A Novel Biologging Tag that Minimizes the Hydrodynamic Loading on Marine Animals

Abstract

Although biologging tags, which are externally attached sensor packages deployed on marine animals, have become essential conservation tools, a core issue with current tag designs is that they are rarely tested for hydrodynamics and may generate substantial hydrodynamic loading (drag and lift forces) on animals. This may cause tags to impede animal physiology, give rise to injuries at the site of attachment, and cause tags to relay unrepresentative data. This study aims to design a new biologging tag form that houses the DTAG3 electronics and reduces the total drag and lift induced on marine animals. One starting model (GPS Phone Tag referred to as Model 0), three iterations, and the final design (Model D), were constructed using CAD software. They were tested with Computational Fluid Dynamics (CFD) simulations to obtain and analyze the drag and lift force. All models were tested at speeds between 1-5 m/s, with 400 trials. The Model D includes a narrow elliptical shape to maintain laminar boundary layers, a pointed tail shape to avoid flow separation, canards for frontal downforce, tabs to reduce form drag, streamlined hydrophones, and dimples to delay flow separation. The CFD simulation results demonstrated that Model D reduced drag by up to 56% and lift by upto 86% compared to Model 0. These results show the potential benefit of this design in reducing the impact of biologging tags on the behavior and energetics of marine animals, and in providing an unbiased and holistic view of the animal behavior for conservation management actions.