I'll put some answers after your questions (see below). I encourage you to
do more research on this both on the WhaleNet site and by searching the
www.wdcs.org site which has good, recent information on the dolphin tuna
Date: Mon, Apr 7, 2003, 4:51 AM
I have to do a report on how dolphin safe tuna fishing and I have to ask
question and get direct answers from a marine biologist. Thanks for your
How have dolphin safe tuna fishing methods improved?
Answer: Fishing gear was modified and observers have been placed on fishing
boats to get accurate counts of the kills, as well as to help ensure better
compliance. But equally important have been political and economic pressures
from conservation groups, particularly in the United States, the main world
market for tuna. By 1994, only dolphin-safe tuna could be sold in the United
States. In 1999, the International Dolphin Conservation Program Agreement,
bound the major fishing countries to strict rules and mortality limits.
What other organisms are effected by these new methods?
Answer: It is known that sharks and sea turtles, among other marine
organisms, are also caught but the effects on their populations are unknown.
How much of an increase in the dolphin population occured?
Answer: There has been a great decrease in the number of dolphins killed.
There were 300,000 to 700,000 (avg.: 500,000/ yr) killed most years between
1960-1972. After the passage of the US Marine Mammal Protection Act in 1972,
the number killed declined to about 20,000 a year. As the world catch
continued to increase, dolphin mortality grew to 133,000 a year by 1986
before lobbying by conservation groups made the US bring in laws about
accepting only dolphin-safe tuna and to propose a series of international
agreements culminating with the International Dolphin Conservation Program
Agreement in 1999. Since then, the dolphin kills have fallen to fewer than
3,000 dolphins per year.
The dolphins most affected by the tuna fishing have been the northeastern
stock of the ofshore pantropical spotted dolphin (Stenella attenuata) and a
subspecies, the eastern spinner dolphin (Stenella longisrostris orientalis).
Both populations declined dramatically between 1960 and 1975 but have
remained constant since then. The spotted dolphins remain at about 15% of
their original abundance when the fishing started in about 1960, and the
spinner dolphins are at 34% of original abundance.
So in fact, although the number being killed has declined from an average of
500,000 a year to 3,000 a year, there has been no increase seen yet in these
populations. Researchers are continuing to study these dolphins to try to
find out why. It could be the stress from repeated chase and encirclement
(effects on reproduction, maybe), or maybe nursing calves are getting
separated from their mothers during the fishing process, or there could be
other important social effects within the dolphin schools, or even
ecological effects from removing tuna from the tuna-dolphin association. But
no one knows for sure - these are all just hypotheses (theories to be
There are other dolphin populations affected as well - but not nearly as
much as these two.
There is lots of work and understanding, and continual effort, needed on
this whole issue. We must not forget that more than 6 million dolphins have
been killed in the tuna dolphin fishery since it began 4 decades ago. This
is the highest known number of cetaceans killed for any fishery, three times
as many as the total number of whales killed during commercial whaling in
the 20th Century (about 2 million). And even today, with 3,000 dolphins
killed a year - this is still a lot of dolphins to die - too many!
(I used several sources for the numbers above, but the most useful was the
Encyclopedia of Marine Mammals, edited by William F. Perrin et al, Academic
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