Indian Council of Agricultural Research
CENTRAL MARINE FISHERIES RESEARCH INSTITUTE

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Perkinsus olseni in the short neck yellow clam, Paphia malabarica from southwest coast of India

Parasites of the genus Perkinsus predominantly infect bivalves, and two species among them, P. olseni and P. marinus, are notifiable to OIE. P. olseni infections are known to cause extensive damage to wild as well as farmed bivalves globally with enormous implications to its fishery. Consequent to the initiation of a surveillance programme for aquatic animal diseases in India, Perkinsus infections were observed in many species of bivalves. The present paper describes P. olseni infections in the short neck yellow clam, Paphia malabarica from the southwest coast of India. Diagnosis of the parasite was carried out using Rays Fluid Thioglycollate Medium culture, histology, in-situ hybridisation and molecular taxonomy. Pathology of infection and development of zoospores is also described. This forms the first report of a P. olseni infection in P. malabarica. High prevalence and intensity of infection of Perkinsus in clams raises concerns, as clam reserves in this geographical area sustain fisheries and the livelihoods of local fishing communities.


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Insights into the credit transactions of small-scale fishers along the south west coast of India

This paper closely scrutinizes the diverse credit transactions undertaken by small-scale fishers along the South West coast of India, based on a field-level survey carried out in the maritime State of Kerala. The study describes alternative modes of fishery credit delivery in the State and explores the tangled inter-linkages in the formal and informal credit contracts. Further, empirical assessment of borrowing pattern of small-scale fishers is conducted by taking the case of ring seiners who constitute an important segment in the local fishery. The main determinants of their borrowing behavior from institutional credit sources are identified using a fractional logit regression approach. The findings point to continuing dominance of the informal financial sector over the institutional credit sector. In the light of the findings, measures such as reforming the fish auction system, linking insurance with formal credit, further strengthening of fishery co-operative societies and exercising stringent state control to curb exploitative lending practices are suggested.


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New species of macrocercous and megalurus cercariae infecting freshwater snail, Paludomus tanschauricus

The present paper describes two new species of cercariae infecting the freshwater snail, Paludomus (Paludomus) tanschauricus from Malabar, Kerala. Paludomus tanschauricus collected from the hill streams at Vattakkundu in the Wayanad district of Kerala harboured a macrocercous cercaria, Cercaria sp. XX Malabar n. sp. characterized by a disproportionately large tail. Developmental stages were recovered from the hepatopancreatic tissues of the snail host. Cercariae encysted on the gills of the fish, Haludaria melanampyx. Snails collected from Papanashini rivulet at Thirunelli, also from Waynad district were infected with a megalurous cercaria, Cercaria sp. XXI Malabar n. sp. possessing an elongated tail with an adhesive cup-like sucker at its tip. Redial stages developed in the hepatopancreas while the cercariae were found to encyst on any available substrate. The morphology and morphometry of these two cercariae along with their developmental stages are studied in detail and compared with related species to establish their systematic positions.


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Morphological and molecular investigations on Paphia malabarica from Indian waters

Paphia malabarica Chemnitz, 1782 is an economically important species of Venerid clam in Indian waters. The fishery of P. malabarica from Ashtamudi estuary, Kollam, Kerala has been certified by marine stewardship council as sustainable and the fishery is now managed by a set of fishery management plans. The name P. malabarica is invalid now as it has been synonymized as Paphia (Protapes) gallus (Gmelin, 1791) in subsequent taxonomic investigations. We examined the taxonomic status of P. malabarica using morphological and molecular methods. Morphological characteristics of the shell mainly, shell structure, size and internal features were compared between P. gallus and P. malabarica indicating significant differences in morphology. Molecular investigations were carried out by amplifying and sequencing mitochondrial Cytochrome C Oxidase 1 (COI) and 16SrRNA sequences of P. malabarica collected from Ashtamudi (Kollam), Dharmadam, Kannur (3 locations in Kerala), Goa, Maharashtra, Gujarat and Tuticorin in order to clear the taxonomic ambiguity and validate the synonymy. Sequences of P. malabarica were compared with sequences of P. gallus and other Paphia species. Substantial genetic divergence was detected between P. malabarica and P. gallus with a K2P genetic distance value of 28.9% and distinct clustering in phylogenetic tree demonstrating that P. malabarica is well diverged from P. gallus. We suggest retaining the name P. malabarica considering that the synonymy with P. gallus is invalid.


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Redescription of Bleekeria kallolepis from Chennai, eastern Indian Ocean

The yellow-striped sandlance, Bleekeria kallolepis Günther, 1862, is a poorly known ammodytid fish from the eastern Indian Ocean, known from fewer than five specimens. No detailed description or colour images of B. kallolepis have previously been available. We hereby provide a short taxonomic account of the species from its type locality Chennai, India with morphometrics and colour description.


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Breeding, early development and larval rearing of cloudy damsel, Dascyllus carneus

As the demand for marine ornamental fish is ever increasing, the industry largely relies on collections from natural habitat due to insufficient breeding and seed production technologies. Fishes of the family Pomacentridae are popular in marine aquaria throughout the world. Among these, damsel fishes of the genus Dascyllus has high demand and are mostly collected from the wild. The present study forms the first-ever report on successful breeding and larval development of Cloudy Damsel (Dascyllus carneus Fischer, 1885). Though there are a few reports on breeding of other species of Dascyllus, there has been no report on the complete larval development of any of the species in this genus. This forms the first description of early larval development of a Dascyllus species. Using the copepod Parvocalanus crassirostris as first feed the larval rearing was done. Successful breeding and larval development were achieved from the wild-caught broodstock of D. carneus at Vizhinjam Research Centre of ICAR-CMFRI, India. Brood stock from the wild took 4 months to spawn, laid 6500–10,500 eggs per spawning and hatching rate ranged from 90.6 to 98.81%. Newly hatched larvae were the smallest among all the reported larvae of pomacentrid fishes and measured 1.95 ± 0.14 mm in total length. Yolk reserve was completely absorbed within 72 h of hatching. Preflexion stage is from 4 to 10 dph, flexion stage is from 11 to 12 dph and postflexion period is 13–15 dph. Larvae accepted only copepod naupliar stages as first feed and calanoid copepod P. crassirostris alone was fed until 25 dph. Larvae settled from planktonic stage in 22–23 days and all the larvae metamorphosed into juveniles by 50 dph. The egg development, larval development and larval pigmentation up to 50 dph has been described. The feeding protocols and feed size preference in relation to their age or mouth gape, the gut contents and mouth gape of the larvae caught from a feed trial with surplus copepods of all stages were analysed at regular intervals. Larvae preferred larger stages of copepods in later stages of their development. Finally larval feeding protocols were modified accordingly and better survival was observed. A final feeding regime has been developed and a strategy for the consistent hatchery production of this species was achieved. Different stages of copepod P. crassirostris were used till the settlement of planktonic stage of larvae and Artemia nauplii were used from 25 dph. The larvae were completely weaned to artificial diet from 50 dph.


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