Gastrosomatic Index Research Articles

Marine litter in stomach content of small pelagic fishes from the Adriatic Sea: sardines (Sardina pilchardus) and anchovies (Engraulis encrasicolus).

Marine litter impacts oceans and affects marine organisms, representing a potential threat for natural stocks of pelagic fish species located at the first levels of the marine food webs. In 2013-2014, on a seasonal basis, marine litter and microplastics in stomach contents from Sardinia pilchardus and Engraulis encrasicolus were evaluated. Selected species are plankitivores of great ecological and commercial importance in the Adriatic Sea. Collected data were correlated to possible factors able to affect ingested levels as well as species, season of sampling, biometry and sex of animals. Almost all tested samples (80 organisms for each species) contained marine litter (over 90% of samples from both species) and also microplastics; while any meso- or macroplastics were recorded. On average, recorded items were as follows: 4.63 (S. plichardus) and 1.25 (E. encrasicolus) per individual. Sardines evidenced a higher number of microplastics characterised by a smaller size than those recorded in anchovies. For sardines, sex, Gastro Somatic Index and sampling season showed negligible effects on the number of ingested litter; conversely, anchovies showed differences related with both sex of animals and dominant colour of ingested materials with prevalence for black and blue colours.

Feeding indices of Isfahan toothcarp (Aphanius isfahanensis) in Zayandeh River in Iran (Teleostei: Aphaniidae)

The feeding characteristics of Aphanius isfahanensis in the Zayandeh River of Isfahan Province were studied by collecting 440 specimens (220 males and 220 females) from July 2016 to May 2017. The specimens were anesthetized in 1% clove oil, fixed in 10% buffered formalin and transferred to the laboratory. The average condition factor for males was 1.7, for female 1.26 and showed significant difference between different months in both sexes ( P <0.05). The average length and weight for all specimens were 38.57±5.24mm and 1.00±0.41g, respectively. The average length of gut (RLG) for all fish was 0.54±0.17 during the year. The mean RLG in different length classes showed significant differences ( P <0.05). The highest Gastrosomatic Index value was in July (0.05) and the lowest in August (0.03) and showed significant differences in different months ( P <0.05). A total of 181 empty stomachs were observed amongst the 440 fish and there were significant differences in different months ( P <0.05). Therefore, it can be concluded that this is a carnivorous fish (mainly aquatic insect larvae) with a modest feeding throughout the year.

The Relative Gut Length and Gastro-somaticindexes of the Mudskipper Periophthalmodon septemradiatus (Hamilton, 1822) from the HauRiver

This study provided an understanding of feeding habit and intensity of the mudskipper Periophthalmodon septemradiatus, which was a potential aquarium pet, by analyzing the relative gut length (RGL) andgastro-somatic (GaSI) indexes. Fish specimens were caught by fishing rods from the estuary in Soc Trang province to the upstream in An Giang province of Hau River during a period of one year from August 2017 to July 2018. Data analysis of a collection of 1,504 fishes showed that RGL did not change with fish size, resulting in the feeding habit of P. septemradiatus did not change with fish size. By contrast, the feeding habit of this mudskipper varied with place, month and season as the RGL significantly different between place, month and season, but both males and females fall into carnivorous fish as RGL was &lt;1. Similarly, the feeding intensity of this specice did not change with fish size, as the GaSI was not significantly different among four fish size groups. Meanwhile, the mudskipper displayed spatial, temporal and seasonal variations in feeding intensity since GaSI significantly changed with place, month and season. The changes of feeding habit and intensity of P. Septemradiatus were not regulated by the interaction of fish size and place, fish size and season, and place and season. These results provided new knowledge on feeding habit and intensity of this fish specice, being used for the understanding of fish adaption and conservation in the study region.&#x0D; Keywords&#x0D; Gastro-somatic index, mudskipper, Periophthalmodon septemradiatus, relative gut length&#x0D; References&#x0D; [1] Murdy, E. O. &amp; Jaafar, Z., Taxonomy and systematics review, In: Z. Jaafar, E. O. Murdy (eds) Fishes out of water: biology and ecology of mudskippers, CRC Press, Boca Raton, pp. 1-36, 2017 [2] Murdy, E. O., A taxonomic revision and cladistic analysis of the oxudercine gobies (Gobiidae, Oxudercinae), Australian Museum Journal, 11 (1989) 93.[3] Murdy, E., Systematics of Oxudercinae, In: R. A. Patzner, J. L. V. Tassell, M. Kovacic, B. G. Kapoor (eds) The biology of gobies, Science Publishers, New Hampshire, United States, pp. 99-106, 2011 [4] Bhatt, N. Y., Patel, S. J., Patel, D. A. &amp; Patel, H. P., Burrowing activities of goby fish in the recent intertidal mud flats along the Navinal coast, Kachchh, Western India, Journal of the Geological Society of India, 74 (2009) 515-530.[5] Al-Hussaini, A. H., On the functional morphology of the alimentary tract of some fish in relation to differences in their feeding habits: anatomy and histology, Quarterly Journal of Microscopical Science, 3 (1949) 109-139.[6] Desai, V. R., Studies on fishery and biology of Tor tor (Hamilton) from river Narmada. I. Food and feeding habits, Journal of the Inland Fisheries Society of India, 2 (1970) 101-112.[7] Le, T., Nguyen, M. T., Nguyen, V. P., Nguyen, D. C., Pham, X. H., Nguyen, T. S., Hoang, V. C., Hoang, P. L., Le, H. &amp; Dao, N. C., Provinces and City in the Mekong Delta, Education Publishing House, Ha Noi, 2006.[8] Khaironizam, M. Z. &amp; Norma-Rashid, Y., First record of the mudskipper, Periophthalmodon septemradiatus (Hamilton) (Teleostei: Gobiidae) from Peninsular Malaysia, Raffles Bulletin of Zoology, 51 (2003) 97-100.[9] Wand, M. P., Data-based choice of histogram bin width, The American Statistician, 51 (1997) 59-64.[10] Vo, T. T. &amp; Tran, D. D., Study on nutritional characteristics of Oxyeleotris urophthalmus fish distributed along the Hau River, Can Tho University Journal of Science, Fishery (2014) 192-197.[11] Dinh, Q. M., Nguyen, D. T. &amp; Danh, S., Food and feeding habits of the broadheah sleeper Eleotris melanosoma from coastline in Soc Trang, Proceedings of the 7th National Scientific Conference on Ecology and Biological Resources, Publishing house for Science and Technology, 1873-1879, 2017.[12] Tran, D. D., Some aspects of biology and population dynamics of the goby Pseudapocryptes elongatus (Cuvier, 1816) in the Mekong Delta, PhD thesis, Universiti Malaysia Terengganu, 2008.[13] Dinh, Q. M., Qin, J. G., Dittmann, S. &amp; Tran, D. D., Seasonal variation of food and feeding in burrowing goby Parapocryptes serperaster (Gobiidae) at different body sizes, Ichthyological Research, 64 (2017) 179-189.[14] Dinh, Q. M. &amp; Tran, M. T. D., Digestive tract morphology, food and feeding habits of the goby Stigmatogobius pleurostigma (Bleeker, 1849) from the Coastline in Soc Trang, VNU Journal of Science: Natural Sciences and Technology, 34 (2018) 46-55.&#x0D;

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

&lt;p&gt;The largehead ribbonfish, &lt;em&gt;Trichiurus lepturus&lt;/em&gt; 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 &lt;em&gt;viz.,&lt;/em&gt; 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&lt;em&gt; T. lepturus&lt;/em&gt; is a carnivore and relatively edacious. Diet of&lt;em&gt; T. lepturus&lt;/em&gt; comprised of fishes (47.16%), crustaceans (45.22%), molluscs (4.33%) and miscellaneous items (3.28%). &lt;em&gt;Acetes&lt;/em&gt; 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&amp;lt;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&lt;br /&gt;ecology-based fishery management models/tools.&lt;/p&gt;

Food and feeding habits, gastrosomatic index and gonado-somatic index of Scylla serrata from Hooghly- Matlah estuary of West Bengal, India

Food and feeding habits, gastrosomatic index and gonado-somatic index of Scylla serrata from Hooghly- Matlah estuary of West Bengal, India

Feeding Habits of Indian Flying Barb Esomus Danrica (Hamilton, 1822) From Upper Assam, India

The feeding habits of Esomus danrica was carried out from the Maijan wetland and fish landing sites at Guijan Ghat of Brahmaputra River, upper Assam. The lowest relative length of gut (RLG) of E. danrica was found as 1.24 (± 0.52) in >5 cm group whereas the highest as 1.6 (± 0.7) in 4-5 cm length group. It reveals that the fish falls in the category of carni-omnivorous fishes. The gastro somatic index (GSI) ranged from 1.799 ± 1.396 (Dec) to 6.499 ± 2.690 (Apr) for males and from 1.81 ± 0.700 (Nov) to 5.960 ± 1.497 (Apr) for females. In male, the minimum GSI (3.31 ± 1.7) observed in immature stage and maximum (5.14 ± 1.04) in mature stage. In case of females, the minimum (2.4 ± 1.1) and maximum (4.55 ± 1.3) were recorded in maturing and ripe stage respectively. The active feeding was recorded during November (66.7%), moderate feeding during May (61.8%), while poor feeding during August (48.6%). Empty stomach was also recorded throughout the year with little percentage. Again, the highest active feeding (41.1%) was recorded in ripe species; moderate feeding (47.4%) and poor feeding (25%) in mature and immature stage respectively while the highest percentage of the empty stomach (25%) was observed in immature.

Food and feeding habits of snow trout, Schizothorax plagiostomus in River Lidder, from Kashmir Himalaya

The food and feeding habits of Schizothorax plagiostomus in river Lidder was studied by examining 500 guts collected throughout the year. The fish samples used in the present study was within the range of 25.5cm to 40.33cm in total length and weight ranging from 250g to 580g in weight and the sampling duration was from July, 2013 to June, 2014. During the analysis of food and feeding habits of S. plagiostomus it was concluded that the fish is benthic herbivorous. Its food mainly consists of plant matter 62.02%. A good amount of miscellaneous food items i.e. mud, sand and detritus 31.01% was also present in the gut of fish along with small quantity of animal food 6.97%. Overall it was concluded that diatoms formed an important constituent of food of S. plagiostomus in all months of the year and the presence of detritus, mud and sand indicates that the fish is a detrivorous, bottom feeder. The gastrosomatic index in case of females ranged from 3.88±0.30 to 7.30±2.128 with minimum in July and maximum GaSI in October and 3.37±0.75 to 7.82±2.22 in males with minimum in July and maximum in December.

A PRELUDE ON THE BIOLOGY OF PUNTIUS AMPHIBIUS

Knowledge on fish biology is essential for improving aquaculture. The present study was focused on the biology of Puntiusamphibius. The fishes were collected from a freshwater body in parlance known as “Arappa”, located in Thalikulam at Thrissur district in Kerala. This water body is in the vicinity of the sea anddebouches into the marine during monsoon season. In the present investigation 106 fishes were collected during March to August 2006. The study revealed that there was no significant difference observed among the length weight relationship of males and females. Composition of gut content showed that it is a selectivefeeder of Bacillariophyceae and a pronounced omnivore. The gastro-somatic index of female and male was high during May indicating the active feeding during breeding.The sex ratio between males and females was variable and female dominated over males. The fecundity of fish was proportional to the weight of the ovary. Gonado-somatic index was comparatively high during spawning seasons. This is a preliminary lesson on the reproductive biology and certain distinctive characters such as length-weight and food and feeding habits of Puntius amphibius.

Investigation on Feeding, Growth and Condition Factor of Certain Ornamental Fish From Brahmaputra River at Dibrugarh, Assam, India

The investigation has been carried out from different landing site of the Brahmaputra River at Dibrugarh, Assam, India during February, 2014 to January 2015. As a whole, the relative length of gut (RLG) value was found to be highest during pre-monsoon and lowest during winter season. Among the examined species, Trichogaster fasciata was recorded as highest RLG value (5.74) and the lowest (1.10) was recorded in Mystus tengara. The value of RLG reveals that the feeding habit shows a variation from species to species. In case of gastrosomatic index (GSI), out of the examined species, Esomus danricus was found to be the highest (6.5) during pre-monsoon and Osteobrama cotio was lowest GSI (2.32) during winter season. The feeding intensity was found to be more or less similar in all the species. Again, in relation to the growth co-efficient ‘b’ of all the examined species, Puntius sophore was recorded as highest ‘b’ value (3.31) during monsoon while Osteobrama cotio was recorded as lowest (2.50) during winter season. Further, it predicts that the examined fish species did not follow the cube law and showed the allometric growth. The highest (1.85) condition factor (K) was recorded in P. sophore and observed in monsoon. In case of its lowest (1.0) was recorded in Salmostoma bacaila and observed in winter seasons. They were found in health and well-being condition

Food and feeding habits of the greenback grey mullet Liza subviridis (Valenciennes, 1836) from Parangipettai waters, south-east coast of India

The feeding ecology and prey preference of greenback grey mullet Liza subviridis (Valenciennes, 1836) were investigated in Parangipettai waters (11°29′25.55″N; 79°45′38.62″E) from May 2011 to April 2012. A total of 328 male and 360 female specimens of L. subviridis were analysed. Detritus and sand particles formed the major food item of L. subviridis in both sexes besides, diatoms, dinoflagellates, algae, zooplankton, foraminiferans, polychaetes and larval forms were also noticed and ranked respectively based on the quantities. Feeding intensity showed that the percentage of ‘empty’ stomachs varied from 7.2% (November 2011) to 19.3% (August 2011) and from 7.1% (March 2012) to 19.2% (August 2011) in males and females respectively whereas the ‘gorged’ stomach in males and females was in the ranges of 4.6% (March 2012) - 14.5% (December 2011) and 4.6% (September 2011) - 14.5% (April 2012). The gastrosomatic index of males and females ranged between 5.9% (October 2011) - 8.2% (May 2011) and 6.1% (March 2012) - 8.1% (May 2011) respectively. The results agree with the previous reports and extend the understanding on its well-being, reproductive seasons and stock of L. subviridis in Parangipettai waters.

Food and feeding habits of marine catfish, Osteogeneiosus militaris (Linn., 1758) off Mumbai waters

The food and feeding habits of the marine cat fish, Osteogeneiosus militaris (Linn.,1758) off Mumbai waters was studied. The species was found to be carnivorous and predacious in feeding habit. Index of preponderance values indicated that, it feeds mainly on crustaceans (shrimps, crabs), molluscs (bivalves, squids) and small fishes ( Coilia spp ., ribbon fish). Among the food groups, crustaceans dominate throughout the year in comparison to molluscs and fishes. In the crustacean group, Acetes spp. was found to be the dominant food item contributing to 43.34 per cent followed by penaeid shrimps, which shared 27.65 per cent of the total food in all the months. Analysis of month-wise percentage food composition revealed that, the species fed the highest percentage of Acetes spp . during the month of November (34.92%) while penaeid shrimps was consumed in the largest percentage in January (35.10%). With respect to the size (length) of the fish, the percentage of Acetes spp. as a food item was highest (52.99%) for the length group of 391-420 mm and lowest (25.64%) for 361-390 mm. The guts were found to be empty for fishes having length of more than 420 mm. Results of the feeding intensity delineated that, the species is not a voracious feeder as none of the individuals studied was found to have gorged or full stomach over the entire period of investigation. Among the different length groups, the highest feeding fishes were in the length group of 211-240 mm. Gastro-somatic index was highest during August for males and during November for females while the pooled value was highest in January (3.206).

Food and feeding habit of Tor putitora of Mahakali River, Nepal

T.putitora is a sight feeder and can be categorized as column feeder, which at some stage resorts to bottom feeding as well. Depending upon the availability of food, the fish consumes a wide spectrum of dietary items varying from microscopic organisms and macrophytes to large number of insects and even small fishes.The feeding activities of T. putitora appeared to be good during pre-spawning (pre-monsoon) and post-spawning season while poor during monsoon or spawning season, which is directly related to the availability of food and maturation of gonads. The estimation of GSI (Gastro-somatic Index) also supported this fact.BIBECHANA 13 (2016) 115-125

Some Biological Characteristics of the Daysciaena albida (Cuvier 1830), on Largest Brackish Water Lagoon of India

An attempt to study length-weight relationship (LWR), condition factor and reproductive aspects of Daysciaena albida was done in Chilika lagoon over one year. The fish specimens for the biological study were collected from landing centers of central and northern sector during pre-monsoon, monsoon and post-monsoon seasons. The LWR from total length and body weight were computed both by sex and seasons. The equations found from the relationships were y=0.010x2.992 for male, y=0.010x2.998 for female and y=0.010x2.996 as unsexed specimens. The highest condition factor (K) value was recorded during monsoon (1.42±0.08) followed by post-monsoon (1.4±0.09) and the lowest (0.92±0.11) during pre-monsoon seasons. The mean condition factor was registered as 1.06±0.09 in all the seasons of unsexed specimens. Among sex, males registered slightly higher K value than females. For reproductive study, maturation stages, gonad somatic index (GSI) and gastro somatic index (GaSI) were analyzed seasonally. Considering maturation stages highest maturation stages (stages 4 to 7) obtained during pre-monsoon season (in both sexes) which are considered as matured conditions for fish. The highest GSI was registered during pre-monsoon followed by postmonsoon and the lowest was during monsoon season among both the sexes. The GaSI value was lowest during pre-monsoon among males and gradually increased during monsoon and postmonsoon. But in case of female, lowest value was during monsoon and again increased afterwards and was highest in pre-monsoon. ECOPRINT 21: 15-21, 2014DOI: http://dx.doi.org/10.3126/eco.v21i0.11900

English

English

Food and Feeding Dynamics ofStolephorus commersonnii(Lacepede, 1803) (Family: Engraulidae) from South Andaman

The feeding dynamics ofStolephorus commersonniialong the coastal waters of South Andaman during October, 2011, to September, 2012, were examined by employing “point’s method.” The results of the present study has shown thatS. commersonniimainly is a planktonivorous carnivore chiefly feeding in the pelagic realm on planktonic crustaceans, bivalves, gastropods, and miscellaneous food items. The copepods formed the main prey item, contributing their maximum during November 2011 (47.55%) and lowest in December (24.21%) which was confirmed by various food preference indices. There was no significant seasonal variation in the feeding preference. Lower length classes fed mainly on planktonic copepods and amphipods whereas the higher length classes fed mainly on postlarval shrimps and planktonic crustaceans likeLucifersp. andAcetessp. Feeding intensity was seasonal, but independent of the length of fish. Gastrosomatic index was highest during monsoon, indicating active feeding. During the period when a maximum percentage of fully mature individuals were present, the feeding intensity was found to be low. The trophic level of this species was found to be2.96±0.11.

Food and feeding habit of a freshwater catfish, Mystus tengara (Siluriformes: Bagridae)

Feeding is the dominant activity in entire life cycle of fish; thus detailed knowledge on food and feeding habit of any fish species is really essential to get success in culture of that particular fish species. Mystus tengara is a popular food fish due to its good taste; and recently it has also got its entry in ornamental fish markets. No such detail works till date has been performed on food and feeding habit of this fish species. So the present study has been performed to get information on the food and feeding habit of Mystus tengara. Gastro Somatic Index, Relative Length of Gut, Gut Fullness & Feeding Intensity and Gut Content Analysis have been performed as parts of the study. Results of the study have revealed that Mystus tengara is a carnivorous fish and zooplankton is the basic food group for this fish species; rotifera has also been observed as the most preferable food class. During the study, feeding activity of this fish species has never been observed to be discontinuous; though it has been observed to vary according to the breeding season; lowest feeding activity has been observed during intense breeding season while highest feeding activity has been observed during pre-spawning months.

Seasonal analysis of the biochemical composition of muscle and liver of Catla catla in a tropical climate of India

Bio-indices have been developed to provide the measurement of general condition of fish population and indicate the physiological status of the individual fish. The objective of this work was to evaluate the changes in the bio-indices of Catla catla as a function of season and gender and to investigate how these indices respond to changes in lipid and protein content of liver and muscle. Both condition factor and gastro-somatic index were greatly increased in pre-mating season. Maximum values of gonadosomatic index (GSI) of fish were observed in the rainy season. The relationship between GSI and the hepatosomatic index (HSI) was found to be negatively significant throughout the study period as well as during the progression of gonad maturation stages. Protein content formed the highest percentage among biochemical components which ranged from 15.2 to 19.0 %. The results revealed that moisture content was high when lipid was low during the peak spawning period. The amount of protein, lipid, and fatty acid levels increase during spring whereas moisture content of muscle and liver increased during summer and rainy season. Seasonal values of the most of the parameters were deteriorating during late summer and rain and showed improvement during winter to reach maximum in spring.

Food and Feeding Ecology of the Non-native Nile Tilapia Oreochromis niloticus (Linnaeus, 1758) in the River Yamuna, India

Nile tilapia Oreochromis niloticus is the dominant invasive species of the river Yamuna. Gut analysis showed that the majority of the food items ingested consisted of Chlorophyceae, Myxophyceae, Bacillariophyceae and detritus. Among the diatoms—Synedra spp. (80.75 %), Melosira spp. (73.5 %), Cyclotella spp. (73 %), Meridion spp. (71.75 %) and Nitzchia spp. (73.25 %), the green algae—Ankistrodesmus spp. (71.00 %), Coelastrum spp. (61.5 %), Scenedesmus spp.(52 %), Tribonema spp. (49.5 %), Protococcus spp. (58.5 %), Oocystis spp. (49.75 %) and Pediastrum spp. (49.5 %) and among blue green algae, Oscillatoria spp. (70.5 %), Anacystis spp. (61.5 %) and Phormidium spp. (46.5 %) showed high frequency of occurrence. The Gastrosomatic Index in males and females ranged from 0.23 to 0.93 and 0.25 to 1.1 respectively with no significant difference between males and females throughout the year (t test, p > 0.05). In addition to this, higher percentage of males and females showing low feeding intensity during all the months except in January indicted the species to be the poor feeder. However, the condition factor >1 suggested the species to be in good condition throughout the year in both males and females. Dominancy of detritus and pollution indicator genera Synedra spp., Anacystis spp., Ankistrodesmus spp., Melosira spp., Nitzchia spp., Oscillatoria spp., Phormidium spp. and Scenedesmus spp. suggested Nile tilapia to be the cleaner of the polluted river Yamuna.

Feeding and Reproductive Biology of Saurida undosquamis (Richardson, 1848) from Parangipettai Coast, Southeast Coast of India

The feeding biology, spawning season, size at first maturity, sex ratio and fecundity of the commercially important lizardfish (Saurida undosquamis) were studied in Parangipettai waters of the southeast coast of India. Fishes formed the predominant food item. Diversity of the prey items showed maximum value (H'log 2-3.61 +/- 0.11) during the postmonsoon season and minimum during the monsoon season (2.89 +/- 0.17). The richness (1-lambda') also showed a similar trend and varied from 0.81 +/- 0.13 (monsoon) to 0.91 +/- 0.01 (postmonsoon). The size at first maturity (50% incidence of mature fish) was 195 mm. But when the size at first maturity was calculated by adjusting the proportion of maturity percentages, the maturity size was found to be 140 mm. This method is advantageous from the point of view of fisheries management as this species can be exploited above 140 mm rather than above 195 mm. The gastrosomatic index was found maximum during postmonsoon and minimum during the monsoon season showing the inverse relationship between feeding and spawning. This species was found to spawn from August to January with a peak in November. The fecundity ranged from 19, 856 in a fish measuring from 20.1 cm in length (97 g) to 79,282 in a fish of 29 cm (290 g). The overall sex ratio (1:1.19) was found to deviate significantly from the expected 1:1 ratio. (chi2 = 19.1, p < 0.005). Month- wise, it conformed to the expected 1:1 ratio during most of the months except January, June, September, November and December. Higher gonado-somatic index values observed during October-December suggested spawning activity during this period. This species is found to a total spawner in the Parangipettai waters.

Evaluation of feeding indices of cobia Rachycentron canadum (Linnaeus. 1766) from Northwest coast of India

Cobia Rachycentron canadum (Linnaeus. 1766) is an esteemed table fish occurring along both east and west coast of India. Feeding indices of the species inhabiting waters of the northwest coast of Indian EEZ was studied to understand the variation of its feeding intensity based on season, sex and life history changes. Monthly variation of stomach condition of cobia male, female, pooled and size wise were analyzed. In general, 56% of fishes were found in either actively fed or moderately fed state. Except during April and July they were found in actively fed condition. Analysis of occurrence of empty stomach in different length classes of fishes revealed that the percentage of occurrence of empty stomachs decreased with the fish growth. Month- wise Mean Index of Feeding intensity (MIF) and Index of Fullness (IF) values showed that cobia fed well during post monsoon periods but poor feeding activity was noticed in July. Gastrosomatic index for male, female and pooled samples of matched with the MIF and IF values. The results indicated a seasonal variation in feeding intensity of cobia. On an average, feeding intensity during July was low.