Parametric profiler using a linearly frequency modulated signal.

At the Kotelnikov Institute of Radio Engineering and Electronics of RAS an experimental prototype of a parametric echo sounder-profiler with linear frequency modulation (LFM) of the sounding signal has been developed, manufactured and tested. Two chirp signals are emitted at frequencies of 144 kHz and 148 kHz. The difference reception frequencies have a frequency range of 1 kHz to 8 kHz. A wide band of differential frequencies is achieved by emitting two chirp signals. Laboratory and marine tests of the experimental model of the echo sounder-profiler have been carried out.

CONTRIBUTION OF BATHYMETRIC MULTI-BEAM SONAR AND LASER SCANNERS IN 3D MODELING AND ESTIMATION OF SILTATION OF DAM BASIN IN MOROCCO

In Morocco, the phenomenon of silting affects all the dams, where more than 75 Mm3 of sediments are deposited every year at the bottom of the reservoirs. The aim of our study is to assess the contribution of the bathymetric multi-beam sonar as well as static and mobile laser scanners in the estimation of siltation of the basin of the Tanger-Med dam in the north of Morocco. The proposed methodology consists of performing and fusion of a bathymetric survey by multi-beam echo-sounder with terrestrial laser scanner surveys in static mode and mobile mode. The result of these surveys is used, for the calculation of the siltation volume and the inspection of the upstream facing of the main structure. Siltation calculation was carried out with comparison to a reference survey obtained by single beam sonar. The comparison between these two instruments showed that the multi-beam presents many advantages: high density of the cloud of points acquired and precision. The density allows providing a better description of the dam's bottom. The comparative study between the two types of scanners showed that static scanner offers a better accuracy. However, mobile scanner gives more accessibility of all parts of the dam. As a conclusion, the multi-beam echo-sounder with additional laser scanner data have many advantages in this study: volume calculation precision, reduction of the acquisition time and the enhancement of the acquired point cloud density. We also obtained a global 3d modelling useful for the monitoring of the infrastructure.

Quantitative assessment of multiple fish species around artificial reefs combining environmental DNA metabarcoding and acoustic survey

Since the early 1970s, many artificial reefs (ARs) have been deployed in Japanese coastal waters to create fisheries grounds. Recently, researchers began to use environmental DNA (eDNA) methods for biodiversity monitoring of aquatic species. A metabarcoding approach using internal standard DNAs [i.e., quantitative MiSeq sequencing (qMiSeq)] makes it possible to monitor eDNA concentrations of multiple species simultaneously. This method can improve the efficiency of monitoring AR effects on fishes. Our study investigated distributions of marine fishes at ARs and surrounding stations in the open oceanographic environment of Tateyama Bay, central Japan, using qMiSeq and echo sounder survey. Using the qMiSeq with 12S primers, we found higher quantities of fish eDNAs at the ARs than at surrounding stations and different fish species compositions between them. Comparisons with echo sounder survey also showed positive correlations between fish eDNA concentration and echo intensity, which indicated a highly localized signal of eDNA at each sampling station. These results suggest that qMiSeq is a promising technique to complement conventional methods to monitor distributions of multiple fish species.

Tuna-AI: tuna biomass estimation with Machine Learning models trained on oceanography and echosounder FAD data

Echo-sounder data registered by buoys attached to drifting FADs provide a very valuable source of information on populations of tuna and their behaviour. This value increases when these data are supplemented with oceanographic data coming from CMEMS. We use these sources to develop Tuna-AI, a Machine Learning model aimed at predicting tuna biomass under a given buoy, which uses a 3-day window of echo-sounder data to capture the daily spatio-temporal patterns characteristic of tuna schools. As the supervised signal for training, we employ more than 5000 set events with their corresponding tuna catch reported by the AGAC tuna purse seine fleet.

The use of singlebeam echo-sounder depth data to produce demersal fish distribution models that are comparable to models produced using multibeam echo-sounder depth

Seafloor characteristics can help in the prediction of fish distribution, which is required for fisheries and conservation management. Despite this, only 5-10% of the world’s seafloor has been mapped at high resolution as it is a time-consuming and expensive process. Multibeam echo-sounders (MBES) can produce high-resolution bathymetry and a broad swath coverage of the seafloor, but require greater financial and technical resources for operation and data analysis than singlebeam echo-sounders (SBES). In contrast, SBES provide comparatively limited spatial coverage, as only a single measurement is made from directly under the vessel. Thus, producing a continuous map requires interpolation to fill gaps between transects. This study assesses the performance of demersal fish species distribution models by comparing those derived from interpolated SBES data with full-coverage MBES distribution models. A Random Forest classifier was used to model the distribution of Abalistes stellatus, Gymnocranius grandoculis, Lagocephalus sceleratus, Loxodon macrorhinus, Pristipomoides multidens and Pristipomoides typus, with depth and depth derivatives (slope, aspect, standard deviation of depth, terrain ruggedness index, mean curvature and topographic position index) as explanatory variables. The results indicated that distribution models for A. stellatus, G. grandoculis, L. sceleratus, and L. macrorhinus performed poorly for MBES and SBES data with Area Under the Receiver Operator Curves (AUC) below 0.7. Consequently, the distribution of these species could not be predicted by seafloor characteristics produced from either echo-sounder type. Distribution models for P. multidens and P. typus performed well for MBES and the SBES data with an AUC above 0.8. Depth was the most important variable explaining the distribution of P. multidens and P. typus in both MBES and SBES models. While further research is needed, this study shows that in resource-limited scenarios, SBES can produce comparable results to MBES for use in demersal fish management and conservation.