A domestic import-substituting portable multipurpose scientific echo sounder (MIEL) with a split beam was developed by Vector Marine Electronics Ltd, Russian Federation. The need to create a domestic echo sounder for carrying out resource surveys in shallow inland waters is due to the fact that foreign scientific echo sounders have narrow beam patterns, which does not allow them to be used at depths less than 3 meters due to small sounding volumes of water medium and hence the low representativeness of the data. In addition, the cost of such devices is not available to the vast majority of Russian scientific organizations. After the introduction of sanctions by Western countries, many foreign manufacturers have stopped selling high-tech products to our country, and those that can be supplied are practically deprived of technical support, since many representative offices in Russia were closed, and the development of any high-tech products implies close cooperation between the developer and the user. By purchasing foreign equipment, our users are deprived of contact with Western manufacturers and the possibility of upgrading and improving the acquired equipment.

Over the past decades, not a single domestic fish-finding or scientific echo sounder has been created in the Russian Federation, therefore, Vector Marine Electronics Ltd managed to overcome a certain technological barrier.

Fig. 1 – A picture of portable multipurpose scientific echo sounder

After development and testing MIEL a hydroacoustic surveys was carried out in the Vazuzskoye reservoir jointly with specialists from VNIRO simultaneously using two echo sounders: the Norwegian EY500 with ES-70-11 transducer (split beam, 70 kHz, beam width 11 degrees), and MIEL (split beam, 200 kHz, beam width 18 degrees). The Norwegian Simrad EY500 echo sounder was used as a reference instrument. The figure 2 shows the EY500 echo sounder, consisting of a split beam transducer, a transceiver, a connecting cable and a computer.

Fig. 2 – Norwegian scientific echo sounder EY500.

In the process of survey echo sounders were connected to GPS systems to link the measurement results to the location on the map. A special outboard device for the mounting two transducers on the rod for a simultaneous pinging was designed and manufactured.

The distance between the transducers was 15 cm, which made it possible to record the same schools and single fish during the survey. The survey was carried on a pre-planned parallel grid of tacks. The equipment was installed on a Voronezh-K boat equipped with a 9.9 hp Yamaha engine. Transducers were placed on the starboard of the vessel. The speed of the vessel during the survey was 5-6 km/h. Ping rate (100 ms) and pulse duration (600 us for EY500 and 512 us for MIEL) of the echo sounders were approximately equal. The time and start of data recording of two echo sounders was synchronized.

According to the results of the analysis of recorded echograms, it is possible to say definitely about 2.5 times excess of the MIEL number of registered objects over the EY500. The difference in the number and geometry of the recorded targets is explained by the different widths of the beam patterns, and some color differences between the recorded objects and the bottom are different operating frequencies. In particular, the MIEL echo sounder recorded sound-scattering layers at depths below 9 m. Figure 3 shows a fragment of the echograms of the hydroacoustic survey carried with the MIEL and EY500 echo sounders. On the MIEL echogram, single targets that are not registered with the EY500 echo sounder are circled in red. Also on the MIEL echogram is visible a aggregation of small sized objects above the bottom surface.

Fig. 3 – A fragment of survey echograms of MIEL and EY500.

Using the Echoview post processing software, distribution of the target strength values for the registered single targets of both echo sounders was calculated and shown in Figure 4.

Fig 4 – Target strength distribution histogram

From the presented results: fragments of echograms of MIEL and EY500, as well as histograms of the target strength distribution reflecting the size distribution of fish, it can be concluded that:

1) the envelopes of the distributions coincide with the accuracy of the scale factor determined by the ratio of the number of registered single targets;

2) the number of fish detected using MIEL is 2.5 times the number of single fish detected by the EY500 echo sounder, i.e. MIEL echo sounder is more informative in comparison with EY500.

MIEL will find wide application in the following areas of fisheries:

- industrial fishing in inland waters and in coastal marine zones;

- study and quantitative assessment of aquatic biological resources of fishing areas (quantitative assessment), as well as an assessment of the effectiveness of fish protection devices in areas of influence of power plants on the local ichthyocenosis;

- automated control of the growth of fish in cages, their quantity, size range and optimization of the process of feeding fish (improvement of industrial aquaculture technologies);

- determination of places of fish concentrations in reservoirs with the aim of increasing the efficiency of recreational and sport fishing, assessment of fish productivity of reservoirs (recreational fishing);

- assessment of the distribution of aquatic biological resources in areas of drilling platforms, gas and oil production platforms, collectors of sewage treatment plants and in other areas of anthropogenic factors (environmental monitoring of potentially hazardous water areas as aquatic biological resources).