TURTLE TARGETING TRAPS: Achieving co-existence with nature
This project is the result of a collaboration between Innoceana and Davis Projects for Peace, two organizations committed to building a sustainable and peaceful future through creative and community-focused solutions. Davis Projects for Peace supports young leaders working to promote peace, while Innoceana is dedicated to protecting the oceans through education, research, and the use of cutting-edge technology.
The primary objective of the project was to study the interaction between sea turtles and artisanal shrimp traps in the waters of the Special Area of Conservation (SAC) “Franja Marina Teno-Rasca” in Tenerife. The project also aimed to develop innovative fishing gear that is compatible with sea turtle conservation.
With an estimated 90% of the region’s fish biomass having disappeared over the last 50 years (Castro et al., 2019), loggerhead turtles (Caretta caretta) are increasingly forced to seek out new food sources, exposing themselves to deadly risks. The project not only investigates these behaviours but also explores innovative fishing techniques that could help safeguard this vulnerable species.
Study area:
The study area is situated on the western side of Tenerife, in the SAC ES7020017, known as the “Franja Marina Teno-Rasca” (Fig.1). Within this protected area is the locality of Playa San Juan, situated in the municipality of Guía de Isora. Playa San Juan stands out from nearby ports for its particular focus on professional fishing.
Fishing sustainability and turtle protection in the Canary Islands:
In the Canary Islands, the professional fishing sector is distinguished by its exclusive use of artisanal methods. This practice relies on small, low-powered vessels operating primarily in coastal areas and employing traditional fishing gear, requiring significant manual labor. Artisanal fishing holds considerable economic and cultural importance and is also recognized for its lower environmental impact compared to industrial fishing (Castro, 2019).
However, it’s crucial to acknowledge the growing challenges that this traditional activity poses to marine wildlife conservation, particularly for the loggerhead turtle, a species widely present in Tenerife alongside the green turtle (Chelonia mydas). Unlike the green turtle, which is herbivorous in adulthood, the loggerhead is carnivorous, feeding on fish, invertebrates, crustaceans, and squid.
Their habit of floating near the water’s surface makes them especially vulnerable to capture and other environmental threats. The primary threats to loggerhead turtles include chemical pollution, plastic waste, and fishing gear such as longlines and nets.
Over eight million tons of plastic enter the oceans each year, making up 80% of all marine debris (UN Global Compact, n.d.). This influx of waste drastically increases the risk of entanglement or ingestion for turtles, negatively impacting their feeding, development, and survival (Fig.2) (Ocean Conservancy, n.d.).
The Canary Islands experience a high incidence of marine turtle strandings, with 96.7% of these cases involving loggerhead turtles (Liria-Loza et al., 2021). These strandings highlight the severe threats that these turtles face due to pollution and marine debris, and this conservation project aims to monitor and mitigate these threats to better protect these species and preserve marine ecosystems.
Figure 2. Turtle tangled in fishing gear
In this context, a conflict has arisen between fishermen using shrimp traps to fish narwal shrimps (Plesionika narval) and marine turtles. It was suspected that loggerhead turtles open the traps in an attempt to access the bait intended to attract shrimps, leading to damaged fishing gear and economic losses for the fishermen. This emerging issue underscores the need to find balanced solutions that protect marine wildlife without compromising traditional fishing practices (Fig.3).
Figure 3. Professional fishermen at the port of Playa San Juan with their catch.
Project methodology:
To achieve the project’s objectives, a methodology was developed and divided into several phases. Initially, the organization collaborated with the fishermen of the “Cofradía Nuestra Señora de la Luz,” conducting interviews and analyzing existing documentation on artisanal shrimp fishing using traps and the interactions between sea turtles and fishing gear. Subsequently, a field study was carried out, documenting the entire fishing process, from the construction of the fishing gear to the sale of the catch. In the next phase, alternative traps were designed to reduce the risk of sea turtle attacks, and these solutions were presented to industry professionals. Finally, the fishermen built traps using more durable materials, and the impact of these solutions on reducing turtle attacks was studied. Cameras were installed inside the fishing traps to gather evidence of the interaction between the species and the fishing gear.
Results:
During the camera recordings, a notable variety of species was observed, including rays such as the common stingray (Dasyatis pastinaca), and other interesting species like trumpetfish (Aulostomus strigosus), which freely entered and exited the traps, and pufferfish (Sphoeroides marmoratus), which remained trapped inside.
The cameras recorded several interactions between loggerhead turtles and the traps. In some of them, the turtles exhibited aggressive behavior towards the traps, managing to break them and expose the bait. However, with the use of the prototype trap made of imported metal mesh, despite aggressive behavior towards the fishing gear turtles were not able to break it (Fig.4).
Figure 4. Photographs taken inside the fishing gear.
Conclusions:
The project successfully documented, for the first time, the interaction between loggerhead turtles and shrimp traps, a behavior previously unobserved. Regarding the design of alternative traps, the use of more durable materials appears to be the most sustainable option, as it could eliminate plastic from trap production while reducing the damages caused by loggerhead turtles. However, the primary challenge remains the cost of materials, as there are no local producers providing suitable metal nets for artisanal fishing.
References:
Castro, J. J. (2019). La pesca artesanal en las Islas Canarias. Okeanos, (8).
Castro, J. J., Divovich, E., Delgado de Molina Acevedo, A., Barrera-Luján, A., & Riera, R. (2019). Reconstruction of marine small-scale fisheries captures in the Canary Islands (NE Atlantic Ocean) from 1950 to 2010. Scientia Marina, 83(1), 7–17.
Liria-Loza, A., Fariñas-Bermejo, A., & Ostiategui-Francia, P., Usategui-Martín, A. (2021). Protocolo de actuación frente a varamientos de tortugas marinas en Canarias. Gobierno de Canarias (Fondos FEDER). ISBN: 978-84-09-32808-6.
Ocean Conservancy. (n.d.). Plastics in the ocean. Ocean Conservancy.
https://oceanconservancy.org/trash-free-seas/plastics-in-the-ocean/
UN Global Compact. (n.d.). End waste entering the ocean. United Nations Global Compact.
https://unglobalcompact.org/take-action/ocean/communication/end-waste-entering-the-ocean