- What has fatty fish got to do with climate change?
For half a century, fisherman Takeo
Nakajo has been catching katsuo fish
in Japan's Kochi prefecture.
But he and his fellow fishermen are getting
concerned about the future.
TAKEO NAKAJO: [SPEAKING JAPANESE]
INTERPRETER: The katsuo we caught this spring are fatty.
Before, the fish were lean with no fat,
but this year, the fish have changed.
They are very fat.
- While heavier fish might sound like a good thing
when it comes to selling it, locals and experts
say it's a side effect of climate change
that in the long run might reduce katsuo numbers, which
are already under threat due to growing demand and overfishing.
Originally from tropical waters, some Pacific katsuo
migrate northward on a warm ocean
current every spring, making Kochi's arc-shaped bay
a fertile fishing ground.
The average surface temperature of the bay in winter
has risen by over 35 degrees Fahrenheit in the four decades
to 2015, according to local fisheries' lab data.
Ample prey in the warmer sea could
be responsible for the plumper fish.
But in the longer term, this warming
may prevent mineral-rich water from rising to the surface,
resulting in a drop in plankton and smaller fish to feed on,
leading to fewer katsuo.
Hiroyuki Ukeda, an agroscientist and vice president
of Kochi University, says it's not just warmer
water that's having an effect.
HIROYUKI UKEDA: [SPEAKING JAPANESE]
INTERPRETER: It is an undeniable fact
that essential nutrients for phytoplankton in coastal areas
are running dry.
As a result, we can say global warming is certainly
a reason why the fish catch is declining
because katsuo are not migrating to this area anymore.
The impact of overfishing and global warming combined
is creating the current critical situation.
- Overfishing has already dealt a blow to the fishermen
in Kochi who have stuck to traditional
single-pole fishing methods.
Government data show catch numbers in Kochi
are only at a quarter of their 1980s peak.
This comes as Japan's aging population is threatening
the sustainability of local fishing
and related businesses such as the production
of dried and fermented katsuo--
katsuobushi.
Production of that, often used as a shaved condiment
over traditional Japanese dishes or as a broth base,
is already suffering, with the number of manufacturers
plunging.
It's not just the fishermen who are
concerned about what's next.
It's also worrying for those at the end of the chain,
like Kosuke Kitamura, the manager
of century-old restaurant Tsukasa in Kochi,
which only serves locally-caught katsuo.
KOSUKE KITAMURA: [SPEAKING JAPANESE]
INTERPRETER: At the moment, we are not yet
at a stage where we don't have katsuo
and cannot provide in meals.
But it is something that might likely
happen in the near future.
If we leave the situation as it is,
we can anticipate that katsuo what will disappear.
Japanese cuisine is built on broth made using katsuobushi.
Without katsuo, it would be very difficult to serve
Japanese food, so I'm very worried.