Study on the food and feeding habits of Decapterus russelli showed that it is a carnivore, subsisting

mainly on crustaceans, fishes, polychaetes, salps, molluscs and miscellaneous items. Crustaceans

were the most dominant item in different size groups. The fish showed preference to other food

fishes as they grew. The intensity of feeding was high during most of the months. Feeding intensity

was high in juveniles followed by immature, maturing and spent fishes

Manojkumar, P P

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427Indian J. Fish., 54(4) : 427-431, 2007Food and feeding habits of Decapterus russelli (Ruppell, 1830)along the Malabar coastP. P. MANOJKUMARCalicut Research Centre of Central Marine Fisheries Research InstituteWest Hill, Calicut – 673005Email: manojppin@yahoo.comABSTRACTStudy on the food and feeding habits of Decapterus russelli showed that it is a carnivore, subsistingmainly on crustaceans, fishes, polychaetes, salps, molluscs and miscellaneous items. Crustaceanswere the most dominant item in different size groups. The fish showed preference to other foodfishes as they grew. The intensity of feeding was high during most of the months. Feeding intensitywas high in juveniles followed by immature, maturing and spent fishes.Study on the food and feeding habits offishes is important to understand their positionin the food web in an ecosystem. In view of itsimportance, considerable attention is being paidto this subject in recent years.Decapterus russelli is an importantresource along the Indian coast. Vekataraman(1960), Basheeruddin and Nayar (1962),Sreenivasan (1979),  Raje (1997) and Reubenet al. (1992) have reported the food and feedinghabits of Decapterus spp. Nair (2000) hassummarised the work done on food and feedinghabits of D. russelli from different parts ofIndia.   However, a detailed study on the foodand feeding habits of this species from Malabarregion is not available.Random samples of D. russelli collectedat weekly intervals during 2001 - 2002 fromPuthiappa and Beypore formed material for thisstudy. A total of 4413 specimens in the lengthrange of 92-248 mm were analysed. Thebiological details such as length, maturity stagesand food and feeding conditions wereexamined. The intensity of feeding wasdetermined based on the degree of distensionof the stomach and the volume of foodcontained in it. The stomachs were classifiedas heavily fed (gorged, full and ¾ full),moderately fed (½ full and ¼ full) and poorlyfed   (trace and empty). The food of the fishwas analysed by index of preponderance(Natarajan and Jhingran, 1961).   Since therewas not much difference in the food and feedinghabits of male and females, the data on boththe sexes were combined.The main food items in the diet of thisspecies were crustaceans, fishes, molluscs,polychaetes, salps and miscellaneous   items(Fig.1).Crustaceans: Crustaceans were present inthe gut throughout the year and the averageindex of preponderance was 55.7 and rankedas the most important item of food. The highestindex was observed in November (68.4) andlowest in March (33.6). The crustaceans in orderof abundance were represented by prawns,Acetes spp., Lucifer spp., amphipods, squilla(Oratosquilla spp.), copepods (Acrocalanusspp. and Calocalanus spp.), mysids and larvaeof crabs.Fishes: Fishes (24.2) formed the seconddominant food item of D. russelli in almost allNote428the months. Maximum index was in March(38.6) and minimum in November (12.8).Leiognathus bindus, Secutor insidiator,Johnieops sina, Johnius belangerii,J. macropterus, Encrasicholina devisi,Stolephorus waitei, S. indicus, Lactariuslactarius, Sphyraena obtusata and fish larvaeformed the food fishes of this species.Polychaetes: Polychaetes (4.9) werepresent   in small quantities in most of themonths   and was represented by Nereis spp.Its index was high during January-May (8.1)and least in December (1.2).Salps: The index value of salps was 7.4and it ranged from 0.5 (December) to 16.3(January).Molluscs: The average value of index ofpreponderance for molluscs was 6.3.This dietwas constituted by squids, cuttle fishes, bivalvesand gastropods which were present in the gutthroughout the year.Miscellaneous items: The intake ofmiscellaneous items indicated that they werenot present in all the months. Average indexfor the study period was 1.4. Maximum indexwas observed in November (5.9) and minimumin June (0.1). Isopods, ostracods andunidentified food materials were included inthis group. Of these, ostracods formed thepredominant item, isopods being next inimportance.Food in relation to lengthAnalysis of food items in relation to sizeof the fish   showed that crustaceans werepreferred by all length groups (Fig 2). Up to asize of 220-229 mm, crustaceans were thedominant food item. Fishes were absent in thestomach content of the juveniles.Index of preponderance1009080706050403020100Fig. 2. Index of preponderance of food items inrelation to different length groups inD. russelli90 110130150170190210230Molluscs Crustaceans Fishes Polychaetes Salps Misc. itemsLength groups (mm)Salps were present in the stomach from100 mm onwards. The indices of salps rangedbetween 3.17 (100-110 mm) and 6.6 (200-209 mm) and in large size groups it occupiedonly a negligible portion (0.5). In general, asthe fish grows, the intake of salps were foundto be increasing in fish up to a size of 200-209 mm. The polychaetes were present in thegut from 100-109 mm size fish onwards andthe intake of polycheates was found increasingas fish grows. The index of preponderance ofmolluscs in the stomach ranged from 0.9 (180-189 mm) to 24.5 (230-240 mm). Themiscellaneous items were present in the fishesof 100-110 mm to 200-209 mm.Feeding intensityFishes with heavily fed, moderately fedand poorly fed stomachs were observed duringmost of the months and the average contributionof fishes in these feeding conditions was34.7%, 41.8%  and 23.5% respectively (Table1). Presence of fishes with heavily fed andmoderately fed stomachs during most of theP. P. ManojkumarIndex of preponderance1009080706050403020100MonthsFig. 1. Index of preponderance of food items inD. russelli during different monthsJanFebMar AprMay Jun JulAugSepOctNovDecMolluscs Crustaceans FishesPolychaetes Salps Misc. items429months indicates that it is an active feeder.Poorly fed fishes had high occurrence duringJanuary-February and August. The feedingcondition of juveniles, immature, maturing,mature and spent fishes is given in Fig 3. Thefeeding intensity was found to be more in allthe fishes except in mature fishes.The composition of food items ofD. russelli of Malabar coast revealed thatcrustaceans and fishes   dominated as the firstand second main  food item in  the orderirrespective of sex, maturity or season, thoughtheir volume varied in the gut contents ofdifferent length groups.   Intake of crustaceansappeared to have relation with the size of thefish. As the fish grows, it was showingpreference for fishes as their principal diet.Salps were preferred by D. russelli as thirditem of food and found in the stomach from110-119 mm to 200-209 mm. The month-wisevariations in the feeding of salps indicate thatmaximum intake of this item was in January-June. Molluscs were present in highestpercentage in the smallest length groups.Although no pronounced difference wasnoticed in season-wise feeding intensity, agradual decrease was observed from post-monsoon to pre-monsoon seasons.From the above, it is clear that D. russelliexhibit a general uniformity of habits and arecarnivorous showing primary preference tocrustacean diet. With the increase in their size theygradually supplement it with fish. Food items suchas polychaetes, molluscs, salps and miscellaneousitems formed insignificant proportions of the foodspectrum. Studies on D. russelli from Indianwaters indicated that they are carnivores feedingpredominantly on crustaceans and fishes(Vekataraman, 1960; Basheeruddin and Nayar,1962; Sreenivasan, 1979; Sivakami, 1996; Raje,Fig. 3.  Feeding intensity of D. russelli in relation todifferent stages of maturityPercentage706050403020100JuvenilesImmatureMaturingMatureSpentStages of maturityPooly fed Moderately fed Heavily fedTABLE 1: Monthly feeding  condition  (%) of D. russelli along the Malabar coastMonths No. of Heavily fed Moderately fed Poorly fedspecimensexaminedJanuary 508 56.5 33.3 10.1February 338 45.3 45.5 9.2March 470 38.9 40.0 21.1April 290 42.6 42.4 15.0May 538 11.8 41.3 46.8June 308 32.4 31.1 36.5July 212 45.1 27.6 27.3August 182 32.8 55.3 11.8September 364 7.1 60.8 32.1October 339 59.3 21.7 19.1November 418 8.9 52.6 38.4December 446 35.2 50.0 14.8Average 34.7 41.8 23.5Food and feeding habits of Decapterus russelli (Ruppell, 1830) along the Malabar coast4301997 and Nair, 2000). Squids and cuttlefishesrepresented the molluscan component in D. dayi(Sreenivasan, 1979).Basheeruddin and Nayar (1962) andSreenivasan (1979) observed similar trend inD. russelli where the planktonic crustaceansformed the main diet in smaller groups and itwas replaced by fishes in higher size groups.Devaraj et al. (1997) too   reported that juvenilesof D. russelli of 4-12 cm size from the Indianwaters fed on Acetes spp., copepods and othercrustaceans.  Magnuson and Heltz (1971)explained that the change in food pattern isdependent on the area of filtration formed bythe gill apparatus. In smaller organisms, gillrakers are closely set with small gaps in betweenand smaller organisms only are sieved, whereasin larger fishes with comparatively larger gapsin between the gill raker, only larger organismsare retained.  Moreover, Sreenivasan (1979) hasconcluded that the smaller fishes cannot moveso swiftly   to prey upon fast moving organismsand therefore need to rely on plankton. Thisincrease in the number of food items has anadaptive significance in utilizing the foodavailable for survival, whenever the availabilityof preferred food items is limited. As observedby the previous workers, the presentobservations also revealed that, with theincrease in size, the variety of food items takenby the fish is narrowed, but the particle size ofthe feed increases. With the increase in size, itshows an affinity towards the column feeding.The preferential feeding on different food itemsin different size groups may be explained asavoiding direct competition and also becauseof the rich oil content available in the planktoniccrustaceans which is essential for thedevelopment of gonad in the sub adult stage(Sivakami, 1996).AcknowledgementsI am grateful to Dr. V. J. Zacharias, formerHead of Department of Zoology, St. Joseph’sCollege, Devagiri, Calicut for the guidance andhelp.  I am thankful to Prof. (Dr.) Mohan JosephModayil, Director, CMFRI, Cochin for theencouragement.  I am also thankful to Dr. E.Vivekanandan, Principal Scientist and Head,Demersal Fisheries Division and Dr. P.NRadhakrishnan Nair, Principal Scientist, CalicutResearch Centre of CMFRI, Calicut forcritically going through the manuscript andproviding their valuable suggestions.ReferencesBasheeruddin,  S. and  Nayar K. Nagappan 1962.  Apreliminary study on the juvenile fishes of thecoastal waters off Madras city.  Indian  J.  Fish.,8 (1) : 169-188.Devaraj,  M, K., N. Kurup, N. G. K. Pillai, K. Balan,E. Vivekanandan and R. Sathiadas 1997. Status,prospectus and management of small pelagicfisheries in India. In : Proceedings of the APFICworking party on marine Fisheries, FirstSession, Small Pelagic resources and theirfisheries in Asia Pacific Region. M. Devarajand P. Martsusubroto (Eds.), Bangkok,Thailand.Magnusson, J. J. and J. G. Heltz 1971. Gill rakerapparatus and food selectivity amongmackerels, tunas and dolphins. Fish. Bull., 68(2) : 361-370.Nair, Radhakrishnan P.  N. 2000.  Carangid resourcesof India. In: Marine Fisheries Research andManagement, p. 317-348. V. N. Pillai andN. G. Menon (Eds.), Central Marine FisheriesResearch Institute, Cochin.Natarajan, A. V. and A. G. Jhingran 1961. Index ofpreoponderance- a method of grading the foodelements in the stomach analysis of fishes.Indian   J.  Fish., 8:45-51.Raje, S. G. 1997. On some aspects of biology ofmackerel scad Decapterus russelli (Ruppell).Indian J. Fish., 44 (1) : 97-99.Reuben, S.,  H.  M.  Kasim,  S.  Sivakami,  P. N. R.Nair, K. N.  Kurup, M.  Sivadas, A.  Noble,K. V. S. Nair and S. G. Raje 1992.  Fishery,biology and stock assessment of carangidresources from the Indian seas.  Indian J.  Fish.,39 (3 & 4) :  195-234.Sivakami,  S.  1996.  On the food habits of the fishesof the family Carangidae. A review.  J.  Mar.Biol.  Ass.  India., 38 (1 & 2) : 118-123.P. P. Manojkumar431Date of Receipt : 12-06-06Date of Acceptance : 10-10-07Sreenivasan,  P. V.  1979.  Food and feeding habitsof Decapterus dayi Wakiya. J.  Mar. Biol.  Ass.India., 21 (1& 2) : 97-102.Vekataraman,  G. 1960. Studies on food and feedingrelationships on the inshore fishes off Calicuton the Malabar coast. Indian  J.  Fish., 7 (2) :275-307.Food and feeding habits of Decapterus russelli (Ruppell, 1830) along the Malabar coast

Food and feeding habits of Decapterus russelli (Ruppell, 1830)

along the Malabar coast

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Food and feeding habits of Decapterus russelli (Ruppell, 1830) along the Malabar coast

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