Indian Council of Agricultural Research
CENTRAL MARINE FISHERIES RESEARCH INSTITUTE

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Development and validation of microsatellite markers in Eleutheronema tetradactylum

The four fingered threadfin Eleutheronema tetradactylum (Shaw, 1804) is a prioritised species for mariculture in India. Their demand in the domestic markets is rapidly growing. Genetic stock structure analysis of fish populations is an important aspect from fisheries management perspective. The present study was conducted to develop microsatellite primers through cross-priming to elucidate the genetic structure of E. tetradactylum. A total of 13 polymorphic microsatellite markers were developed from the resource species, Pacific salmon Polydactylus sexfilis. The observed mean and the effective number of alleles were found to be 11.962 and 6.927 respectively. The mean of observed heterozygosity (Ho) and expected heterozygosity (He) values obtained were 0.784 and 0.798 respectively. These new microsatellite markers can be used as effective tools for studying genetic disparity as well as for elucidating evolutionary relationships among E. tetradactylum populations.


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New record of starry flying gurnard, Dactyloptena peterseni from Wadge Bank

Five specimens of dactylopterids measuring 220.5–320.0 mm standard length caught commercial trawler fishing in 80–120 m deep waters of Wadge Bank off Kanyakumari coast (8.02 N, 76.80 E) were collected from the landing centre at Jeppiaar fishing harbour, Muttom, Southwest coast of India. The specimens were identified as Dactyloptena peterseni (Nystrom, 1887) on the basis of morphometric measurements and the key identification character like absence of second free spine between the occipital and the first dorsal spine. The occurrence of the species suggests that the extended distribution of D. peterseni to Southwest coast of India. The detailed morphometric and meristic characters are described and discussed in this paper. Molecular identification was done by using partial sequence of mitochondrial cytochrome oxidase sub-unit I gene for confirmation of the species.


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Hepatic lesions associated with induced aflatoxicosis in the estuarine teleost Etroplus suratensis

Aflatoxicosis is the disease caused due to ingestion or inhalation of aflatoxins, one of the most potent and dangerous groups of mycotoxins, which is produced by fungi of the genera Aspergillus. This fungus grows on feed as well as on feed ingredients used in aquaculture and the tropical humid climate is conducive for its growth and toxin production. The present study was undertaken to assess the susceptibility of a tropical estuarine teleost, Etroplus suratensis (Bloch, 1790) to this toxin by exposing the fishes to aflatoxin B1 (AFB1) incorporated feed at a rate of 0.4 mg AFB1 kg-1 feed, over a period of 8 weeks. On termination of experimental feeding, gross changes such as pale liver with numerous black spots were observed in aflatoxin treated fishes. Progressive damages to the liver which ultimately led to the induction of hepatoma was demonstrated through histopathological and electron microscopic studies. The major histopathological changes such as shrunken pyknotic nuclei, formation of basophilic foci, polyhedral hepatocytes in different sizes, multiple nuclei and mitotic nuclei were observed. The ultrastructural changes such as appearance of electron dense inclusions in the nucleus, loss of structure of microvilli, fragmentation of endoplasmic reticulum, separation of desmosomes, loss of continuity of plasma-lemma and nuclear membranes were also evident. In the present study, susceptibility of the species to aflatoxicosis was demonstrated clearly and the resultant induction of hepatoma indicated the possibility of using this species as an animal model in studies on induction of hepatocarcinomas.


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Copepod parasite Lepeophtheirus kabatai infestation in orange spotted grouper, Epinephelus coioides

Parasitic infection in the orange spotted grouper Epinephelus coioides (Hamilton, 1822) and its control measures in captive conditions were studied. Wild collected groupers after 8 weeks of rearing in captivity showed lethargy and sluggishness. The caligid parasite, Lepeophtheirus kabatai (Ho & Dojiri, 1977) was identified from the affected fishes. This parasite was also prevalent in wild fish, however at lower prevalence (11%). The mean intensity of L. kabatai in fishes reared in captivity was 92.85±10.71, whereas in wild fish it was 3.54±1.61. Infected cultured fish were randomly assigned to one of five treatment groups (Group A, B, C, D and E). Group A fishes were given dip treatment in freshwater for 5 min, whereas groups B, C, D and E were given bath treatment in formalin @ 50, 100, 150 and 200 mg l-1 respectively for 30 min, followed by 5 min dip in freshwater. Group E fish were fully free of the infestation and no re-infestation was seen in them even after two months. This is the first study to confirm L. kabatai infestation in orange spotted grouper in both wild and cultured fish; and formalin treatment @ 200 mg l-1 was found effective to control the infestation in captivity.


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Examination on biological economics of inshore shore seine fishery: A case study from Dhanushkodi Island

Shore seining at Dhanushkodi, Tamil Nadu was an age old practice and its approach to fish, fisheries and fishers were detailed in the present study. The entire beach seining was carried out on the sea grass meadows which forms the breeding and feeding grounds of commercially important fishes and in turn showed the over dominance of juveniles in the catch. Gonadal examination itemised that, the majority of the fishes were in immature and maturing stage of ovarian development. The economic evaluation of juveniles of six important fish species reported a total economic loss of about INR 44.64 crores during 2015-16 by shore seining at Dhanushkodi. The gross revenue of fish landed per day varies from Rs 300 to Rs 15,000 and average reported being Rs. 5000/day in one unit. A total of 22 to 24 fishers involved in the activity and the profit has to be distributed accordingly.


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Biosonar dysfunction and mass stranding of short-finned pilot whale Globicephala macrorhyncus at Manapad

A mass stranding of 81 short-finned pilot whale (SFPW) Globicephala macrorhynchus along Manapad coast from 11th to 15th January, 2016 was reported. Along the same coast, 147 SFPW were reported to have stranded in the same month, 43 years ago. Morphometric measurements of stranded specimens were taken. Based on the necropsy and subsequent findings, the animals showed no obvious signs of health problems. The single most predominant cause to have triggered the recent mass stranding could be possibly biosonar dysfunction.


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