Working With Fishers:
the Tuna-Dolphin Problem Was Almost Solved
- Cheif Scientist, Inter-American Tropical Tuna Commission
can be an important tool in mitigating some of the ecological impacts of
fisheries. Their knowledge of the ways in which the gear works and of the
behavior of target and non-target species are critical elements to reduce
bycatches. There is a large accumulation of information on these subjects
in the minds of the captains and crews who participate in a fishery. One
of the main roles of the scientists involved in solving bycatch problems
is to tap this resource, and to separate the insightful observations from
the misconceptions and myths that are mixed with them.
In the eastern Pacific purse-seine fishery, three species
of tunas are the target: yellowfin tuna (Thunnus albacares), bigeye tuna
(T. obesus), and skipjack tuna (Katsuwonus pelamis). The schools are detected
and caught in different ways: they are found associated with groups of dolphins,
associated with floating objects, or at the surface, often in association
with seabirds. For many years, the main component of the fishery was the
capture of large yellowfin tuna in “dolphin sets”. Early in the development
of this fishery, many dolphins were killed, and for over a decade the levels
of dolphin mortality were high, and probably non-sustainable.
This mortality caused major concerns among managers, environmental groups,
and sectors of the industry that saw the public response to the figures,
and realized that the issue had to be addressed. In the case of the tuna-dolphin
problem in the eastern Pacific, most of the technical and operational solutions
came directly from the fishers, or resulted from the interactions between
scientists and fishers. Dolphin mortality in the tuna purse-seine fishery
results from a combination of factors that include environmental conditions
(e.g. currents, visibility), gear and equipment, good judgment by the fishers
deciding when to make a set, and skill to perform the maneuvers to release
Scientific studies helped to separate the factors causing or increasing
dolphin mortality, but fishers provided the initial clues as to the factors
to consider, and most of the suggestions for technical and operational solutions.
Seminars for fishing captains became opportunities for the exchange of ideas
and experiences among fishers and between them and boat owners, scientists,
and managers involved in the problem. The evaluation of the level of skill
of the fishers in releasing dolphins also required the development of scientific
methods that eliminated confounding effects, after the fishers had identified
these as a major source of variation in the results.
The heterogeneity of the performances led to the proposal
to utilize individual vessel limits to reward those better qualified to
fish with a reduced impact on the ecosystem. This system promotes “natural
selection” of fishers, rewarding those who combined the best knowledge with
the motivation to solve the problem. It provided a significant incentive
for the continued acquisition of knowledge that resulted in a dramatic reduction
in dolphin mortality of almost 99% between 1986 and 2000.
In recent years, some environmental groups tried to solve the problem by
shutting down the fishery on dolphins. This pushed a section of the fleet
to concentrate their efforts on the other “dolphin-safe” ways of fishing
that have no, or very little, impact on dolphins. Unfortunately, these alternative
methods resulted in catches of juvenile individuals of some of the tunas
with the consequent reduction in yield of the fishery. This shift also brought
to the surface the other ecological impacts of the alternatives. Instead
of dolphins, the bycatches were composed of small, immature tunas, sharks,
billfishes, mahi-mahi, wahoo, and other species.
The trade-offs posed a dilemma to all participants,
including managers and environmental groups. Would it be ecologically sound
to replace a low and controlled dolphin bycatch with a much larger and more
diversified bycatch of other species, whose significance couldn’t be assessed?
When is total dolphin protection a rational objective for ecosystem management?
To the scientists, it presents the challenges of having to provide advice
that requires a comparison of “apples and oranges” (i.e. how many sharks
and billfishes is a dolphin worth?), and of dealing with perhaps the more
fundamental question of bycatch management: is a very highly selective fishery
a sustainable way to harvest an ecosystem?
Martin Hall started his education in Argentina completing his first degree
at the University of Buenos Aires and earning his Ph.D. in Fisheries at the
University of Washington. Dr. Hall has served as the Head of the Tuna-Dolphin
Program of the Inter-American Tropical Tuna Commission since 1984. Martin
is also an Adjunct Professor at the University of British Columbia and a
Member of the Board of Directors of the National Fisheries Conservation Center.
His current research and writing involves global bycatch issues often focusing
on the Tuna-Dolphin problem.
HALL, M.A. 1996.
On bycatches. Rev. Fish Biol. and Fisheries. Vol. 6:319-352.
HALL, M.A. 1998
. An ecological view of the tuna-dolphin problem. Rev. Fish Biol. and Fisheries.
HALL, M.A. and DONOVAN, G. P
. Environmentalists, fishers, cetaceans and fish: is there a
balance and can science help to find it? In Evans, P. and
Raga, A, (eds.) “Marine Mammals: Biology and Conservation” A chapter
in a book to be published by Plenum Press in December 2001
HALL, M.A., CAMPA, M. and GOMEZ, M
. Solving the tuna-dolphin problem in the eastern Pacific purse-seine fishery.
Accepted for publication by the Ocean Yearbook Vol 17.
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