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Bycatch is one of many threats to large marine vertebrates that reach late maturity and have low reproductive rates, among which figure marine turtles. Marine turtles are often found entangled or hooked in the fishing gear, and in some cases still alive when captured. However their mortality following their release back to sea by fishermen is not well determined.
Some fishing gears have been modified (TED, circle hook etc.) in order to reduce bycatch. Yet, not all countries use them and the numbers of turtles estimated to die because of bycatch is still alarmingly high. In 2000, the number of loggerhead and leatherback turtles accidentally caught was estimated respectively at 200,000 and 50,000 worldwide (Lewison et al., 2004).
Although such estimates are difficult to make, it is still important to protect marine turtles at all life stages, as well as during their migratory phases. This is why Ifremer and Kelonia, in association with the fishermen from Reunion Island, launched a programme that aims at studying the trajectory and diving behaviour of accidentally caught marine turtles in order to better understand their migration patterns, and decrease turtle bycatch.
 Since the programme started in 2008, four accidentally caught loggerhead turtles have been brought back to Kelonia's care centre and released back to sea with an Argos satellite tag that recorded both their trajectory and diving profile. Justatao was the first loggerhead to be released with an Argos system in October 2008. Since then, three other loggerhead turtles have followed their way back to the ocean: Circle released in March 2009, Vetyver in October 2009 and Josette in December 2009.
These turtles were immature loggerheads caught off the coasts of Reunion Island and were brought to the care centre with a hook in the throat. At the exception of Josette, who was slightly injured and thus took only a few weeks to recover, the other turtles remained almost a year at Kelonia before release. Convalescence depends on the feeding behaviour of the turtle; they are released only when they start feeding again and increasing in weight.
As part of the educational activities, Kelonia proposes to the schools to participate at the recovery programme. Classes can "adopt" a turtle to be released and follow its recovery and release back to the ocean. With the Argos system, pupils can follow the trajectory of the turtle through the Indian Ocean until the end of transmission. Ifremer Reunion provides update on the trajectories of the turtles on the internet at the following address: http://wwz.ifremer.fr/lareunion/les_tortues_en_direct.
Reference:
Lewison, Freeman & Crowder (2004) Quantifying the effect of fisheries on threatened species: the impact of pelagic longline on loggerhead and leatherback turtles. Ecology Letters 7: 221-231
Read A (2007) Do circle hooks reduce the mortality of sea turtles in pelagic longlines? A review of recent experiments. Biological Conservation 135: 155-169
http://www.smartgear.org/about_smargear/smartgear_pressroom/?131602/New-website-on-reducing-marine-turtle-bycatch-in-the-Eastern-Pacific
This feature was kindly contributed by:
Marie LAURET-STEPLER
Environmental Educator and Research Assistant
Kélonia, l'observatoire des tortues marines
46 rue du Général de Gaulles
97436 St Leu
La Réunion
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