Daily variations in the occurrences of pelagic fishes and zooplankton within a coastal fishing ground of the southwestern Japan Sea

Seasonal variation in microplastics abundance, occurrence, and distribution in pelagic and demersal fishes was observed in this study during December 2021 to November 2022. One hundred percent presence of microplastic in inedible (gut and gills) tissue, while 82% and 54% in edible tissue (muscle) of pelagic and demersal fishes respectively were seen. Post-monsoon period showed high prevalence of microplastics followed by monsoon and the least during pre-monsoon in both pelagic and demersal fishes. In pelagic fishes, the edible tissue had microplastics abundance of 1.56 to 13.34 numbers per 10g of tissue whereas inedible tissue had 3.36 to 16.67 numbers per 10g of tissue. In demersal fishes, the edible tissue had microplastics abundance of 1.04 to 5.26 numbers per 10g of tissue while it was 2.67 to 8.34 numbers per 10g of inedible tissue. There was significant variation in abundance of microplastic in edible and inedible tissue of all the fishes (Mann-Whitney test, p < 0.05). The most dominant microplastics size was 0.005-0.05mm followed by 0.05-0.5mm and the least of greater than 0.5mm in pelagic and demersal fishes respectively. Taking microplastic shape into consideration, the most dominant was fiber followed by fragment and the film in inedible tissue of all the fishes. The edible tissue of all the fishes had only fiber in them (100% occurrence). The dominance of blue color microplastics was observed followed by red, green, yellow, and orange at least in edible as well as inedible tissues of the fishes. More than 99% microplastics polymer observed in this study include polyethylene (PE), polypropylene (PP), and polystyrene (PS); only less than 1% was unidentified. This is the first study done on seasonal variation of microplastic in the marine fish population of Gujarat waters, Northeast Arabian Sea. The study highlights the nature of micro-pollutant in marine environments, emphasizing the need for comprehensive monitoring and management strategies.

Late summer zoogeography of the northern Bering and Chukchi seas

This study was carried out in southwestern Caspian Sea coastal area to elucidate demersal bony fishes distribution and abundance. Twenty two species were found in shore line, which belong to 6 families. In deeper waters down to 7 meters only 5 species of Gobiidae and 1 species of Syngnathidae were identified. Two species Neogobius caspius and N. pallasi were the main components of demersal fishes; however in some regions Rutilus caspicus, Rutilus kutum and Liza spp. were dominated. Most places were dominantly occupied by Atherina boyeri, which had the highest abundance among the pelagic fishes. Conversely, the Ponticola gorlap, N. melanostomus and Proterorhinus nasalis showed the lowest abundances (less than 1 ind./100 m2). Benthophilus stellatus and P. nasali had the lowest niche overlaps with other species. Both of these two species and P. gorlap are suggested to be classified as endangered or vulnerable species based on their low abundance. The distribution of Syngnathus abaster depends on algae, while algae grow up into the stony construction of the coastal line. A negative insignificant correlation was observed between pelagic and demersal fish abundances. The commercial fisheries data of 76 beach seines in our study area during 2002–2013 was compared with our results on fish abundance and species composition. More than 93% of total fish catch constituted Liza spp. and Rutilus kutum. The relationship between the abundance and distribution of the studied species, and the restocking activities performed by Iranian fisheries organization are discussed. The high abundance and distribution of small size fish in tidal zone could be related to the distribution of crustacean, which provide a good source of food for these fish species.

Studies of geographical patterns of diversity have focused largely on compiling and analysing data to evaluate alternative hypotheses for the near‐universal decrease in species richness from the equator to the poles. Valuable insights into the mechanisms that promote diversity can come from studies of other patterns, such as variation in species distributions with elevation in terrestrial systems or with depth in marine systems. To obtain such insights, we analysed and interpreted data on species diversity, depth of occurrence and body size of pelagic fishes along an oceanic depth gradient. We used a database on pelagic marine fishes native to the north‐east Pacific Ocean between 40°N and 50°N. We used data from the Pacific Rim Fisheries Program that were obtained from commercial, management and scientific surveys between 1999 and 2000. Depth of occurrence and maximum body length were used to assess the distributions of 409 species of pelagic fishes along a depth gradient from 0 to 8000 m. A presence–absence matrix was used to classify the depth range of each species into 100‐m intervals. Atmar &amp; Patterson's (1995) software was used to quantify the degree of nestedness of species distributions. Pelagic fish species diversity decreased steeply with increasing depth; diversity peaked at less than 200 m and more than half of the species had mean depths of occurrence between 0 and 300 m. The distribution of species showed a very strong nested subset pattern along the depth gradient. Whereas species with narrow ranges were generally restricted to shallow waters, wide‐ranging species occurred from near the surface to great depths. The relationship between maximum body size and mean depth range differed between teleost and elasmobranch fishes: being positive for teleosts, but negative for elasmobranches. Results support hypotheses that some combination of high productivity and warm temperature promote high species diversity, and reject those that would attribute the pattern of species richness to the mid‐domain effect, habitat area, or environmental constancy. The data provided a clear example of Rapoport's rule, a negative correlation between average depth range and species diversity.

Fish stocks and their management are paramount for sustainable fisheries under the ongoing changes in atmosphere–sea interactions. The Aegean Sea, one of the composite seas influenced by different water masses, is characterized by a diverse ecosystem. Small pelagic fish are abundant and tend to form schools that vary in size. One of the most efficient and rapid techniques for sampling fish schools over a large area is the use of acoustic methods. Therefore, an acoustic survey was conducted in the coastal areas along the entire Turkish Aegean waters between June and August 2024, using a scientific quantitative echosounder equipped with a split-beam transducer operating at 206 kHz. During the survey, environmental parameters, including water physics, optics, and bathymetry, were measured at 321 stations. Additionally, satellite data were used to obtain water primary production levels for each sampling month across the entire study area. Using a custom computer algorithm written during the present study in MATLAB (2021a), fish schools were automatically detected to measure various morphological and acoustic features. Through a series of statistical analyses, three optimal clusters, validated with the total silhouette sum of distances (1317.38), were identified, each characterized by specific morphological, acoustic, and environmental variables associated with different areas of the study. School morphology and acoustic properties also varied with bottom depth. Cluster 1 was mostly found in open and relatively deep waters. Cluster 2 appeared in areas impacted by anthropogenic sources. Principal Component Analysis (PCA) revealed that the first component (PCA1) was correlated with school height from the bottom (HFB) and overall school height (SH), followed by minimum depth (MnD), maximum depth (MxD), and volume backscattering strength at the school edge (SvE). The second component (PCA2) was associated with school width (SW) and area (A). Cluster 1 was characterized by schools with large SW and A, and relatively high HFB and SH. Cluster 2 showed low HFB and SH, while Cluster 3 had high MnD and MxD and low SvE. Based on the descriptors for these clusters, each cluster could be attributed to fish species at different life stages inferred based on target strength (TS), namely sardine, horse mackerel, and chub mackerel, distributed along the entire Turkish Aegean coast.

The breeding seabird community reveals that recent sea ice loss in the Pacific Arctic does not benefit piscivores and is detrimental to planktivores

Nearshore Fish Distributions in an Alaskan Estuary in Relation to Stratification, Temperature and Salinity

Atlantic Multidecadal Oscillation (AMO) modulates dynamics of small pelagic fishes and ecosystem regime shifts in the eastern North and Central Atlantic

Reprint of “Atlantic Multidecadal Oscillation (AMO) modulates dynamics of small pelagic fishes and ecosystem regime shifts in the eastern North and Central Atlantic”

Paleoecological studies on variability in marine fish populations: A long-term perspective on the impacts of climatic change on marine ecosystems

[EN] Marine aquaculture production has increased considerably in recent years due to the scarcity of fisheries resources and increased demand. Gilthead sea bream and European sea bass are among the most interesting species for cultivation in Spain and is usually cultivated in floating cages systems. Fish growth and biomass estimations are essential to prepare the production plan of fish farms, as well as to organize and to perform management operations. It is necessary to optimize these production processes, not only to improve economic profitability but also to minimize the environmental impact of the facilities. \nAcoustic techniques are most appropriate for remote sensing in the water, because acoustic waves travel long distances. For several decades acoustic methods have been employed to detect shoals of fish, so that the information provided by sonars and echo sounders is an important factor in the efficiency of current fishing operations.\nToday acousticians are investigating ways to accurately determine the biomass in cages by noninvasive techniques, which go through the estimation of fish abundance and size distribution. The methodology of scientific or commercial echo sounders have been directed mainly towards pelagic fishing, and it is necessary to evaluate whether the equipment and algorithms can be applied in the control of marine aquaculture farms. \nIn order to evaluate the biomass of fish in cages, two techniques for estimating size are evaluated in this thesis, whilst the study of energy returned by the school of fish is addressed to estimate abundance, as discussed in Chapter 1. Also the acoustic response of pellets by size is characterized.\nIn Chapter 2 general information about gilthead sea bream and European sea bass and their farming in floating cages is included. The basic concepts and formulations used in acoustics to estimate biomass are described in Chapter 3, which are useful for understanding this thesis. \nIn Chapter 4 the suitability of using scientific sounders for estimating size is studied, with the peculiarity that fish are close to transducer. Ventral and dorsal aspects of the target strength (TS) are measured for different sizes of gilthead sea bream. TS measurements at close distances to transducer imply a series of complications and uncertainties. The relationship between TS and size will allow indirect estimation of fish size from acoustic measurements.\nIn Chapter 5, applicability of scientific echo sounders for estimation of average size and abundance of fish in cages of gilt head sea bream and European sea bass in production conditions, which are characterized by a reduced distance between transducer and fish as well as high densities, is evaluated. The study of dorsal TS for determining fish size is limited to the volume above the shoal where detections from isolated fish are obtained, being unviable the evaluation at greater distances where the high density of school hinters the echo detection from multiple targets. The abundance of fish is evaluated by integrating energy backscattered by the school.\nIn Chapter 6 an alternative method for estimating fish size is proposed, based on measurement of the difference of flight time between two peaks of the same echo, which correspond to reflections of the pulse transmitted in different parts of fish body. \nFinally, in Chapter 7 the acoustic response of pellets versus their size is measured using a scientific echo sounder, enabling the detection and identification of pellets fall.

Despite efforts to use environmental DNA (eDNA), accurately quantifying fish populations remains a challenge. A recent eDNA approach provided reliable estimates of coastal fish population abundance, but it was not as effective for assessing spatial distribution due to a lack of eDNA samples relative to the study area. Therefore, we conducted a numerical case study to evaluate the ability of the eDNA approach to estimate fish (Jack mackerel) abundance and distribution based on the number of eDNA samples in a semi-enclosed bay (Jinhae Bay). Our study revealed that the eDNA approach can provide reliable estimates of fish abundance, even with knowledge of the eDNA concentration in just 1% of the study area. However, for estimating spatial distribution and fish school, significant estimates were obtained only when the eDNA concentration was identified in more than 70% of the study area. Our results confirm that the eDNA approach can reflect fish abundance but has limitations in estimating fish distribution.

Twenty-two fish aggregation devices were deployed in 14 m of water off South Carolina. Species composition and abundance were determined by diver visual census on eight occasions from May through November, 1985. A total of 21 families and 36 species of fishes was observed at 121 stations. Pelagic fishes dominated the fauna with a 99.3% relative abundance, and Decapterus punctatus accounted for 97.6% of the individuals. Caranx crysos, Diplectrum formosum, Decapterus punctatus, Centropristis striata and Monacanthus hispidus were the most frequent species. Total fish abundance, number of species and abundance of four of the six most common species were significantly affected by season. Hurricane activity may have caused a significant drop in pelagic fish abundance at the FADs in July. No significant correlations among species abundances were found after removal of season and FAD type effects. Spatial zonation and seasonal occurrence patterns suggest some competition among pelagic fishes. Several factors that regulate FAD faunal abundance and composition are hypothesized, including: juvenile fish availability, availability of shelter, availability of adequate food resources, interspecific and intraspecific competition, severe sea conditions, and sporadic intrusions of large predatory fishes. It is hypothesized that the abundances of benthic and pelagic FAD fishes are correlated and that there is a direct or indirect energetic link between shallow water pelagic and benthic fish assemblages near FADs.

The correlation between the depth-areal distribution of the ostracod fauna in surface sediments and water mass properties in the open sea area of the southwestern-northeastern Japan Sea is presented. This is the first report of the temperature and salinity ranges for the ostracod fauna in this sea giving specific values for summer and winter. The fauna on the shelf and continental slope was divided into four assemblage types based on species composition. The depth distribution of these assemblages is stratified and differs between the northern and southern areas. The four assemblages are distributed according to the four different water masses; Tsushima Warm Current Surface Water (TWS), Tsushima Warm Current Core Water (TWC), Japan Sea Intermediate-Proper Water (JSI-P) and Japan Sea Central Water (JSC). Each assemblage is characterized by the following species and temperature-salinity range; (1) TWSA: Aurila spinifera, Schizocythere kishinouyei, 15–25°C and 33–34.5‰, (2) TWCA: Bradleya spp., Acanthocythereis munechikai, 7–20°C and 34–34.5‰, (3) JSI-PA: Krithe sawanensis, Acanthocythereis dunelmensis, 0–10°C and around 34‰, and (4) JSCA: Laperousecythere robusta, 5–15°C and around 34‰. The JSCA consists of a part of the species in the cryophilic Omma-Manganji ostracod fauna, which flourished during glacial periods in the Japan Sea. These species inhabit the characteristic and intercalated water mass between the shallowest-warmest current water (TWS) and deepest-coldest water (JSI-P). Their southern distributional areas have decreased since the Pleistocene due to the warm current flowing during interglacial periods. These species live in the restricted water mass environment, changing their depth distributions between the south and north of the Tsugaru Strait. They are interpreted to be the survivors of the cyclic environmental fluctuations in the Japan Sea during the glacial-interglacial periods since the Pleistocene. The results may indicate a water mass temperature of 5–15°C during glacial periods in the shallow-open areas in the Japan Sea.

Oceanographic data of 81 stations in the Gulf of Thailand and EastCoast of Peninsular Malaysia from two survey cruises of MV.SEAFDEC of theSoutheast Asian Fishery Development Center were used in the study. Thefirst cruise was during 3 September to 3 October 1995 and the second cruisewas during 23 April to 23 May 1996. It is the first systematic andintensive field observation, after the Joint Thailand-Vietnam-US NAGAExpedition in 1959-1961. Water masses in the Gulf of Thailand and East Coast of PeninsularMalaysia were classified by Temperature-Salinity diagram,Temperature-Salinity-Time diagram and Optimum Multi-parameter Analysis.Their relationships with available biological data were determined. Five water mass; Gulf of Thailand water mass (GOT), Mekong water mass(MK), Surface of the South China Sea water mass (SSCS), Mixed of Gulf ofThailand and Surface of South China Sea water mass and subsurface SouthChina Sea water mass (SuSCS) were found in the study area. Thedistributions of each water mass varied seasonally. Relationship between water mass and biological distribution indicatedthat SSCS water mass was the indicator of low total abundance ofzooplankton with high proportion of chaetognatha. The result also showedpositive relationship between lower layer of GOT water mass and abundanceof phytoplankton but negative relationship with abundance of pelagic fish