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Fish stocks that are grown under diverse environmental conditions have different biometric relationships and growth patterns. The biometric length-weight relationship (LWR) is an essential fishery assessment tool, as fish growth is continuous and depends on genetic and environmental factors. The present study attempts to understand the LWR of the flathead grey mullet, Mugil cephalus Linnaeus, 1758, from different locations. The study area encompassed its distribution in the wild across freshwater location (one), coastal habitats (eight locations), and estuaries (six locations) in India to determine the relationship between various environmental parameters. Specimens ( n = 476) of M. cephalus were collected from commercial catches and the length and weight of individual specimens were recorded. Monthly data from the study locations were extracted for nine environmental variables from the datasets downloaded from the Physical Oceanography Distributed Active Archive Center (PO.DAAC) and the Copernicus Marine Environment Monitoring Service (CMEMS) over 16 years (2002 to 2017) on the Geographical Information System platform. The parameters of the LWR, intercept ‘a’ and slope or regression coefficient ‘b’, varied from 0.005321 to 0.22182 and 2.235 to 3.173, respectively. The condition factor ranged from 0.92 to 1.41. The partial least squares (PLS) score scatter plot matrix indicated differences in the environmental variables between the locations. PLS analysis of the regression coefficient and environment parameters revealed that certain environment variables viz. , sea surface temperature, salinity, dissolved oxygen, nitrate, and phosphate, played a positive role. However, chlorophyll, pH, silicate, and iron played a negative role in influencing weight growth across various locations. The results revealed that the M. cephalus specimens from three locations, Mandapam, Karwar, and Ratnagiri, possessed significantly higher fitness to their environment than those from the other six locations. The PLS model can be used to predict weight growth under the various environmental conditions of different ecosystems. The three identified locations are useful sites for the mariculture of this species considering their growth performance, the environmental variables, and their interactions. The results of this study will improve the management and conservation of exploited stocks in regions affected by climate change. Our results will also aid in making environment clearance decisions for coastal development projects and will improve the efficiency of mariculture systems.

Motile Aeromonas septicaemia (MAS), caused by Aeromonas hydrophila , is one of the most significant bacterial disease responsible for mortality in Indian catfish, Clarias magur , a potential aquaculture species in the Indian subcontinent. In fish, innate immunity elicited by pathogen recognition receptors (PRRs) plays an important role in providing protection against bacterial infection. Information on PRRs including Toll-like receptors ( tlrs ) and their response to bacterial pathogens remains unexplored in magur. Toll-like receptor 2 ( tlr2 ), a phylogenetically conserved germ-line encoded PRR recognizes specific microbial structure and trigger MyD88-dependent signaling pathway to induce release of various cytokines responsible for innate immune response. In the present study, tlr2 gene of magur was characterized and downstream signaling was studied following challenge with A. hydrophila . The full-length cDNA of magur tlr2 ( mtlr2 ) comprised of 3,066 bp with a single open reading frame of 2,373 bp encoding 790 amino acids having a theoretical pI value of 6.11 and molecular weight of 90 kDa. Structurally, it comprised of signal peptide (1–42aa), one leucine-rich repeat region (LRR) at N-terminal (LRR1-NT: 50–73 aa) and C-terminal (LRR-CT: 588–608 aa), twenty LRRs in between, one trans-membrane (Tm) domain (609–631aa) followed by cytoplasmic TIR domain (670–783aa). Phylogenetically, mtlr2 is closely related to pangasius and channel catfish. Highest basal expression of mtlr2 , myd88 and il-1β in spleen, nf-kb in anterior kidney was observed. Lowest basal expression of mtlr2 in skin and myd 88, nf - kb and il-1β in muscle was detected. Significant up-regulation of mtlr2 and downstream expression occurred at 3, 8, 24 h post infection to A. hydrophila in important immune organs such as liver, spleen, intestine and kidney. These findings highlight the vital role of tlr2 in eliciting innate immune defence against A. hydrophila infection.

Milkfish ( Chanos chanos ) belongs to the family Chanidae and it is a potential candidate species for aquaculture with the best biological characteristics. This study investigates the genetic diversity and population structure of C. chanos along the Indian coast using cytochrome b (cyt b) sequences of mitochondrial DNA (mtDNA). A total of 90 samples collected from five different locations across the Indian coast were sequenced for analysis using cyt b. The sequencing of a 1100-bp cyt b mtDNA fragment revealed the presence of 38 haplotypes with a haplotype diversity value of 0.835 and a nucleotide diversity value of 0.00400. The variation within and among populations accounted for about 97.33% and 2.67%, respectively. The fixation index analysis indicated that there is no significant genetic divergence among the populations from different geographical areas. Neighbour-joining tree analysis of the haplotype data showed no distinct patterns of phylogeographic structure. Results from this study indicated that there is a lack of genetic divergence between the populations of C. chanos along the Indian coast. The haplotype network showed star-like geneology which indicated the demographic expansion of the C. chanos population in these locations. The recent demographic expansion of the C. chanos population was also supported by the results of Tajima’s  D  statistics. Results from this study can be used for planning effective strategies for the conservation and management of the C. chanos population in the wild.

Background Butter catfish ( Ompok bimaculatus ) is a preferred species in South East Asia, with huge aquaculture potential. However, there is limited information about genetic stock composition due to insufficient markers. The goal of this study was to develop de novo microsatellite markers. Methods and results For sequencing, genomic SMRT bell libraries (1.5 Kbp size) were prepared for O. bimaculatus . A total of 114 SSR containing sequences were used for primer designing. Polymorphic loci were validated by genotyping 83 individuals from four distant riverine populations, viz., Brahmaputra, Bichiya, Gomti and Kaveri. A total of 30 microsatellite loci were polymorphic, of which five were found to be associated with functional genes and eight (four positive and four negative) loci were found to be under selection pressure. A total of 115 alleles were detected in all loci and PIC ranged from 0.539 to 0.927 and pair-wise F ST values from 0.1267 to 0.26002 (p < 0.001), with an overall F ST value of 0.17047, indicating the presence of population sub-structure. Cross-species transferability of 29 loci (96.67%) was successful in congener species, Ompok pabda . Conclusion The novel SSR markers developed in this study would facilitate stock characterization of natural populations, to be used in future selection breeding programs and planning conservation strategies in these species. Identified non-neutral markers will give insights into the effect of local adaptation on genetic differentiation in the natural population of this species.

Rhabdosargus sarba , the goldlined seabream, is a euryhaline marine fish of great aquaculture potential. Genome sequencing and assembly of R. sarba was carried utilizing a multi-platform sequencing strategy that included long-read sequencing (PacBio HiFi), short-read sequencing (Illumina), and chromatin interaction mapping (Hi-C). The final genome assembly size after scaffolding was 764.59 Mb in 31 scaffolds with an N50 length of 33.98 Mb. Repeat profiling of primary assembly showed that 28.71% of the genome comprises of repeat elements. Gene prediction utilising the evidence from ab initio prediction and transcriptome data revealed 26,913 protein encoding genes and functional annotation and pathway analysis showed their participation in 332 pathways. This genome is an excellent resource for future research on genetic improvement and molecular breeding programmes for R. sarba .

Chitala chitala (Hamilton, 1822) is an economically important food fish species occurring throughout Indian rivers, which also has ornamental value. This study focuses on morphological variations in C. chitala from seven river basins across India namely; Son, Tons, Ken, Brahmaputra, Ganga, Gomti and Gandak. A truss network was constructed by interconnecting nine landmarks to generate 36 morphometric variables extracted from digital images of specimens sampled from the study locations. Transformed truss measurements were subjected to principal component analysis (PCA), canonical discriminant function analysis (CDFA) and discriminant analyses of principal components (DAPC). DAPC function coefficients performed much better in capturing the variation pattern and discrimination between the rivers which was not achieved using CDFA. Eight truss variables were identified with significant and highest loading for truss variables on principal components and coefficients on discriminant function from DAPC contributing to maximum variation between the rivers. Performance graph and functional distribution of identified truss variables clearly indicated distinction between the rivers. Thin plate spline analysis and procrustes shape analysis further showed the variation in morphology between specimens across the rivers. The significant parameters differentiating specimens from different rivers were linked to dorsal fin origin, the base of the pectoral fin and the perpendicular point on the anal fin from the dorsal fin origin. Variation in the hydrodynamics of the rivers studied might be possibly affecting the fin kinematics and consequently leading to adaption seen as phenotypic variation in C. chitala . The results showcased in the present study shall help in better understanding of intra-specific diversity which is significant for management and conservation of a species.

Shrimp is a key commodity constituting one-third of the global annual seafood trade of USD 171 billion (2024) constituting for approximately 25% of the agricultural trade. Farmed shrimp contributes significantly to foreign exchange earning in major producer countries. The sector faces biological, climatic, and market risks, including viral pathogens like White Spot Syndrome Virus (WSSV), microsporidian infections such as Enterocytozoon hepatopenaei (EHP), cyclones, floods, and global price volatility. Insurance is one of the major de-risking tools providing financial protection to farmers. Inherent vulnerability to risks of the aquaculture limits the interest of the insurers to offer cover to the shrimp farming. Aquaculture crop insurance is a crucial mechanism for achieving several Sustainable Development Goals (SDGs), particularly those focused on poverty reduction (SDG 1), food security (SDG 2), and climate action (SDG 13). By safeguarding farmers against losses from events like natural disasters and crop diseases. It promotes income stability, encourages the adoption of sustainable farming practices, and enhances agricultural productivity, ultimately building the resilience of coastal rural poor communities against the impacts of climate change. This review synthesizes global experiences with indemnity and parametric insurance models, evaluates challenges and adoption rates across countries, and presents a detailed case study of India. Further, it explores different insurance policy models and highlights the role of regulatory agencies. The study discussed modern scientific measures like, Better Management Practices (BMPs) and application of digital technologies; Artificial Intelligence (AI), Internet of Things (IoT) and satellite imaging in reducing the risk and efficient loss assessment for swift claim settlement. Recent ongoing efforts to revitalize Indian shrimp crop insurance products through institutional and industry linkage with enhanced participation of farmers and other stakeholders are highlighted. This review advocates policy alternatives and other options available such as, insurance linked credit flow, government supported re-insurance, group insurance and affinity insurance for sustainable aquaculture insurance. Challenges include low awareness, limited parametric adoption, and historical disease outbreaks. Key lessons emphasize government support, premium subsidies, digital monitoring systems, and coordinated stakeholder partnerships. The findings provide actionable guidance for policymakers, insurers, and other stakeholders on designing effective, inclusive, and sustainable shrimp aquaculture insurance frameworks globally. Recommendations focus on subsidized premiums, streamlined claims processes, and farmer education programs.

A new species of the genus Pangasius, is described based on 17 specimens collected from the Cauvery River, India. It can be distinguished from its sister species from South and Southeast Asia, by its widely placed, small and rounded vomerine and palatine tooth plates, longer maxillary and mandibular barbels, greater vertebrae count 50 (vs. 44–48), and smaller caudal peduncle depth (6.5–8.2% SL vs. 9.89–13.09% SL). The tooth plates of the new species closely resembles that of Pangasius macronema but can be clearly distinguished from the latter by having lesser gill rakers (16–19 vs. 36–45); a smaller eye (2.4–4.4% SL vs. 5.2–9.6% SL); and larger adipose-fin base (1.5–2.9% SL vs. 0.1–1.2% SL). The mitochondrial cytochrome c oxidase (COI) gene sequence of the new species shows the genetic divergence of 3.5% and 5.1% from P. pangasius and P. silasi respectively, the two sister species found in South Asia and India. The species delimitation approaches, Poisson Tree Processes (PTP) and assemble species by automatic partitioning (ASAP) clearly resolved that the P . icaria is distinct from its sister species. Phylogenetic position of the species with its sister species was evaluated using maximum likelihood and Bayesian analysis. The discovery of this previously unknown species of genus Pangasius from the Cauvery River of peninsular India indicates important biogeographical insight that this genus migrated till the southern division of Western Ghats.

Stem cell research has come into prominence because of its applications in assisted reproductive technology and the treatment of deadly diseases. In teleost fishes, spermatogonial stem cells have been effectively used to produce surrogate gametes and progeny through germ cell transplantation technique. The present study is the first report of an innovative application of stem cell therapy in fish species for revitalising the reproductive competence of senescent individuals. Senescent male goldfish, Carassius auratus , approximately 10 years of age were procured from a fish-breeding farm and were reared locally in the lab for an additional two years. The senescence of the individuals was then evaluated and confirmed using histological analysis, gonadal index assessment, and germ-cell specific vasa gene expression. Analyses revealed absence of spermatogonial cells and other germ cells in the testes of the senescent fish ( n  = 5). Spermatogonial cells from sexually immature C. auratus male donor were isolated using discontinuous percoll gradients, labelled with the fluorescent dye PKH-26, and transplanted into the gonads of senescent C. auratus males through urogenital papilla. Six months after the transplant, spermatozoa were collected through applying gentle manual pressure on the abdomen and were observed under a microscope. All C. auratus males with the transplant had produced spermatozoa from the transplanted cells. This was confirmed by the retention of PKH-26 in the spermatozoa and diagnostic SSR locus. Gravid C. auratus females were artificially inseminated with the spermatozoa of those senescent males and natural spawning was allowed. As a result viable progeny were produced. These observation suggests that the reproductive competence of senescent male fishes can be revitalised through spermatogonial stem cell therapy to produce functional gametes.

Pycnocraspedum squamipinne Alcock, 1889 is a rare species of pelagic cusk eel described from specimens collected off the Bay of Bengal. The descriptive literature on P. squamipinne is limited to the original description owing to the rarity in collections. The genus and the species need a thorough revision to identify specific characters of taxonomic importance as the descriptive information regarding the species in the genus Pycnocraspedum is limited to the holotypes and syntypes. Fifteen fresh specimens of P. squamipinne were collected from the Chennai coast, Tamil Nadu, Bay of Bengal region. The syntypes of P. squamipinne (ZSI F 11700 and ZSI F 11703) available at the Zoological Survey of India, Kolkata were examined. The morphometric and meristic characters of P. squamipinne were compared with those of syntypes and other species of the genus. Molecular analysis was carried out using partial mtDNA cytochrome oxidase subunit I gene (COI). The specimen is deposited in the national fish repository of the ICAR, National Bureau of Fish Genetic Resources, Lucknow, India. A detailed redescription of P. squamipinne based on the syntypes and fifteen recently collected specimens are provided. A detailed comparison with other species of the genus is also provided which helps in establishing the taxonomic identity of P. squamipinne . Molecular information was generated which would help in the species identification of this rare deep-sea species. This study provides morphological and molecular information of the rare cusk eel, P. squamipinne , which would help in the precise identification of the species. However, due to paucity, the majority of species of the genus are still only known from single specimens and comprehensive examination of holotypes and intensive sampling is needed to better understand the species identity and distribution.