Mediterranean lagoons undergo pronounced seasonal cycles and steep environmental gradients. As a result, phytoplankton composition can vary considerably both across space and over time. We investigated seasonal changes in diatom community beta diversity in El Mellah Lagoon (Algeria) based on four field campaigns performed in 2016 at 31 stations spanning littoral and pelagic sectors. Spatial beta diversity within each season was estimated using Jaccard dissimilarity and decomposed into turnover and nestedness components to clarify whether among-station differences were primarily driven by species replacement or richness-related patterns. Temporal change between successive seasons was quantified using the Temporal Beta Index (TBI), separating species losses from gains at the station level. The contribution of individual taxa and sites to overall compositional variability was assessed using species (SCBD) and local (LCBD) contributions to beta diversity, and spatial dependence was evaluated using Moran’s I and variogram parameters prior to kriging-based mapping. Seasonal typologies were further explored using a Factor Analysis of Mixed Data (FAMD) integrating beta-diversity descriptors with measured environmental variables. Spatial beta diversity was significantly dominated by species replacement only in spring, after adjusting for multiple comparisons across seasons (Replacement Dominance Index, RDI; Holm procedure), while other seasons showed weaker, non-significant trends. Temporal transitions showed pronounced and largely robust asymmetric losses and gains, indicating that seasonal change in composition was not symmetric across the annual cycle. Spatial autocorrelation of community composition was strong in fall but largely absent in winter and summer, while spatial autocorrelation and variogram ranges for temporal change also varied by season and by beta-diversity component, highlighting shifts between more clustered and more spatially diffuse configurations. A limited set of taxa contributed disproportionately to beta diversity, while several stations emerged as recurrently distinctive assemblages. Overall, these results illustrate how integrating beta-diversity partitioning, contribution metrics and geostatistical analyses can be used to describe seasonal and spatial community change in Mediterranean lagoon systems.
This study assesses the environmental quality of Bou-Ismail Bay (Algerian coast) using Posidonia oceanica as a bioindicator of trace-metal contamination. The spatial distribution and temporal evolution of Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn were investigated at three stations (Bou-Ismail, Ain Benian, Kouali’s cove) using tissue-specific analysis combined with lepidochronology over the period 2008–2020. Concentrations spanned several orders of magnitude and followed a general abundance order of Fe > Cu > Zn > Mn > Cr > Ni > Pb > Cd, with the lithogenic elements Fe and Mn generally more abundant than the predominantly anthropogenic metals. Thin scales reached up to 8270 µg g⁻¹ Cu and 2941 µg g⁻¹ Zn at the port-influenced Bou-Ismail station and 19.2 µg g⁻¹ Cd at Ain Benian, whereas rhizomes remained comparatively low and stable (e.g. Cd 0.4–0.8 µg g⁻¹), reflecting chronic background contamination. Among-station differences were statistically significant for Cu, Zn, Mn and Pb (one-way ANOVA, p < 0.05), and the Metal Pollution Index decreased significantly in the order Bou-Ismail > Kouali’s cove > Ain Benian (Kruskal–Wallis, p < 0.001), confirming a stronger metallic footprint at the urban- and port-influenced stations, particularly for Cu, Zn and Pb. This integrated spatio-temporal approach confirms the high sensitivity of Posidonia oceanica to metal contamination and its relevance for long-term coastal biomonitoring in Mediterranean ecosystems.
The present study examined the growth dynamics of engraulid fishes landed along the Southeast Coromandel coast of Tamil Nadu, India, with particular reference to the Nagapattinam region, using length–weight relationships (LWR) and relative condition factor (Kn). Sampling was conducted over a one-year period from February 2025 to January 2026, during which 3,523 unsexed specimens representing thirteen engraulid species were collected from commercial trawl landings. Total length and body weight were measured, and LWR parameters were estimated using the equation W=aL^b . The regression coefficient (b) ranged from 2.5658 in Coilia dussumieri to 3.3562 in Encrasicholina heteroloba, indicating negative allometric, isometric, and positive allometric growth patterns among the species. The coefficient of determination (r²) varied from 0.6864 to 0.9599, demonstrating moderate to strong relationships between length and weight. Relative condition factor (Kn) values ranged from 0.3192 to 0.8240, reflecting interspecific variability in physiological condition. New LWR records for Coilia neglecta, E. heteroloba and Thryssa hamiltonii not previously reported from the Indian waters, were established. New maximum total length records for Thryssa malabarica (28.4 cm), Thryssa mystax (25.8 cm), and Thryssa vitirostris (25.7 cm) were also documented. These findings provide essential baseline information for comparative growth studies, biomass estimation, and the sustainable management of engraulid resources along the Southeast coast of India.
The brown numbfish Narcine timlei (Bloch and Schneider 1801) is a vulnerable electric ray frequently taken as bycatch in Indian coastal fisheries, yet its biology remains poorly documented. This study analysed 341 specimens obtained from trawl and gillnet bycatch landed along the Tamil Nadu coast between March 2024 and February 2025 to estimate length–weight relationships (LWR), assess sexual dimorphism, and document key biological traits. The log₁₀-transformed pooled LWR showed a strong fit (R² = 0.9243) following the equation log₁₀(W) = − 4.339 ± 0.113 + 2.7484 ± 0.0503 log₁₀(TL), with b = 2.7484 (95
Coral reef ecosystems in the Maldives have experienced increasing pressure from climate-driven disturbances and localized anthropogenic stressors. This study investigated temporal changes in benthic composition, reef fish assemblages, and macro-invertebrate communities on the restoration-assisted lagoon reef of Gulhifushi Island (South Malé Atoll, Maldives) between September 2023 and March 2026. Ecological surveys were conducted along fixed transects using standardized Reef Check protocol to quantify substrate composition, key fish taxa, and indicator macro-invertebrates. Live hard coral cover increased from 14
This study investigated skeletal deformities in wild European sea bass (Dicentrarchus labrax) and gilthead sea bream (Sparus aurata) obtained from commercial fishery catches along the Turkish Aegean Sea coast (İzmir and Muğla). A total of 103 specimens (55 D. labrax and 48 S. aurata) were examined for external skeletal abnormalities. Skeletal deformities were detected in four D. labrax (7.27
The present study reports the length–weight relationships (LWRs) and relative condition factors (Kn) of 25 flatfish species (Order: Pleuronectiformes) collected from three major fish landing centres namely Kottaipattinam fishing harbour, Thoothukudi Fishing Harbour and Jeppiar Fishing Harbour along the southern coast of Tamil Nadu, India. A total of 4,588 individuals were sampled on a monthly basis caught from commercially operated bottom trawl nets between January to December 2025. Novel LWR records were established for Cynoglossus lachneri, Zebrias synapturoides, Pardachirus marmoratus, Heteromycteris oculus, Bothus myriaster, Crossorhombus valderostratus, Pseudorhombus diplospilus, Paraplagusia bilineata, Pseudorhombus arsius and Synaptura albomaculata, for which such data were previously unavailable in Fish Base. Additionally, new LWR records were established for Zebrias quagga, Bothus pantherinus, and Pseudorhombus javanicus, which had not earlier been documented from Indian waters. The estimated growth coefficient (b) values varied significantly (P < 0.005) from the isometric value of 3, ranging from 2.5114 in Cynoglossus lida to 3.3214 in Paraplagusia bilineata. The overall findings indicate that the majority of species exhibit negative allometric growth. The coefficients of determination (R2) were consistently high, varying from 0.8870 in C. macrostomus to 0.9930 in C. puncticeps, demonstrating a strong length–weight relationship and reflecting the universal growth pattern observed among living organisms, with highly significant length–weight regressions (P < 0.001). Furthermore, Kn values were equal to or greater than one across all species, suggesting favorable environmental conditions for growth. Overall, these results offer important insights into the health status, ecological characteristics, and growth patterns of flatfish populations, while also providing valuable baseline data for fisheries research, stock assessment, and sustainable resource management.
Understanding patterns of age and growth is essential for fisheries management, particularly for ecologically and economically important groups such as Sciaenidae. This study provides a comprehensive scientometric and quantitative synthesis of age and growth studies in Sciaenidae, aiming to identify temporal trends, geographic patterns, methodological approaches, and variability in growth parameters. A total of 162 studies were selected from the Scopus database following PRISMA guidelines. Scientific production increased exponentially over time (R2 = 0.78), reflecting growing interest in population dynamics and stock assessment. However, important gaps persist, particularly regarding the low representation of several species and geographic regions. Sectioned otoliths were the most frequently used method, followed by length-frequency approaches, highlighting differences in methodological application across studies. Significant differences in the growth coefficient (k) were detected among methods, indicating that methodological choice can influence parameter estimation. Despite this, biological and environmental factors remain the primary drivers of growth variability among genera, indicates broad patterns. Growth parameters varied widely among genera, reinforcing that Sciaenidae do not exhibit a uniform growth pattern. Among studies that validated annulus periodicity, annual annulus formation consistently supported the reliability of otolith-based age estimation. Overall, this study highlights the importance of integrating methodological, ecological, and spatial perspectives to better understand growth dynamics. These findings provide valuable insights for improving stock assessments and emphasize the need to expand research efforts, particularly for underrepresented species and tropical regions, to support more effective and sustainable fisheries management.
Despite playing a critical role in small-scale fisheries worldwide, women largely undertake responsibilities that go unrecognized. This study examines the socio-demographic characteristics, roles in fishing activities, and contributions to the production process of women participating in fisheries in the Black Sea Region (Samsun province), based on face-to-face survey data conducted with 52 female fishers in 2025. The findings indicate that women primarily participate in the pre- and post-harvest stages, specifically in labor-intensive tasks such as net cleaning and repair. Conversely, their access to institutional mechanisms, such as fishing licenses and cooperative memberships, remains significantly limited. Although women mostly perform informal, unpaid labor, they make vital contributions to the continuity of household income and the sustainability of fishing operations. High fuel costs, limited institutional access, and exclusion from decision-making processes are the primary factors restricting women’s visibility and economic empowerment in the sector. For the sustainability of small-scale fisheries in the Samsun case examined here, implementing gender-sensitive policy approaches is important; confirming whether this extends to the broader Black Sea Region would require further comparative research.
Length–weight relationships (LWRs) and condition factors are fundamental biological metrics for assessing growth, status, and health of exploited marine species. Despite the commercial importance of loliginid squids in the Arabian Sea, comparative information on these parameters for Uroteuthis duvaucelii, U. edulis, and U. singhalensis remains limited. The present study addresses this knowledge gap by examining sex ratio, length–length relationships (LLRs), length-weight relationships (LWRs), condition factors (Fulton’s, K and relative, Kn) in these three commercially important squids. Specimens were collected from the southeastern Arabian Sea and analysed using standard morphometric and statistical approaches. The estimated allometric exponent (b) were 2.51 for U. duvaucelii, 1.82 for U. edulis, and 1.56 for U. singhalensis, indicating negative allometric growth. Significant interspecific differences were observed in sex ratio, K, and Kn, reflecting variability in growth, and physiological condition. These findings provide the first standardized, region-specific comparison of morphometric relationships and condition indices for these species from the Arabian Sea. The generated baseline data enhance the biological understanding and offer valuable inputs for better taxonomic identification, assessing growth dynamics and population health and overall well-being of the squids in the south-eastern Arabian Sea which are highly imperative for the sustainable exploitation of squid fisheries in Indian waters.
Surveys and monitoring in Indonesia’s Marine Protected Areas (MPAs) have primarily focused on shallow reefs (± 10 m depth) using visual census methods, leaving mesophotic coral ecosystems (MCEs; >30 m) largely unexplored. This gap limits understanding of biodiversity distribution and ecological connectivity across depth gradients. To address this, we conducted an environmental DNA (eDNA) survey at Burung Island, Karimunjawa National Park (KNP), an area known for its extensive coral reef ecosystems. Invertebrates and algae were analyzed using the COI locus, while fishes were assessed using the 12 S locus. Seawater samples (1 L each) were collected from shallow (5–10 m) and upper-mesophotic (30–40 m) zones, with three replicates per depth, totalling six samples. eDNA analysis detected 15 families of marine invertebrates in the shallow zone and 13 in the upper-mesophotic zone, with six families shared between depths. Similarly, 14 algae families were recorded in the shallow zone and 10 in the upper-mesophotic zone, with 7 families occurring at both depths. For fishes, 25 families, 43 genera, and 39 species were identified, with 4 families and 5 genera presence in both shallow and upper-mesophotic zones. Alpha and beta diversity showed no significant differences between depths (p > 0.05). Co-occurrence network analysis revealed low clustering and positive interactions among several taxa across depths, indicating ecological connectivity between shallow and mesophotic reefs. These findings highlight the ecological importance of mesophotic reefs in supporting shallow reef communities and emphasize the potential of integrating eDNA with conventional surveys to strengthen biodiversity monitoring and management in Indonesian MPAs.
Mussels are commonly transported along the supply chain without adequate storage, equipment, or packaging, which may compromise product quality and shorten shelf life. This study evaluated the effects of three transport methods on the meat yield and proximate composition of green mussels (Perna viridis) after transport. The transport methods were: (1) sack packaging without ice or expanded polystyrene (EPS) box (PS), (2) layered damp cloth and ice in an EPS box (LC), and (3) nylon-net packaging in an EPS box with ice (PN). During transport, temperatures in the LC and PN treatments ranged from 9 to 20 °C, whereas temperatures in the PS treatment ranged from 28 to 34 °C. At 12 h, meat yield was highest in PN (37.39
The present research aimed to evaluate the biological characteristics and stock condition of Scolopsis bimaculata along the Nagapattinam coast in Tamil Nadu. This species forms a major component of the fish landings in the area throughout the year. For biological studies, a total of 398 specimens of S. bimaculata ranging from 10.0 to 25.5 cm in total length were examined, whereas 1,720 specimens measuring between 9.1 and 31.0 cm in total length were collected for stock assessment studies. Mean length varied seasonally (13.8–20.7 cm), peaking in December and April, with most individuals in the 17.0–21.9 cm size class (51.7
A new species of the marine nematode genus Ceramonema, Ceramonema arenicola sp. nov., is described from intertidal sandy sediments of the Gopalpur coast, eastern India. The new species belongs to the group characterized by indistinct zygapophyses and is distinguished from its congeners by a unique combination of morphological characters, including a short cephalic capsule, absence of cloacal structure, non-enlarged cloacal annule, and lower numbers of body and tail annules. Morphological observations were supplemented with molecular data based on the small subunit SSU gene. Bayesian inference phylogenetic analysis recovered C. arenicola sp. nov. within a well-supported Ceramonema clade. The phylogenetic relationships recovered were not entirely congruent with morphological similarities, likely reflecting the limited molecular representation currently available for the genus. The addition of C. arenicola sp. nov. increases the number of global valid species of Ceramonema to 26 and raises the number recorded from Indian waters to six. An updated identification key for species of Ceramonema with indistinct zygapophyses is also provided. The present study contributes to the knowledge of marine nematode diversity in the Indian Ocean and expands the molecular framework available for future phylogenetic studies of Ceramonematidae.
Length–weight relationships (LWRs) and condition factor provide rapid, non-lethal indicators of growth form, body condition and population status, particularly for elasmobranchs that are vulnerable to incidental capture in demersal fisheries. This study evaluated sex-specific and overall LWRs and Fulton’s condition factor (K) for three cartilaginous fishes incidentally captured by commercial demersal trawls along the Samsun and Sinop coasts of the southern Black Sea during the 2023–2024 and 2024–2025 fishing seasons. A total of 174 trawl hauls yielded 1038 thornback rays Raja clavata, 227 common stingrays Dasyatis pastinaca and 210 spiny dogfish Squalus acanthias. For each individual, total length, body weight and sex were recorded on board, and live individuals were released promptly after measurement. The overall LWRs were W = 0.0024·TL3.225 for R. clavata, W = 0.0019·TL3.340 for D. pastinaca and W = 0.0049·TL2.928 for S. acanthias (R2 = 0.970, 0.933 and 0.934, respectively). Allometry was tested formally against b = 3 (t-test): R. clavata and D. pastinaca showed significant positive allometry (p < 0.001), whereas S. acanthias did not differ significantly from isometry (b = 2.928, p = 0.18). Sexes were compared by analysis of covariance (ANCOVA) on log-transformed data. In R. clavata the sexes shared a common slope but differed significantly in intercept, with females showing higher condition (K = 0.632) than males (K = 0.601; p < 0.001); in D. pastinaca and S. acanthias the length-adjusted LWRs did not differ significantly between sexes, although females had marginally higher Fulton K. The sex ratio was female-biased in R. clavata (1.68:1) and S. acanthias (1.47:1) and balanced in D. pastinaca. The results provide updated baseline LWR and condition data for Black Sea elasmobranch bycatch and support monitoring-oriented, animal-welfare-sensitive management of demersal trawl interactions.
The pervasive presence of microplastics (MPs) in coastal ecosystems, particularly in ecologically sensitive habitats such as sandy beaches, poses a growing environmental concern due to their potential to effect sedimentary and biological dynamics. This study presents the first comprehensive seasonal and spatial assessment of MP pollution on Alagadi Beach, a protected nesting site for sea turtles in Northern Cyprus. The investigation aimed to quantify MP abundance, characterize seasonal and spatial distribution patterns, and to analyze morphological, chromatic, and polymeric properties using Fourier-transform infrared spectroscopy (FTIR). MP occurrence was quantified as the number of particles per kilogram of dry sand (PKS) and the weight of the MPs in a kilogram of dry sand (mg/kg). Data were analysed as mean ± SD. Sampling from the site revealed an annual average of 626 ± 75 PKS; 0,2816 mg/kg. Distinct seasonal variation was observed, with lower concentrations in spring (447 ± 65 items/kg; 0.1442 ± 0.021 mg/kg) compared to summer (805 ± 85 items/kg; 0.4189 ± 0.0330 mg/kg). Notably, the physical attributes of MPs also varied seasonally; white MPs predominated in spring (62
Potentially toxic elements (PTEs) in aquatic biota pose significant ecological and public health concerns in oil-impacted coastal ecosystems. This study evaluated the distribution, seasonal variability, accumulation patterns, and human health risks of Pb, Cd, Cr, Cu, Mn, Ni, and Zn in crab, periwinkle, and mangrove leaf samples collected from Goi, St. Patrick, and Kozo in Gokana, Niger Delta, Nigeria. Metal concentrations were determined using standard analytical procedures, while statistical and multivariate analyses were employed to assess spatial and seasonal variations in contamination patterns. Crab accumulated comparatively higher concentrations of Cr (0.7517 ± 0.7473 mg/kg), Cu (1.1739 ± 1.2839 mg/kg), and Ni (0.7633 ± 0.7450 mg/kg), whereas Mn showed greater enrichment in periwinkle and mangrove leaf tissues. Mean Pb and Cd concentrations in edible crab and periwinkle tissues were generally below selected international guideline values for seafood, and Cu and Zn concentrations were substantially lower than commonly referenced food safety limits. Seasonal differences were evident, with most metals exhibiting higher concentrations during the wet season, suggesting enhanced runoff-driven transport and bioavailability. Principal component analysis revealed strong associations of Cr, Cu, and Ni with crab samples, whereas Cd, Mn, and Zn were more closely associated with periwinkle and mangrove leaf tissues, reflecting differences in accumulation patterns among biota. Non-carcinogenic risk assessment indicated hazard index values below the USEPA threshold of 1.0 for both adults and children. However, carcinogenic risk assessment showed that Cd contributed substantially to estimated cancer risks, particularly during the wet season, with maximum cancer risk values reaching 2.80 × 10⁻³ in children. Children consistently exhibited higher exposure risks than adults. Overall, the findings highlight the importance of continued biomonitoring and pollution management in the Niger Delta. Risk estimates are subject to uncertainties arising from sample size limitations, exposure assumptions, and probabilistic model inputs. Crab showed significantly higher accumulation of Cr, Cu, and Ni than other biota. Wet season enhanced PTE accumulation across most sampling locations. Cd was the major contributor to carcinogenic health risks. Children exhibited higher carcinogenic and non-carcinogenic risks than adults. PCA identified distinct biota-specific metal accumulation patterns. Most PTE concentrations remained below international food safety limits.
The size selectivity of experimental longlines for two commercially important grouper species viz., Brown lined grouper, Epinephelus undulosus and Malabar grouper, E. malabaricus was investigated in the Gulf of Mannar, southeast coast of India. J-type hooks of three different sizes (hook no. #12, #9 and #6) were evaluated during experimental longline trials conducted between February 2020 and January 2022 in fishing grounds of 20 m to 30 m depth. Eight different models namely, Normal location, Normal scale, Lognormal, Gamma, Logistic, Richards, Binormal and Bilognormal were fitted using the SELECT method. Model selection based on Akaike’s Information Criterion (AIC) indicated that the lognormal model provided the best fit for E. malabaricus, while the binormal model best described selectivity for E. undulosus. The estimated mean lengths increased consistently with hook size, indicating a shift towards larger individuals with increasing hook size. Comparison of estimated mean lengths with length at first maturity revealed a substantial reduction in the probability of capturing immature fish with larger hooks. These results suggest that the use of larger hook sizes can reduce the capture of undersized individuals without compromising catch, thereby improving both selectivity and sustainability of grouper fisheries in the Gulf of Mannar.
This study investigates the influence of El Niño–Southern Oscillation (ENSO) on the Indonesian Throughflow (ITF) in the Halmahera Sea (HS) during 2013–2023. Although ITF variability has been widely studied, the response of the HS to different ENSO phases remains insufficiently understood. Using a validated CROCO model, we quantified changes in HS throughflow and associated oceanographic conditions under El Niño and La Niña events. EOF analysis of sea surface height (SSH), meridional velocity, and salinity revealed dominant modes explaining more than 50
