News Navigator: Why have there recently been large catches of sardines around Japan?

The Mainichi Shimbun answers some common questions readers may have about the huge amounts of sardines recently caught around Japan.

Question: I saw a news report that large numbers of sardines have been netted off Japan, is that right?

Answer: Since the beginning of February, there have been big catches of sardines in various parts of Japan. In Toyama and Fukui prefectures, hefty numbers of sardines were caught in nets, and in Aomori and Niigata prefectures, many were reportedly washed up on the coast. There are several types of sardines, but most of them are “spotlined sardines.”

Q: We can eat a lot of them. It’s a good thing, isn’t it?

A: Spotlined sardines at this time of year are very tasty because they have a lot of fat on them ahead of the spawning season. However, if too many are harvested, the price drops and the costs of labor to sell them and of fuel for boats cannot be covered. In Toyama Prefecture, large amounts of sardines sometimes enter the nets targeting firefly squid, a local specialty, damaging the squid. So, a large catch is not always a good thing.

Q: Have spotlined sardine catches increased all of a sudden?

A: In recent years, the catch has tended to rise. According to past records, good catches and poor catches of sardines have been in a cycle of about 20 years in the vicinity of Japan. Very few of them had been caught until around 1970, but there were good catches between the mid-1970s and mid-1990s. After that, there was a sharp decline, but the number began to pick up again from the mid-2010s. In other words, we are now in a period of abundant catches.

Q: Why is it sometimes possible to catch the fish and sometimes not?

A: It may have something to do with a “regime shift,” a change in the ocean environment every few decades. Although there is a tendency for Japanese flying squid to increase when seawater is warm and for spotlined sardines to increase when seawater is cold, the relationship with the recent large catches is not known. It is said that it will take some time before the mechanism is clarified. Sardines are a familiar fish, but they are also a mystery.

(Japanese original by Mirai Nagira, Osaka Science & Environment News Department)