This study investigated the length–weight relationships (LWRs) and condition factors (CF) of five fish species (Atherina pontica, Engraulis encrasicolus, Neogobius melanostomus, Chelon auratus, and Knipowitschia caucasica) inhabiting the Küçükçekmece Lagoon (Istanbul, Türkiye). Fish samples were collected using gillnets and seine nets between September 2023 and August 2024. A total of 1213 individuals from five fish species were analyzed for LWR and CF. The allometric coefficient (b) estimated from the linear regression model of the LWR ranged from 3.071 for A. pontica to 3.454 for N. melanostomus, it was determined that the relationships of the species examined exhibited allometric growth. The coefficient of determination (R2) values of the LWRs ranged from 0.9581 (E. encrasicolus) to 0.9897 (C. auratus). Fulton’s CF values ranged from 0.27 in E. encrasicolus to 2.00 in K. caucasica. This study provides the first report of LWR and CF parameters for four species (E. encrasicolus, N. melanostomus, C. auratus and K. caucasica) in this lagoon. These findings contribute to future assessments of ecosystem health and its impact on fish growth within the lagoon basin.
Objectives This study provides an integrated assessment of the population structure, growth and reproductive biology of the kuruma shrimp (Marsupenaeus japonicus) in the Gulf of Antalya, based on monthly sampling between January and December 2018. Methods A total of 516 individuals (267 females, 249 males) were collected using shrimp trammel nets. Sex ratio, total length (TL), body weight, gonadosomatic index (GSI) and gonadal maturity stages were analyzed. Length-weight relationships (LWR) and size at first sexual maturity (TL50) were estimated. Results The sex ratio (1.07:1) did not differ significantly from 1:1 (p > 0.05). Females were significantly larger than males, with mean TLs of 16.9 +/- 2.16 cm and 14.9 +/- 1.23 cm, respectively (p < 0.001). GSI values pointed to a prolonged reproductive period from April to November, with peak activity in July (6.13) and August (6.06). Monthly GSI was strongly correlated with seawater temperature (r = 0.85, p < 0.01). TL50 for females was estimated at 15.3 cm TL. Conclusions The findings suggest that M. japonicus maintains an extended reproductive season in the Gulf of Antalya and exhibits sex-specific growth patterns. The estimated TL50 and peak spawning period offer useful reference points for fisheries management, particularly for setting minimum landing sizes and seasonal fishing restrictions to support stock sustainability.
Length-weight relationships (LWRs) are widely used in fisheries science to describe growth patterns and assess fish condition, yet they are based on total body weight, which includes variable non-structural components such as stomach contents and gonads. The effects of these components on LWR parameters and condition indices remain poorly understood. This study evaluated the influence of stomach fullness and gonad mass on LWRs and Fulton's condition factor (K) in three fish species with different body shapes: Diplodus annularis, Boops boops, and Citharus linguatula. A total of 159 individuals were analyzed using three weight definitions: total body weight (TW), gutted weight (F), and gonad-adjusted weight (TWG) estimated from the literature-based gonadosomatic index (GSI) values. LWR parameters and K values were statistically compared among weight types. The allometric coefficient (b) did not differ significantly among weight definitions, indicating that internal biological components had little effect on estimated growth patterns. In contrast, body weight and Fulton's K differed significantly (p < 0.05), with significant differences detected only in D. annularis. Sensitivity analysis identified GSI thresholds (similar to 5% and similar to 13%) at which gonad mass affects weight-based comparisons, emphasizing the importance of standardized weight definitions in condition assessments.
This study examines the influence of climate variability associated with the Indian Ocean Dipole (IOD) on the habitat suitability of E. cottonii cultivation in the coastal waters of Cilacap and Kebumen, southern Java. A Habitat Suitability Index (HSI) model was developed using a Boolean threshold implemented in Python. Environmental parameters included sea surface temperature (SST), salinity, nitrate concentration, surface current velocity, and bathymetry. The analysis focused on three representative years reflecting different climate conditions: negative IOD (2016), normal conditions (2018), and positive IOD (2019) from June–September. Results indicate that seasonal upwelling in southern Java tends to reduce habitat suitability for E. cottonii. During normal and positive IOD conditions, stronger upwelling from July to September corresponded with lower HSI values compared with June. In contrast, during the negative IOD phase, when upwelling signals were weaker, HSI values remained relatively stable. Kruskal–Wallis results indicate significant differences in SST, salinity, and nitrate among climate conditions, whereas surface currents show no significant variation. Sensitivity analysis suggests that bathymetry contributes more strongly to habitat suitability, while other parameters vary under different IOD conditions. Because the analysis is based on only three representative years, the results should be interpreted as exploratory rather than a generalized climatic pattern.
The aim of this study was to document new records for Poland of Planothidium species occurring in running waters of southern Poland and to characterise their morphology, ecology and distribution. The study material was collected during the spring (April–June) and autumn (September–October) seasons in years 2013, 2017, 2023 and 2024. Species identification was conducted using light microscopy and scanning electron microscopy. Environmental parameters were measured in situ and complemented by laboratory analyses of water chemistry. Ecological status was assessed using diatom indices (Specific Pollution Sensitivity Index, Generic Diatom Index). Five Planothidium species not previously reported from Poland were identified: Planothidium cavilanceolatum, Planothidium daui, Planothidium gallicum, Planothidium hinzianum and Planothidium potapovae. Most taxa occurred rarely and predominantly as individual valves, which limits the precise interpretation of their ecological preferences. In our study, P. daui exhibited a broad ecological amplitude, occurring under oligo- to eutrophic conditions, whereas P. cavilanceolatum, P. gallicum and P. hinzianum were restricted to specific habitats and showed low abundances. In contrast, P. potapovae reached dominant status in the upper course of the Szum River, where it was associated with oligotrophic conditions, sandy substrates and high calcium concentrations.
This study presents the first data on the growth and reproductive characteristics of a population of the freshwater fish Garra turcica outside its natural distribution area (Antalya–Ilıca Stream). It is thought that the species was most likely introduced to the region through “fish spa” practices. In all, 505 individuals were captured during sampling in 2025. The total length of the individuals ranged from 32.38 to 136.65 mm, and their ages ranged from 0 to 5 years. The average (absolute) fecundity was 1533.44 ± 133.02 eggs, and the breeding season occurred between May and August. The average age at first sexual maturity was 1.03 years, and the average length was 69.47 mm. Although four endemic and one native species were recorded in the study area, G. turcica exhibited the highest population density. However, as direct ecological impacts were not assessed in this study, its potential influence on native communities remains to be clarified. These findings provide baseline data for future evaluations of the species’ establishment dynamics and possible ecological implications.
In this study, a total of eight Alburnus escherichii individuals were captured from the Sakarya River Basin, Türkiye. In only one of these specimens, a skeletal deformity (scoliosis) was observed and examined. The scoliosis affected the caudal region of the vertebral column, presenting two curves originating posterior to the dorsal fin. These curves formed two angles, measuring 135° and 152°. Externally, at the point of scoliosis onset, the body contour and lateral line scales were deformed. The deformity affected the posterior part of the dorsal fin and the anterior part of the anal fin. Additionally, the neural and hemal spines of the ultimate abdominal vertebra were slightly deformed. This study discusses the possible causes of scoliosis and the significance of reporting such deformities for anatomical and broader ichthyological research.
As an intense tropical cyclone (TC) formed over the Bay of Bengal (BoB) in May 2023, Cyclone Mocha provides a significant opportunity to examine upper ocean responses to cyclonic forcing. Here, a spatio-temporal analysis has been done for cyclone induced Cold wake and sea surface height (SSH) changes through high-resolution daily satellite datasets combined with cloud computing through Google Earth Engine (GEE) and statistical analysis supported by Python-based processing. Buffering a spatial extent of 300 km along the cyclone track, the pre-cyclone period of 15 days was taken as the baseline for examination, 15th April’23–1st May’23, with a broader examination attempted from 15th April to 31st May’ 2023. Results indicated a strong cold wake occurring along Mocha’s track with sea surface temperature (SST) falling by around 2°C. Sea Surface Height Anomaly SSHA exhibited a moderate positive relationship with SST and a weaker recovery. The statistical interpretation from the results of Pearson’s correlation, Linear Trends and Causality (Granger) indicated a specific impact of the cyclone on SST and SSHA. The results validated cyclone-ocean interactions with strong indications of spatial and temporal alignment of regional dynamics, wind, SST and SSH. It also highlighted the strength of cloud computing and satellite outputs for ocean monitoring, forecasting, re-analysis, and resilience.
This study examines the reproductive biology of the European pilchard using samples collected from commercial fisheries in the northern Aegean Sea and the southwest Marmara Sea in 2024. Specimens were collected monthly using purse seines between September 1st and April 15th and gillnets between April 15th and August 1st. Mean total length and body weight of individuals sampled by both fishing gears were generally higher in the Aegean Sea than in the Marmara Sea. The female-to-male ratio was estimated as 1.0:0.77 in the Aegean Sea and 1.0:1.12 in the Marmara Sea. Length–weight relationship analyses indicated predominantly negative allometric growth for both sexes and for the overall population in both regions, except females from the Aegean Sea. The length at first maturity was higher in females than in males and was greater in the Aegean Sea compared to the Marmara Sea. Based on gonadosomatic index, condition factor, and maturity stages, the spawning period extended from November to April, with peak spawning in February. These findings provide updated regional information on key reproductive parameters of European pilchard and contribute valuable data for stock assessment and the sustainable exploitation of this ecologically and economically important species in Turkish seas.
The thunder crab, Myomenippe hardwickii, has been reported to be seen across Southeast Asia, including the Indian coast. However, previous research has lacked detailed taxonomic descriptions, color photographs, or the molecular characterization of Indian specimens. This study presents the first comprehensive documentation of M. hardwickii in India, combining both morphological and molecular taxonomy techniques. It also represents the first recorded occurrence of this species along the Malabar Coast. DNA barcoding was performed using mitochondrial cytochrome c oxidase subunit I (COI) and 16S ribosomal RNA (16S rRNA) gene markers to validate the species identity based on taxonomic classification. Previous taxonomic references indicate that the gonopods of M. hardwickii and its sister species, Myomenippe fornasinii Bianconi, 1851 are similar. However, this study marks the first instance of presenting a detailed description and illustration of the male gonopods (G1 & G2) and outlining the characteristics of the vulvae in female individuals of M. hardwickii. Consequently, we have provided species identification supported by appropriate illustrations and ecological information.
Thermocyclops taihokuensis (Harada, 1931) was recorded for the first time in Ukraine (Kyiv region). The species was found in the Bucha River and the Sovki River in 2020, and from 2021 to 2025 it was continuously present in high numbers and was the dominant zooplankton taxon in the warm seasons in Nyvky Park pond (Syrets River), indicating successful establishment of this Asian Thermocyclops species in the ponds of the right-bank tributaries of the Dnieper River. Of the three species of the genus native to Ukraine, Thermocyclops oithonoides (Sars G.O., 1863) is most similar to T. taihokuensis morphologically. Distinguishing features between the Asian Thermocyclops and native congeners, as well as the ecology of T. taihokuensis in its native range, are discussed. No native Thermocyclops species co-occurred with T. taihokuensis in the studied water bodies, which may indicate competitive replacement of the local species by the new non-native invasive one.
Heavy metal pollution in the coastal areas is a widespread environmental problem that may threaten seafood safety. This study aimed to determine Cd, Pb, Cu, and Zn concentrations in the gill, liver, and muscle tissues of marketed Liza aurata and to evaluate the potential health risks for consumers. Fish samples were seasonally collected during 2017-2018 from the Urla coast of Izmir Bay. Metal concentrations in all tissues followed the order Zn > Cu > Pb > Cd. Consumer health risks were assessed using estimated weekly intake (EWI), estimated daily intake (EDI), target hazard quotient (THQ), total target hazard quotient (Sigma THQ), and CR indices. The EWI values for Cu and Zn were within safe limits, whereas Cd exceeded the provisional tolerable weekly intake (PTWI) based on a 70 kg adult in both years. THQ values for all metals were below 1, and Sigma THQ values were 0.144 in 2017 and 0.182 in 2018, indicating no non-carcinogenic risk from consumption. In addition, CR values for Cd and Pb were acceptable according to US EPA guidelines. Pb levels approached the 1 & times; 10(-6) threshold, indicating negligible risk, while Cd showed low acceptable risk between 1 & times; 10(-6) and 1 & times; 10(-4). Overall, the results suggest that L. aurata can be considered a useful bioindicator species for monitoring heavy metal pollution in Izmir Bay.
This study investigates the seasonal shifts in phytoplankton communities in the Manyas Reservoir (Balıkesir, Turkey) and their relationships with key physicochemical variables. A total of 59 taxa belonging to Heterokontophyta, Chlorophyta, Cyanobacteria, Euglenozoa, Charophyta and Miozoa were identified. The dominant species were Cyclotella meneghiniana, Fragilaria capucina, Nitzschia lorenziana, Navicula radiosa and Ulnaria acus from Heterokontophyta; Desmodesmus communis, Desmodesmus protuberans and Pediastrum simplex from Chlorophyta; and Trachelomonas volvocina from Euglenozoa. The analysis of the data clearly showed that electrical conductivity (EC), dissolved oxygen (DO), nitrate-nitrogen, total nitrogen (TN) and pH significantly shaped phytoplankton species distributions. The findings highlight the importance of hydrodynamics driving diatom dominance in turbulent zones contrary to the previous studies showing that high flow rates cause low diversity and abundance of phytoplankton in turbulent waters.
Halogens and oxyanions play essential roles in marine biogeochemical cycles, yet studies on their distribution in algae remain extremely limited. This work provides the first baseline profile of these ions in the macro- and microalgae of St. Martin’s Island, Bangladesh. Eight species representing Chlorophyta, Phaeophyta, Rhodophyta, and Cyanophyta were collected during the post-monsoon period, when algal abundance is highest. Anion measurements were carried out using Ion chromatography. Chloride and sulfate were consistently present across all species, with chloride ranging from 3.83 mg · g−1 to 23.94 mg · g−1 and reaching its highest level in Ceramium fastigiatum, while sulfate ranged from 2.88 mg · g−1 to 21.35 mg · g−1 and peaked in Padina tenuis. Fluoride was generally below detection except in Lyngbya confervoides (0.10 mg · g−1) and two red macroalgae, including Hypnea boergesenii (3.83 mg · g−1). Nitrate accumulation varied among species, with L. confervoides showing the lowest level (0.06 mg · g−1) and Cladophora echinus the highest (0.32 mg · g−1). As an exploratory dataset, the study documents only the post-monsoon ion patterns and does not capture seasonal or fine-scale spatial variability. Even within this scope, the findings fill a critical regional gap and offer an initial biochemical reference for future ecological assessments and environmental monitoring programs around St. Martin’s Island.
Karataş Lake is a significant lake in Türkiye and completely dried up in 2021. In subsequent years, the lake intermittently retained water due to redirected water resources and increased precipitation. This seasonal study conducted between October 2019 and July 2020 investigated the concentrations of Cd, Cr, Cu, Fe, Mn, Mo, Ni, Zn, and Se in sediment samples collected from four stations. Metal concentrations were measured by an inductively coupled plasma optical emission spectrometer (ICP-OES). Pollution levels and possible sources were assessed using indices, including enrichment factor (EF), geoaccumulation index (Igeo), pollution load index (PLI), contamination factor (CF), contamination degree (CD), modified contamination degree (mCD), modified ecological risk (mER), and modified potential ecological risk (mPER). The levels of metals in sediments followed the order: Fe > Mn > Ni > Zn > Cr > Cu > Pb > Se > Mo > Cd. These results indicated considerable ecological risk, particularly associated with Ni and Se. Comparisons with sediment quality guidelines revealed the annual concentrations of Ni exceeded multiple threshold and effect levels. These findings emphasize the need for urgent management measures to regulate agricultural runoff, control water abstraction, and increase water input to protect Karataş Lake and ensure its long-term sustainability.
This study documents the first recorded case of vertebral compression syndrome (VCS) in an Atlantic bonito (Sarda sarda) from the southwestern Black Sea. The affected specimen exhibited distinct morphometric deviations, including a shortened vertebral column and an increased body depth, compared to a normal conspecific. Radiographic analysis revealed mild compression initiating at the 13th vertebra, which progressed to severe compression affecting vertebrae 21–40. Within this region, vertebrae showed a marked reduction in width and an increase in height, accompanied by localized dislocations and abnormal bulging along the spinal column. The deformity is consistent with a response to altered mechanical load, which likely disrupted bone growth zones and prompted the replacement of intervertebral tissue with cartilage. This study underscores the utility of high-resolution digital radiography as a nondestructive tool for detailed biological investigation. The exact etiology of the mechanical load, whether from an acute pressure event or chronic overexertion, remains unknown and warrants future investigation.
Tidal flats (TFs), the global hotspots of biodiversity and providers of coastal protection, are changing due to land reclamation, industrialization, and climate change. However, conventional mapping methods are often inadequate for site-scale monitoring due to their coarse resolution and computational demands. This research has tried to generate accurate spatial-temporal maps of TFs by using a pixel-based composite method and satellite data for Karachi Port Trust (KPT), Pakistan, and Yangma Island, Yantai, China. High- and low-tide images were generated using the maximum value composite algorithm (MVCAmax) and the minimum quantile composite algorithm (MQCAmin). The results show that (i) over 40 years, KPT has an area decrease of 270 ha (16.1% reduction), divided into three phases: minimal reduction (1986–1991), reduction (1991–2003), and expansion (2003–2024), (ii) Yangma Island experienced a more drastic reduction of 682 ha, with reduction rate of 70.16%, and (iii) annual 10-m resolution TF maps from 2017 to 2024 revealed a slight increase in KPT area, while Yangma Island exhibited a decreasing trend. This study provides a baseline for monitoring TF dynamics, offers guidelines for preserving coastal biodiversity, and supports sustainable coastal management to mitigate anthropogenic impacts on these vital ecosystems.
Ocean acidification monitoring relies predominantly on field test and numerical modeling, while bioindicators are emerging as practical and economic approaches for seawater pH monitoring. Here, we report indoor dissolution experiments on the scale of red seabream (Pagrosomus major) under varied pH (from 7.1 to 7.9), showing that the mean aspect ratio of ventral ctenii and caudal/ventral lepidonts negatively correlated with pH. We propose to employ these ultrastructures of fish scale to be a novel bioindicator for marine pH reconstruction. This semiquantitative proxy would be applicable to both contemporary biomonitoring and paleo-oceanic pH reconstruction for the extensive occurrences of fish in modern oceans and fossil records.
Seagrasses absorb CO2 for photosynthesis and convert it into new biomass. This study aims to assess the correlation between seagrass aboveground biomass (AGB) growth and percent cover, map and analyse AGB growth using Sentinel-2 imagery and estimate CO2 uptake by multispecies seagrass meadows on Menjangan Besar Island. Correlation analysis revealed a strong relationship between AGB growth and percent cover at the community level (r = 0.64) and for Enhalus acoroides (r = 0.60), and a very strong relationship for Thalassia hemprichii–Cymodocea rotundata assemblages (r = 0.89). AGB growth mapping was conducted using random forest (RF) regression, resulting in root mean square errors (RMSE) of 60.8, 125.6, 94.2 and 94.9 gDW · m−2 · year−1 for E. acoroides, T. hemprichii–C. rotundata, E. acoroides–T. hemprichii, and bare substrate (BS) classes, respectively. The corresponding coefficients of determination (R2) were 0.87, 0.67, 0.70, and 0.78. The total seagrass AGB growth on Menjangan Besar Island was estimated at 672.21 MgDW · year−1, with an average of 331.7 gDW · m−2 · year−1 The estimated total CO2 uptake by seagrass meadows was 197.85 MgCO2 · year−1, with an average of 97.6 gCO2 · m−2 · year−1.
The concentrations of eight metals (Cu, Fe, Mn, Zn, Cd, Pb, Se, and Hg) in the tissues (liver, gill, and muscle) of Dicentrarchus labrax and Saurida undosquamis living in Gökova Bay and their relationship with health risk indexes (target hazard quotient [THQ], total target hazard quotient [TTHQ], estimated daily intake [EDI], and carcinogenic risk [CR]) and condition factor (CF) were determined. The calculated EDI for metals shows a low value for adults in comparison with the recommended intake limit, but for children the values for Cd and Mn in both fish were above the recommended values. Based on the metal analyses, the THQ and TTHQ for fish were calculated to be <1 for both adults and children. CR for Cd and Pb were determined at negligible levels. In addition, metal accumulations were modeled by random forest regression using season, tissue type, THQ weight, and fish length as covariates. The models explained about 55%–93% of the variation in metal concentrations and had high correlations between the observed and predicted values (mostly above 0.80), so they can be used as a practical tool to predict tissue-specific metal levels in similar studies.
