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Minimizing bycatch of sensitive species groups in marine capture fisheries:lessons from tuna fisheries


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Gilman, E and Lundin, C 2009 , 'Minimizing bycatch of sensitive species groups in marine capture fisheries:lessons from tuna fisheries', in Q Grafton and R Hilborn and D Squires and M Tait and M Williams (eds.), Handbook of Marine Fisheries Conservation and Management , Oxford University Press, Oxford UK, pp. 150-167.

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11.1.1. Ecological, Economic, and
Social Issues Related to Fisheries
Bycatch in marine capture fisheries is the retained
catch of nontargeted but commercially viable species
(referred to as “incidental catch”) plus all
discards (Food and Agriculture Organization of
the United Nations [FAO] 2005).1 It is an increasingly
prominent international issue, raising ecological
concerns, as some bycatch species of cetaceans
(whales, dolphins, and porpoises), seabirds, sea turtles,
elasmobranchs (sharks, skates, and rays), and
other fi sh species are particularly vulnerable to overexploitation
and slow to recover from large population
declines (FAO 1999a, 1999b, in press; Fowler
et al. 2005; Gales 1998; Gilman et al. 2005, 2006a,
2006c, 2008; Lutz and Musick 1997). Bycatch can
alter biodiversity and ecosystem functions by removing
top predators and prey species at unsustainable
levels (Myers et al. 2007). It also alters foraging
behavior of species that learn to take advantage of
discards. Economic effects of bycatch on fi sheries
include loss of bait, reduced availability of baited
hooks when they are occupied with unwanted
bycatch species, and concomitant reduced catch
of marketable species; the imposition of a range of
restrictions, closed areas, embargos, and possible
closures; allocation among fi sheries, where bycatch
in one fi shery reduces target catch in another, and
bycatch of juvenile and undersized individuals of
a commercial species can adversely affect future
catch levels (Brothers et al. 1999; Hall et al. 2000).
Discarded bycatch raises a social issue over waste:
From 1992 to 2001 an average of 7.3 million metric
tons of fi sh were annually discarded, representing 8
percent of the world catch (FAO 2005).
Prominent bycatch issues include dolphins and
porpoises in purse seine fi sheries and driftnets; fi sh
discards in shrimp trawl fi sheries; and seabird,
sea turtle, marine mammal, and shark bycatch in
longline, purse seine, gillnet, and trawl fi sheries (FAO
1999a, 1999b, 2005, in press; Hall et al. 2000). In
commercial tuna fi sheries, the incidental bycatch of
sensitive species groups (seabirds, sea turtles, marine
mammals, and sharks) and bycatch of juvenile and
undersized tunas are allocation and conservation
issues. In addition to problematic bycatch, overexploitation
and illegal, unreported, and unregulated
(IUU) fi shing, which complicates bycatch management,
are additional conservation issues facing the
management of tuna fi sheries. This chapter employs
examples of bycatch in commercial tuna fi sheries to
describe (1) the range of options to reduce bycatch,
(2) principles and approaches to successfully introduce
effective bycatch reduction measures, and (3)
initiatives taken by intergovernmental organizations,
the fi shing industry, and retailers to address
bycatch. Changes needed to improve the sustainability
of tuna production are recommended.

Item Type: Book Section
Authors/Creators:Gilman, E and Lundin, C
Publisher: Oxford University Press
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© 2009 Oxford University Press

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