are Costa Rica’s most famous divers – and they have a problem. For
decades, in the eastern tropical Pacific, the commercial fishing
industry has hunted dolphin species that form enormous congregations,
such as pantropical spotted, spinner, bottlenose, common and Risso’s
Tuna always school beneath
large groups of dolphins, so corralling the dolphins with helicopters
and speedboats causes the tuna to form a more easily netted mass below.
Unlike most sport fishers who catch a few fish in a sustainable way,
many commercial operations set vast nets around dolphins in hopes of
grabbing all the tuna possible. This technique has killed millions of
dolphins, and continues to kill them as recently as last month off the
Southern Zone’s Osa Peninsula.
and tuna are often about the same size, and eat the same size of prey.
The vast groups of yellowfin tuna constantly following large dolphin
groups are led to lunch. The tuna seem to instinctively follow the
dolphins, as do birds and other fish, because dolphins will find the
food. The big brains of these marine mammals figure to look for chow a
few miles offshore of an island, when the tide is high, the moon is
full, the wind is clam, the water temperature is just right and the
coast is clear, and the needlefish are schooling. The tiny brain of the
tuna might just think: follow the dolphin.
being so social and traveling in such large groups, actually create a
sort of structure, like a reef, in which smaller fish can hide as well
as collect scrapes. Many species of fish, besides tuna, cruise in groups
with the dolphins, including silky sharks, blue marlin and sailfish.
call this famous phenomenon the tuna-dolphin association of the eastern
tropical Pacific, not because it’s just tuna and dolphins but because
huge commercial fishing fleets use dolphins breathing at the surface to
find the tuna swimming below them. Many different species die in the
nets of commercial fishing fleets. You may have heard of “dolphin-safe
tuna”; this catchy phrase is better described as “some dead dolphin and
mixed-species tuna.” The aforementioned catching method, sometimes still
used, is “major dead dolphin and mixed species tuna.” As far as I know,
none of the forms of massive-scale tuna fishing is even remotely safe
for dolphins – some ways just kill less than others do.So, how do the
methods differ? One is called a “backdown.” After netting all the tuna
and dolphins through the normal process, the ship motors slowly in
reverse. This, with the help of a few speedboats, lowers a part of the
net down below the surface. Hopefully, the freaked-out dolphins will
then swim out. Sometimes they do. Sometimes boats chase them out. But if
the tuna follow them, the net is quickly yanked up. All the while,
daylight is fading, the crew and workers are on the clock, and fuel is
being guzzled. This is “dolphin-safe” tuna. Other methods don’t even use
Waiting to catch the tuna
when they are away from dolphins requires more time, effort and money,
but is the only way to ensure dolphins are safe from slaughter.
Reportedly, some boats do not set on dolphins, but until tuna consumers
make this distinction, the prices of unscrupulous competitors will hurt
the real “dolphin-safe” businesses.
tourism can sometimes be at odds with commercial fishing interests. It
makes it a little harder to surround a group of dolphins with
helicopters, speedboats and a factory ship when a happy group of
photosnapping tourists is in the way. On rare occasions, frustrated
pilots in rickety helicopters that look more like lawn mowers than
aircraft will attempt to drive off the people by buzzing a tourist boat
near dolphins. If you are rooting for the dolphins, you can stay with
them until there is not enough daylight for the time-consuming process
of chasing and netting.
Why don’t the
dolphins just smack a few boat captains on the head as they jump over
the nets and swim away giggling? Because, like humans, dolphins, once
they start to panic, are not so smart. Ancient instincts, such as
freaking out, take over. And, as with humans, being in large groups
makes panic worse. Dolphins are used to vast spaces; a net causes panic,
and they just don’t think to jump over.
wonder how commercial fishers will fare once the big pods are gone.
This may sound distressingly familiar if you know about the vast herds
or flocks of animals, such as American bison and passenger pigeons,
which have disappeared on land and in the air. As the buffalo once did,
the dead dolphins rot in waste or fall to scavengers, and, as with the
passenger pigeons, a point may arrive when the population crashes
suddenly to extinction.
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The opinions expressed herein are my own personal opinions and do not represent my employer's view in anyway.
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