Shark Depredation and Unwanted Bycatch in Pelagic Longline

Shark Depredation and Unwanted Bycatch in Pelagic Longline Fisheries
and threshers) for which there is sufficient value for their meat.
Furthermore, many operators in this fishery will only retain a shark
that is of a marketable species if it is dead or dying when hauled to the
vessel, which can be safely and relatively easily landed.
The South Africa longline tuna and swordfish fishery is subject to
a shark landing limit of 10% of the total swordfish and tuna catch.
This theoretically has been economically detrimental to the industry.
From 1998-2005, the total number of caught sharks was 18% of the
total number of caught swordfish and tunas. Thus, vessels would
need to discard about 44% of their caught sharks to comply with
the shark limit. Because only about 18% of caught blue sharks and
10% of makos have been observed to be released alive in this fishery,
and the literature demonstrates that a much larger proportion of
these shark species (>85%) are likely alive when hauled to the vessel
(e.g., Beerkircher et al., 2002), it is likely that fishers are not complying
with this measure.
A prohibition on the use of a wire trace in the Australian longline
tuna and billfish fishery and South Africa longline tuna and swordfish
fishery has likely resulted in an increased economic cost from shark
interactions as this has likely caused an increase in the loss of terminal
tackle to sharks. A substantially larger number of hooks, bait and
line are likely now bitten off of branch lines compared to when wire
trace was used. However, fishers generally do not consider this to
be a large concern. It is not known how the injury to sharks from
retaining hook and trailing monofilament line affects their survival
prospects. This is a research priority. This may be an improvement to
their previous fate when caught on lines with wire trace when they
would soak on the gear for hours, be gaffed and hauled onboard the
vessel and then have hooks removed by cutting with a knife or pulled
out by force. Available but limited information indicates that a large
proportion of sharks caught in longline gear that are released after
removal of the hook will survive (Section 6.2.4; U.S. National Marine
Fisheries Service, 2005). In fisheries where a large proportion of caught
sharks is killed either for retention or discarding, prohibiting the use
of wire leaders will almost definitely reduce shark fishing mortality.
Prohibiting wire leaders may exacerbate seabird bycatch problems:
Fishers will be less likely to attach weights close to hooks on branch
lines lacking a wire leader due to safety concerns, thus, reducing the
baited hook sink rate, and increasing seabird catch rates.
Shark fisheries in Peru are regulated by the Ministry of Fishery
through size limits for certain elasmobranch species (Diario Oficial
El Peruano, 2001). However, there is little enforcement of these
regulations and few fishers are aware that the regulations exist
(Alfaro and Mangel, 2002). Of the few interviewed fishers who
reported that they were aware of the regulations (5%), all report that
they still retain sharks that are under the minimum size limit.
4.2. International Initiatives Addressing Shark Finning
There have been several recent international initiatives addressing
shark finning. Fisheries subject to restrictions on finning sharks
are expected to have a high incentive to avoid shark interactions.
A summary of international initiatives related to shark finning follows.
• Food and Agriculture Organization of the United Nations:
In 1999 the Food and Agriculture Organization of the United
Nations (FAO) endorsed the International Plan of Action for the
Conservation and Management of Sharks. This is a non-legally
binding voluntary initiative calling on States to ensure the
conservation and management of sharks, including by minimizing
waste and discards from shark catches such as through requiring
the retention of sharks from which fins are removed (FAO, 1999b).
• International Commission for the Conservation of Atlantic
Tunas: In November 2004, the International Commission
for the Conservation of Atlantic Tunas (ICCAT) adopted
with consensus a binding measure requiring full utilization
of shark catches (fishers must retain all parts of the shark
except the head, guts, and skins to the point of first landing)
and prohibiting vessels in ICCAT fisheries from retaining on
board, transshipping, or landing any shark fins that are taken in
contravention of the measure. Countries must ensure that their
vessels retain fins totaling no more than 5 percent of the weight
of sharks onboard up to the first point of landing, or otherwise
must ensure compliance with the ratio through certification,
monitoring, or other means.
• United Nations General Assembly: In November 2004, the
United Nations General Assembly adopted by consensus a
resolution on Oceans and the Law of the Sea Sustainable Fisheries,
including through the 1995 Agreement, which includes a provision
that discourages shark finning, calls for implementation of the
FAO International Plan of Action on sharks, and invites FAO
to study the impact on shark populations of shark catches from
directed and non-directed fisheries.
• International Union for Conservation of Nature and Natural
Resources: In November 2004, the International Union for
Conservation of Nature and Natural Resources (IUCN) adopted
a recommendation urging all States to ban shark finning and
require shark fins to be landed attached to their bodies.
• Inter-American Tropical Tuna Commission: In June 2005,
the Inter-American Tropical Tuna Commission (IATTC)
adopted a Resolution on the Conservation of Sharks Caught in
Association with Fisheries in the Eastern Pacific Ocean, which
bans shark finning and mandates the collection of information
and advice on stock status of shark species. The resolution also
requires members to comply with the FAO International Plan of
Action on sharks and take measures to require that their fishers
fully utilize any retained sharks.
• North Atlantic Fisheries Organization: In September 2005,
the North Atlantic Fisheries Organization (NAFO) adopted
a resolution modeled after the IATTC and ICCAT measures,
banning shark finning in all NAFO-managed fisheries, and
mandated the collection of information on shark catches.
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