Indian Council of Agricultural Research
CENTRAL MARINE FISHERIES RESEARCH INSTITUTE

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Impact of increase in temperature and light intensity on development and metamorphosis of hatchery reared silver pompano larvae

The largehead ribbonfish, Trichiurus lepturus Linnaeus, 1758 forms a major fishery along north-west coast of India comprising the two coastal states of Gujarat and Maharashtra. Diet composition was analysed for five years (2010-2014) to understand shifts if any in the prey items. Seasonal changes in the prey items were studied for three years (2012-2014) to explore the temporal dynamics of prey availability in the ecosystem and in largehead ribbonfish guts. Feeding indices viz., Stomach fullness index (SFI), empty stomach ratio (ESR), gastrosomatic index (GaSI) and relative gut length (RLG) explained the feeding behaviour, seasonal dynamics and ontogenetic shifts in prey items. The Vacuity Index (VI) was estimated as 37.56%, indicating that T. lepturus is a carnivore and relatively edacious. Diet of T. lepturus comprised of fishes (47.16%), crustaceans (45.22%), molluscs (4.33%) and miscellaneous items (3.28%). Acetes sp. was the most dominant prey item during the study period. Feeding intensity was found to be high during the post-monsoon months which coincided with the period of gonadal maturation of the fish. Significant variations (p<0.05) were seen in the feeding indices during different months, different sizes and between sexes due to the availability of prey items, physiological changes and ontogenetic shifts. A detailed knowledge on diet composition, temporal dynamics in diet patterns and feeding indices can reveal the trophic interaction of prey-predator, resource abundance and fluctuations which are important inputs in ecology-based fishery management models/tools.


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Broodstock development, induced breeding and larval rearing of Indian pompano, – A new candidate species for aquaculture

The present study describes the first trial on broodstock development, induced breeding and larval rearing of Indian pompano, Trachinotus mookalee. Indian pompano fingerlings were collected from wild and raised to adults having an average size of 2.84 ± 0.10 kg weight and 47.6 ± 1.43 cm length. These adult fishes were stocked in 125 t capacity circular tank having re-circulatory facility for broodstock development. The fishes were fed with squid along with clam meat and matured in four months. Mature females with>500 ?m ova and oozing males were selected in the ratio of 1:2 (female:male) and were induced with single dose of hCG at the rate of 350 IU /kg body weight. Three trials with same sex ratio and hormonal doses were tried. The fish spawned after 36–38 h of induction at a temperature 29 ± 1 °C. Eggs were collected and treated with iodophore and stocked in 1 t FRP tank for hatching. The eggs hatched out after 18–20 h of incubation at a temperature of 29 ± 1 °C. The overall fertilization and hatching rate was found to be 69 ± 1.55% and 87.67 ± 0.81%, respectively. Larval rearing was carried out in 2 t capacity fibre reinforced plastic (FRP) tanks using green water system. The newly hatched larvae was 2.12 ± 0.02mm in total length, with an oval shaped yolk sac of 0.55mm2 and an oil droplet of 0.06mm2 in area. The mouth opening was formed 40–46 h post hatch with mouth gape measuring 228.10 ± 1.31 ?m. A systematic and overlapping regime of live feed beginning from copepod nauplii, rotifer, Artemia nauplii and artificial pellet were utilized during larval rearing. Weaning of larvae to inert diet was started from 15th day post hatching (DPH) onwards. Larvae started metamorphosis by 17th DPH onwards and was completed by 21st DPH, when the larvae reached 27.33 ± 0.10 mm. The larval rearing protocol resulted in an average survival rate of 21.53 ± 1.45% till complete metamorphosis. The present study showed T. mookalee to mature in captive conditions. The potential for induced spawning in captivity and larval rearing with a survival rate of 21.53% makes Indian pompano an excellent candidate for mariculture. This forms the first report of broodstock development, induced breeding and larval rearing of this species in captivity. The results of this study would facilitate mass scale seed production of Indian pompano in captivity, which is essential for its aquaculture.


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Diet composition and feeding dynamics of Trichiurus lepturus Linnaeus, 1758 off Gujarat, north-west coast of India

The largehead ribbonfish, Trichiurus lepturus Linnaeus, 1758 forms a major fishery along north-west coast of India comprising the two coastal states of Gujarat and Maharashtra. Diet composition was analysed for five years (2010-2014) to understand shifts if any in the prey items. Seasonal changes in the prey items were studied for three years (2012-2014) to explore the temporal dynamics of prey availability in the ecosystem and in largehead ribbonfish guts. Feeding indices viz., Stomach fullness index (SFI), empty stomach ratio (ESR), gastrosomatic index (GaSI) and relative gut length (RLG) explained the feeding behaviour, seasonal dynamics and ontogenetic shifts in prey items. The Vacuity Index (VI) was estimated as 37.56%, indicating that T. lepturus is a carnivore and relatively edacious. Diet of T. lepturus comprised of fishes (47.16%), crustaceans (45.22%), molluscs (4.33%) and miscellaneous items (3.28%). Acetes sp. was the most dominant prey item during the study period. Feeding intensity was found to be high during the post-monsoon months which coincided with the period of gonadal maturation of the fish. Significant variations (p<0.05) were seen in the feeding indices during different months, different sizes and between sexes due to the availability of prey items, physiological changes and ontogenetic shifts. A detailed knowledge on diet composition, temporal dynamics in diet patterns and feeding indices can reveal the trophic interaction of prey-predator, resource abundance and fluctuations which are important inputs in ecology-based fishery management models/tools.


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Reproductive biology, diet and feeding pattern of longtail tuna Thunnus tonggol in the north-eastern Arabian Sea off Gujarat, India

Longtail tuna Thunnus tonggol (Bleeker, 1851) is the major tuna resource in the neritic realms of the northern Arabian Sea and forms considerable fishery in the coastal nations in the region. Gujarat, on the north-west coast is the major province landing longtail tuna in India. The paper attempts to add to the hitherto sparse knowledge base on biology of the longtail tuna fished along the north-west coast of India, through a study spanning from 2011 to 2015. Reproductive biology, spawning, food and feeding dynamisms of the species were investigated. Sex ratio of the species was estimated as 1:2.1 and depicted an increase in male preponderance as the size increased. The fish attains maturity at 607 mm and it spawns during summer months starting from May. The fish is typically a non-selective feeder and over 22 taxa comprising of fishes, cephalopods and crustaceans formed the diet at varying rates over the year. Variation in feeding intensity at different reproductive stages is discussed besides the constraint posed by the large presence of unidentifiable, partially digested gut content.


Trends in penaeid shrimp landings by sona boats at Visakhapatnam Fishing Harbour, Andhra Pradesh

Sona boats operate mostly in the northern part of the Bay of Bengal up to sand heads. The boats (13-15 m OAL) worthy to conduct voyage fishing for 10-20 days exploit resources upto a depth of 100 m. The present study analysed the trends in penaeid shrimp landings by sona boats at Visakhapatnam Fishing Harbour, for the period from 2001 to 2010. During the period, annual fishing effort ranged from 4,77,710 to 16,31,507 h with an average of 10,15, 230 h. Annual penaeid shrimp catch varied from 1,409 to 7,496 t, average being 4,892 t. Average catch per hour (CPH) was estimated at 4.81 kg. Annual penaeid shrimp contribution from the sona boats to the total fish landings was 10.2 to 22% (average 15.9). Both fishing effort and penaeid shrimp catch showed increasing trend during the period. Penaeid shrimp fishery was supported by 14 genera/species dominated by Metapenaeus monoceros followed by M. dobsoni. Mean annual species composition and CPH for each species were computed for two span, first being 2001-2005 and the second during 2006-2010. The CPH for the penaeid shrimps increased by 1.5% from span-1 to span-2. CPH for smaller shrimp species declined whereas increased for commercial species. Expected catch for each year estimated by Schaefer production model (CEDA; r2=0.72) showed underexploitation during 2001 and 2004; optimum state of exploitation for four years during 2005, 2006, 2007 and 2009 and overexploitation for four years during 2002, 2003, 2008 and 2010. In terms of total fish landings, 2001 and 2002 showed underexploitation, optimum state during six years i.e., 2003, 2006, 2007, 2008, 2009 and 2010; while overexploitation during 2004 and 2005. Considering the exploitation rate of both penaeid shrimps and total fish, by sona boats, the study suggests restriction of fishing effort at the 2009-2010 level to ensure sustainability of the resources.


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Biomass and carbon stocks in mangrove stands of Kadalundi estuarine wetland, south-west coast of India

Mangroves are keystone ecosystems which provide numerous environmental services. Mangroves assume significance as standing stores of sequestered atmospheric carbon and are therefore, important in the light of climate change mitigation. In this study, we attempted to assess the biomass of mangroves in the Kadalundi wetland, south-west coast of India and evaluated the potential of these mangroves to sequester and store carbon. The C-stocks of above-ground and root biomass were 83.32±11.06 t C ha-1 and 34.96±4.30 t C ha-1 respectively, while the C-stock in sediment was estimated to be 63.87±8.67 t C ha-1. The estimates of mean combined C-stocks in the mangrove biomass and sediment of Kadalundi shows that this estuarine mangrove wetland stored 182.15 t C ha-1, which was equivalent to 668.48 t CO2 ha-1. The mangroves which cover an area of 13.23 ha in the Kadalundi wetland is assumed to have a potential to sequester and store a substantial quantity of 2,409.84 t C which is equivalent to 8,844.11 t CO2. The study underscores the importance of these intertidal forests for climate change mitigation and stresses the importance of protecting the mangroves which provide many other important ecosystem services that benefit communities.


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