Thalassas: An International Journal of Marine Sciences最新文献

The black rockfish Sebastes schlegelii, a valuable commercial fish, is one of the most important fish species for marine fishery stock enhancement in China. In this study, genetic diversity of the hatchery-released stock and two restored-natural stocks (SSNAC1 and SSNAC2) of S. schlegelii from Rongcheng Bay, Yellow Sea, China was analyzed using 15 microsatellite DNA loci, and the genetic differentiation between natural and hatchery-released stocks was also investigated. The mean effective number of alleles (Ae) in the hatchery-released stock was 3.6, the observed heterozygosity (Ho) was 0.506, and the expected heterozygosity (He) was 0.606, while the Ae, Ho and He values in the SSNAC1 and SSNAC2 stocks were 2.9 and 3.9, 0.381 and 0.577, and 0.569 and 0.692, respectively. The F_ST values between the hatchery-released and natural stock and the natural stocks before and after restocking were 0.055 and 0.013, respectively. The results showed that there was low differentiation between the natural and hatchery-released stocks even though the hatchery stock displayed slightly higher genetic diversity and heterozygosity than the natural stock. Furthermore, there was no differentiation on genetic diversity indices between the S. schlegelii natural stock before release and the mixed stocks after release in the short term. However, larger differentiation was found between the natural stock and restored-natural stock SSNAC2. Consequently, more detailed surveys are required to elucidate the long-term genetic effects of the stock enhancement. The present study would be helpful for the future stock enhancement strategy of black rockfish.

Southeastern Arabian Sea (SEAS) shows the variation of chlorophyll concentration (CC) associated with Sea Surface Temperature (SST) due to the seasonal effects of wind and current patterns. The present study carried out using MODIS-Aqua datasets (2017–2019) and discussed the seasonal variation of CC and SST in SEAS. Seasonal trend of CC at SEAS shows higher concentration during southwest monsoon months (July-September, ~ 5.0 mgm^− 3), which is supported by cold pool of SST (gradient of 1°C) and starts dissipating during northeast monsoon (November-January). The causative factor for the cold pool of SST is due to the uplift of bottom cold waters, strong alongshore wind stress and WICC (West Indian Coastal Currents). Satellite based observation of Sea Surface Height anomaly (SSHa) showed cold core circulation with negative anomalies (< -5 cm) in regions of cold pool of SST at the SEAS (July-August). This leads to the formation of Lakshadweep Low (LL). During August 2018, the extent of low SST (27°C) and negative SSHa (-10.5 cm) extended up to 15°N, whereas it confined up to 10°N during 2017 (-9 cm) and negligible during 2019 (+ 0.7 cm) due to strong positive Indian Ocean Dipole (IOD). The reversal of above phenomenon occurred during northeast monsoon (November-January) and inter-monsoon months (February-May), leads to the formation of Lakshadweep High (LH). The present study observed low CC (~ 0.50 mg m^− 3) around LH with positive SSHa and higher SST. The above mechanism is evident in SSHa images showed positive SSHa ( > + 16 cm) at the southern tip during November and propagates northwestward with positive anomaly. A warm pool observed with very high SST (30–31°C) and it spreads to offshore regions associated with NMC (northeast monsoon currents). Multiple regression analysis accomplished between CC, SST and SSHa over coastal and offshore sub-regions and entire study region. Gaussian fit resulted that SST and SSHa correlated better (R² = 0.83 and SEE = 20.09%) with phytoplankton productivity for the coastal subset than offshore and total region during LL/LH phases.

The Laguna Madre artisanal fishery accounts for approximately 25% of the total shrimp catch in the Mexican Economic Exclusive Zone in the Gulf of Mexico. This coastal lagoon is vulnerable to metal pollution because of the use of agrochemicals in the surrounding agricultural and animal sectors. Spatiotemporal variations in metal contents (Cd, Cu, Fe, Mn, Ni, and Pb) in water, sediment, and shrimp (Penaeus aztecus) samples were evaluated using univariate and multivariate approaches to examine the variability of each metal individually, as well as the composition of all metals as a whole, additionally analyzing the relationship between metal levels in the three sample types. Seasonal variations in metal content were more important than differences across fishing sites, according to univariate and multivariate analyses. Furthermore, seasonal patterns in the mean metal levels were consistently similar in both sites. The correlation between the sediment and shrimp metal matrices was significant, indicating that the composition of metals (matrix of all metals together) in shrimp is associated with the sediment metals but not water metals. Additionally, metals content matrices in shrimp and sediment revealed significant correlations with various environmental factors (e.g., salinity, temperature, dissolved oxygen), which was not the case for metals in water. On the other hand, Cd and Cu levels in shrimp were positively related to the same metals in sediment, providing further evidence of the significant association between metals in sediment and the shrimp P. aztecus.

Bigeye barracuda is a commercially valued species as food and game fish in the Indo-Pacific region. The taxonomic details of bigeye barracuda Sphyraena forsteri Cuvier, 1829 is poorly reported in the literature from Indian waters. The current taxonomic study identifies the S. forsteri based on different sizes of the specimens ranging from 255 to 376 mm total length and 83–271 g weight collected from three different landing stations along the Southeast coast of India. Totally, forty-five specimens were examined which include 21 males (46.67%) and 24 females (53.33%). Sphyraena forsteri is diagnosed with enlarged eyes; covered with very tiny cycloid scales all over the body; 101–120 lateral line scales; cheek scales 5–6.5; seven branchiostegal rays. Sphyraena forsteri differs from its congeners by having the gill raker counts; upper limb rough with tiny bony setae, 10–20 small tubercle spines on the first-gill arch (in lower limb) uniformly arranged with 4 to 5 bony setae in a single group with one large spine, gill raker absent. The genetic confirmation of S. forsteri was investigated using 668 bp sequences of mitochondrial cytochrome oxidase subunit I gene. The species S. forsteri formed a stoutly supported clade against the five other congeneric species within the same family Sphyraenidae. This study provides a better taxonomic interpretation of S. forsteri with the molecular and combination of comprehensive morphological with detailed description of scale, otolith, vertebral characters of specimens from the Southeast coast of India.

The Hooghly Estuary plays a critical role in supporting both the livelihoods of a significant human population and maintaining marine biodiversity, thus necessitating regular and precise evaluations of its water quality. Analyzing various parameters like Chlorophyll-a, Total Suspended Matter (TSM), Kd490 (a proxy for turbidity), Adg443 for Coloured Detrital Organic Matter (CDOM) concentration, Sea Surface Temperature (SST), Nitrate, Phosphate, Silicate, pH, Dissolved Inorganic Carbon (DIC), and Molecular dissolved oxygen (DO) across seasons and years revealed distinct patterns. Leveraging datasets from OLCI, SLSTR, and the Copernicus Global biogeochemical analysis and forecast products, concentration maps and time series depicted significant fluctuations, notably during the monsoon and post-monsoon periods. During these seasons, elevated river discharges due to heavy rainfall led to increased sediment flow from adjacent land and tributaries, consequently raising nutrient levels. During the pre-monsoon and monsoon periods, higher values of SST and increased chlorophyll-a concentration were observed primarily attributed to intensified solar radiation. Notable effects from cyclonic storm in October 2022 were also observed. The analysis showcased strong correlations among different parameters. Nutrients (silicate, phosphate, nitrate) exhibited positive correlations with pH (ranging from 0.47 to 0.78) and negative correlations with DIC (ranging from − 0.25 to -0.83). Additionally, pH showed a positive correlation with DO (r = 0.67), while chlorophyll-a correlated notably with turbidity (r = 0.86) and TSM with CDOM (r = 0.59). These robust correlations substantiate the relevance of the datasets for understanding the dynamics of the Hooghly Estuary.

In this work, the total-interdorsal length and precaudal-interdorsal length relationships for 16 species of sharks in the eastern-central Pacific Ocean are presented. Sampling was carried out during 2019 at the artisanal landing site of Playita Mía, located in the city of Manta, province of Manabí, Ecuador. A simple linear regression model was used to obtain these relationships, and the coefficient of determination was used to assess goodness of fit. A total of 3 606 sharks from 16 different species were used to obtain the total-interdorsal length relationship. For the precaudal-interdorsal length relationship, measurements from 1 957 sharks from 14 species were used. The goodness of fit was satisfactory for most species. This information is important because it allows us to reconstruct mutilated shark carcasses, which are common in commercial landings in Ecuador. Once reconstructed, the information from these sharks can be used in life history studies (e.g., age and growth, maturity), which inform population models. Therefore, this information can help improve shark management in the Ecuadorian Pacific.

Feeding habits of fish larvae were analysed in a comparative study of five species (Oreochromis niloticus, O. aureus, Tilapia zilli, Mugil cephalus and Liza ramada) from the Burullus Lake. We investigated the potential influence of larvae size on their feeding and looked for common patterns in larval prey preference. Gut contents of a total of 1068 larvae were examined. The feeding habits of the examined larvae shared some characteristics. As larvae of the five species grew, the preferred prey size and the number and diversity of prey in the gut increased. On the other hand, larval feeding also differed in several aspects, especially differences in the composition of preferred prey items. For Cichlidae larvae, the dominant prey was the rotifer Brachionus plicatilis followed by copepodite stages. For M. cephalus larvae, the copepods Paracalanus sp and Acartia sp were the most important diets, while for L. ramada, decapod larvae were the most important. The Mugilidae larvae consumed significantly larger prey than the cichlid larvae, which could be related to their morphology, especially the mouth size. Ivlev’s selectivity index calculated for larvae showed positive selection for particular prey. In all the species, copepods were the most selected, particularly for Mugillidae larvae, but for Cichlidae larvae, the rotifer Brachionus competed with copepods as a selected prey. This dietary study of fish larvae of these important species is essential for the development of fisheries and can be implemented in further related studies of other areas.

The finding of two specimens of oarfish, Regalecus glesne, in the north-western Ionian Sea (central Mediterranean), in the years 2021 and 2022 and at depths of 525 and 350 m respectively, is reported to update the current information on the distribution of this teleost fish in the Mediterranean waters. In fact, to date, that most of the R. glesne findings are distributed in the western part of the Mediterranean basin, between the Ligurian Sea (Italy) and the Gulf of Lion (France), with 22 and 17 findings, respectively. The TL recorded in the Ligurian Sea ranges from 86.5 to 433 cm, and in the Gulf of Lion from 88 to 446 cm. For the two captured specimens during these surveys, the estimated total length were 650 and 2700 mm, respectively. Macroscopic examination of the gonads identified these specimens as an indeterminate and a female in the early stage of gonad maturity.

Abstract

In the marine environment, pelagic ecosystems are vast and complex, with their biodiversity still being underestimated. In these regions, specifically in mesopelagic zones, the dominance of filter-feeding fish is remarkable, as is the case with Ceratoscopelus warmingii, a taxon that is globally distributed. Despite its recorded occurrence in the Atlantic, Indian, and Pacific Oceans, there is limited understanding of its genetic aspects and evolutionary cohesion across its distribution. In this study, we investigated the genetic diversity in C. warmingii on a global and temporal scale, using phylogenetic and phylogeographic approaches based on the mitochondrial marker cytochrome oxidase I. Georeferenced genetic information was obtained from the BOLD Systems Platform. Our analyses revealed the presence of seven highly structured clusters with genetic divergences exceeding 7%, widely distributed across various marine provinces. The cladogenetic events that gave rise to these clusters date back from the Miocene to the Pleistocene.These findings suggest the possibility that C. warmingii may constitute a species complex, indicating the need for extensive taxonomic revision. This study sheds light on the fundamental importance of comprehensive genetic investigation regarding underestimated species, thus contributing to a better understanding of global marine biodiversity. The implications of these results underscore the need for more careful attention to these often-overlooked ecosystems.

The ecological surveys with special reference to the dynamic of macrobenthos in the estuaries have not been comprehensively studied in Sri Lanka. Hence, this study was conducted to determine the correlation between physicochemical parameters and macrobenthos diversity and evaluate the pollution level in the estuary using macrobenthos diversity. Macrobenthos and bottom water samples were collected from randomly selected 19 sampling locations using a Grab and Ruttner sampler respectively from May to July 2015 every month. The results revealed that the macrobenthos consist of 13 families belonging to the phylum Mollusca and Arthropoda. The most abundant families were Planobidae (12200 individuals/m²), Veneridae (11400 individuals/m²), and Haminoidae (11000 individuals/m²). A total of 21 species belonging to 15 gastropoda; five bivalvia and one crustacea were recorded. The Venerid sp and Muricid sp were the most abundant (7240 individuals/m²) and the least abundant (520 individuals/m²) species, respectively. The highest species richness and diversity were reported at PE7, exposed to the canal which mainly carried hospital wastes. The lowest species richness and diversity were reported at PE6, consisting of an underlying rock layer, making it difficult for sediment collection. Macrobenthos diversity showed that the sampling locations were separated into several clusters. BOD and nitrate-nitrogen were the main physicochemical parameters affecting macrobenthos diversity based on the correlation analysis. CCA showed that macrobenthos assemblage was affected by the convergence of anthropogenic and natural stressors presented at the lower and upper estuary parts, respectively. Furthermore, H’ index and Pollution Tolerance Index in the estuary were between 2 and 3 and ≤ 20, respectively. Both indices confirmed that the water quality of the estuary was in poor condition. This study is important to determine the baseline information of the Panadura estuary’s macrobenthos.