Tuna fisheries are one of the most important fisheries in
the world? Many countries
are nutritionally and economically dependent on the health
of the tuna fisheries. Unfortunately the demand for more and
more fish combined with increasing technology in the fishing
industry enabling them to catch more and more fish, has led
to the decline of many fish species including tuna.
There are three major conservation issues to consider:
- Over fishing - Simply, this is just taking too many
fish out of the ocean for the populations to maintain sustainable
levels. If the fish are being removed at a faster rate than
they can reproduce, eventually the populations will disappear.
- By catch - This is all of the "other" unwanted animals
caught in nets. For example, for every one pound of shrimp
caught, between 4 and 10 pounds of other animals is also caught
and thrown back into the ocean either dead or dying. By catch
includes fish, sea turtles, birds, etc...
- Habitat destruction - Increasing development by
the worlds growing population can be very harmful to fish
populations. Coastal areas around the world are very rapidly
growing -at the same time; coastal areas are often feeding,
breeding and nursery habitats for valuable commercial fish.
Any type of development can lead to problems - siltation,
increased pollution, runoff, that harm fish. Also, certain
fishing methods destroy habitat in the process of catching
There are 13 species of tuna - six are intensively fished
on a commercial basis: skipjack, northern blue fin, southern
blue fin, big eye, yellow fin (Ahi), and albacore.
Albacore - Almost all albacore in the US is from Pacific
fisheries. Here they are managed at sustainable levels with
hook-and-line methods (little to no by catch). In the North
Atlantic, they are considered over fished, and in the South
Atlantic, they are considered stable.
Skipjack - Populations still large and don't seem
to be in decline.
Yellowfin/ahi - The populations are relatively healthy
and stable, but they are caught using long-lines and purse-seines,
which are two fishing methods with very high by catch rates.
If they are troll-caught there is little to no by catch.
Blue fin - The Atlantic blue fin catch is said to
be only 10% of what it was 10 years ago, due to over fishing
and poor management. Northern Pacific blue fin seem to be
in trouble primarily because of over fishing and high catches
of juveniles. Southern Pacific blue fin are also considered
Big eye - There isn't enough data on these to really
determine their status. The juvenile big eye is very difficult
to distinguish from juvenile yellow fin tuna. There also are
no regulations for big eye in the Pacific and in the Atlantic
there are only minimum size regulations.
Author Sonja Tiegs
Conservation Programs Coordinator
Shedd Aquarium Chicago