Off Its Anchovy Season in 2023
Peru's anchovy, called anchoveta there, is the world's largest single-species fishery. It yields about 4.4 million tonnes in an average year and makes up about 75 percent of Peru's landings, according to the United Nations Food and Agriculture Organization (FAO) [3]. Most of the catch is turned into fishmeal and fish oil, not eaten as fresh fish.
In 2023 the fish were in trouble. To start the first season, Peru's Ministry of Production allowed a short trial fishing trip from June 3 to 7. The national sea institute, Imarpe, measured the landings. The smallest legal size is 12 cm (about 4.7 inches), but the catch ranged from 7 to 15 cm. Young fish made up 86.3 percent of the fish by number and 77 percent by weight [4]. Fishing could have harmed the anchoveta population before the young fish had a chance to lay eggs, so the ministry cancelled the whole season [4].
FAO links this to the El Niño of 2023–2024. In strong events, anchoveta lose habitat and food, which affects where they live, how they reproduce and how many young survive. The amount of fish caught by Peru's industrial fleet in 2023 was 50 percent lower than in 2022 [3]. Note the careful wording: the direct reason for the cancellation was the young fish, and El Niño is the background that FAO and others point to [3] [4].
4. How Fewer Anchovies in Peru Can Raise Fish Feed Costs Elsewhere
Why would that matter in other countries? Fishmeal is a main ingredient in feed for farmed fish. About three quarters of the world's fishmeal and fish oil goes to aquaculture, and Peru has produced about 20 percent of the global supply over the past decade [5]. FAO says that when the anchoveta catch falls, it affects farmed fish production worldwide [3].
After the 2023 cancellation, trade press expected feed companies to face higher raw-material prices [4]. An industry spokesperson also said the shortage would be sorted out by the market: the fishmeal and fish oil would go to buyers who could pay the most, such as farms of high-value fish and the pet food sector [5]. This is why a warm ocean can matter to a fish farm on the other side of the planet. It is also a chain with many links, because prices depend on more than the weather. Exchange rates, stored supplies and demand also play a part, so no one price rise can be blamed only on El Niño.
5. Why Skipjack Tuna Fishing Moves East When the Warm Pool Spreads
In the western Pacific there is a huge region of very warm surface water, often called the warm pool. FAO reports that during the 2023 El Niño it started moving east into the central Pacific [3]. Skipjack tuna, the fish in many canned tuna products, are tied to that warm water. Their suitable habitat shifts east with it [3].
The effect differs from place to place. FAO says that through the end of 2023, El Niño helped skipjack fishing in the easternmost Pacific island waters [3]. Tuna are not simply “disappearing.” They are in a new place. For island nations that earn money by licensing tuna fishing in their waters, a shift of this kind can bring gains to some and losses to others.
6. What Is Happening in 2026 and What Nobody Knows Yet
El Niño is back this year. A Pacific news agency reported in October 2026 that NOAA said El Niño conditions were present, with a more than 90 percent chance of a very strong event this autumn and winter, likely lasting into February 2027 [6]. The same report says fishing effort in the Pacific is already changing, and Ecuador's fishing industry expects catches to fall by 90,000 tonnes in 2026 [6]. This comes from a news report summarizing industry bulletins, so treat the numbers as early.
What will happen to Peru's anchovies, fishmeal prices or any particular fish farm is not something these sources can say. The 2023 case shows why: even when the ocean link is clear, other things, such as money and markets, push on prices too.
7. How to Follow an El Niño Yourself
Open a globe or world map and find Peru, the equator and the International Date Line. How far is the date line from the coast of South America? That stretch is where the warm water spreads.
Then look at NOAA's Climate.gov pages on El Niño and the Oceanic Niño Index, which publish the latest sea temperature numbers. Check whether the latest index value is above or below 0.5 °C. It is a three-month average, so one warm month does not make an El Niño. If you are with an adult at a store, look at a package of seafood. The label may say where the fish came from, but it will not show the feed, so notice what a label can and cannot tell you.