 Studies of the Costa Rican mahi
mahi longline pelagic fishing fleet have shown that even though
incidental capture of sea turtles is extremely high, the observed death
rate upon catch of hooked turtles is almost zero. Nevertheless, when
the turtles are released from the hooks, injuries are sustained which
can lead to death.
Yonat Swimmer and Richard Brill,
researchers at the University of Hawaii, who develop methods to
mitigate the impact of longline fishing on sea turtles, became
interested in the opportunities Costa Rica offers for studying sea
turtle post hooking mortality: the presence of a fishery where many sea
turtles are captured, a longline fleet that is open to research and
willing to collaborate (Papagayo Seafood and Nutria Marina S.A.), and a
team of local researchers with experience in the issue of incidental
capture of sea turtles (PRETOMA).
To conduct the research, sea
turtles captured during longline operations, which had the hook deeply
embedded in their throats, were tagged with satellite trackers.
Additional free swimming turtles were tagged with satellite trackers to
be used as controls.
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 The
satellite trackers are known as Pop Up Satellite Archival Tags
(PSATs). They record depth, temperature, and geographic position, to
determine migratory patterns and associated environmental
surroundings. This data can provide the basis for improving management
policies, and increasing acceptance of these measures on behalf of the
fishermen.
The preliminary results of this
study were presented during the 2nd International Fishers Forum in
Honolulu, Hawaii, November 2002. To quote these preliminary results,
please use the following source:
Swimmer, Y., R. Brill, R. Arauz,
L. Mailloux, M. Musyl, K. Bigelow, A. Nielsen, and J. Sibert. 2002. Use
of pop up archival satellite tags to quantify mortality of marine
turtles incidentally captured in longline fishing gear. 2nd
International Fishers Forum, November, 2002. Western Pacific Fisheries
Council. Honolulu, Hawaii.
Since November 2001, 9 sea
turtles (olive ridleys and Pacific greens) have been tagged with
PSATs. Six were tagged after they were captured by longline gear, with
the hook deeply embedded in their throat, while the other three were
control turtles, captured while swimming freely. The tags fell off
after 6-8 weeks, much less than the expected one year.
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 These
are the most probable routes of 2 olive ridleys that had been captured
by longline gear with hooks deeply embedded in their throats, and then
released. The daily diving patterns of one of these turtles shows
it diving to depths no greater than 90 meters (300 feet).
Different methods of attaching the PSATs to the turtles' carapaces
are currently being study. Furthermore, there are plans to study the
effectiveness of devices known as "deehookers" which have been designed
to remove hooks from turtles and reduce injury.
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