Lakes and Reservoirs: Research and Management最新文献

The assessment of nutrient and heavy metal accumulation in lake sediments is essential for understanding their role in the ecohydrological dynamics of lake ecosystems, as sediments can function both as a sink and source of nutrients, metals and various contaminants aquatic ecosystem. The main objective of this study was to evaluate the concentrations of nutrients and heavy metals and their accumulation in the sediments across different sampling locations of Loktak Lake and to compare them against geochemical background values and sediment quality guidelines. The key findings of the study revealed substantial nutrient accumulation in sediments from the Keibul Lamjao National Park site, which can be attributed to the decomposition of organic matter from dense floating vegetative masses called ‘Phumdis’. Iron concentrations in sediments were significantly high, ranging from 909.83 to 1004 mg/kg and its enrichment is likely due to diffused surface runoff from the iron-rich soils from the surrounding catchment entering the lake through feeder rivers and other anthropogenic influences. The average metal concentrations were in the order of Fe > Mn > Zn > Cu, and all values were below the average shale concentrations and the Interim freshwater Sediment Quality Guidelines (ISQG) set by the Canadian Council of Ministers of the Environment (CCME). The evaluation of the heavy metal pollution status of the lake sediments based on various pollution indices such as the contamination factor, degree of contamination, modified degree of contamination, geoaccumulation index, pollution load index and potential ecological risk index, suggested an overall low level of metal pollution in the sediments of Loktak Lake. The findings of this study provide a crucial baseline for understanding on the sediment-associated nutrient and metals dynamics in Loktak Lake which can aid in the formulation of long-term lake management strategies for preserving the ecological integrity and health of this precious lake ecosystem of the region.

Given the limited and geographically narrow research on macroinvertebrate distribution in subtropical wetlands, this study aims to provide a comprehensive assessment of species assemblages and ecological health across multiple sites in Deepor Beel, a well-known wetland and Ramsar Site in north-eastern India. The current study examines the complex impact of anthropogenic pressures on benthic macroinvertebrates. During the post-monsoon and winter seasons of 2023–2024, samples were collected systematically from three important locations, including touristic destinations (Station-1), garbage dump sites and densely inhabited areas (Station-2), and flow-out points (Station-3). The recorded dataset includes 467 members from 14 families spread throughout 8 orders and 3 separated phyla. The phylum Mollusca appeared as the major taxonomic group (53.74%), controlling the gathered samples, with Arthropoda (45.18%) and Annelida following in hierarchy. Within this taxonomic framework, significant information was discovered, identifying Viviparidae, Lymnaeidae, and Planorbidae as the most abundant families, accounting for 16.27%, 15.84%, and 15.84% of total individuals, respectively. Furthermore, an in-depth examination of richness (Margalef richness) and diversity (Shannon-Wiener Index) indices demonstrated a deteriorating tendency from areas less affected by human interventions to those bordered by a trash dump and residential agglomeration. Macroinvertebrate saprobic scores show that Station-3 near the flow-out point to the river Brahmaputra (5.5) is in good environmental condition, whereas Stations-1 and 2 (4.9 and 4.66) are moderately polluted and impacted by anthropogenic activity. Redundancy analysis highlights the association between moderate pollution indicator taxa Gerridae (Hemiptera), Hydrophilidae (Coleoptera), and Hirudidae (Hirudinea) and increasing organic loads (BOD, COD) at Station-1 and 2. The combination of macroinvertebrate family data and water quality parameters underlines the need for a comprehensive approach to assess the health and sustainability of lake ecosystems. The study's findings have implications for developing educated conservation and management policies in the face of growing anthropogenic threats.

The widespread use of plastic materials globally has sparked concerns regarding microplastic (MP) pollution, which is prevalent in water bodies worldwide and poses threats to aquatic life. Despite this, there remain uncertainties regarding the quantity, types and chemical makeup of MP, particularly in tropical urban lakes. This study aimed to examine the presence, distribution, types and chemical composition of MP in both the surface water and sediment of Air Hitam Lake, located in Samarinda City, East Kalimantan, Indonesia. Field sampling was conducted in February 2023 at 10 sites within the lake. The average concentration of MP in water was measured at 0.91 particles per litre, while sediment concentrations reached 375 particles per kilogram of dried sediment. Higher concentrations were observed near the lake inlet. Fibres were the most commonly observed type of MP in both surface water (79%) and sediment (76%) samples, followed by fragments and films. There was no significant correlation between MP concentrations in water and sediment. Fourier Transform Infrared (FTIR) analysis revealed the presence of polyester, polypropylene, nylon fibres, polyethylene, polystyrene polyvinylchloride in the samples, with polyethylene being the predominant compound, accounting for 46% of all surface water and sediment samples. The presence of MP derived from the degradation of larger plastic debris originating from visitors and the local community who dispose of plastic trash improperly highlights the importance of implementing effective plastic waste management strategies in communities surrounding the lake. This is crucial for preserving the ecosystem benefits provided by the lake. This study contributes to addressing knowledge gaps regarding MP pollution in tropical urban lakes and lays the groundwork for further research into inland freshwater environments.

Lake Ahémé is one of the main fishing areas in the Couffo basin. Porogobius schlegelii (Gunther, 1861) is one of the fish most exploited by artisanal fishing after the cichlid species. Sustainable management of the species requires reliable data on the current pressure of traditional fishing in order to find measures to adjust fishing activities to the recruitment capacity of the species. Therefore, from January to December 2020, data on total length, total weight and sex were collected monthly on a total of 3447 specimens of P. schlegelii caught by local fishermen. The size at first maturity (L₅₀) determined with the statistical package sizeMat was estimated at 6.5 and 6.2 cm for males and females, respectively. The asymptotic length obtained with the TropFishR statistical package was 14.8 cm for both sexes. The growth coefficient and growth performance index were 0.87 year⁻¹ and 2.28, respectively, with a normalised adjustment value of 0.21. Estimates of total, natural and fishing mortality were 3.55, 1.53 and 2.02 year⁻¹, respectively. The current exploitation rate was 0.57 and as such remained above the exploitation rate at 50% of its unexploited biomass (E_0,5 = 0.37). Therefore, a reduction in the current exploitation rate is required by at least 35.1% to maintain sufficient biomass. The estimated size at first capture of 5.9 cm is smaller than L₅₀ for both sexes. These parameters clearly reflect a current trend of overexploitation. Monitoring of fishing efforts and sensitisation of fishermen to catch fish measuring at least 9.3 cm (optimal length) are among the management measures recommended to sustain the P. schlegelii fishing in Benin.

The present study describes the length-weight relationships (LWRs) and length-length relationships (LLRs) for three species: Parambassis baculis (Hamilton 1822), Gagata cenia (Hamilton 1822) and Mystus tengara (Hamilton 1822) from the Jorasar river in Sonitpur district of Assam, India. The study shows positive allometric growth (3.133) for M. tengara, isometric growth (2.916) for G. cenia, and negative allometric growth (2.295) for P. baculis, with regression coefficients (r²) 0.953, 0.969, and 0.955, respectively. The Parameter a was recorded as 0.007 for M. tengara, 0.013 for G. cenia, and 0.030 for P. baculis. The current study will contribute to the conservation of these ichthyofaunas while enhancing fish stock analysis for appropriate management.

Identification of Schizothorax curvifrons (Sattar gad) stocks in Kashmir water bodies is crucial for the conservation of species that are losing ground daily. Because of substantial overfishing and pollution in the fish's natural environment, the wild population of these fishes is drastically dropping, which is a troubling situation that justifies a high priority for conservation. Fish populations can acquire morphometric variations as a result of prolonged isolation and interbreeding. The goal of this study was to use the truss network approach to delineate the stock structure of S. curvifrons based on morphological attributes. A total of 167 fish specimens were gathered from the three sampling stations of Kashmir waters, viz. Telbal Nallah, Dal Lake and Anchar Lake. A total of 37 truss distance measurements were established by joining 15 morphometric landmark points on the fish body. For the fish species currently targeted, MANCOVA demonstrated significant (p < 0.001) morphological heterogeneity among sampling locations. Univariate ANOVA test showed statistically significant differences in 21 out of the total 37 studied morphometric variables among the three sampling sites for S. curvifrons. Based on principal component analysis, the first component (PC1) explained the maximum amount of variation in samples, which is 26.9%. The second component (PC2) contributes 16.5%, and the third (PC3) 10.3% of the total variance. Wilk's lambda test found substantial (p < 0.001) differences in the morphometric measures of the fish across all sampling sites. The discriminant function analysis identified two morphological indices that explained 58.8% and 42.2% of the differences between the groups. Discriminant function analysis further revealed 84.6% correctly classified individuals into their respective populations. The findings from this investigation can be used to develop stock-specific management and conservation strategies for the long-term protection of S. curvifrons in Kashmir water bodies.

A badid, Badis assamensis Ahl, 1937, was recorded for the first time from the intermediate zone of a semi-torrential stream called Basistha in Assam, which is a small tributary of the river Brahmaputra. The fish species Badis assamensis is currently listed in the data deficient (DD) category of IUCN. The species has previously been reported in swampy wetlands in the upper reaches of the Brahmaputra valley in Assam; with no detail description on its biology however. The current work redescribes morphology and presents detail reproductive biology of this species based on fresh collection of 377 individuals from the Basistha. length-weight relationships (LWR) analysed in this species indicated an isometric growth; and condition factor (K) indicated a suitable habitat for this species. Badis assamensis exhibits a non-seasonal breeding behaviour twice a year, as analysed from the Gonado-somatic and ovarian indices. During certain period of the year, local people use unscientific ways of fish collection thereby resulting in a steep decline in fish population. The study is believed to lay an insight into this species' geographical range from a swampy wetland habitat in upper reaches of the Brahmaputra basin; to a semi-torrential hill stream habitat in the lower Brahmaputra sub-basin; thereby providing baseline information on this DD species. Analysis of morphometric and reproductive parameters of this species not reported earlier is the major highlight of the present study.

The Kaptai reservoir is one of the important fisheries hubs in Bangladesh for its significant role in the national economy and socio-economic sector. However, easy accessibility to the reservoir along with other human-driven disturbances are pushing the stocks at risk. The sustainable fishery management depends on estimating a stock's total allowable catch (TAC), therefore, a recently developed Monte Carlo method (CMSY) was used for five data-limited stocks (catfish, Sperata aor; snakehead, Channa marulius; carp, Labeo rohita; cichlids, Oreochromis mossambicus and featherback, Notopterus notopterus) to estimate their fishery reference points using their catch, resilience and exploitation record at the first and last catch of the year. A Bayesian state-space implementation of the Schaefer surplus production model (BSM) was also used to compare and justify the output of the CMSY. CMSY estimated the maximum sustainable yield (MSY) to be 378, 110, 74.5, 432 and 99 mt for S. aor, C. marulius, L. rohita, O. mossambicus and N. notopterus, respectively. The result suggests that C. marulius, L. rohita and O. mossambicus fisheries were rebuilding naturally and at underfishing and underfished state according to the values of F/F_MSY and B/B_MSY as per BSM (value < 1). Value of B_MSY greater than present biomass estimated by BSM for L. rohita and O. mossambicus predicts that the stock's overexploitation state seeking serious attention. Although the S. aor fishery seemed to be sustainable and had the potential to produce more, F/F_MSY and B/B_MSY values close to 1 recommend strict management actions for further sustainability. However, F/F_MSY 1.31 for N. notopterus reveals that the stock depleted remarkably making this fishery unsustainable. The study reveals that Kaptai reservoir fisheries require intensive care to maintain sustainable resources. Strict implication of allowable catch limit, mesh size regulation, maintaining water quality, and protection of breeding and nursery ground is highly recommended.