Himantura bleekeri and Amphotistius imbricatus are bottom carnivores, with

crustaceans ranking first in the food items followed by teleosts, molluscs and

polychaetes. Number of poorly fed individuals was high in both the species.

These species breed throughout the year. The male : female ratio of H. bleekeri

for 1989-’05 and of A. imbricatus for 1997-‘05 were 1:0.98 and 1:1.36 respectively.

The length-weight relationship was: Log W= -8.7298 +2.7297 Log L for H. bleekeri

and Log W = - 6.4691 +2.3119 Log L for A. imbricatus

Raje, S G

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235Indian J. Fish., 54(2) : 235-238, Apr.-Jun., 2007Some aspects on the biology of Himantura bleekeri(Blyth) and Amphotistius imbricatus (Schneider)from MumbaiSADASHIV GOPAL RAJEMumbai Research Centre of Central Marine Fisheries Research InstituteMumbai - 400 061, IndiaABSTRACTHimantura bleekeri and Amphotistius imbricatus are bottom carnivores, withcrustaceans ranking first in the food items followed by teleosts, molluscs andpolychaetes. Number of poorly fed individuals was high in both the species.These species breed throughout the year. The male : female ratio of H. bleekerifor 1989-’05 and of A. imbricatus for 1997-‘05 were 1:0.98 and 1:1.36 respectively.The length-weight relationship was: Log W= -8.7298 +2.7297 Log L for H. bleekeriand Log W = - 6.4691 +2.3119 Log L for A. imbricatus.NoteInformation on the biology ofHimantura bleekeri from Indian seas arelimited except  for the brief account givenby Setna and Sarangdhar (1949) fromBombay and Devadoss (1978a), fromCuddalore. Some aspects of the biologyof A. imbricatus have been reported byDevadoss (1978b, 1984) from Porto Novo,Tamil Nadu. Since no biologicalinformation on these species is availableoff Mumbai, an attempt was made to fillthe gap to certain extend and resultsobtained are presented. Biological dataon H. bleekeri collected during 1989-2005and on A. imbricatus during 1997-2005from New Ferry Wharf were analysed forthis study. The details on the length(across the disc) in cm, weight in kg, sex,maturity of females and food habit of bothspecies were collected.  Rays withstomach in gorged, full and ¾ fullcondition were considered as activefeeders. The food composition wasidentified up to genus level and, whenpossible, up to species level. The dietaryimportance of each food item wasdetermined using the index ofpreponderance (IP). Reproductive stagesof females were assessed as: immature(ovary only as loose cells and oviduct thinand slender), mature (ripe ovarian eggsor large yolked eggs, distended uterus),pregnant (embryo in the uteri) and postnatal (uteri baggy with pit inside andtrophonemata worn out).A total of 496 specimens of H.bleekeri were examined for stomachcontent, of which 429 (86.5%) were nearlyempty (Table 1) and found predominantlyin all the months. Out of the 742stomachs of A. imbricatus, 598 (80.6%)were empty. The maximum number ofsuch stomachs (94.0%) were recorded inAugust and the minimum in May236(71.2%). In H. bleekeri, the meanvolume of food per fish was 3.36 mland in A. imbricatus 0.48 ml. H.bleekeri fed primarily on crustaceans(61.8%) followed by teleost (17.0),molluscs (12.7%) and polychaetes(0.6%).Among crustaceans, three mostfrequently preferred food items wereSquilla spp. (26.7%), Nemato-palaemon tenuipes (18.4%) andSolenocera spp. (12.9%). Other fooditems found were Parapenaeopsisstylifera (2.3%), Exhippolysmataensirostris (0.7%), prawn remains(0.6%) and crabs (0.6%). Crustaceansformed the dominant food itemsduring January, March-June andOctober-November. The teleost fooditems in the order of abundance were:Coilia dussumieri (11.1%), sciaenids,Polynemus heptaductylus, catfishes,Bregmaceros macclellandi, Trypau-chen vagina, Harpodon nehereus,Apogon spp., Cynoglossus spp.,Myctophum spp. and egg mass, theiravailability being highest in Februaryand lowest in January. Molluscan foodcomprised mainly of bivalves andrarely by Loligo spp. Molluscs wereconsumed maximum in May andminimum in December. Polychaeteswere noticed in March only.In A. imbricatus also crustaceans(75.8%) formed the most dominantfood followed by teleosts (2.8%),molluscs (0.03%) and polychaetes(0.01%).Acetes spp. (20.7%) was the mostcommon prey among the crustaceans.The other crustaceans found in thestomach in the order of abundance (%)were N. tenuipes (6.6), Solenocera spp.(3.8), Squilla spp. (1.4), P. stylifera(0.1), Parapenaeopsis spp. (0.03), E.ensirostris (0.02), and crab (0.02).Sadashiv Gopal RajeTABLE 1: Feeding intensity and average volume of stomach content in H.bleekeri (Pooled 1989 - 2005) and A.imbricatus (Pooled 1997 - 2005)H.bleekeriA.imbricatusMonthsNo. ofCondition of stomachs ( %)Average vol.No. ofCondition of stomachs (%)Average vol.specimensActiveNormalPoorof food (ml)specimensActiveNormalPoorof food (ml)January287.114.378.61.775—14.785.30.43February842.48.389.31.65671.514.983.60.54March30—6.793.35.7708.691.40.25April1226.69.883.64.86851.221.277.60.57May845.911.982.25.42663.025.871.20.45June11—9.190.95.6318—27.872.21.23July—————16—12.587.50.32August—————50—6.094.00.16September—————76—17.182.90.40October323.1—96.91.5166—33.366.70.51November53—3.896.21.1976—22.477.60.61December521.919.278.91.777—20.879.20.60Pooled4963.89.786.53.367420.518.980.60.48237Crustaceans constituted more than62.0% of the food in January, April-Mayand September-November. Among theteleost diet %, Coilia dussumieri (0.4%),Apogon spp. (0.01%), Cynoglossus(0.01%) and Myctophum spp. (0.01%)were represented. The highest IP forteleosts was noticed in August and lowestin September. Molluscan diet wasrepresented by Octopus spp. (0.02%) andSepia spp. (0.01%) in January and April.Polychaetes were represented only byNeries spp. Digested matter composed offish scales, bones, mucus and mud.It is evident that these rays forageon the bottom living organisms likecrustaceans, molluscs and polychaetes.Similar observations were made byDevadoss (1978 and 1984) on rays fromPorto Novo and Cuddalore region and byRaje (2003) from Mumbai waters.A total of 267 specimens of H.bleekeri and 428 specimens of A.imbricatus were examined for breedingbehaviour. Mature females of H. bleekeriwere recorded during January-June andOctober-December, pregnant ones duringFebruary- June and post natal in April-May. Availability of mature females ofA. imbricatus in almost all the monthsand post natal in January-February,April-May, September and Novemberindicated prolonged breeding activities.This assumption is supported by theoccurrence of free swimming young onesof H. bleekeri (16-30 cm) and A.imbricatus (10-15 cm) all round the year.The ovary with large mature ova andfull term embryos were also noticed inuterus of both the species. It indicatedthat copulation, ovulation andfertilization take place almostimmediately after the termination of thecurrent pregnancy as indicated by Ford(1921) and Devadoss (1978 c, 1998) inbatoid fishes. Prolonged breeding activityof D. imbricatus has been observed byDevadoss (1978 b) off Porto Novo coastand Jones and Sujansingani (1954) inChilka Lake.The overall sex ratio of H. bleekeriwas 1 male to 0.98 females. Thedistribution of sex ratio was significantin February and June due to dominanceof females and in March and October dueto predominance of males. The pooledratio of males to females in A. imbricatus(1:1.4) was significantly different at 1%level. Monthwise sex ratio showedsignificant difference in February, Apriland November with preponderance offemales. Devadoss (1978 b) noted sexratio as 1 female : 1.05 male in D.imbricatus off Porto Novo.The log value of length across discin cm and weight in kg were regressedas per least square method.The regression equation for 355males (24-82cm) and 383 females (27-101cm) of H. bleekeri and 652 males (14-34cm) and 970 females (13-36cm) of A.imbricatus were determined. Analysis ofcovariance revealed no significantdifference between the sexes of both thespecies, and therefore a commonequation for each species was derived as:H. bleekeri :Log W = - 8.72967 + 2.72967 Log L(r = 0.86)A. imbricatus:Log W = - 6.46910 + 2.3119 Log L(r = 0.83)AcknowledgementsThe author is grateful to Prof. (Dr.)Mohan Joseph Modayil, Director; Dr. E.Vivekanandan, Head of D. F. DivisionC. M. F. R. Institute, Cochin and Dr.V. D. Deshmukh, for their encourage-ment. Help rendered by technical staff,Biology of Himantura bleekeri and Amphotistius imbricatus238Mr. Thakurdas, B. B. Chawan, J. D.Sarang, J. R. Dias, and S. K. Sujit, in thefield and Veena. S, for typing the MS isacknowledged.ReferencesDevadoss, P. 1978 a. A preliminary study onthe batoid fishery of Cuddalore with anote on the biology.  Indian J. Fish.,25(1&2): 180-187.Devadoss, P. 1978 b. Maturation and breedinghabit of Dasyatis imbricatus (Schneider)at Porto Novo. Indian J.Fish., 25(1&2):29-34.Devadoss, P. 1978 c. On the food of rays,Dasyatis uarnak (Forskal), D. alcockii(Annadale) and D.sephen (Forskal).Indian J. Fish., 25(1&2): 9- 13.Devadoss, P. 1984. Further observation on thebiology of the sting rays, Dasyatisimbricatus (Schneider) at Porto Novo.Matsya, 9&10:129-134.Devadoss, P. 1998. Observations on thebreeding and development in somebatoid fishes. Indian J. Fish., 45(3): 271-283.Ford, E. 1921. A contribution to ourknowledge of the life histories ofdogfishes landed at Plymouth. J. Mar.Biol. Ass. U.K., 12 (3): 486 – 505.Jones, S. and Sujansingani 1954. Fish andfisheries of the Chilka Lake withstatistics of fish catches for the year1948-50. Indian J. Fish., 1: 256-344.Raje, S. G. 2003. Some aspects of biology offour species of rays off Mumbai water.Indian J. Fish., 50(1): 89-96.Setna, S. B. and P. N. Sarangdher 1949. Thebreeding habit of Bombay elasmo-branchs. Rec. Ind. Mus., 47: 107-124.Sadashiv Gopal RajeDate of Receipt : 19-08-06Date of Acceptance : 23-03-07

Some aspects on the biology of Himantura bleekeri

(Blyth) and Amphotistius imbricatus (Schneider)

from Mumbai

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Some aspects on the biology of Himantura bleekeri (Blyth) and Amphotistius imbricatus (Schneider) from Mumbai

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