Fish are diverse aquatic organisms, economically significant as a primary source of food and nutrients. Accurate species identification is crucial for conservation, taxonomy and management. This study combined morphological and COI gene-based approaches to identify and characterize fish diversity from three locations in Malakand Division, Khyber Pakhtunkhwa Pakistan. All species were identified morphologically. DNA was extracted using phenol-chloroform method followed by PCR and sequencing. The consensus sequences were then utilized as search queries in BLASTn. BioEdit was used for trimming and MEGA X for phylogenetic study. Fourteen specimens representing eight species (Tariqilabeo latius, Mastacembelus armatus, Tor putitora, Carassius auratus, Cyprinus carpio, Garra gotyla, Channa punctata and Channa gachua) from three orders were analyzed. Results showed AT (54.23%) and GC (45.77%) contents, and a high Simpson’s diversity index (0.925), indicating rich species presence and evenness. Density, relative density, frequency, relative frequency and morphometric measurements were also calculated. This study validates the effectiveness of integrating morphological and molecular identification using COI gene for fish species in the region, highlighting its potential for broader application. Biodiversity metrics provide insights into its distribution in the area. Our findings contribute to the understanding of fish diversity in Pakistan and inform conservation and management efforts.

This study aims to determine the fatty acid composition of Pontastacus leptodactylus Eschscholtz, 1823 crayfish living in Cernek Lake in Bafra Fish Lakes in four seasons. The study was carried out over a period of one year. The crayfish used in the study were randomly sampled from their natural habitat at legal catch sizes. It was found that there was no difference in saturated fatty acid (SFA) concentrations among autumn/summer and spring/winter seasons, but there was a difference (p < 0.05) among autumn/winter and spring/summer seasons. It was found that there was a difference (p < 0.05) between the concentrations of monounsaturated fatty acids (⅀MUFA) in the spring and summer seasons. While the concentrations of polyunsaturated fatty acids (⅀PUFA) showed similar characteristics in the summer and autumn seasons, it was found that the concentrations were different in the other seasons (p < 0.05). It was also found that eicosapentaenoic acid (EPA) concentrations were lowest in spring and highest in summer, and the annual mean was 13.16 ± 1.10. Docosahexaenoic acid (DHA) concentrations were highest in winter and the annual mean was 6.79 ± 0.33. EPA+DHA concentrations were highest in the summer season and the annual mean was 19.96 ± 1.26. Omega-3 (ω-3) concentrations were highest in spring and lowest in autumn. In addition, the average annual ⅀Omega 3 (ω-3) concentration was 25.05 ± 4.62. ⅀Omega 6 (ω-6) concentrations were highest in winter and lowest in summer, and the annual general average was 18.60 ± 2.12. The annual average of ⅀ω-3/⅀ω-6 ratios was 1.36 ± 0.33. Based on the results of this study, these crayfish are an important source of (ω-3) fatty acids. This investigation will have a beneficial impact on the local market and potential aquaculture activities.

ABSTRACTS It is widely recognized that rivers serve as significant sources of greenhouse gas emissions. However, the monitoring and analysis of factors influencing methane (CH4) emissions from the Yellow River remain inadequate, particularly regarding high-frequency and detailed temporal differentiation studies. This study selected six sampling points in the Inner Mongolia section of the Yellow River (IMYR) to investigate the spatio-temporal variations in CH4 flux (FCH4) and CH4 concentration (CCH4) at the water-gas interface, along with their influencing factors. The results indicate that the range of FCH4 at the gas-water interface in IMYR is −30.41 to 84.75 mg·m−2·d−1. The CCH4 in water varies from 0.07 to 0.22 μmol·L−1, indicating an overall ‘source’ effect on atmospheric CH4. Both FCH4 and CCH4 exhibit higher values in summer and lower in spring, primarily driven by temperature fluctuations. Significant spatial differentiation of FCH4 and CCH4 is observed in the Inner Mongolia section of the Yellow River, with the highest CCH4 and FCH4 values recorded in Baotou (BT) and Wuhai (WH), respectively. On a seasonal scale, dissolved oxygen (DO) and water temperature (Tw) are the primary determinants affecting CH4 emissions. Given its importance within freshwater ecosystems, greater attention should be paid to CH4 emissions from river ecosystems.

The prospect of using fallowing as an ecosystem management measure to restore ecosystem functions in disturbed aquatic environments under cage culture was evaluated in this study. The cage aquaculture site in the Southeast arm of Lake Malawi was studied following the abandonment of cage aquaculture activities in 2022 after 18 years of operation. A Hydrolab CTD MS5 series probe was cast at each station to a maximum depth to collect electronic data and provide in situ depth profiles of temperature, dissolved oxygen, oxygen saturation, pH and salinity. Chlorophyl-extraction was done using a mixture of acetone and methanol and analyzed on a turner series 10 fluorometer. The study found that physical-chemical parameters such as temperature, pH, ammonia, turbidity and dissolved oxygen were not significantly different (p > 0.05) across the cage and non-cage sites and between seasons. However, ammonia levels recorded in this study were lower than the values reported during the cage culture operations period, an indication that some recovery processes are happening at the site. Chlorophyl a level was found to be insignificantly higher in cage and non-cage sites (p > 0.0.5) and significantly different between season (p < 0.05). High levels of Chl-a observed in this study are independent of cage aquaculture but might be linked to external inputs associated with tributaries as they collectively drain into the lake. Chl-a was found to be significantly and directly correlated to temperature, followed by total suspended solids and pH. Overall, the site is undergoing recovery with respect to the abandonment, but the effect is masked by external inputs of nutrients into the Lake. Although the study confirmed the oligotrophic status of the lake, the increasing levels of Chl-a are alarming and calls for inclusion of watershed management in agriculture and environmental management programming to sustainably safeguard the health of the Lake.

Global climate change and human activities have exacerbated changes in spatial and temporal patterns of precipitation, resulting in inundation stress for many wetland plants. We employed the double basin method to investigate the impact of varying inundation depths on Phalaris arundinacea aiming to elucidate its adaptive mechanisms to inundation. Water levels were set at various depths, ranging from 0 cm to 84 cm in 12 cm increments, and the experiment was conducted over a period of 60 days. It was found that different water levels had significant effects on the growth and physiological indices of the wetland plant (p < 0.01). As the water level increased from 0 cm to 84 cm, the overall plant height and biomass decreased significantly. The plant height in the 0 cm water level group increased significantly from 48.36 cm to 103.36 cm within 60 days (p < 0.01), and the plant died after 20 days at water levels of 48 cm and above; Chlorophyll (a + b) content showed a bimodal fluctuation and overall significant decrease in the 0 cm − 36 cm water level group (p < 0.01), and carotenoid content increased significantly (p < 0.01); POD activity was higher in the 0 cm − 36 cm water level groups, and SOD activity was higher in the 48 cm − 84 cm water level groups; the SP content increased significantly (p < 0.01), and the total soluble sugar and proline content decreased significantly (p < 0.01); The effects of water level gradient and testing time on the indices were significant (p < 0.01) and the interaction was significant (p < 0.01). In general, P. arundinacea exhibits tolerance to water stress, surviving within the 0 cm − 36 cm water levels range, with the 0 cm water level being most favorable for its growth and development.

Prey abundance and size vary seasonally, creating a dynamic connection between predator and prey. The natural complexity related to consuming multiple prey types as fish undergo ontogenetic diet shifts combined with the frequent sampling and substantial laboratory time investment required to investigate seasonal predator-prey dynamics limits understanding of seasonal prey availability and age-0 prey taxa and size selection. Our study used frequent prey sampling spanning a four-year period to understand which prey taxa and sizes are seasonally available to age-0 walleye Sander vitreus, which were sampled from May to November across all four years of this study to document food habits and prey sizes. Consumed prey were then compared to available prey within the reservoir to evaluate prey taxa and size selection. Age-0 walleye seasonal food habits were consistently simplistic as age-0 walleye in this study largely consumed a single zooplankton taxa (calanoida) and then shifted directly to piscivory where they again focused consumption on a single taxa, and age group (age-0 gizzard shad Dorosoma cepedianum) while passing over available benthic macroinvertebrates. The ontogenetic shift to larval gizzard shad coincided with peak larval shad availability. Interestingly, age-0 walleye were size selective for both prey types, selecting the largest calanoida available when zooplanktivorous but consuming some of the smallest age-0 gizzard shad despite increasing gape size that would have allowed for consumption of larger shad.

The assessment of wetland ecosystem services value can provide theoretical basis for regional social and economic development, ecological environment protection and other planning and measures. Based on the factors of hydrology, meteorology, society, economy, resources, environment and culture, the value of wetland ecosystem services in the Yellow River Delta was evaluated by the revised equivalent factor method. The results showed that from 2005 to 2020, the area of tidal flat wetland decreased by 54.35%, and aquaculture increased by 206.91%. The total value of wetland ecosystem services increased from 28.03 billion CNY to 35.77 billion CNY, an increase of 27.63%, showing an N-shaped change of "increase - decrease - increase" on the whole. The ecosystem service value per unit area was more in coastal areas and less in inland areas. From 2005 to 2020, the ecosystem service sensitivity coefficient of the Yellow River Delta wetland was all less than 1. Under the premise of rational development and utilization, it is predicted that the value of ecological services will continue to increase in the future.

In order to understand the current status of plankton and fish population structure and diversity after the construction of the ‘One Dam and Three Routes’ project in the Dazhangxi River, plankton and fish samples were collected in the Dazhangxi River watershed in June and October 2023.A total of 149 species of phytoplankton from 7 phyla were found. The biomass of phytoplankton ranged from 0.88 to 21.35 mg/L, the Shannon ∼ Wiener diversity index (H’) ranged from 2.04 to 3.99, the Margalef abundance index (D) ranged from 1.56 to 3.72, and the Pielou homogeneity index (J’) ranged from 0.41 to 3.72. The permanganate index (CODMn) and pH were the most important environmental factors affecting the distribution of phytoplankton, and the variation of Margalef’s richness index (D) ranged from 1.56 to 3.72, and Pielou’s uniformity index (J’) ranged from 0.41 to 0.76. Seventy species of zooplankton were found in the survey, the biomass of zooplankton ranged from 0.0042 to 3.20 mg/L, the Shannon ∼ Wiener diversity index (H’) ranged from 0.1972 to 3.22, the Margalef abundance index (D) ranged from 1.50 to 5.17, the Pielou index (J’) ranged from 0.41 to 0.76, and CODMn and pH were important environmental factors affecting the distribution of phytoplankton. The variation range of Pielou’s evenness index (J’) was 0.066 ∼ 0.824. ammonia nitrogen∼, Secchi depth, and electrical conductivity were important environmental factors affecting the distribution of zooplankton. A total of 38 species of fish were collected in the survey, belonging to 7 orders, 13 families, and 33 genera, with the predominance of Carpiformes accounting for 50%, Perchiformes accounting for 23.68%, the diversity index of the fish ranged from 1.703 to 2.386, the richness index from 1.763 to 3.882, the predominance index from 0.754 to 0.888, and the uniformity index from 1.504 to 2.144, and the diversity index from 1.504 to 2.14. The fish community was obviously miniaturized, but some rare and uncommon fish were found. The diversity index of zooplankton in the Dazhangxi River fluctuated greatly, and the fish resources showed a declining trend and obvious miniaturization.

This study investigated the spatial heterogeneity of dissolved organic matter (DOM) composition and characteristics in the central reaches of the Huaihe River Basin. The dry season DOM content and composition of three river bodies (the main stream of Huaihe River, the Huaihe tributaries and agricultural drainage ditches) in the Huaihe River Basin were studied using UV-Vis and three-dimensional fluorescence spectroscopy combined with parallel factor analysis (EEMs-PARAFAC). The degree of DOM humification and the relative molecular weight of tributaries and agricultural drainage ditches were significantly higher than those of the main stream (p < 0.01), and regarding the autogenetic characteristics of the three types of water bodies the tributaries and drainage ditches were more strongly affected by exogenous interference than the main stream. Three kinds of chemical components were determined by PARAFAC mode(C1:terrsstrial humus-like;C2:tryptophan-like;C3:protein-like), protein-like components were the main fluorescent components in DOM during the dry season, the proportion of different water systems exceeds 50%. Principal component analysis (PCA) showed that the fluorescence intensity of humus was closely related to the TP(Total phosphorus) concentration in the Huainan section water body of the Huaihe River Basin during the dry season. The absolute principal component-multiple linear regression model showed that the contribution of water nutrition to the C2 and C3 of protein-like fluorescent components was greater, while exogenous interference had a greater effect on the TP physicochemical index.

As global temperatures increase, the spatiotemporal arrangement of thermal habitats in Florida rivers may shift, creating the potential for greater dispersal and establishment of nonnative tropical freshwater fishes. To understand how water temperature changes may affect the spatial distribution of these nonnative species, more effective water temperature prediction models are necessary. Currently, most models employ either a generalized air–water temperature relationship or require expensive and complicated tools to measure hydrometeorological factors (e.g. groundwater input). Thus, we developed a novel modeling approach that is accurate, accessible, and cost-effective in allowing fisheries managers to project water temperatures in rivers across Central and North Florida. To characterize the potential for nonnative fishes to spread northward, we evaluated two hardy and abundant species currently found primarily in South Florida: Mayan Cichlid (Mayaheros urophthalmus) and Oscar (Astronotus ocellatus). Our results show an increase in thermally suitable winter days for both species in 10 of 11 rivers studied, consistent with predicted water temperature warming under 16 climate-change scenarios spanning different levels of air temperature warming (+1 °C, +2 °C, +3 °C, +4 °C) and precipitation/groundwater thermal sensitivity (0, 0.33, 0.66, 1). Considering resource limitations, fisheries managers can use our water temperature modeling approach to predict effects of climate change on Mayan Cichlid and Oscar survival, growth, and dispersal and take actions to manage potential northward movement of these species.