Movement tracing and analysis of benthic sting ray ( Dasyatis akajei ) and electric ray ( Narke japonica ) toward seabed
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Movement tracing and analysis of benthic sting ray (Dasyatis akajei) and electric ray (Narke japonica) toward seabed exploration Shun‑ichi Funano1 · Nobuyuki Tanaka1 · Satoshi Amaya1 · Akira Hamano2 · Toyoki Sasakura3 · Yo Tanaka1 Received: 19 August 2020 / Accepted: 25 November 2020 © The Author(s) 2020 OPEN
Abstract Creation of a seabed map is a significant task for various activities including safe navigation of vessels, commercial fishing and securing sea-mined resources. Conventionally, search machines including autonomous underwater vehicles or sonar systems have been used for this purpose. Here, we propose a completely different approach to improve the seabed map by using benthic (sting and electric) rays as agents which may explore the seabed by their autonomous behavior without precise control and possibly add extra information such as biota. For the first step to realize this concept, the detail behavior of the benthic rays must be analyzed. In this study, we used a system with a large water tank (10 m × 5 m × 6 m height) to measure the movement patterns of the benthic rays. We confirmed that it was feasible to optically trace the 2D and 3D movement of a sting and an electric ray and that the speed of the rays indicated whether they were skimming slowly over the bottom surface or swimming. Then, we investigated feasibility for measuring the sea bottom features using two electric rays equipped with small pingers (acoustic transmitters) and receivers on a boat. We confirmed tracing of the movements of the rays over the sea bottom for more than 90 min at 1 s time resolution. Since we can know whether rays are skimming slowly over the bottom surface or swimming in water from the speed, this would be applicable to mapping the sea bottom depth. This is the first step to investigate the feasibility of mapping the seabed using a benthic creature. Keywords Benthic ray · Electric ray · Sting ray · Seabed mapping
1 Introduction In the past few decades, there have been increasing demands for seabed mapping [1, 2]. Seabed maps are important for safe navigation of vessels, securing natural resources including fossil fuels and minerals and undertaking better commercial fishery activities. The use of autonomous underwater vehicles (AUVs) is one common
method for seabed searching [3–6]. AUVs are convenient tools for getting the shape of the sea bottom in detail. Alternatively, sonar systems have been used for this purpose [7–9]. These use acoustic remote sensing from ships and are very powerful tools to search the sea bottom even at great depths. Multibeam echosounders (MBES) are currently the main devices which are used for high-resolution seabed mapping [10–13]. Optical methods using
Shun-ichi Funano and Yo Tanaka have contributed equally to this work. Electronic supplementary material The online version of this article (https://doi.org/10.1007/s42452-020-03967-6) contains supplementary material, which is available to authorized users. * Yo Tanaka, [email protected] | 1Center for Biosystems Dynamics Researc
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