An Overview Of Our Solution
Developing Bycatch Reduction Solutions for Gillnet Fisheries while Empowering Marine Conservation Leaders
Who is this solution impacting?
Ecosystem
Océans/Côtes
Community Type
Rural
Additional Information
- Population Impacted:
- Continent: Amérique du Nord
Problem
Describe the problem
Our solution is to illuminate gillnets using widely available fishing lights such as LEDs or chemical lightsticks in order to reduce sea turtle bycatch by ~60% without reducing target catch or catch value. The modification satisfies all the requirements for successful adoption of bycatch reduction technology—it is inexpensive, easy to deploy, and does not result in loss in time (handling) or profitability. In addition, recent testing of UV LEDs suggest that certain wavelengths may increase the catch of target species (e.g. California Halibut) while reducing the capture rates of discarded, unwanted finfish. This research is conducted as a collaborative effort of scientists, local fishermen, and underrepresented high school and college students preparing to pursue careers in conservation.
Biodiversity Impact
Bycatch associated with fisheries is a significant source of mortality for sea turtle species. While strategies have been developed to reduce the sea turtle bycatch in pelagic longline fisheries, far fewer tools are available in coastal gillnet fisheries. Studies suggest that sea turtle bycatch in gillnet fisheries occurs in many of the world’s coastlines. As such, developing methods to reduce the incidental capture of sea turtles in gillnet fisheries is a priority. Our solution addresses this issue by testing net illumination as a method to reduce sea turtle interactions in gillnet fisheries. Our studies compared sea turtle catch rates (# of turtles/100m of net X 12 hours) between control (no illumination) and illuminated nets. These experiments show 40-60% reductions in green sea turtle catch rates. Results demonstrated an interesting trend in which the catch and catch value of halibut increased by 50% on illuminated nets. Halibut is the primary target species in many gillnet fisheries along the Baja California coast and is among the highest value/kilo. UV LEDs also demonstrated a 40% decrease in the number of non-targeted fish. We are now examining how each individual species may be affected by net illumination. In addition, by empowering fishers and students as integral members of the research team, participating in all phases of research, the project is building communities of skilled, knowledgeable future resource decision makers.
Solution
Bycatch in fisheries is a significant source of mortality for numerous species and a threat to biodiversity (Chan et al. 1988, Chan & Liew 1996, Lewison et al. 2004, Lum 2006, Lewison & Crowder 2007, Peckham et al. 2007). In particular, concerns have been raised over the high rates of capture and mortality of sea turtles and other non-targeted species (e.g. marine mammals, sea birds, fin fish, elasmobranchs) in gillnet fisheries (Chan et al. 1988, Chan & Liew 1996, Lum 2006, Lewison & Crowder 2007, Peckham et al. 2007, 2008). The use of gillnets throughout the world is ubiquitous, rendering their total fishing effort nearly impossible to quantify. Nonetheless it has been suggested that sea turtle mortality attributed to gillnet fisheries located along the Pacific coast of Baja California Sur, Mexico may be comparable to that of industrial-scale pelagic longline fisheries (Peckham et al. 2007, Peckham et al. 2008). While a number of strategies have been developed to reduce bycatch in pelagic longline fisheries, few are available for coastal gillnet fisheries. One useful approach to developing techniques to reduce sea turtle interactions with gillnets examines their sensory and behavioral ecology (Swimmer & Brill 2006, Southwood et al. 2008). By identifying cues that may act as deterrents we may develop strategies that enable a decrease in bycatch and an increase in biodiversity. Adapting these strategies to a gillnet fishery and testing their effectiveness can develop solutions to decrease sea turtle catch, while maintaining target catch rates. // This work has been developed in a small-scale bottom-set gillnet fishery in Bah??a de los Angeles, Baja California, Mexico and in an area of high green sea turtle populations, Punta Abreojos, Baja California, Mexico. The strategy is now being tested in gillnet fisheries found in Northern Peru, Southern Brazil, and plans for testing this solution are being developed in gillnet fisheries centered at Lopez Mateo in Baja California Sur, Mexico. These small scale fisheries all have documented issues with sea turtle interactions. While the research has been conducted in these specific sites, the application of the technology is highly transferable may be used in gillnet fisheries globally. In addition, as we continue to examine the use of UV-illuminated nets and their effects on finfish bycatch, there is the potential to increase fish selectivity in gillnet fisheries worldwide
Replicability
How many years has your solution been applied? 7 years // Have others reproduced your solution elsewhere? Yes // We have established a unique research platform to manage and test sea turtle bycatch mitigation strategies. A major stumbling block to the development of mitigation strategies is the need for high interaction rates with sea turtles in order for robust statistical analyses. Even in fisheries with large numbers of estimated turtle interactions, catching an individual turtle is still a relatively infrequent event. Working in Baja California, we have identified two sites - one of which has extremely high catch rates of sea turtles (10-80 sea turtles in a 12 hour period) in large meshed gillnets used to monitor turtle populations - and a second location with a commercial gillnet fishery that allows us to manipulate their gear to test potential mitigation strategies. This two-prong approach has enabled us to examine five methods that may reduce sea turtle bycatch as well as determine their impacts on target fish catch when adopted into a gillnet fishery. These methods include the illumination strategies described here as well as the use of shark shapes, which proved to be an effective visual deterrent for sea turtle interactions, and the use of photo-luminescent pigments, which requires additional development. Using this platform, we plan to continue developing net illumination as well other strategies aimed to reduce sea turtle bycatch (e.g. acoustic alerts, chemical deterrents).
Human Well Being and Livelihood Impact
In many areas of the world, the accidental capture of sea turtles is regulated and this bycatch may result in fisheries closures. This solution enables continued fishing efforts, by providing a mechanism to decrease interactions of sea turtles with gillnets and maintaining target catch and profits. In addition, recent investigations using UV illumination reveal that certain spectrums of light may result in increasing the catch rates of target species, leading to increased profitability. While the findings to date are local, they do seem consistent in the two different regions they’ve been tested—Mexico and Peru, suggesting that potential application of these findings on a much larger scale. The educational aspect of the project has integrated more than 20 high school and 10 college students, all from demographics highly underrepresented in science and conservation fields. Through their participation in the research, these young people have been empowered to pursue careers in these fields. 8 out of 10 of the high school students have directly entered four-year universities (as compared to less than 3 out of 10 at their school) and 7 out of 10 students have declared majors in science and conservation. Many of the students are particularly interested in pursuing careers in fisheries science and management and after participating in the project, have completed internships including Bluefin tuna research at Southwest Fisheries Science Center and interviewing fisheries observers in Vietnam. These young people will become our future decision makers and conservation workforce. // Managing small scale gillnet fisheries is a challenge. One reason for this is that there are few tools available to fisheries managers. Developing cost-effective methods that are both effective in reducing bycatch while increasing the target catch of desirable species is a major step in providing fisheries managers with a strategy to help develop clean fisheries. If the use of UV illumination is able to improve the selectivity of gillnet fishing and results in a higher proportion of halibut catch, a highly valued species, there may be sufficient financial incentive to encourage fishers to choose this strategy.