gillnet illumination reduces sea turtle bycatch · gillnet illumination reduces sea turtle bycatch...
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GILLNET ILLUMINATION REDUCES SEA TURTLE BYCATCH
John Wang1 Yonat Swimmer2
Joel Barkan3 and Shara Fisler3 Jeff Mangel4 and Joanna Alfaro-Shigueto4
1University of Hawaii – JIMAR 2NOAA – Pacific Island Fisheries Science Center
3Ocean Discovery Institute 4ProDelphinus
Longline fisheries
NOAA – Pacific Islands Fisheries Science Center: Development and Testing of
Bycatch Reduction Technologies (BRTs)
Coastal Pound Nets Coastal Gillnet fisheries
Sensory cues
Visual Auditory
Chemosensory
Behaviors
Electromagnetic
Understanding sensory physiology and behaviors can drive the development of bycatch reduction
technologies (BRTs)
Endangered Species Research (2008)
Coastal gillnet fisheries - Coastal gillnets are a common form of fishing - Problematic due to non-selective impacts - Studies indicate large sea turtle bycatch in some fisheries
Baja California Sur - 800 loggerheads/yr (Peckham et al, 2008) - 68% mortality rate
Northern Peru – 300 sea turtles/yr (Alfaro-Shigueto et al, 2011) - 41% mortality rate
• Drift gillnet salmon fisheries in Puget Sound, WA
• Diving birds (Common Murre) are bycatch
• Exploited visual cues - highly visible netting - upper portion of net
• Bird interaction rates reduced by 45%
Conservation Biology, 1999
Can we develop visual cues that act as alerts for sea turtles?
Attach lightsticks onto a net - illuminating portions of the net - creating a visual alert
VS
Control Net – not illuminated Activated lightsticks
Lightsticks used to attract fish
Bahia de los Angeles
Punta Abreojos
• Punta Abreojos – Green turtle (Chelonia mydas) monitoring site that uses large mesh gillnets.
• Bahia de los Angeles – Commercial gillnet fisheries willing to modify their gillnets (e.g. net illumination) and allow observers onboard.
Punta Abreojos
Research sites along the coast of Baja California
Bahia de los Angeles
N=15
117 turtles
70 turtles
Mean CPUE decreased by 40%
Net illumination reduces C. mydas catch rates
Wilcoxon Matched-Pairs Signed-Rank test, significance: *P<0.05 Wang et al (2010) MEPS
N=6
81 turtles
34 turtles
Mean CPUE decreased by 59%
LED lightsticks
Chemical lightsticks
N=15
117 turtles
70 turtles
N=23 N=23
Mean CPUE decreased by 40%
Net illumination reduces C. mydas catch rates
Wilcoxon Matched-Pairs Signed-Rank test, significance: *P<0.05 Wang et al (2010) MEPS
N=6 N=17 N=17
81 turtles
34 turtles
Mean CPUE decreased by 59%
Chemical lightsticks
LED lightsticks
What about other wavelengths?
Electro-retinographs studies with sea turtles and fish
Loggerheads and Leatherbacks Summer flounder (P. dentatus)
Adapted from Horch et al, 2011 Adapted from Horodysky et al, 2010
N=11
209 turtles
123 turtles
N=36 N=36
ns
ns
Wilcoxon Matched-Pairs Signed-Rank test, significance: *P<0.05 Wang et al., (2013) Biology Letters.
Mean CPUE decreased by 40%
*
UV net illumination reduces sea turtle interactions
N=11
209 turtles
123 turtles
N=36 N=36
ns
ns
Wilcoxon Matched-Pairs Signed-Rank test, significance: *P<0.05 Wang et al., (2013) Biology Letters.
Mean CPUE decreased by 40%
*
UV net illumination reduces sea turtle interactions
All elasmobranch catch (all the sharks, rays, guitar fish, torpedo rays) had a significant difference in catch between the two net treatments
If we look just at the sharks – we see also a significant difference with the mean CPUE in the experimental nets
If we looked at the scalloped hammerhead sharks (S. lewini) – we also see a significant difference in catch rates.
I. Peruvian coastal gillnet fishery - Northern Peru (Constante) bottomset gillnets - 300+ sea turtles/year
- Collaboration with ProDelphinus
II. Indonesian coastal gillnet fishery - West Kalimantan (Borneo)
- Fishery occurs off major nesting beach - Collaboration with WWF-Indonesia,
Indonesia’s Ministry of Marine Affairs and Fisheries (IMMAF), Bogor University
Testing net illumination in coastal gillnet fisheries
A. Key Developments in Peru
- Tested control nets versus nets illuminated by green LED lights (10m) - Completed 114 paired trials - Show no change in target catch rates (guitarfish, rays, Pacific halibut) - Illuminated nets had significant decreases in catch rates for: Green sea turtles, cormorants, and sea horses.
- Collaboration with WWF - Indonesia - Rapid assessment of a coastal fishery indicates: - Operates off a major sea turtle nesting beach - Sets are in a leatherback foraging region - Interact with green, leatherback, hawksbill, olive ridley sea turtles - Other bycatch species include finless
porpoise, Irrawaddy dolphin, whale sharks, and other elasmobranchs
- In 2013, conducted a Fisheries Bycatch Workshop - Brought together Indonesia’s MMAF,
fishermen, fishery academics, NGOs - Designed an initial net illumination trial for 2014
B. Key Developments in Indonesia
Ongoing and Future Research
1. Baja, MX: Examine how different wavelengths can be used to change the catch composition
Continue to develop novel sensory based BRT in gillnet fisheries using visual and auditory cues
2. Peru: Move from the testing phase to an adoption phase
Extend research from small coastal fisheries into larger drift gillnet fisheries
3. Indonesia: Conduct net illumination trials through 2014 - Establish baseline data on bycatch - Test the applicability of net illumination Conduct rapid assessment of additional
coastal gillnet fisheries
Funders:
WWF-Smartgear NOAA-FIsheries-Office of International Affairs, NOAA-PIFSC, NOAA-SWRO, NOAA-PIRO, NOAA-BREP NOAA – Office of Education, University of Hawaii FDRP, Ocean Discovery Institute Supporters,
Fishers: Fishers and community of Punta Abreojos and Bahía de los Angeles Grupo Tortugero de las Californias, Baja California Fishers and community of Constante, Peru Fishers and community of Paloh, West Kalimantan
Special Thanks to: CONANP, IMARPE, IMMAF, I. Kelly, C. Fayh, C. Godinex-Reyes, B. Higgins, E. Kane, D. Lawson, M. Lopez, K. Dean, J. Rodriguez, A. Salazar, J. Sandoval, J. Seminoff, E. English, L. Benaka, K. Bigelow, C. Boggs, T.T. Jones, H. Peckham, Pro Delphinus, WWF-Indonesia, Grupo Tortugero, N. Marcovaldi, B. Giffoni, I. Mustahofa, A. Gautama.
ODI Staff and Students of Hoover High School (San Diego, CA)
Acknowledgements