The Spatial Variation of Acoustic Water Column Data and Its Relationship with Reef-Associated Fish Recorded by Baited Remote Underwater Stereo-Videos off the Western Australia Coast

Spatially explicit information on coral fish species abundance and distribution is required for effective management. Nonextractive techniques, including echosounders and video census, can be particularly useful in marine reserves where the use of extractive methods is restricted. This study aimed to investigate the possibility of combining echosounders and baited remote underwater stereo-videos (stereo-BRUVs) in providing more holistic information on the distribution of demersal and semidemersal reef-associated fish. The spatial distribution of fish biomass was assessed using both methods in two small areas, one in Cockburn Sound (CS), a temperate body of water, and the other in the tropical waters of the Ningaloo Marine Park (NMP). The results showed high correlations between the acoustic and stereo-BRUV data in CS, suggesting the potential use of both for a better estimation of biomass in the area. The results for the NMP showed weaker correlations between the two datasets and highlighted the high variability of the system. Further studies are required, but our initial findings suggest a potential benefit of combining both techniques in the reef-associated fish distribution assessment.

Caractérisation De La Diversité, De La Structure Des Tailles Et Du Stress Écologique Au Niveau Du Peuplement Des Poissons Sur Le Fleuve Bandama (Côte d’Ivoire, Afrique De l’Ouest)

La connaissance de la faune ichtyologique des eaux ivoiriennes préoccupe à la fois les scientifiques et les responsables de développement du secteur de la pêche. En effet, l’intensification croissante de l’exploitation des ressources halieutiques en milieu continental fait planer de réels risques de régression et de disparition des espèces.Cette étude vise à caractériser la variation spatio-temporelle de la fauneichtyologique et d’identifier les indices biologiques qui déterminent la distribution des espèces de poissons et l’état d’exploitation de ces poissons dans le fleuve Bandama.Les poissons ont été échantillonnés de juillet 2019 à juin 2020 à partir des captures des pêcheurs locaux. Chaque spécimen identifié, est pesé et mesuré.L’analyse spatio-temporelle a indiqué une variation non significative (p > 0,05) de la faune ichtyologique et des indices de diversité H’ et E. Néanmoins, L’analyse de la structure du peuplement (H’ de 2,09 à 2,34; E de 0,83 à 0,85) a révélé un milieu fluvial assez diversifié. Il est dominé par les Cichlidae et Cyprinidae au niveau des familles et Labeo coubie, Coptodon zillii et Chrysichthys nigrodigitatus au niveau des espèces quel que soit le site de pêche. Ce peuplement est composé majoritairement de spécimens juvéniles. Les résultats de ce travail constituent une étude de base pour les gouvernants dans la mise en place de plan de gestion durable des ressources halieutiques en milieu continental.L’essentiel de la production du fleuve Bandama est fourni par les Cichlidae et dans la localité de Tiassalé. Néanmoins, les indices de diversité calculés montrent une ichtyofaune diversifiée. Cette ichtyofaune est dominée par des juvéniles. Knowledge of the ichthyological fauna of Ivorian waters is of concern to both scientists and those responsible for the development of the fishing sector. In fact, the increasing intensification of the exploitation of fishery resources in the continental environment poses real risks of regression and disappearance of species.This study aims to characterize the spatio-temporal variation of the ichthyological fauna and to identify the biological indices which determine the distribution of fish species and the state of exploitation of these fish in the Bandama River.The fish were sampled from July 2019 to June 2020 from the catches of local fishermen. Each identified specimen is weighed and measured.The spatio-temporal analysis indicated a non-significant variation (p> 0.05) in the ichthyological fauna and the indices of diversity H 'and E. Nevertheless, the analysis of the structure of the stand (H' of 2.09 at 2.34; E from 0.83 to 0.85) revealed a fairly diverse fluvial environment. It is dominated by Cichlidae and Cyprinidae at family level and Labeo coubie, Coptodon zillii and Chrysichthys nigrodigitatus at species level regardless of the fishing site. This stand is mainly composed of juvenile specimens. The results of this work constitute a basic study for those in charge in the establishment of a plan for the sustainable management of fishery resources in the continental environment.Most of the production of the Bandama River is supplied by the Cichlidae and in the locality of Tiassalé. Nevertheless, the calculated diversity indices show a diversified ichthyofauna. This ichthyofauna is dominated by juveniles.

Distributions of environmental parameters and fish at Humbold Bay, Jayapura

Research on the distribution of fish and plankton in waters that are equipped with environmental parameters is needed to obtain maximum results and increase accuracy also it provides comprehensive information. The research, which was conducted in Humbold Bay, aimed to map the fish and plankton distribution data both vertically and horizontally and combine it with environmental parameters in the bay. Fish and plankton’s data was the volume backscattering strength (Sv) value obtained using the SIMRAD EK-15 device while environmental parameter data, such as temperature, salinity, and chlorophyll obtained from marine.copernicus.eu which processed in the 5-80 m depth range. The results showed that Humbold Bay had the highest average surface temperature distribution was 30 °C, with the highest average salinity from 35.89 ppt and the highest average chlorophyll value from 0.3859 mg/m3. The horizontal distribution of plankton had an average SV value of -76.63 dB, while the fish was -56.00 dB that evenly distributed. Vertically, the Sv of plankton decreased with increasing depth as well as the Sv of fish which its’ also did not have a distribution pattern in certain environmental parameters.

Seasonal variation in fish school spatial distribution and abundance under the Kuroshio regular pattern and the large meander in Suzu coastal waters

The Kuroshio Current can take two paths; usually it follows the regular pattern but occasionally it follows a pattern known as the large meander. In this study, we investigated the abundance of fish that migrate to coastal waters and the spatial distribution of fish schools under both Kuroshio patterns in Suzu district, Kochi prefecture, where the set net is the main fishery industry. We clarified the seasonal variation in the density and distribution of fish schools using a quantitative echo sounder. The effects of the Kuroshio large meander (LM) depended on the season. There was no effect of current pattern in summer or autumn, but in winter and spring the LM altered the marine environment and fish distributions. Cold water masses were formed in the survey area during winter and spring during the LM, and the water temperature dropped significantly compared with during the Kuroshio non-large meander (NLM). This altered the fish species and the distribution of fish schools in the survey area. The catches of Japanese horse mackerels (Trachurus japonicus) and Yellowtails (Seriola quinqueradiata) were much higher during the LM compared with those during the NLM. Unlike these two species, the small-sized pelagic fishes in spring has decreased significantly during the LM.

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.

A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean

Harith MN, O’ Donnell C, Johnston G, Power AM. 2021. A snapshot on composition and distribution of fish larvae across the North Atlantic Ocean. Biodiversitas 22: 4496-4504. This study aims to describe the composition and distribution patterns of fish larvae communities across the North Atlantic Ocean. Several cruises were involved in the effort to collect the fish larvae samples. The sampling took place on the east side of the North Atlantic Ocean, towards the mid-Atlantic Ocean, and on the west side of the North Atlantic Ocean, near the eddies approaching Flemish Cap. A total of 9522 fish larvae were collected and identified from these surveys. These larvae came from 79 taxa and 29 families. Referring to the total abundance, considering all the sampled stations, Atlantic mackerel (Scomber scombrus) was the most abundant species (38.82% of the total fish larvae abundance), followed by blue whiting (Micromesistius poutassou) (15.9%). Referring to the Multi-dimensional scaling (MDS) ordination plots, two major stations clusters separate the on-shelf and off-shelf stations supported by SIMPER analysis. This study provides a snapshot of larval fish concentrations and assembly structure, but current knowledge suggests that the distribution of larval fish assemblages will be highly spatially variable, more research into plume front dynamics and their effects on the region's biota is needed to predict and understand changes.