International Journal of Research in Biological Sciences

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1 Available online at International Journal of Research in Biological Sciences Universal Research Publications. All rights reserved ISSN Original Article TAXONOMY AND OTHER BIOLOGICAL ASPECTS OF Rhinomugil corsula (Hamilton) Shamima Sultana 1, Md. Saifuddin Shah 2, Shikder Saiful Islam 1, Alokesh Kumar Ghosh 3* 1 Lecturer, Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh 2 Professor, Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh 3 Assistant Professor, Fisheries and Marine Resource Technology Discipline, Khulna University, Khulna-9208, Bangladesh Tel: , Mob: alokesh_ku@yahoo.com Received 23 June 2013; accepted 28 July 2013 Abstract The present study was conducted to obtain an idea on the taxonomy and other biological aspects like fecundity, gonadosomatic index, food and feeding habit, alimentosomatic index and hepatosomatic index of Rhinomugil corsula during December 2010 to March Total 130 specimens were assayed during the study period. The taxonomical study showed that the total length (cm), standard length (cm), head length (cm), length of upper jaw (cm), body depth (cm) and body weight (g) ranged from 19-24, 15-20, , , and The taxonomic formula for the species appeared like; D1. 4, D2. 7, P , P2. 5-6, A. 9/11, C. 18, RC. 4. Number of scales on, above and below the lateral line ranged from 46-49, 7-9 and The biological investigation revealed that the fish weight (g), gonad weight (g), fecundity, GSI, liver weight (g), gut weight (g), alimentosomatic and hepatosomatic index and condition factor ranged from , , , , , , , and Present investigation indicated that the species is omnivorous in its feeding habits. The mean values of hepatosomatic and alimentosomatic indices indicated greater liver activity and feeding intensity. This study thus can be treated as an attempt for contribution of some information to this direction Universal Research Publications. All rights reserved Key words: Rhinomugil corsula, taxonomic formula, gonadosomatic index. 1.0 INTRODUCTION In Bangladesh, there are 442 species of marine fishes and 266 species of inland fishes in 61 families and 14 orders. Among them the mullets are a large group of estuarine fishes and serving as an important source of food in Bangladesh as well as all over the world. The family includes about 80 species in 17 genera. They have a small mouth, a rounded snout and a flattened head. They have a soft second dorsal fin, and their lateral line is indistinct or nearly absent. Rhinomugil corsula (Ham.) locally known as Corsula is one of the most popular and commercially important fish due to its high nutritive and market value. The fish R. corsula (Ham.) belongs to the family Mugillidae commonly known as corsula mullet and widely distributed in the coastal waters. It usually swims over sandy-muddy bottoms and sea grass meadows, in relatively still waters. It commonly occurs at water depths of 65.6 ft (20 m) but may be found offshore or in deeper water. In eastern part of Indian Ocean (77 E E; 55 S - 24 N) R. corsula is generally found. It is pelagic, found in brackish water region [1]. In Asia this fish is distributed in the water body of India, Bangladesh, Nepal and Myanmar. It can tolerate wide ranges of environmental fluctuation and found in freshwater, brackish and marine water at a depth range of m [2]. It is a surface dweller fish and takes small fish, insects, leaves of plant, organic matter and plays an important role in our ecology. Breeding time of this fish starts in the month of April and continues till July. The fish is oviparous, eggs are pelagic and non-adhesive [3]. Corsula is being cultured in many developing countries, as a brackish water fish commonly available in shallow coastal waters, estuary and mangrove swamps of Bangladesh. The popularity of this species in aquaculture is due to high quality of its flesh, its extreme tolerance of a wide range of temperature and salinity, which is important for culture in intertidal ponds. In general R. corsula is hardy a fish and is best suited for fish farming [4]. As they are caught almost throughout the year, they are a valuable source of food fish during the offseason of the other commercial fisheries. Body of corsula is sub-cylindrical in 123

2 anterior region and moderately compressed in posterior. Dorsal profile is nearly straight. Head is flat in above and compressed at sides. Mouth position is ventral and eye is elevated. The first dorsal commences somewhat nearer to the base of the caudal than the tip of the snout. The second dorsal arises from a bit behind the origin of the anal. Pectoral fin reaches beyond the origin of the pelvic. Caudal fin is slightly emarginated. Scales is ctenoid. Body color is grayish brown on surface, lighter along the abdomen and dorsal and caudal stained with gray. Scale number in the lateral series is 50 to 52. Scale number is mentioned by other writers as scales before dorsal and scales along lateral series [5]. Taxonomy, the study of the theoretical bases, principles, and procedure necessary to an understanding of relationship is the source of information for classification. Morphometric and meristic characters of fish is a very important tool for identifying any species. Different methods are used for identification but meristc counts and morphometry are considered as the earliest and authentic methods for the identification of species [6]. Several studies have been carried out on mullet biology with brief accounts on fecundity, GSI, reproductive characteristics and spawning [7], [8], [9]. But so far, very few works have been done on the fecundity and GSI of R. corsula [10], which is not sufficient to assess reproductive potential and induced breeding of R. corsula. Marine finfish hatchery techniques are not well developed in Bangladesh due to the lack of technical knowledge. Collection of the naturally produced fry of corsula is not popular and as a result there is limited seed available and farmers are not interested to develop this type mullet farming in coastal areas. Identification and development of successful breeding and culture technique of R. corsula require clear information on the taxonomy, general biology and food-feeding habit of this species. But very little work has so far been reported on the taxonomy, general biology and food-feeding habit of R. corsula in region of Bangladesh. Detailed investigations on important aspects, and like taxonomy, biological characteristics and food and feeding habit in order to evaluate their utility in aquaculture are very meager. Thus a detailed study on taxonomy, general biology and food-feeding habit of R. corsula was needed. The present study was conducted to obtain an idea on the taxonomy and other biological aspects like fecundity, gonadosomatic index, food and feeding habit, alimentosomatic index and hepatosomatic index of R. corsula. This paper is an attempt to contribute to the knowledge on taxonomy, general biology and food-feeding habit of Rhinomugil corsula which is one of the common species in Bangladesh. The reports of investigations on its taxonomy, general biology, food and feeding habits have been dealt with in detail in this paper. 2.0 MATERIALS AND METHODS 2.1 Study area and period The present study was carried out in the greater Khulna, Bagerhat and Satkhira district during December, 2010 to March Sample collection A total of 150 specimens of R. corsula were sampled, of them, 50 female broods were subjected to fecundity estimation and gonadosomatic index determination, 50 for food and feeding habit determination and 50 samples for taxonomic study. After collection from the markets, the samples were immediately preserved in ice in plastic box and carried out to the Fish Biology Laboratory of Fisheries and Marine Resource Technology Discipline of Khulna University. 2.3 Taxonomic study Morphometric data measurement Eighteen morphometric characters viz., the total length, standard length, height of the body, head length, pre-orbital length, eye diameter, post-orbital length, pre first dorsal length, pre second dorsal length, length of first dorsal fin base, length of second dorsal fin base, height of the first dorsal fin, height of the second dorsal fin, distance between first dorsal and second dorsal fin, least depth of caudal peduncle, length of caudal peduncle, length of anal fin base, length of pectoral fin and length of pelvic fin was recorded separately. The measurements were taken by using normal centimeter scale, fine pointed divider, forceps and slide calipers and recorded to the nearest cm Meristic data counts Ten meristic characters were recorded. These characters were recorded by counting the different parts of the body including scale on, above and below the lateral line, number of total fin ray of first dorsal, second dorsal, caudal, anal, pectoral and pelvic fins of the fish. Number of rudimentary fin ray was counted separately. In case of counting scales above and below lateral line, the fraction of the scale was ignored because it was included in number of scale on the lateral line. 2.4 Biological study Gonadosomatic index (GSI) GSI was recorded according to the following equation. This is more suitable to explain the maturity of fishes. GSI = [Weight of gonad / Body weight] 100 Here, GSI = Gonadosomatic index Fecundity estimation The fecundity was estimated by the following formula: Fecundity = [Total gonad weight / Weight of small portion of ovary] N Here, N = number of eggs from small portion of total ovary Food and feeding habit For food and feeding habit study, 50 fresh samples were collected randomly from local ghers and conditioned in varsity pond. Some days later they were catched from the ponds. The digestion of food items of fishes was stopped within few minutes by degutting the fish and preserving them in formalin. The fishes were dissected by giving a vertical incision on the ventral side. Guts and livers were removed, weighted and immediately preserved in separate numbered bottles containing 5% formalin solution Hepatosomatic index Fifty samples were used for recording hepatosomatic index. Hepatosomatic index was determined by the following equation: HIS = [Liver weight / Body weight] 100 [11] Alimentosomatic Index Fifty samples were used for recording alimentosomatic 124

3 Index (ASI). The alimento-somatic index was determined by the following equation: ASI = [Total weight of the gut / Body weight] 100 [12] Condition factor determination The growth of fish was estimated by determining the condition factor, which was calculated by the formula as suggested by [13]. Condition factor (CF) was estimated by the following equation: CF = [BWt 100] / TL 3 Where, BWt= body weight in g, TL= total length in cm Food items identification Subsequently the contents of the stomach were analysed in the laboratory. The preserved guts of 30 live samples were used for food items identification. The preserved gut of each fish was dissected out and the contents of the stomach were removed very carefully in a Petri dish and then collected in glass vials making up the volume to 10 ml to determine the different food items eaten by the fish. After that, the food items were identified under a binocular microscope with the help of Sedgewick Rafter counting cell. Food particles were identified by investigating the external morphology. Attempts were made to identify the chief constituents of the stomach contents. 2.5 Data analysis All the data were arranged and analyzed. The data were then presented in tabular and graphical forms. In the present study, mean and range of each type of data and mean of ratio of some morphometric characters were estimated. Linear regression analysis was used to determine the relations between different characters of the species. SPSS 12.0 for windows software was used for statistical analysis. 3.0 RESULTS 3.1 Taxonomic study of Rhinomugil corsula The males and females of the species were more or less similar in external feature. But mature females had swollen and larger body. The body is sub-cylindrical in anterior region and moderately compressed in posterior. Dorsal profile is nearly straight. Head is flat in above and compressed at sides. Mouth position is ventral and eye is elevated. The first dorsal fin commences from somewhere nearer to the base of the caudal fin than the tip of the snout. The second dorsal arises from a bit behind the origin of the anal. Pectoral fin reaches beyond the origin of the pelvic. Scales is ctenoid. Body color is grayish brown on surface, lighter along the abdomen and dorsal and caudal stained with gray Morphometric characters of Rhinomugil corsula Mean value of different morphometric characters of R. corsula are present in the table 1. The relationship among different parameters is shown by figures 1, 2, 3, Meristic characters of Rhinomugil corsula R. corsula had two dorsal fins. First dorsal fin had spines and second dorsal fin had soft rays. Other had soft rays. Number of rudimentary rays of caudal fin was included in the number of total caudal fin rays (Table 3). 125

4 Table 1. Mean of various morphometric characters of Rhinomugil corsula Characters Mean ± SD Range TL 21.56± SL ± HL 3.90 ± PrOL 0.59 ± EDia 0.73 ± PsOL 2.53 ± LUJ 0.95 ± BHt 3.93 ± PrFtDFL 9.12 ± PrScDFL ± LFtDFBs 1.15 ± HtFtDFBs 1.62 ± LScDFBs 1.53 ± HtScDF 2.23 ± LtDtCP 1.92 ± LCP 3.87 ± LAFBs 2.05 ± HtPecF 3.60 ± HtPelF 2.58 ± BWt ± DisFtScDF 3.84 ± (TL-Total length, SL-Standard length, HL-Head length, PrOL - Pre orbital length, EDia-Eye diameter, PsOL - Post orbital length, PrFtDFL - Pre first dorsal fin length, PrScDFL - Pre second dorsal fin length, LFtDFBs- Length of first dorsal fin base, LScDFBs - Length of second dorsal fin base, DisFtScDF- Distance beween first and second dorsal fin, HtFtDFBs Height of first dorsal fin, HtScDF - Height of second dorsal fin, LtDtCP- Least depth of caudal peduncle, LCP-Length of caudal peduncle, LAFBs- Length of anal fin base, BHt-Height of the body, LUJ-Length of the upper jaw) Table 2. Various body proportions of Rhinomugil corsula Proportion (Mean ± SD) Range TL : SL 1.21 ± SL : HL 4.51± SL : PrDL 1.95± SL : HtB 4.51± HL : PrOL 6.64± HL : EDia 5.41± HL : PsOL 1.53± SL : LFtDFBs 15.37± SL : LScDFBs 11.40± SL : LCP 4.50± HL : LUJ 4.04 ± SL : LtDtCP 9.06± HtB : LtDtCP 2.01± LCP : LAFBs 1.90± SL : EDia 24.42± BHt : EDia 5.41± HtFtDF : LFtDFBs 1.41± HtScDF : LScDFBs 1.46± SL:PrScDL 1.25± SL:DisFtScDF 4.5.± (TL-Total length, SL-Standard length, HL-Head length, PrOL - Pre orbital length, EDia-Eye diameter, PsOL - Post orbital length, PrFtDFL - Pre first dorsal fin length, PrScDFL - Pre second dorsal fin length, LFtDFBs- Length of first dorsal fin base, LScDFBs - Length of second dorsal fin base, DisFtScDF- Distance beween first and second dorsal fin, HtFtDFBs Height of first dorsal fin, HtScDF - Height of second dorsal fin, LtDtCP- Least depth of caudal peduncle, LCP-Length of caudal peduncle, LAFBs- Length of anal fin base, BHt-Height of the body, LUJ-Length of the upper jaw.) Table 3. Meristic characters of Rhinomugil corsula Characters Mean±SD Range Number of scales on the lateral line ± Number of scales above the lateral line 8.00 ± Number of scales below the lateral ± 0. line Number of total spines in first dorsal fin ray 4.00 ± Number of total soft-rays in second dorsal fin ray 7.00 ± Number of total caudal fin ray ± Number of rudimentary rays of caudal fin 4.00 ± Number of total anal fin ray ± Number of total soft-rays in pelvic fin ray 5.55 ± Number of total soft-rays in pectoral fin ray ±

5 127

6 Table 4. Fecundity estimation of Rhinomugil corsula Variables Mean ± SD Range Total length (cm) ± Standard length (cm) ± Body weight (g) ± Gonad weight (g) 18.94± Fecundity 50790± Biological study Fecundity estimation The total number of eggs ranged from 8924 to in the specimen of the total length ranged from to cm. The maximum number of eggs was obtained from a specimen of cm in total length and 202 g in body weight whereas the minimum number of eggs was obtained from a specimen of 23 cm in total length and 100 g in body weight the fecundity ranged from 8924 to (Table 4). The relationship of fecundity with different parameters are shown by figures 5, 6, Gonadosomatic index The mean gonadosomatic index of all samples R. corsula was found ± The gonadosomatic index of R. corsula specimens ranged from 8.13 to The relationship of gonadosomatic index with others parameters are shown by figures 8, Hepatosomatic index Mean liver weight (g) of all samples R. corsula was found ± Liver weight (g) of R. corsula specimens ranged from 0.96 to Mean hepatosomatic index of all samples of R. corsula was ± The hepatosomatic index of R. corsula specimens ranged from 0.83 to The relationship of hepatosomatic index with others parameters are shown by figures 10, 11, Alimentosomatic Index The intensity of feeding was studied by determining by alimentosomatic Index. Mean Gut weight (g) of all samples R. corsula was found ± Gut weight (g) of R. corsula specimens studied ranged from 3.81 to Mean alimentosomatic Index of all samples R. corsula was found ± Alimentosomatic Index of R. corsula specimens studied ranged from 2.78 to The relationship of Alimentosomatic index with others parameters are shown by figures 13, 14, 15, Condition factor determination Mean condition factor of all samples of R. corsula was found ± The condition factor of R. corsula specimens ranged from 0.57 to The relationship of Condition Factor with others parameters are shown by figures 17, Food and feeding habit Food materials The stomach contents were found to contain mixed food items. The fishes were all with full stomachs. None of the specimens had an absolutely empty stomach. It was noted that in the case of small fish samples, almost all had their stomachs in full or gorged state during the investigation period. Different types of algae, phytoplankton, zooplankton, copepods and microscopic organisms were observed in the gut contents. The contents of the rectum were examined, but since it contained only a well ground pulpy mass, the exact nature of the constituents could not be fully determined. Apparently, these miscellaneous items of food are accidentally swallowed by the fish, while feeding on detritus, algae and diatoms (Table 5). Table 5. Food items found in stomach of Rhinomugil corsula Phytoplankton Group/Species Most abundant Zooplankton Others Blue green algae, Green algae, Diatoms, Demis, Nostoc, Anabaena, Asterionella, Spirogyra, Spirulina, Ulothrix, Oscillaboris, Cyclotella, Cosmarium, Protococcus, Pinnularia, Microspora, Closterium, Euglena, Chaetomorpha, Enteromorpha, Polysiphonia, Lyngbya etc. Rotifers, Cladocerans, Ostracods, Copepods, Polychaete moults, Mysids, Microscopic organisms etc. Eggs and nauplii, Small benthic organisms, Small benthic organisms, Sand, Mud, Detritus, Decayed organic matter, Miscellaneous matter etc. 4.0 DISCUSSION The present study showed total length of Rhinomugil corsula ranging from to cm and total weight ranging from to g. The mean total length and total weight were ± 1.57 cm and ± g. Hamilton [14] stated that maximum total length of Rhinomugil corsula was 45.0 cm. Mortuza and Rahman [15] found the males of Rhinomugil corsula to be ranged from 8.7 to 25.6 cm in total length and the total weights were found to be ranged from 6.0 to 189.6g. In case of female the total length and total weight ranged between 8.6 to 26.7 cm and 7.2 to 198.3g respectively. The mean total length for male was calculated to be ± cm and the mean total weight calculated at ±47.708g (N=534). For females, the mean total length and total weight were calculated to be ±5.6241cm and 128 Chlorophyceae and Myxophyceae group sp. Rotifers, Cladocerans, Copepods. Decayed organic matter, sand, mud, detritus ±59.061g (N=666), respectively. So it can be said that the results of the present study agree with the findings of both Hamilton [16] and Mortuza and Rahman [17]. Daham and Wahab [18] said that total length of Liza subviridis was 145 to 310 mm. Females were slightly larger and longer than the males. These results are more or less similar with the present findings. In the present study the taxonomic formula of R. corsula appeared like the following: D1. 4, D2. 7, P , P2. 5-6, A. 9/11, C. 18, RC. 4, however, the formulas of the species recorded by different aurthors are as follows: D1. 4, D2. 1/7-8, P1. 15, P2. 1/5, A. 3/9 [19]; D1. 4, D2. 1/7-8, P , P2. 1/5, A. 3/9 [20]; D1. 4, D2. 1/ 8, P1. 16, P2.1/5, A. 3/9 [21]. The morphological description of this species obtained in the present study was almost similar to the descriptions of the above studies. Present study

7 revealed that scale number on the lateral series is 46 to 49 and mean value ± The number of scale above and below the lateral line ranged from 7 to 9 and 10 to 12. Mean of scale above and below the lateral line in all the specimens found to be 8.00 ± and ± Research finding of Talwar and Jhingran [22] showed that scales in lateral series is 48 to 52. Rahman [23] found that scales number in the lateral series is 50 to 52. Scales number is mentioned by them are 23 to 25 scales before dorsal and 50 to 53. Das [24] reported that the fecundity of Mugil cephalus ranges from 43,000 to 5, 13,000 ova in specimens varying in lengths from 140 mm to 315 mm. The fecundity of mullet increases with the increase in total length. The relationships between fecundity and fish weight, gonad weight were linear. In present study, the fecundity of corsula ranged from 8924 to ova in specimens varying in lengths from 230 mm to 318 mm. The fecundity of corsula changed with the total length, body depth and body weight. The relationships between fecundity and fish weight, gonad weight were linear. Fatima and Khan [25] stated that size and feature of ovaries of R. corsula change with age of maturatity. The mature ovaries get yellowish, elongated and extend almost occupying whole body cavity. The GSI values according to them range from to McDonough [26] reported that the gonadosomatic index (GSI) for fecund striped mullet ranges from 7.7 to The oocytes count ranges from to fish ranging in size from 325 mm to 600 mm in total length. The gonadosomatic index itself is more useful to evaluate reproductive potential when used in conjunction with other techniques, such as histological analysis and oocyte diameter. The models of potential fecundity as they relate to size (total length and body weight) could be useful when applied to catch statistics of length and weight in populations with known size- and age- frequency distributions. This application would allow reasonable estimates of potential fecundity for the populations of R. corsula. The findings of the present study agreed well the findings obtained by [27] and [28]. Mean gonadosomatic index of all samples of R. corsula was found to be ± ranging from 8.13 to The relationships between fish weight, gonad weight and GSI were linear. The hepatosomatic index is an indicator of activity of liver. The findings of the present study stated that the mean hepatosomatic index of R. corsula was ± ranged from 0.83 to This indicated the greater activity of liver in Rhinomugil corsula. It also concluded that R. corsula is omnivorous species. Parihar and Saksena [29] also stated similar findings. They concluded that carnivorous fishes require more intense liver activity than the herbivorous fish. According to their research findings, mean value of hepato-somatic index of S. seenghala, X. cancila and L. boggut were 0.73 ± 0.04, 1.74 ± 0.23 and 0.54 ± The intensity of feeding was studied by determining by alimento-somatic Index. Present study stated that mean alimentosomatic index of all samples R. corsula was ± ranged from 2.78to This indicated the greater feeding intensity in R. corsula during December to March. Khan and Patina [30] (1994) stated feeding intensity of Rhinomugil corsula was maximal in winter and declined towards the monsoon. Pillay [31] (1953a) stated that gut contents of Mugil tade had revealed a marked increase in feeding activity during the winter. The findings of present study agreed with the finding of [32] as well as [33]. The condition factor is the relationship between length and weight of fish. The value of it is influenced by several factors. In this study, mean condition factor of all samples of R. corsula was found ± Condition factor of Rhinomugil corsula specimens ranged from 0.57 to For the observed weights the condition factor (K) ranged from to with a mean of ± (male), in female to with a mean of ± and in combined sexes it ranged from to with a mean of ± The mean calculated condition factor (k) was ± with a range of to for male. For female, the mean calculated condition factor was ± with a range from 0.92 to In case of combined sexes, it was ± with a range of to Research findings of Parihar and Saksena [34] stated that the mean value of condition factor of S. seenghala, X. cancila and L. boggut were ± , ± and According to Pillay [35], the food of the mullet includes tough filamentous algae, and silicious diatoms. He also stated that larger quantities of diatoms and algae consumed by the fish in a marine environment. In the enclosed brackishwater farm, the fish feed on copious quantities of Chlorophyceae and Myxophyceae. Miscellaneous animal matter, mostly appendages of copepods, cladocerans, moults of polychaetes, etc., found in the stomachs of adults. Khan and Patina [40] stated that the predominant occurrence of diatoms, green algae, blue-green algae, desmids, fragments of macrovegetation and semi-digested parts of crustaceans, rotifers, larvae of oligochaetes, nematodes and dipterans in the guts of R. corsula strongly suggested they were illiophagous and omnivorous. They also said that the feeding intensity was maximal in winter and declined towards the monsoon. Seasonal variations in feeding intensity were determined by the percentage of empty guts. They said blue green algae, green algae, unicellular and filamentous algae, diatoms, rotifer, copepods, microscopic organisms, decayed organic matter etc. are the main food items of corsula. Present investigation showed the blue green algae, unicellular and filamentous algae, diatoms, rotifer, copepods, cladocerans, microscopic organisms, decayed organic matter etc. were the main food items of R. corsula. It also indicated that, the Rhinomugil corsula is omnivorous in its feeding habits. The findings of present study agreed with the finding of [41]. From these view, it also agreed with findings of [42] and [43]. 5.0 CONCLUSION Capture production from the open waters of the country is declining because of overharvesting and lack of proper biological knowledge of different fish stocks. Rhinomugil corsula is moderately abundant in natural water bodies and 129

8 its culture is fully dependent on the natural fry source. The taxonomical study of this paper revealed that the total length (cm), standard length (cm), head length (cm), and length of upper jaw (cm) and body weight (g) ranged from 19-24, , , and The taxonomic formula for the species appeared like; D1. 4, D2. 7, P , P2. 5-6, A. 9/11, C. 18, RC. 4. Number of scales on, above and below the lateral line ranged from 46-49, 7-9 and The mean values of hepatosomatic and alimentosomatic indices indicated greater liver activity and feeding intensity in R. corsula during the investigation period. The biological and food-feeding habits investigation of this work showed that the fish weight (g), gonad weight(g), fecundity, GSI, liver weight(g), gut weight (g), alimentosomatic and hepatosomatic index and condition factor ranged from , , , , , , and , respectively. The relationships between different variables were found to be linear. Present investigation also showed that the blue green algae, unicellular and filamentous algae, diatoms, rotifer, copepods, microscopic organisms, decayed organic matter etc. were the main food items of R. corsula. It indicated that the species is omnivorous in its feeding habit. It was also noted that fish samples, almost all had their stomachs in full or gorged state during the investigation period. For better production of R. corsula, appropriate breeding technique should be developed since; R. corsula is one of the most important commercial species of Bangladesh. 6.0 REFERENCES 1. P.K. Talwar, A.G. Jhingran, Inland fishes of India and Adjacent countries. Oxford and IBH Publishing Co. Pvt. Ltd, 2001, pp: K. Riede, Global register of migratory species - from global to regional scales. Final Report of the R&D- Projekt Federal Agency for Nature Conservation, Bonn, Germany, 2004, pp: C.M. Breder, D.E. 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