Search Results (17)

This study aimed to assess various social–ecological traps of hilsa shad (Tenualosa ilisha) fisheries and to investigate the factors that significantly impact livelihood adaptation strategies during the ban period, based on fieldwork in coastal fishing communities. To collect empirical data, a total of 247 in-depth interviews were conducted using a semi-structured questionnaire along with six focus group discussions, oral history, and ten key informant interviews in the Chattogram and Patuakhali districts of Bangladesh. A conceptual framework derived from a strategy for reducing poverty, known as the Sustainable Livelihood Approach (SLA), is applied to determine the livelihood outcomes of hilsa fishers. The results showed that low income (<5000 BDT/month), high interest in loans from dadondar (lender) (10–12%) and aratdar (lessor of the vessel) (5%), high harvesting costs, an increasing number of hilsa fishermen, and intergenerational traps (81.78%) are creating social–ecological traps (SETs) in the hilsa fishery. The significant factors affecting the choice of adaptation strategies include family members, training facilities, home ownership, and belonging to a formal society. Apart from fighting against some extreme climate events, negative feedback comes from the absence of cold storage facilities, illegal use of fishing nets, frequent ban seasons, ignorance of conservation laws, limited opportunities for alternative occupations, and poor supply of drinking water. Hilsa fishermen in these regions depended on aratdar and dadondar for their financial support, which resulted in lower prices than the prevailing market prices. To escape from the SETs, this study identifies potential alternatives, such as government–community finance schemes, the promotion of alternative livelihoods, opportunities for technical education of their children, improvement of the local framework, and strong cooperation between local stakeholders and management authorities that are necessary to maintain the sustainability of hilsa fisheries. Full article

Gonadotropin-Releasing Hormone (GnRH) is a crucial neuropeptide that regulates reproductive functions in vertebrates. The study identifies and characterizes (GnRH) in the brain of Tenualosa ilisha, an iconic and lucrative Clupeiform fish from River Ganga, India. The current study aimed to analyze the GnRH gene in T. ilisha using an in silico study. The GnRH gene of T. ilisha comprises a full-length nucleotide sequence of 605 base pairs with an open reading frame of 312 base pairs, which encodes 103 deduced amino acids (aa), respectively. It was found that leucine (L) is the most abundant amino acid in the GnRH protein. Additionally, the ligand interactions of the GnRH were analyzed using computational approaches. The structural validation showed an excellent stereochemical quality of the GnRH protein sequence, with over 88% of residues in Ramachandran plot-favored regions. The binding site prediction revealed 6 ligand-binding pockets, with the largest pocket containing 12 amino acids. After ADME screening, 16 drug-like compounds were docked to GnRH protein. Top five ligands N-Ac-(4-Cl-Phe)-Trp-Lys-AlaNH2, LHRH_LYS (6), Seabream_GnRH, Leuprolide, and LHRH_Des-tyr (5) had binding affinities ranging from −7.5 to −5.6 kcal/mol. The stable binding site was confirmed by 100 ns molecular dynamics simulations, with RMSD values below 10 Å and key residues retaining ligand contacts. The GnRH-protein resulted in the development of a suitable peptide sequence of T. ilisha, showing similarity with the similar anadromous American shad (Alosa sapidissima). This will certainly aid in future therapeutic and captive breeding advances, thereby fostering the culture and conservation of the wild species. Full article

Anadromous migration toward riverine tributaries is often challenged by altered environmental cues, food scarcity, and energy demands, sometimes at the expense of life itself. Tenualosa ilisha (Clupeiformes: Dorosomatidae), the national fish of Bangladesh, an anadromous shad, offers a model for understanding the molecular mechanisms of migration. To this end, we present a chromosome-level genome of T. ilisha and compare its transcriptomic imprints from muscle and liver across environments to trace the physiological shifts driving the migration. We observed rapid expansion of gene families to facilitate efficient signaling and osmotic balance, as well as a substantial selection pressure in metabolism regulatory genes, potentially relevant to a highly anadromous fish. We detected 1298 and 252 differentially expressed transcripts between sea and freshwater in the liver and muscle of T. ilisha, respectively, reflecting habitat and organ-specific adaptations. Co-expression analysis led us to hypothesize that the strength required for breeding migration toward upstream rivers is fueled by muscle protein catabolism forming ubiquitin-proteasomal complexes. In the liver, we observed a group of genes promoting fatty acid (FA) synthesis significantly in the riverine habitat. Regulation of FADS2 and ELOVL2 in the river reasoned the natural abundance of LC-PUFAs with better energy utilization in T. ilisha. Moreover, active gluconeogenesis and reduced insulin signaling in the liver are possibly linked to glucose homeostasis, potentially induced by prolonged starvation during migration. These genomic resources will accelerate the future evolutionary and functional genomics studies of T. ilisha. Full article

An integrated multivariate approach was applied to gain a deeper understanding of the feeding biology of hilsa shad, Tenualosa ilisha, collected from six different aquatic habitats across Bangladesh. This approach involved linking climatic factors, ecological factors, plankton abundance in water, reproductive traits, and plankton ingestion data. Climatic data were obtained from the National Oceanic and Atmospheric Administration (NOAA) and Climate Data Online (CDO) databases on a monthly basis. Water quality parameters were observed on-site at various sampling sites. Plankton data from water bodies and hilsa guts were collected monthly from the study areas and analyzed in the laboratory. The results obtained were averaged for each month. The correlation tests, multivariate approaches, cluster analyses, and regression analyses revealed that the gonadosomatic index was primarily influenced by climatic factors, the abundance of ingested gut plankton, and heir compositions. The analysis of selectivity indices confirmed that plankton preferentially ingested selective taxa. Thirteen plankton groups were identified in the water column of six different hilsa habitats. The dominant phytoplankton groups were Bacillariophyceae (34–53%), Chlorophyceae (31–50%), Cyanophyceae (4–8%), and Euglenophyceae (1–3%). Additionally, Copepoda, Rotifera, and Cladocera were the most numerous zooplankton groups. Hilsa shad primarily consumed Bacillariophyceae (38–57%), Chlorophyceae (35–53%), and Cyanophyceae (4–6%). However, they also exhibited selective ingestion of higher quantities of Bacillariophyceae and Chlorophyceae to fulfill specific and unique metabolic needs. Cluster analysis revealed the variability of phytoplankton and zooplankton abundance in water and gut in relation to diverse locations. Combining all the datasets, a principal component analysis (PCA) was applied. The first two principal components explained more than 54% of the variability. The first component explained the association between the gonadosomatic index and eco-climatic factors, while the second component extracted the cluster of ingested gut plankton in relation to salinity and pH. Pearson’s correlations and linear regression analyses showed that the number of gut plankton had a positive influence on the gonadosomatic index (GSI). Finally, the outcomes from these extensive datasets have provided a better understanding of the selective feeding behavior and the influence of feeding biology on the gonadal maturation of T. ilisha. This understanding is likely to be useful for maintaining and improving the growth and productivity of the existing production systems for this transboundary species. Full article

Seasonal changes in feeding habits of hilsa (Tenualosa ilisha) were studied monthly in 2019 in the upper Meghna estuary, Bangladesh, through gut content analyses. Tychoplanktonic diatoms followed by copepods were abundant in all months and size groups of hilsa. The inverse relationship between niche breadth and relative length of the gut revealed hilsa consume a variety of food at their early stages while their feeding habit changes towards diatoms during the adult stage with the development of gill rakers. Young hilsas prefer mostly tychoplanktonic diatoms (Aulacoseira sp., Triceratium sp., Nitzschia sp., Synedra sp., and Coscinodiscus sp.) and copepods (Pseudodiaptomus sp.). However, adult hilsas rejected Aulacoseira sp. during their spawning season. Ingested sand grains correlated with tychoplankton, revealing their food value from epipelic microalgae and bacteria clinging to them and epibenthic foraging by young hilsas. Thus, this study revealed that young hilsas primarily feed on tychoplanktonic diatoms and copepods from water and near bottom of the upper Meghna estuary during January to June while later stages with the development of gill rakers allow hilsas to feed on planktonic diatoms. Epibenthic feeding needs to be considered more fully in evaluating the biology of hilsa and, perhaps, other clupeids, and in evaluating possible human impacts on this foraging habitat. Full article

Sanctuaries are widely regarded as a protected area where fishing has been placed under some restrictions by local, state, regional and national authorities for the conservation and management of fisheries resources. These sanctuaries have a broad array of positive and negative social, economic, cultural and political impacts on fishers. This study aims to analyze the socio-economic and ecological benefits and costs of hilsa sanctuaries to protect single most important hilsa species using Sustainable Livelihood Approach (SLA). Under the Protection and Conservation of Fish Act of 1950, six sites along the Padma, Meghna, Tetulia, and Andharmanik rivers have been designated as hilsa sanctuaries. Findings of the current study revealed that most fishers perceived production of hilsa and other species were increased as a direct consequences of sanctuaries establishment. However, a considerable proportion of hilsa fishermen was found to have low socioeconomic capital, as measured by monthly income, housing circumstances and asset ownership. During the restricted fishing season in the sanctuaries, these households are particularly vulnerable to food insecurity. The government’s compensation scheme is a good example of payment of ecosystem services in an open water fishery; however, this scheme does not include all the affected fishers. It is found that hilsa sanctuaries lead to income loss of the poor fishers which is insufficiently compensated by government support program. To compensate income loss, fishers resort illegal fishing which undermine the success of sanctuary. If the sanctuaries are to function effectively, affecting fishers must be addressed by offering enough compensation schemes so that fishers are able to support their families. Moreover, some fishers believed that a co-management approach involving fishers and government is the possible best management option for operating sanctuaries in a sustainable way. Full article

Hilsa shad (Tenulosa ilisha) is Bangladesh’s most important single-species fishery that contributes to 11% of total catch and employment for millions of people. However, heavy metals (HMs) toxicity in the edible organs of T. ilisha and their plausible public health threats have received weak attention. To provide insights on this issue, we determined, using ICP-MS, the concentration of Zn, Cu, Cr (VI), Pb, and Cd in the edible organs of five different sizes of T. ilisha and the surface water collected from the Padma–Meghna River confluence, Chandpur (Bangladesh). Multivariate analysis indicated that T. ilisha gills and liver contained higher HMs than muscle, and the surface water was below the safety limits. The study revealed that only Cr crossed the safety limits and bioaccumulated in the smaller-sized gills and liver. To assess the public health risks, target hazard quotient (THQ), total THQ (TTHQ) and carcinogenic (CR) risks were calculated. Only Cr imposed non-carcinogenic risks to consumers, while TTHQ showed higher chronic health risks. There was no CR risk measured for consumers, except for the largest-sized gills for children. Randomly positive relations between HMs and sizes were found; whereas, consistently positive relations were found among the tissue types. The outcomes of our study may aid policymakers in managing pollutants, especially the Cr sources in the greater Chandpur regions. Full article

Hilsa fish (Tenualosa ilisha) have become an essential factor behind the well-being of the fishing community, giving fishers their identity as a source of cultural heritage. A field survey was conducted to understand the socio-economic conditions of hilsa fishers at the Meghna river estuary of Chandpur District using well-structured questionnaire interviews (N = 250) with hilsa fishers. The survey revealed that fishers’ livelihoods and living conditions were still below average due to low literacy levels, lack of professional skills, and low incomes. More than two-thirds of the fishers were entirely dependent on hilsa fishing, while more than one-third had between 11 and 20 years of fishing experience. More than two-thirds of the fishers did not have an alternative occupation during ban periods, and the incentives provided by the government were not adequately received by half of the fishers. Fishers were divided into three groups according to their dependence on hilsa fishing. Significant differences were found between these groups in terms of the age of fishers, annual income from fishing, and annual fishing activity days. Therefore, the government, Fisheries cooperatives, NGOs, and other relevant organizations must unite to support fishers for sustainable hilsa fishery management. Full article

Despite different approaches used to assign the risk scores for missing information in productivity susceptibility analysis (PSA)—a widely used semi-quantitative risk assessment tool for target and non-target fisheries stocks—for the selected attributes of a given species, no formal comparison has been made between scoring approaches in terms of how well they can predict species vulnerability. The present study evaluated the PSA findings of 21 bycatch stocks of the Hilsa (Tenualosa ilisha) gillnet fishery of Bangladesh using two different scoring approaches (the conservative scoring approach, CSA; and the alternative scoring approach, ASA) to determine the most reliable approach to minimize false estimates of species vulnerability. Our analysis revealed that the V scores increased by 0.0−0.20 with a mean value of 0.09 for 21 selected bycatches when CSA was applied. The inconsistency between the vulnerability (V)-score-suggested fishing status (V ≤ 1.8 = underfishing, V > 1.8 = overfishing) and the fishing status defined by exploitation rate (E > 0.5 = overfishing, E < 0.5 = underfishing) were 38.1% and 19.0% under CSA and ASA, respectively. Likewise, the consistency between the V-score-suggested fishing status and fishers’ perceived catch trends was found to be higher when using ASA than when using CSA. Our analysis suggests that CSA could overestimate species vulnerability. Therefore, ASA is more reliable than CSA in PSA, which may increase the confidence of fisheries stakeholders in PSA. Full article

The anadromous tropical Hilsa shad formed the largest single-species fishery in Bangladesh, making the highest contribution to the country’s total fish production (14%) and nearly 83% of the global Hilsa catch in 2018. However, increased fishing pressure made the fishery vulnerable, and hence, information on the stock condition and its response to the current degree of removal is essential to explore the future potential for sustainable exploitation. This study carried out a rigorous assessment based on three different methodological approaches (traditional length-frequency based stock assessment method for fishing mortality and exploitation, Froese’s length-based indicators for fishing sustainability, and a surplus production-based Monte Carlo method-CMSY, for fisheries reference points estimation) for the best possible estimates of the Hilsa stock status in the water of Bangladesh. The present findings revealed that the stock is likely to be overfished due to over-exploitation. Depending on the outputs, this study recommended a lower length limit for the catch (>33 cm), distinguished a selectivity pattern (mesh size limit ≥ 8 cm), and proposed a yearly landing limit (within the range of 263,000–315,000 tons) for the sustainable management of the Hilsa fishery in Bangladesh. Full article

Long-term frozen storage deteriorates the quality of hilsa fish (Tenualosa ilisha), famous for its delicious taste and flavors. Vacuum packaging may retain the flavor and quality of hilsa fish. To this end, biochemical and microbiological analyses were used to assess the quality of hilsa fishes under whole without pack, whole with vacuum pack, dressed without pack, and dressed with vacuum pack, at a monthly interval during a year of frozen storage at −18 °C. There were no significant differences (p > 0.05) in the values of pH, free fatty acids (FFA), total volatile base nitrogen (TVB-N), and aerobic plate count (APC) among the treatments, and the values remained within the acceptable limit during the storage period. However, thiobarbituric acid reactive substances (TBARS) were significantly (p < 0.05) lower in samples under vacuum (whole and dressed) compared to samples without pack. TBARS values did not cross the acceptable limit for vacuum pack samples in nearly the entire storage period but were exceeded for samples without pack within the first month. It is assumed that the vacuum packaging reduced the secondary oxidation of fatty fish like hilsa during the frozen storage, which can ensure a year-round supply of quality hilsa fish without altering its distinctive taste and flavor. Full article

The present study aimed to map out the current threats and anticipated impacts of climate change on the most important hilsa shad (Tenualosa ilisha) fishery and the associated fishing communities based on fieldwork in six coastal fishing communities. To collect empirical data, individual interviews, focus group discussions, oral history, and key informant interviews were conducted. To supplement the empirical findings, time-series data of cyclones and sea-borne depressions in the Bay of Bengal were also analyzed. Analysis of secondary data regarding climate change-induced events and regional studies suggested that the biophysical conditions of the Bay of Bengal are likely to be aggravated in the future, potentially causing more frequent extreme events and affecting the livelihoods of coastal fishing communities in Bangladesh. The fisher respondents revealed that the main target hilsa shad fishery is particularly vulnerable to climate change in terms of alterations to migration patterns and breeding and growth performance. The fishers reported constant climate-related risks because they live in seafront locations, exposed to extreme events, and their occupation entails risky sea fishing. Fishers claimed that they often need return to the coast due to unsuitable weather conditions related to cyclones and frequent tropical depressions, which can cause financial losses or even causalities. Such events negatively affect fishers’ livelihoods, and wellbeing. To cope with the impacts of climate change the fishers have adopted various strategies at both sea fishing and household levels. However, these strategies only support the fishers in terms of immediate survival; they are not enough for long-term resilience. To improve the resilience of the hilsa fishers, the study argues for the implementation the Small-Scale Fisheries Guidelines (SSF Guidelines), which call for longer-term development goals, including in the immediate relief phase, and rehabilitation, reconstruction, and recovery to reduce vulnerabilities to climate and anthropogenic risks. Full article

This paper considers the hilsa shad (Tenualosa ilisha) fishery of southern Bangladesh as a case study regarding governance and power dynamics at play in a small-scale fishery, and the relevance of these for the sustainable management of coastal fisheries. Qualitative methods, involving in-depth individual interviews (n = 128) and focus group discussions (n = 8) with key stakeholders in the hilsa fishery, were used to capture multiple perspectives on governance from those in different positions in the relative power structures studied, while facilitating insightful discussions and reflections. The analysis here is based on a power cube framework along three power dimensions (levels, spaces, and forms) in Bangladesh’s hilsa fishery. The study displays an imbalance in the present hilsa governance structure, with some stakeholders exercising more power than others, sidelining small-scale fishers, and encouraging increasing illegal fishing levels that ultimately harm both the fisheries and those dependent on them. To overcome this, we propose a co-management system that can play a vital role in equalizing power asymmetry among hilsa fishery stakeholders and ensure effective hilsa fishery governance. Our results suggest that recognizing analyzed power dynamics has substantial implications for the planning and implementation of such co-management and the long-term sustainability of the hilsa fishery. Full article

The migration of anadromous fish in heterogenic environments unceasingly imposes a selective pressure that results in genetic variation for local adaptation. However, discrimination of anadromous fish populations by fine-scale local adaptation is challenging because of their high rate of gene flow, highly connected divergent population, and large population size. Recent advances in next-generation sequencing (NGS) have expanded the prospects of defining the weakly structured population of anadromous fish. Therefore, we used NGS-based restriction site-associated DNA (NextRAD) techniques on 300 individuals of an anadromous Hilsa shad (Tenualosa ilisha) species, collected from nine strategic habitats, across their diverse migratory habitats, which include sea, estuary, and different freshwater rivers. The NextRAD technique successfully identified 15,453 single nucleotide polymorphism (SNP) loci. Outlier tests using the F_ST OutFLANK and pcadapt approaches identified 74 and 449 SNPs (49 SNPs being common), respectively, as putative adaptive loci under a divergent selection process. Our results, based on the different cluster analyses of these putatively adaptive loci, suggested that local adaptation has divided the Hilsa shad population into two genetically structured clusters, in which marine and estuarine collection sites were dominated by individuals of one genetic cluster and different riverine collection sites were dominated by individuals of another genetic cluster. The phylogenetic analysis revealed that all the riverine populations of Hilsa shad were further subdivided into the north-western riverine (turbid freshwater) and the north-eastern riverine (clear freshwater) ecotypes. Among all of the putatively adaptive loci, only 36 loci were observed to be in the coding region, and the encoded genes might be associated with important biological functions related to the local adaptation of Hilsa shad. In summary, our study provides both neutral and adaptive contexts for the observed genetic divergence of Hilsa shad and, consequently, resolves the previous inconclusive findings on their population genetic structure across their diverse migratory habitats. Moreover, the study has clearly demonstrated that NextRAD sequencing is an innovative approach to explore how dispersal and local adaptation can shape genetic divergence of non-model anadromous fish that intersect diverse migratory habitats during their life-history stages. Full article

Small-scale fisheries (SSFs) have been playing a crucial role in meeting the basic needs of millions of people around the world. Despite this, the sustainability of global fisheries is a growing concern, and the factors enabling or constraining the sustainable management of small-scale fisheries remain poorly understood. Hilsa shad (Tenualosa ilisha) is the single most valuable species harvested in Bangladesh waters, serves nutrition, income, and employment to the large population. This study analyzed the state and challenges of hilsa fishery in the Gangetic River systems (Padma and Meghna Rivers) by using two frameworks, namely the social-ecological systems (SES) and drivers-pressure-state-impact-responses (DPSIR) frameworks. Primary data for this analysis were collected by in-depth interviews (n = 130) and focus group discussions (n = 8) with various stakeholders in the hilsa fisheries. The perspectives explored here have been both critical and constructive, including the identification of problems and suggestions for improving the management of this particular social-ecological system. Hilsa fisheries, however, have come under severe threat since 2003 because of population growth, overfishing, pollution, climate change, the disruption of migration routes due to siltation, etc. All these have caused reduced catches and less stable incomes for fishers. This, in turn, has led to poverty, malnutrition, social tensions, stakeholder conflicts, and debt cycles amongst more impoverished fishing communities. These problems have been compounded by improved fishing technology amongst larger-scale ventures, the use of illegal fishing gears, and the non-compliance of government fishery management programs. Recommendations include the promotion of community-supported fisheries, the enhancement of stakeholder’s social resilience, the introduction of co-management approach, an increase in incentives and formal financial supports, and possible community-managed sustainable ecotourism including hilsa fishing-based tourism. Full article