Fish aggregating devices could enhance the effectiveness of blue water marine protected areas

Abstract

In the past two decades, drifting fish aggregation devices (FADs) have revolutionized pelagic fisheries, and are now responsible for the majority of tuna purse seine catches. Here, we argue that by taking advantage of the same proven aggregative properties, FADs could be used to enhance the benefits provided by blue water marine protected areas (MPAs). Using models of commercially targeted fish populations, we explore the potential benefits that could be achieved if unfished conservation FADs—designed as self‐powered devices capable of remaining semi‐stationary—were deployed within blue water MPAs. By increasing the residence time of exploited species in MPAs, conservation FADs will reduce average mortality rates. By increasing the local density of exploited species, they may also improve the function of ecosystems in blue water MPAs. Conservation FADs could, therefore, amplify the benefits of blue water MPAs. We find this amplification is largest in those contexts where blue water MPAs have attracted the most criticism—when their area is small compared to both the open ocean and the distribution of fish stocks that move through them.

Numerical Study of the Hydrodynamic Response of Biodegradable Drifting Fish Aggregating Devices in Regular Waves

“…Globally, approximately 4.8 million tons of tuna were caught in 2021, and approximately 36% of the catch was derived from the sets of purse seining on DFADs [4]. DFADs are extensively utilized, and it is estimated that more than 100,000 DFADs are deployed annually [5,6]. DFADs can freely drift in the ocean and are typically made of a raft (to ensure buoyancy) and a submerged substructure to slow down the drifting speed and provide shade, both of which are considered helpful for improving tuna aggregation.…”