Operational protocol for the sighting and tracking of Portuguese man-of-war in the southeastern Bay of Biscay: Observations and modeling

This paper describes the operational protocol established in the southeastern Bay of Biscay (study area) for the sighting and tracking of Portuguese man-of-war. This action protocol combines sightings of Portuguese man-of-war at sea with hourly surface currents and winds obtained with the Regional Ocean Modeling System (ROMS) and the Weather Research and Forecasting model (WRF), respectively. These data are used in the Sediment, Oil spill and Fish Tracking model (SOFT) to estimate the drift of Portuguese man-of-war. Here we provide information on sightings of Portuguese man-of-war in the study area and show the most relevant results of the SOFT calibration obtained using trajectories from eight satellite pop-up tags for fish tracking. These tags have similar characteristics (such as weight and density) to the Portuguese man-of-war that reach the study area. In 2012 and 2013, there were a total of 48 sightings of Portuguese man-of-war, most of them located in the Zarautz beach area (Basque Country coast). The SOFT calibration shows that the tag drift is mainly controlled by the wind. With winds from the southern and western sectors (third quadrant), SOFT is able to reproduce the tag drift using surface current velocities estimated as ~1.8% of the WRF wind velocities. The SOFT simulations carried out using the ROMS current velocities (with or without the WRF wind velocities) do not improve the results.