08 Mar 2023
 | 08 Mar 2023

Assessing the drift of Fish Aggregating Devices in the tropical Pacific Ocean

Philippe Friederickus Vincentius Wenceslaus Frankemölle, Peter Dirk Nooteboom, Joe Scutt Phillips, Lauriane Escalle, Simon Nicol, and Erik van Sebille

Abstract. The Tropical Pacific Ocean is characterized by its dominant zonal flow, strong climate dependence on the El Niño Southern Oscillation (ENSO) and abundant tuna stocks. Tuna fisheries in the West and Central Pacific Ocean accounted for 55 % of world-wide tuna catch in 2019 and are one of the main sources of income in many Pacific island nations. One of the dominant fishing methods in this region relies on the use of drifting Fish Aggregating Devices (dFADs): rafts with long underwater appendages (on average 50 m deep) that attract and aggregate fish. Although currents such as the North Equatorial Countercurrent (NECC) and South Equatorial Current (SEC) in the tropical Pacific Ocean vary strongly with ENSO, little is known about the impact of this variability in flow on dFAD dispersion. In this study, virtual Lagrangian particles are tracked for the period 2006 to 2021 over the domain in a 3D hydrodynamic model and are advected in simulations with only surface flow as well as simulations using a depth-averaged horizontal flow over the upper 50 meters. The particle trajectories are used to determine zonal displacements, eddy-like behaviour and ENSO variability for drifters that are subjected to either surface or depth-averaged currents. It was found that virtual particles that are advected by only surface flow are displaced up to 35 % farther than those subjected to a depth-averaged flow, but no other major differences are found in dispersion patterns. Strongest correlations between ENSO and dFAD dispersion for the assessed variables were found in the West Pacific Ocean, with Pearson correlation coefficients up to 0.59 for dFAD displacement. Connections between ENSO and eddy-like behaviour were found in the western part of the SEC, indicating more circulation and meandering during el Niño. These findings may be useful for improving sustainable deployment strategies during ENSO events, and understanding the ocean processes driving the distribution of dFADs.

Philippe Friederickus Vincentius Wenceslaus Frankemölle et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-315', Anonymous Referee #1, 26 Mar 2023
  • RC2: 'Comment on egusphere-2023-315', Anonymous Referee #2, 02 May 2023

Philippe Friederickus Vincentius Wenceslaus Frankemölle et al.

Model code and software

dFAD_drift_WTPO: v1.0.0 P. F. V. W. Frankemölle

Philippe Friederickus Vincentius Wenceslaus Frankemölle et al.


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Short summary
Tuna fisheries in the tropical Pacific often use drifting Fish Aggregating Devices (dFADs): rafts that attract fish, while advected by subsurface flow through underwater appendages. Using a particle advection model, we find that virtual particles advected by only surface flow are displaced up to 35 % farther than virtual dFADs. We find a relation between ENSO and circular motion in some areas, influencing dFAD densities. This information helps understanding processes that drive dFAD distribution.