Results of the large-scale biodegradable FAD experiment in the eastern Pacific ocean

Purse-seine effort on the fish-aggregating device (FAD) fishery in the EPO has steadily increased since the early 1990s due to its efficiency in capturing tropical tunas that aggregate under FADs. However, as with most fishing methods, FADs can have negative effects on associated species and ecosystems, such as entanglement of vulnerable species like sea turtles or sharks, accumulation of marine debris and pollution, and stranding events in vulnerable habitats (e.g., coastal nursery areas). Therefore, the IATTC required scientific recommendations to transition from traditional to biodegradable FADs that would reduce these impacts. A total of 780 biodegradable FADs, known as NEDs (non-entangling degradable FADs) (114 prototype 1; 395 prototype 2; 271 prototype 3) were deployed along with their corresponding traditional FAD controls for a total of 1,544 experimental FADs. Results showed similar catch per set values between NEDs and traditional FAD controls (NEDs = 33.6 mt/set, traditional control FADs = 31.7 mt/set). Prototype 1 was found to be in good and very good condition after a minimum of two months at sea, while prototype 2 materials were from good to fair condition for at least three months. The NED design of prototype 3 was the least durable, but some modifications made in collaboration with the fleet improved its durability and were found to be in good to excellent condition during longer periods of soak time (at least two-three months). Satellite buoys were used to determine the lifespan (i.e., ‘operational’ life) of the experimental FADs, with traditional FADs having a lifespan of 854 days and NED prototypes 1,2, and 3 having maximum lifespans of 790, 379 and 686 days, respectively. Comparisons of drifting trajectories showed that pairs with similar drifting patterns had lower differences in speed, while pairs with divergent trajectories had greater separation distances. Tuna biomass aggregation analyses using echo -sounder information of satellite buoys showed similar biomass index values for both traditional FADs and NEDs, with a consistent increasing trend up to 80 days for traditional FADs and up to 50-60 days for NEDs. The IATTC staff’s conclusions, future actions, challenges and lessons learnt from positively engaging with the industry and fishers are also described. This study suggests that starting a transition to biodegradable FADs to reduce negative impacts on the associated species and ecosystems may be possible without compromising the effectiveness of the fishing method.