Hydroacoustic Methods Research Articles

A new approach to assessing and forecasting the stock of sprat in the Baltic Sea in modern conditions

The aim of this article: analysis of information and software for forecasting of the Baltic Sea sprat stock Sprattus sprattus balticus at 22–32 ICES subdivisions in the context of the suspension of Russia’s activities in the International Council for the Exploration of the Sea (ICES).Methods used: The data of estimates of sprat abundance and biomass by hydroacoustic methods, commercial and biostatistical characteristics of the species were used to assess the stock and predict its catch in the Baltic Sea. Estimation of the sprat stock was carried out using the traditional method of virtual population analysis (VPA) adjusted according to the method of extended survival analysis (XSA) using the internationally approved VPA module software within the framework of ICES and the R software environment. The recruitment calibration program RCT3 (Recruitment calibration) was used for the abundance of recruitment (age 1 year) according to XSA and forecast. A multivariate short-term forecast was carried out at different levels of development of the total allowable catch (TAC) under the MFDP program (Multi Fleet Deterministic Projection). As an alternative, the domestic software «KAFKA» was tested.Novelty: for the first time, estimates of the sprat stock were made in the conditions of limited access of Russian specialists to primary data in ICES in full.Result: modern methodological and informational support of scientific research in the Baltic Sea in the conditions of the suspension of the activities of Russian experts in ICES makes it possible to obtain information in the minimum necessary amount for assessing the stock of sprat and predicting its catch. Modeling with the «KAFKA» software showed satisfactory results.Practical significance: The current level of information support for forecasting the state of the stock and catch of sprat in the Baltic Sea will allow solving a complex of problems of managing this resource in modern conditions.

Assessment the state of the omul stock <I>Coregonus migratorius</I> in the waters of Northen Baikal according to hydroacoustic investigations

Recently in Lake Baikal there was observed decrease in population of the most abundant species among commercial fish – Baikal omul (Coregonus migratorius). That is why restrictive measures have been imposed on its catches. A hydroacoustic method based on hydroacoustic surveys was used to assess the evolution of the Omul population during the period of restrictive measures in one of the most productive fishery areas – the Northen Baikal. This work represented the results of three-year hydroacoustic research (2021, 2022 and 2023) in the first decade of June. Taking into account the confidence intervals for estimating the number and biomass of Omul, the stock in Northen Baikal is quite stable. The omul spatial distribution on the investigated areas is also stable.

Use of Hydroacoustic Methods to Assess Ecological Status Based on Fish: A Case Study of Lake Dejguny (Poland)

The idea of the article was to verify the thesis that acoustic studies of ichthyofauna in lakes provide sufficient information to determine the necessity (or lack thereof) of carrying out a full procedure for assessing the ecological status based on fish. The manuscript compares acoustic data collected in 2008 and 2021 in Lake Dejguny (Poland) as a result of acquisition carried out with the same EY-500 echosounder, on the same routes (transects), and the echogram analyses were carried out using software dedicated to this echosounder. Target strength (TS) distribution was determined in the lake and in individual water layers with a thickness of 2 m, as well as, using the mapping method, changes in the distribution of fish in selected water layers. Large changes in TS distribution in the vertical profile were demonstrated between both years of the study, as well as a clear reduction in the space available for fish in waters below 24 m in 2021, which was associated with a reduction in the concentration of dissolved oxygen below this depth to a value lower than 2.5 mg L−1. It was suggested that it could be possible to develop a simple index enabling the assessment of changes in fish structure, based, similarly to the Large Fish Index, on the ratio of the number of large fish to small fish. The obtained results confirmed that the proposed methods of acoustic data analysis can be the basis for the decision on the necessity (or lack thereof) of conducting an assessment using the Polish national LFI-EN method based on the results of one-off fishing with Nordic multimesh gillnets.

Hydroacoustic method and GIS-Dashboard visualization for fish size in Banggai Sea Waters

Estimating fish stocks, including their distribution and density, plays a vital role in the management of capture fisheries. Hydroacoustic technology is widely utilized for fish stock estimation study. In September 2022, BRIN and IPB University conducted hydroacoustic data measurement in the Banggai Sea as part of the “Banggai Upwelling Dynamics Exploration and Experiment” to estimate fish stocks. Very large fish (>58 cm) has a density of 12,452 fish km-2. The spatial distribution of fish occurs in the eastern waters of Banggai Island and the northern waters of Taliabu Island. The most significant potential is the epipelagic layer (0 to -200 meters), with very small-sized fish having the highest density, followed by large-sized and small-sized fish. To summarize the analysis results of fish density distribution , a GIS-Dashboard is utilized. This online platform integrates various maps and charts, offering an engaging and easily understandable visualization of the information.

THE MANIFESTATION OF DEGASSING IN THE SEDIMENTARY COVER AND RELIEF OF THE YUZHNO-NOVOZEMELSKY TRENCH (PECHORA SEA)

The results of detailed geological and geomorphological studies in the waters of the Pechora Sea using a complex of hydroacoustic methods in the 52 cruise of the R/V “Academic Nikolaj Strakhov” revealed numerous gas funnels (pockmarks) at the bottom of the Yuzhno-Novozemelsky trench. These forms are widespread on most of the bottom of the Barents Sea, while on the Pechora shelf there is very little information about their distribution. Analysis of seismoacoustic sections at the sites of development of gas funnels showed the presence of vertical chimneys in unconsolidated sediments of the Yuzhno-Novozemelsky trench, through which gas rises to the bottom surface and its release into the water column with the formation of negative landforms, which is accompanied by churning bottom sediments.

Картирование опасных геологических объектов и процессов северной и центральной частей шельфа Баренцева моря по данным гидроакустического комплекса НИС «Академик Николай Страхов»

Mapping of dangerous geological objects and processes by hydroacoustic methods is being intensively developed in the areas of the Arctic shelf of Russia. Considerable experience has been accumulated in identifying of these objects and in compiling of thematic maps showing their properties, spatial distribution and correlation with geological and tectonic structures. A large amount of data and the development of economic activity make it necessary to develop a methodology for compiling these maps, design of legends and an approach to updating them. The paper presents map samples of dangerous geological objects compiled according to the data of RV “Academik Nikolai Strakhov” expeditions.

Гидроакустическая оценка запасов байкальского омуля (Coregonus migratorius) по результатам двухлетних исследований в весенне-летний период 2021 и 2022 годов

Taking into account the depressive condition of the Baikal omul resource, the decree of the Ministry of Agriculture of the Russian Federation No. 450 dated August 29, 2017 strict restrictions were established on the catch of Baikal omul in order to restore its reserves. Since 2021, a hydroacoustic method based on hydroacoustic surveys has been used to estimate its recovery. In 2021, on the fishing areas of Lake Baikal (Selenga shallow water and Northern Baikal) there were conducted surveys. In 2022, in addition to these areas, the researches were conducted in the Barguzin Bay and the Small Sea. Significant increase in the number of small omul was observed in the Selenginsky shallow water area in 2022. The results of a comparative analysis on Northern Baikal within the water area of 2021 showed that, taking into account confidence intervals, the number of omul and its biomass practically did not change. The averages omul biomass and number per unit area in the Small Sea were significantly lower than in the waters of the Selenginsky shallow water and the Northern Baikal. The lowest average densities were recorded in the Barguzin Bay.

Fish Stock Status Assessment in Alue Naga Waters Using A 200 Khz Single Beam Echosounder

Monitoring fish stocks is an important part of sustainable management of fisheries resources. Conducting the current evaluation is very difficult since there are no reliable data on the potential for fisheries in the waters surrounding Banda Aceh city. The hydroacoustic method was used for the first time in the waters of Alue Naga, located north of Banda Aceh, to evaluate the condition of fish stocks. A single beam scientific echosounder with a frequency of 200 kHz was used to collect hydroacoustic data in the area. The collected data was then processed using the Sonar5-Pro software. Cell integration was carried out at an interval of 10 meters vertically with an elementary sampling distance (ESD) of 200 m. While the volume backscattering strength (SV) value tends to be the highest in intermediate layers, the target strength (TS) value was found to be maximum in deeper layer, reaching a maximum value of -49.46 dB at a depth of 51–60 m. Area density value (#.ha-1) was found to be the highest at a depth of 11-20 m, while Biomass (g.ha-1) at a depth of 21-30 m was the highest among other depth layers with a value of 1558 g.ha-1. According to the in-situ catches of Carangoides, Selaroides, Aphareus, Variola, and Priacanthidae, there are a number of potential reef fish resources in the waters of Alue Naga. The findings of this study strongly support the conclusion that the hydroacoustic method effectively provides comprehensive information on the horizontal and vertical distribution of fish in Alue Naga waters.

Target strength of seahorse (Hippocampus kuda) based on presence dorsal and ventral aspect of brood pouch: a experiment hydroacoustic using artificial neural network

Hydroacoustic technology is a tool can be used to study the behavior of organisms. The target strength of an object is main key in hydroacoustic technology. The value of target strength is strongly influenced by level of hardness of object, in this case the seahorse has a different level of hardness between dorsal and ventral aspect. The unique of male seahorse that experiences pregnancy and keeps it’s baby in brood pouch until it hatches. This can be used as a difference between males and females based on value of target strength. Acoustic data recording using single beam scientific echosounder SIMRAD EK-15 and Sonar-4 processing software. The results showed that mean TS value of pregnant male seahorses (with brood pouch) was smaller than of female seahorses (without brood pouch), there were differences in structure composition and anatomy of the brood pouch which backscattering strength to decrease. The artificial neural network shows that there is a difference in response between seahorse (having a brood pouch/male) compared seahorse (without a brood pouch/female). The results showed that was a difference in dorsal aspect of 87.5% and ventral aspect of 98.6%. The results of this study can be used as key to distinguish sex of seahorses using the hydroacoustic method.

Acoustic-trawl studies of the Coregonus migratorius (Georgi,1775) in the Selenga shallow water zone of Lake Baikal, 2023

Study of peculiarities of distribution of aggregations and size-age structure of the Baikal omul feeding stock in the Selenga shallow water zone of Lake Baikal were studied using the hydroacoustic method in combination with control trawls. Comparative analysis of the results of 2023 with the data of 2015-2022 showed significant changes in the general character of distribution of the Baikal omul aggregations in the water area and depth. Standard length of fish from different shallow water zones ranged from 10 to 39 cm with a sample median of 17 cm. In terms of weight, individuals of 18-26 cm in length were dominant. A “length-age” equation allows making an operational assessment of age class abundance correlation based on the probability of assigning individuals of a certain length to them. It is shown that 3-5 years old fish form the basis of the biomass of feeding stock in the Selenga fishing zone. A significant proportion of young fish indicates that there is sufficient recruitment to increase the biomass of the Baikal omul stock in 5 years perspective.

Influence of near bottom fish distribution on the efficacy of a combined hydroacoustic video survey

Abstract Combining hydroacoustics and underwater video is an effective tool for generating fish population estimates. However, hydroacoustics cannot be used to differentiate fish from the seafloor within an area known as the acoustic dead zone. A common way to address this is to exclude data near the bottom. The effect of this exclusion zone on population estimates of nearshore semi-pelagic rockfish is unknown. This study explores the effect of a near bottom (0–1 m) exclusion zone by comparing ROV video data to data from a combined hydroacoustic and video method. Higher densities of semi-pelagic species (Black and Blue/Deacon Rockfish) were observed in the combined acoustic and video method, suggesting that most of the population resides above the exclusion zone. Demersal rockfish observed by the ROV did not contaminate acoustic data of semi-pelagic species, since they remained within the exclusion zone. Results demonstrate that extrapolation of school data into the exclusion zone provided a realistic correction to the acoustic data for Black Rockfish. Our work demonstrates that excluding the data within 1 m of the bottom does not negatively affect the ability of the combined video hydroacoustic method to sample semi-pelagic rockfish.

Modern hydroacoustic methods for studying the bottom relief and bottom sediments of the Dnieper River: ways of using it in the exploration and development of river sand deposits

The difficult state of the economy of the state entailed a practical lack of funding for geological survey, prospecting work, a comprehensive geological study of the territory of Ukraine, natural and anthropogenic changes in the geological environment in the mode of its constant monitoring; the rates and volumes of reproduction of its own mineral resource base do not meet the needs of the country. Reforming the geological industry to ensure the effective functioning of institutions in the field of subsoil use and environmental protection is an extremely important task; proper provision of state control over subsoil use processes. The development of modern hydroacoustic methods for studying the bottom topography and bottom sediments of the Azov-Black Sea basin in order to search and assess the state of deposits of nonmetallic minerals, protect the environment will improve a specialized hydroacoustic complex (hydroacoustic tools, algorithms and software) for performing survey work, allowing the collection of ground maps and sections of bottom soil without taking samples, and to detect objects in the bottom layer of the water column.

A Method of Analysis of Independent Components for Hydro-Acoustic Control of the Flotation Process

The application of algorithms for the analysis of independent components together with a hydroacoustic method for determining the disperse composition of the gas phase in water is proposed. Mathematical modeling of the effect of emission of acoustic waves by bubbles demonstrated the principle of blind separation of the measured signals into components and the possibility of determining the size distribution of air bubbles without taking into account the geometry of the relative position of the flow of bubbles and measuring points. It is proposed to use signal spectra, rather than temporal signals as initial mixtures for decomposition.

History of hydroacoustic surveys of small pelagic fish species in the European Mediterranean Sea

The study of small pelagic fish by hydroacoustic methods in the Mediterranean Sea began in the Adriatic in the 1950’s. Since 2009, internationally coordinated, extensive, regular surveys have been conducted in the framework of the MEDIAS - Mediterranean International Acoustic Surveys – action, under the EU Data Collection Framework, to provide inputs for the management of small pelagics, particularly European anchovy (Engraulis encrasicolus) and European sardine (Sardina pilchardus). The surveys cover EU Mediterranean waters and monitor the distribution and abundance of small pelagic species using a common protocol. The hydroacoustic surveys, historically conducted by each Country separately, have since been standardized and harmonized. This is a review of the evolution of the surveys from the beginning up to the present and discusses the future prospects. It reports the historical time series of anchovy, sardine and other small pelagics in different areas and describes the spatial and temporal distribution of small pelagic species in decadal maps of the major areas of their distribution in the European Mediterranean Sea. Furthermore, it discusses the use of MEDIAS data for stock assessment purposes, the collection of auxiliary information for an ecosystem-based management approach, the need for further standardization and future challenges.

Target strength measurement of Caroun croaker (Johnius sp.) and acoustic fish density estimation in Musi Estuary, South Sumatra

Caroun Croaker ( Johnius sp.) is one of the dominant estuarine fish that has a reasonably high economic value. The target strength (TS) value measurement is essential in calculating the density of fish stocks using the hydroacoustic method. Target strength measurement of Caroun Croaker (Johnius sp.) and an acoustic survey in Musi Estuary Waters of South Sumatra Province was conducted in December 2019. The result of TS measurement will be used to estimate the acoustic density along the survey area. The TS measurement used the standard tethered method, tying placing the fish in a fixed cage, transmitting the acoustic pulse, and analyzing its return using the scientific acoustic instrument Biosonic DT-X 200 KHz. The fisheries acoustic survey was carried out in the area around the Musi estuary with a predetermined survey design. The results of the measurements have obtained the TS-length relationship, as TS= 20 LOG L-78.79 with determinant value of R2= 0.67 for fish length ranges from 18.1-23.3 cm, and an acoustic survey showed that the estimated stock density value was 286 kg/ha for the total surveyed area of 1.612 ha.

Community structure of mesopelagic fishes constituting sound scattering layers in the eastern tropical North Atlantic

Mesopelagic sound scattering layers (SSLs) are predominantly associated with mesopelagic fish taxa with gas-inflated swimbladders that perform active nocturnal diel vertical migration (DVM), like species of the families Myctophidae, Gonostomatidae, Sternoptychidae and Phosichthyidae. Larger-sized species with limited, partial, asynchronous and non-migratory migration pattern (non-DVM) and without gas-bearing swimbladders are presumably invisible by hydroacoustic methods operating at lower frequencies (18–38 kHz). Their vertical migration behaviour and functional role in the mesopelagic community remain largely disregarded. The present study investigated (i) the taxonomic and functional mesopelagic fish composition (migration behaviour and feeding guild as traits) of the main SSLs and (ii) regional variation in the vertical community structure related to the presence of the oxygen minimum zone (OMZ) in the eastern tropical North Atlantic. We analysed hydroacoustic and biological trawl data collected concurrently with a pelagic midwater trawl in distinct SSLs between 45 and 680 m depth by means of ordination, cluster and compositional analyses. Whereas daytime hydroacoustic backscatter profiles demonstrated higher mean Sv (38 kHz) backscatter at shallower depths at low-oxygen (LO) station 309 compared to the equatorial (EQ) station 330, night-time hydroacoustic profiles at LO stations could not be directly related to OMZ conditions. Catch abundances and biomass showed no clear regional pattern between EQ and LO stations. The analysis of trawl samples emphasised the importance of non-DVM species to the composition of tropical SSLs and further indicated regional and vertical variation in the mesopelagic fish community structure. At all stations, non-DVM species made up the largest proportions of total tow community composition (abundance and biomass) in the principal and secondary mesopelagic SSL during night-time (375–680 m) and during most daytime tows (LO: 390–555 m, EQ: 325–500 m). Our analysis suggests a more pronounced gradient structure in the vertical community composition of the LO compared to the EQ. On the one hand, shallower tows at eastern LO stations 306 and 311 were clustered with comparatively deeper tows. The eastern LO stations 306–315 had the highest numbers of non-DVM species in the principal epi- and mesopelagic SSL and the largest proportions of mesopelagic predatory species in the principal mesopelagic SSL. On the other hand, only the dominant DVM-species of the LO (i.e., Nannobrachium isaacsi, Ceratoscopelus warmingii, Notoscopelus resplendens, Lepidophanes guentheri and Hygophum macrochir) also showed consistent presence in the principal mesopelagic SSL during night-time. Moreover, our study demonstrates the usefulness of using biomass as additional parameter, when investigating functional aspects of mesopelagic community structure.

Meander reshaping – the formation process of a wintering riverbed depression of fish

The study of the spatiotemporal distribution of fish is an important and poorly studied aspect of the ecology of aquatic organisms. The research work was performed using the modern hydroacoustic method and geographic information systems. A section in the lower reaches of the Irtysh, a large transboundary Siberian river (in Western Siberia, Russian Federation), was studied. It has a strong development of meandering. The merging (i.e., reshaping of closely spaced meanders and erosion-accumulating channel processes) results in development of wintering riverbed depression, which is a critical “temporal bottleneck” during the winter period of the fish life cycle. The average density of fish in the study area in summer and autumn was 8,031 and 9,194 individuals per ha, respectively. Analysis of the distribution of fish showed that the distribution in the horizontal aspect had a more aggregated character in the autumn. In the vertical aspect, it had a more surface (pelagic) character. The ichthyofauna in the water area of the riverbed depression is mainly represented by cyprinids. The loop-shaped evolution of the channel formed a section of the river with multidirectional, circulating, and counter-current flows. It also created zones with depths exceeding 20 m and aggregations of fish. These features characterize the studied water area as a wintering riverbed depression of the fish of the Lower Irtysh. This section of the river should be included in the list of protected wintering biotopes of fish in the West Siberian fishery basin, which will ensure the conservation of fish at the critical stage of the life cycle.

Meander reshaping – the formation process of a wintering riverbed depression of fish

The study of the spatiotemporal distribution of fish is an important and poorly studied aspect of the ecology of aquatic organisms. The research work was performed using the modern hydroacoustic method and geographic information systems. A section in the lower reaches of the Irtysh, a large transboundary Siberian river (in Western Siberia, Russian Federation), was studied. It has a strong development of meandering. The merging (i.e., reshaping of closely spaced meanders and erosion-accumulating channel processes) results in development of wintering riverbed depression, which is a critical “temporal bottleneck” during the winter period of the fish life cycle. The average density of fish in the study area in summer and autumn was 8,031 and 9,194 individuals per ha, respectively. Analysis of the distribution of fish showed that the distribution in the horizontal aspect had a more aggregated character in the autumn. In the vertical aspect, it had a more surface (pelagic) character. The ichthyofauna in the water area of the riverbed depression is mainly represented by cyprinids. The loop-shaped evolution of the channel formed a section of the river with multidirectional, circulating, and counter-current flows. It also created zones with depths exceeding 20 m and aggregations of fish. These features characterize the studied water area as a wintering riverbed depression of the fish of the Lower Irtysh. This section of the river should be included in the list of protected wintering biotopes of fish in the West Siberian fishery basin, which will ensure the conservation of fish at the critical stage of the life cycle.

СУТОЧНАЯ И МЕЖСЕЗОННАЯ ДИНАМИКА ПРОСТРАНСТВЕННОГО РАСПРЕДЕЛЕНИЯ РЫБ В АКВАТОРИИ ЗИМОВАЛЬНОЙ РУСЛОВОЙ ЯМЫ

To study the dynamics of the spatial distribution of fish under ice cover the research was carried out in the water area of the riverbed depression located in the lower reaches of the Irtysh River (Western Siberia, Tyumen region). The research was conducted by using the hydroacoustic method based on a computerized hydroacoustic software-hardware complex. It was found that, in the diurnal aspect, throughout the entire observation period (December - April), the number of fish in the riverbed increases during the dark period of the day, and during the light period it decreases. The dominant groups of fish change with the change of the period of the day: December - cyprinids prevail in the dark period of the day, in March and April - in the light period of the day, the rest of the time the group of percids predominated. With an increase in water temperature from December to April from 3.7 to 6.5 °C, it was noted that the density of fish decreases from 184 
 to 8 sp/hect. in the daytime and from 2157 to 91 sp/hect. at night (dark period), respectively. Fish explore the horizons of the water column of the riverbed depression during the day and night from the surface to the bottom with the highest density indicators near the surface, except - the daytime in December. With increasing density of fish at nightfall at the same time, there was an increase used water area of riverbed depression. In the vertical aspect, cyprinids avoid predators (pike, in-connu, burbot) in the diurnal dynamics; the distribution of cyprinids has a significant negative cor-relation with the distribution of the second group of fish. Thus, the features of the vertical and hori-zontal distribution of fish in the diurnal dynamics throughout the entire observation period are the strategy of their survival: for prey - escape from predators, for predators - search for food objects

Adaptive Resolution Imaging Sonar (ARIS) as a tool for marine fish identification

Assessment and monitoring of marine biodiversity, including fish populations, is essential for evidence-based conservation management of coastal marine resources. The effectiveness of monitoring techniques for stock assessment varies with sea conditions. In dynamic marine environments with high turbidity, such as those found in estuaries, mangroves, coastal straits, fjords, and bays, traditional assessment methods include the use of destructive techniques such as trawling. Hydroacoustic sampling techniques overcome such restrictions, equipment such as echosounders have commonly been used for biodiversity assessments including fish community structure, biomass, behaviour, and dynamics studies. However, hydroacoustic methods have been shown to be less reliable for species identification.The high frequency Adaptive Resolution Imaging Sonar (ARIS) is widely used for underwater object detection and imaging. Our study investigated the suitability of ARIS 3000 for the species identification of North-East Atlantic marine species using experimental aquarium studies, field surveys and multi investigator assessments. Aquaria results showed that 82 % of species were detected by observers, of which five were identified correctly identified consistently. The remaining four species were identified correctly <67 % of the time. During field surveys, a 150 % higher confidence in identification was given to more morphologically distinct groups such as elasmobranchs.Whilst our results highlight the suitability of the ARIS for accurate and repeatable identification of some of the model species used in this study, we have also shown that factors such as size and morphological traits limit the accuracy of identification for all species. We suggest that monitoring techniques combine the use of ARIS sonars alongside other sampling tools for assessing motile faunal communities.