The flourishing dorab fishery along the coasts of

Palk Bay and Gulf of Mannar in Ramnad District

in South India is constituted chiefly of

Chirocentrus dorabJ probably the only clupeoid

fish growing to a size of nearly 100 crn

Prabhu, M S

CMFRI Digital Repository

No. 10 ) Oct. 1953 Letters 10 tlte Editor 309 very similar to those of the coffee stem-borel,', Xylotrechus quadripes Chev. Our grateful thanks are due to Dr. M. Putta-r~driah for kindly identifying the insects, to Dr. H. Mar i Gowda for kindly iden-tifying the croton ,species, and to Dr. B. T. Narayanan and Mr. R. L. Narasimhaswamy for kind encouragement and helpful advice. Coffee Res. Station, Balehonnur • September 4, 1953 . H. T . RANG A SETTY. H . HANUMAN THA RAO. 1. Beeson and 13hatia. Ind. For. Rec., 1939, 5, 1 (Entomology), 192-94; 199-200. 2. Subramaniam, T. V.," The Coffee Stem-Borer." En! . Series Bleil., Vet. of Agr., Mysore , 1941, 11 . SP OILA GE O F MAC K ERE L S P R E SERVE D IN O IL WHILE studying the preservation of mackerels in oil, we came across a type of spoilage simi-lar to "sulfide stinker". Evolution of a stream of bubbles was noticed in less than 48 hours and within a week the fish disintegrated into a pulpy mass. Bacterial counts on sulfite agar were of the order of 106 . Twenty-one colonies were isolated and restr eaked on Brewer's agat" in Fildes jar and the pure colonies examined. Morphological features showed that all of them were small moltile rods, clavate, with ter-minal spores typ ical clostridia. Th~ rods Were single and in pairs with rounded ends. They all produced gas from cooked meat medium and Holman's medium and blackened the meat with partial digestion. Putrid smell was aJso noted but indole was not detected. Milk was coagulated but without 'storm~ fermentation'. The bacteria belong to the genus clostridium, which is knovm to be the agent for the spoil-age of canned foods. 1 .:l The source is suspected to be the guts of mackerels and fur ther in-vestigation on thi-s is continuing. Our thanks are due to the Director of Fish-eries for permission to publish this note and to Sri. A. G. Vasavan for his assistance. Fisheries Technological Stati01!, K ozhikode June 25. 1953. R. VEl\'XATARAMA N. A. SREENIVASAN. 1. Tanner, F . \V ., llficrobiology (If F oods, 2nd Ed., 1944, Garrard P ress, Champaign, Illinois. 2. Jarvis, N. D., Pri1uip/u and Methods i1t the Canning of Fisfury Products. Research Report No.7, Fish and Wildlife Service. Wa:;hington, D. C., 1043. PRELI MIN A RY O B SERVATIONS ON TH E B IOL OG Y O F CHIROCE NTRUS ., DORA B FO·RSK .* THE flourishing dorab fishery along the coasts of Palk Bay and Gulf of Mannar in Ramnad Dis-trict in South India is constituted chiefly of Chirocentrus dorabJ probably the only clupeoid fish growing to a size of nearly 100 crn. In spite of its importance as a marine fishery re-source, very little attention seems to have been paid towards a detailed study of this fish ex-cept for preliminary accounts on taxonomy by Hardenberg1 and Deraniyagala,2 general notes by Devanesan and Chidambaram:1 and descrip-tion of eggs and larvre by Delsman.4 Owing to 'the occurrence of large shoals of dorab in the coastal as well as off-shore waters of Palk Bay and Gulf of MannaI', a detailed study of its bio-logy was taken up at th~ suggestion of Dr. N. K. Panikkar, as part of the research programme of the Central Marine Fisheries Research S ta -tion. The data collected. from weekly samples of fish from fish landing places indicate that the dorab fishery is constituted of individuals rang-ing in size from 18- 86 cm. Specimens in the larger size groups are caught in gill-nets where-as smaller as well as bigger ones are caught in shore-seines. Almost all the individuals landed from gill-nets are either in mature or post-mature stages and those caught in shore-seines possess immature as well as mature and post-matuTe gonads. An interesting peculiarity noticed in the commercial fish landings was that no male was observed in any of the size groups above 60 cm. Studies on size frequency dis-tribution made for the past 18 months (from October 1951 ) have shown that the dorab fish-ery is constituted of individuals from 1-4 year classes. The average sizes attained by the first to fourth year class fishes were calculated to be 28, 44, 62 and 78 cm. respectively. Observa-tions indicate that the first year class indivi-duals ranging in size up to 22 cm. remain in the off- shore waters until the end of first year or the beginning of the -second year of their life and that they do not make a significant contribution to the dorab fishery. The results obtained from size frequency dis-tribution studies were checked by a critical exa-mination of the growth zones on the scales and otoliths of .specimens in different year classes. In the scales of fishes ranging in size from 22-• Published with the permission of the Chief Research Officer, Central r-,'la rine Fishe ries Research Slation, Mandapam Camp. 310 Letters to tlte Editor [Current Science 86 em.., growth rings varying in number from {..ne to fOllr were observed and the average lengths of individuals were calculated to be 30·8, 42· 03, 64·33 and 76·43 em. Comparing these values with those arrived at from size frequency distribution stUdies, it CQuid be seen that both the values arc in good agreement. Similarly, the occurrence of identical growth rings rang-ing from one to fo ur on otoliths also confirm the inferences made from the size frequency. distribution and scale s tudies. Although it is rather difficult to ascribe special reasons for th,= formation of annuli in the scales and otoliths of these tropical fishes, it is probab~e that they are formed owing to the fol -lowing reasons. In the immature spe-cimens the change in environment from the deep and off-shore waters to the coastal waters may have some effect on the formation of annuli on the scales. In the mature fish the cessation of growth or the decrease in feeding activity soon after spa wning (once a year) may well cause a drop in the rate of growth. These can, however, be established only on the basis of more intensive work. As this species is not a plankton feeder it is doubtful if tbe scarcity conditions of plankton are likely to cause growth checks to the same extent as in plankton f eed-ers like the Malabar sardine. ti Similarly, the effects of the monsoon in th is area being not so marked as on the Malabar coast , thz growth rings observed here are also not likely to be caused by fac tors ascribed by Seshappa and Bhimachar'7 to the monsoon-rings in the Mala·· bar sale. Regular examination of gonads of C. dorab from different size groups indicates that thi~ species attains sexual maturity when about 50 cm. long, during the third year of life or at the completion of two years and that the mature individuals spawn during J uly -August. A sta-tistical study of the measurements of the intra-ovarian eggs shows that spawning is restricted to a short and definite period, as. the mature stock of ova are sharply differentiated from the immature. However, the spawning place of C. dorab which undoubtedly migrates away. from the inshore area, is yet to be located. Other aspects relating to the biology of C. dorab under investigation are the fecundity, rate of growth of gonads in relation to the growth of individuals, length-weight relation-ship in pre- and post- mature males and females, taxonomic and racial studies, development and seasonal variations, if any, on the food and feeding habits. The au thor is grateful to Dr. N. K. Panikkar for guidance and encouragement. Central Marine Fisheries M. S. PRABHU. Research Station, Mandapam Camp, September 7, 1953. 1. Hardenberg, j. D. P., 1930, 12, 51. 2. Deraniya" gala, P. E P. , A Coloured Atlas 0/ Some Verteorates from Ceylo'll, f. Fishes, 1952, p. 10. 3. Devanesan, D. V·,.r . and Chidambaram, K., The CommQtlF(}(Jd Fishesoftlu Afad· r(1S Presidmcy, 1948 (A Madras Government publicatioa, p. II). 4. Delsman, O. W., " Fish eggs and larv.:e from Java Sea, 2," CMrOCellt1'tlS dorab, Trettbia, 1922, 3, 38. 5. Prabhu, 1\1. S., Thesis ~ubm!tted to the University of Madras for the M.':ic. Degree, 1952 (unpublished). fi. Nair, R. V., Curl'. Sci., 1949, 18, I , n. 7. Se:.happa, G. and Bhimachar, B. S., .Ibid., 1951, 20, 10,260. FIRST RECORD OF AN ICHTHYOBDELLAN LEECH BRANCHELLION SAVIGNY FROM THE INDIAN WATERS BrancheUion Sav. has been recorded from the Atlantic, the Mediterranean, and the Pacific, but not so far from any Indian sea. A specimen of Branchellion collected by Mr. G. J . Phanuel from a fish market in Madras was kindly passed on to me for observation. The host is unknown. This is the largest spzci-men of BrancheUion recorded so far, measur-ing 64 mm. in length. It resembles the type specimen of BrancheUion torpedenis Sav. in most features but agrees with Moore'sl speci-men in having biannulation on the dorsal side of the abdomen. There are 33 pairs of bran-chice, and 11 pairs of pulsating vesicles, but in view of the highly lobed or frilled nature of the branchial edge not observed in any specimen recorded so far, a new specific name is .suggested for it and is designated as Bran-chellion plicusbranch'Hs. This is the first record of the genus Bran-cheUio'n Sav. from the Indian waters. A de-tailed account of this w ill be shortly published elsewhere. My thanks are due to Mr. G. J . Phanuel for kindly placing the specimen at my -.:J.isposal, and to Dr. J. P. Joshua for his valuable guid-ance in the study. Dept. of Zoology, P. J. SANJEEVA RAJ. Madras Christian College, Tambaram, July 20, 1953. 1. Moore, J. ]'., A1l1l. flIng . Nnt. Hisl . , 1944 (11) , 11, 383. 310 Letters to tlte Editor [Current Science 86 em.., growth rings varying in number from {..ne to fOllr were observed and the average lengths of individuals were calculated to be 30·8, 42· 03, 64·33 and 76·43 em. Comparing these values with those arrived at from size frequency distribution stUdies, it CQuid be seen that both the values arc in good agreement. Similarly, the occurrence of identical growth rings rang-ing from one to fo ur on otoliths also confirm the inferences made from the size frequency. distribution and scale s tudies. Although it is rather difficult to ascribe special reasons for th,= formation of annuli in the scales and otoliths of these tropical fishes, it is probab~e that they are formed owing to the fol -lowing reasons. In the immature spe-cimens the change in environment from the deep and off-shore waters to the coastal waters may have some effect on the formation of annuli on the scales. In the mature fish the cessation of growth or the decrease in feeding activity soon after spa wning (once a year) may well cause a drop in the rate of growth. These can, however, be established only on the basis of more intensive work. As this species is not a plankton feeder it is doubtful if tbe scarcity conditions of plankton are likely to cause growth checks to the same extent as in plankton f eed-ers like the Malabar sardine. ti Similarly, the effects of the monsoon in th is area being not so marked as on the Malabar coast , thz growth rings observed here are also not likely to be caused by fac tors ascribed by Seshappa and Bhimachar'7 to the monsoon-rings in the Mala·· bar sale. Regular examination of gonads of C. dorab from different size groups indicates that thi~ species attains sexual maturity when about 50 cm. long, during the third year of life or at the completion of two years and that the mature individuals spawn during J uly -August. A sta-tistical study of the measurements of the intra-ovarian eggs shows that spawning is restricted to a short and definite period, as. the mature stock of ova are sharply differentiated from the immature. However, the spawning place of C. dorab which undoubtedly migrates away. from the inshore area, is yet to be located. Other aspects relating to the biology of C. dorab under investigation are the fecundity, rate of growth of gonads in relation to the growth of individuals, length-weight relation-ship in pre- and post- mature males and females, taxonomic and racial studies, development and seasonal variations, if any, on the food and feeding habits. The au thor is grateful to Dr. N. K. Panikkar for guidance and encouragement. Central Marine Fisheries M. S. PRABHU. Research Station, Mandapam Camp, September 7, 1953. 1. Hardenberg, j. D. P., 1930, 12, 51. 2. Deraniya" gala, P. E P. , A Coloured Atlas 0/ Some Verteorates from Ceylo'll, f. Fishes, 1952, p. 10. 3. Devanesan, D. V·,.r . and Chidambaram, K., The CommQtlF(}(Jd Fishesoftlu Afad· r(1S Presidmcy, 1948 (A Madras Government publicatioa, p. II). 4. Delsman, O. W., " Fish eggs and larv.:e from Java Sea, 2," CMrOCellt1'tlS dorab, Trettbia, 1922, 3, 38. 5. Prabhu, 1\1. S., Thesis ~ubm!tted to the University of Madras for the M.':ic. Degree, 1952 (unpublished). fi. Nair, R. V., Curl'. Sci., 1949, 18, I , n. 7. Se:.happa, G. and Bhimachar, B. S., .Ibid., 1951, 20, 10,260. FIRST RECORD OF AN ICHTHYOBDELLAN LEECH BRANCHELLION SAVIGNY FROM THE INDIAN WATERS BrancheUion Sav. has been recorded from the Atlantic, the Mediterranean, and the Pacific, but not so far from any Indian sea. A specimen of Branchellion collected by Mr. G. J . Phanuel from a fish market in Madras was kindly passed on to me for observation. The host is unknown. This is the largest spzci-men of BrancheUion recorded so far, measur-ing 64 mm. in length. It resembles the type specimen of BrancheUion torpedenis Sav. in most features but agrees with Moore'sl speci-men in having biannulation on the dorsal side of the abdomen. There are 33 pairs of bran-chice, and 11 pairs of pulsating vesicles, but in view of the highly lobed or frilled nature of the branchial edge not observed in any specimen recorded so far, a new specific name is .suggested for it and is designated as Bran-chellion plicusbranch'Hs. This is the first record of the genus Bran-cheUio'n Sav. from the Indian waters. A de-tailed account of this w ill be shortly published elsewhere. My thanks are due to Mr. G. J . Phanuel for kindly placing the specimen at my -.:J.isposal, and to Dr. J. P. Joshua for his valuable guid-ance in the study. Dept. of Zoology, P. J. SANJEEVA RAJ. Madras Christian College, Tambaram, July 20, 1953. 1. Moore, J. ]'., A1l1l. flIng . Nnt. Hisl . , 1944 (11) , 11, 383. 

Preliminary observations on the biology of Chirocentrus dorab Forsk

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Preliminary observations on the biology of Chirocentrus dorab Forsk

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