Growth rings on the scales and otoliths of 'Koth' have been recorded by Karandikar and Thakur (1951). Mention of growth checks on the scales of this fish and their probable utility in -age determination has also been

made by Seshappa (unpublished). Studies on the scales and otoliths of 'Koth' from the local 'dol' net catches landed at Bombay and the catches of the trawlers working along the Bombay coast were begun by the author in February 1958 with a view to assess their value in age determination of

the fish. Material for the present study was also collected subsequently from the gill-net catches at Bedi in the Gulf of Kutch

Kutty, M N

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SCALES AND OTOLITHS OF T H E 'KOTH' OTOLITHOIDES BRUNNEUS (DAY) AS AGE INDICATORS* BY M. NARAYANAN KUTTY {Central Marine Fisheries Research Institute) GROWTH RINGS on the scales and otoUths of 'Koth' have been recorded by Karandikar and Thakur (1951). Mention of growth checks on the scales of this fish and their probable utility in -age determination has also been made by Seshappa (unpublished). Studies on the scales and otoliths of 'Koth' from the local 'dol' net catches landed at Bombay and the catches of the trawlers working along the Bombay coast were begun by the author in February 1958 with a view to assess their value in age determination of the fish. Material for the present study was also collected subsequently from the gill-net catches at Bedi in the Gulf of Cutch. Five to six scales each from the pectoral region of 554 fish, ranging in size from 5-0 to 150-5 cm., were examined. Scales of 'Koth' are found to lack zonations of wide and narrow sclerites, the concentric markings of the rings being abrupt breaks in the pattern of the circuli. This feature in the scales has been reported in Lates calcarifer also by Australian workers (Ommaney, 1957). Generally, 'Koth' above 30 cm. in length (total length) had one or more clear rings on their scales. A maximum of twelve rings were counted on the scales of a fish of 149-0 cm. in length. The progressive increase in the number of scale rings with fish size was evident from the observed mean fish size for each ring, from the first to the twelfth {vide Table I). The mean fish sizes for the first three scale rings, i.e., 41-8, 60-0 and 74-1cm. respectively, more or less correspond to the first three modes in the length frequency curves of 'Koth' from the catches landed at Bombay. The modes of the curve for the 1958-59 catches were at 38-5, 59-5 and 80-5 cm., for the 1959-60 catches at 24-5, 59-5 and 87-5 cm. and for the 1960-61 catches at 31-5, 59-5 and 73-5/80-5 cm. In order to check the annual nature of the formation of the scale rings, counts of circuli in the 'terminal zone' of the scale (PI. Ill, Fig. 1) from 305 10 TABLE I Distribution of scale rings of 'Koth', Otolithoides brunneus at various size groups* Size group in cm. Number of rings 1 24 (2) S5 (4) 33 (18) 4 (17) (3) " * •• •• •• 2 •• • • (i) 2 (11) 1 (46) (20) (5) (2) * * •• 3 •• •• •• •• (6) (io) (6) 1 (11) (6) •• 4 •• •• •• •• •' (i) (3) (9) (4) 10 I I 12 5-0- 27-9 28 .0- 34-9 35-0- 41-9 42-0- 48-9 49-0- 55-9 56-0- 62-9 63-0- 69-9 70-0- 76-9 77-0- 83.9 84-0- 90-9 91-0- 97-9 44 40 35 10 2 (1) fc-l a o M CO 98-0-104-9 105-0-111-9 il2-0-118-9 119-0-125-!) 126-0-132-9 133-0-139'9 140-0-146-9 147-0-153-9 j3 Dol net catches, Bombay 265 "S Trawler catches, Bombay (214) •S Gill net catches, Bedi 75 B ^ Combined total 554 Mean fish size in cm. 4 J . . H -• 131 (1) 132 ••' 116 (44) 160 41-8 3 (85) 88 60-0 1 (39) 40 74-1 (4) (3) (2) •• •• •• •• •• •• (26) 26 83-1 (4) (10) •• 1 •• •• 1 (14) 15 107-9 -• •• ••• 2 (i) 2 •• 2 (1) 2 5 127-1 -•• •• --1 i 1 8 • • •• 2 • • 12 14 134-7 •• •• •• • • "i il)22 {l)"i •• (2) 30 32 136-1 --•• -• .. • • {2)16 2 5 1 3 (2) 21 26 138-5 -• -• -• • • •• 3 2 4 1 2 • • S 10 142-0 •• -• •• • • •--• 1 1 2 1 3 2 5 148-2 -• -• •• • -•--• -• 1 1 .. -• 1 149-0 * Figures in brackets denote fish from the trawler catches off" Bombay; and figures in Italics denote fish from the Gill-net catches off Bedi (Gulf of Cutch). Figures not marked denote fish from the 'Dol ' net catches off" Bombay. Co ST-O o »-^ & i o 13 O P in S-rs" 4»-- 4 148 INDIAN JOURNAL OF FISHERIES juvenile and adolescent 'Koth'* were made, as done by Perlmutter and Clarke (1949) in Sebastes marinus. The fish were then grouped into two categories, (i) those with < 10 circuli in the terminal zone of the scale and (ii) those with > 10 circuli in the terminal zone. The width of the sclerites was more or less uniform irrespective of the season when they were formed and the number of circuli in the scale increased with the growth of the fish. Con-sequently the period, when scales with the smaller counts of circuU (< 10 circuli) in the 'terminal zone' were dominant, would represent the period closely following the formation of an annulus. Curve A in Fig. 1 shows % -60 40 20 t 40 20 F A J A 0 D /9S8 F A J A O D F A \959 I960 FIG 1. Correlation between period of annuli formation in the scales and period of low feed-ing activity in Otolithoides brunneus. (A) shows monthwise percentage number of juvenile and adolescent fish with <' 10 circuli in the 'terminal zone' in their scales. (B) shows monthwise per-centage of average fulness of stomach (points method) of juvenile fish from the inshore waters of Bombay. that this period was between November and February. Studies on the feeding habits of the fish revealed that this period of scale annuli formation as judged from the circuU counts more or less coincides with the periods of low-feeding activity. The average fulness of stomach of juvenile 'Koth' from the inshore catches of Bombay, calculated month-wise, was found to be least during February 1958, December and January in 1958-59 and December, * The fish attains first maturity at the size of about 120 cm. Scales & Otoliths of'Koth' Otolithoides brunneus as Age Indicators 1 ^ TABLE II Distribution of the first six rings on the otoliths of ^Koth', Otolithoides brunneus at various size groups. * 3'0- 6-9 7-0-13-9 U-0-20-9 21'0-27-9 28-0 34-9 35-0-41-9 42-0-48-9 49-0-i55-9 sc-o-ns-g 63-0-69-9 70-0-76-9 77-0-83'9 84-0-90-9 j3 'Dol'net catches, Bombay 299 "S Trawler catches, Bombay 73 . . B §, Combined total 372 Mean fish size in cm. 1 5 61 35 11 112 112 13'8 2 ,^ 5 22 20 8 (1) 2 •• •• •• •• 57 1 58 23-4 Number 3 • • 2 31 52 (1) 15 (4) 6 (3) 1 (1) • • 107 9 )16 39.3 of rings 4 4 13 5 (6) 1 (8) (6J (2) 23 21 44 45-5 5 .. •• • • •• •• (i) U) (12) (7) (2) (i) 27 27 61-5 6 .. • • • • • • • • •• • • (i) (4) (4) (6) .. 15 16 80-3 • Figures in brackets denote fish from trawler catches off Bombay and figures not marked denote fish from 'Dol' net catches off Bombay. January and February in 1959-60 (Fig. 1 B). The annual lowering of feeding intensity can thus be made out as a probable cause for the formation of the scale annuli, It is also of interest to note that the period from November 150 INDIAN JOURNAL OF FISHERIES to February happens to be the period of lowest bottom and surface tempera-tures in the Dwaraka region, where there is a good fishery for 'Koth' (Jayaraman and Gogate, 1957 and Jayaraman et al, 1959). Otoliths of 372 fish were studied by the method followed by Fairbridge (1951). With a few exceptions all of them showed clear rings which increased progressively in their number with the size of the fish (Pi. Ill, Fig. 2 and Table II). The otoliths contain concentric opaque and hyaline zones. The concentric hyaline zones were counted as rings. The clearer pattern of rings in the otoliths of younger fish enabled its study better and there was clear indication to show that 2 to 3 rings were formed in the otoliths by the time the scale developed only a single ring. While the otoliths of very small 'Koth' studied showed a clear ring it was evident that the first scale ring appeared only when a much larger size was attained by the fish. A comparison of Tables I and II shows the disparity in the distribution of rings on the scales and otoliths of 'Koth'. The occurrence of more number of rings in the otoliths than on the scales is perhaps an indication as Saetersdal (1953) pointed out that "the otolith is a more sensitive instrument than the scale, and records smaller differences in the conditions of the fish than does the scale". The formation of more than one ring on the otoliths in the first year of life of fishes such as Clupea pilchardus, where 2 to 4 rings are formed in the first year, Pleuronectes platessa and Drepanosetta platessoides, is reported by Kotthaus (1958 and personal communication). The present studies clearly indicate that the scales of 'Koth' are more reUable than the otoliths as age indicators. I am thankful to Dr. S. Jones and Dr. G. Seshappa for their criticism and encouragement during the course of this work and to W. D. Pachare, Artist-Photographer, T. N. Medical College, Bombay, for photographing the otoliths. REFERENCES 1. Fairbridge, W. S. 1951 .. The New South Wales Tiger Flathead A'eoptoj'cepAfl/ttj TWICAO-don (Ogilby). I. Biology and age determination. Auitr. J. Mar. Freshw. Res., 2(2), 117-78. 2. Jayaraman, R. and Qogate, Salinity and water temperature variations in the surface waters S. S. 1957 of the Arabian Sea oflf the Bombay and Saurashtra coasts. Proc. Ind. Acad. Sci., 45, 151-64. , Seshappa, G,, Observations on the trawl fisheries of the Bombay and Mohamed.K. H.and Saurashtra waters, 1949-50 to 1954-55. Indian J. Fish.. Bapat, S.V. 1959 6, 58-144. Karandikar, K. R. and Sciunoides brunneus Day. Zool. Mem.. Univ. Bombay Thakur.S. S. 1951 3, 1-89. Indian Journal of Fisheries, Vol. VIII, PI. Ill FIG. I. Photographs of scales of OtolillwUles hnimieus (scales used ;is negatives), (o) Scale showing 6 rings, x 5. (Total length 125-Ocm. female captured on 6-3-1959 from Dwaraka region by the bull trawlers "Arnala and Paj"). T, terminal zone. (6). Scale showing II rings, X4. (Total length 146'5cm. Sex not known, captured on 30-11-1958 from Satpati—examined at Crawford Market, Bombay.) FiQ. 2. Photograph of otoliths of Ololithoiiles brunneiis, x l -4 . The external sculpturing on thj otoliths are ssen as shaded markings, which are seen darker at the opaque growth regions and are marked here as rings. The external prominences at the opaqus growth regions are clearly seen because of the dilTused lighting technique used in photographing these otoliths. (a) Otolith showing one ring-Fish length: l l-2cm.; (.ft) Otolith showing two r ings-Fish length: 20-7cm.; (t) Otolith showing four rings—Fish length: 35-5cm., male; ((/J Oto-lith showing live rings—Fish length: 45-9cm.,female; (e) Otolith showing six rings—Fish length: 63-4cm., male. Scales & Otoliths of'Koth' Otolithoides brunneus as Age Indicators 151 Kotthaus. A. 1958 Onunaney, F. D. 1957 . Perlmuttei, A. and Claike, G. M. 1949 Saetersdal.G. S. 1953 Seshappa,G. Age and growth of Red fish, Sebastea marinus (L.). International Commission for North- West Atlantic Fisheries Spec. Publ., 1, 217-22. Report oj the Sea Fisheries, Panel B, l.P.F.C, Proc. 7th Session, Bandung, 47-56. Age and growth of immature rose fish, Sebastes marinus in the Gulf of Marine and off Western Nova Scotia. U.S. Fish. Wildl. Serv. 51(45), 207-28. The haddock in Norwegian wateis, II. Methods in age and growth investigatiors. Rep. Nor^eg. Fish. Invest., 10(4), 1-46. Report on Woik Relating to ScUenid Fisheries tot 1955-56, Offshore Fisheries Research Unit of C.M.F.R.I. (un-published). FURTHER OBSERVATIONS ON T H E FISHERY AND BIOLOGY OF'CHOODAI' (SARDINELLA spp.) OF MANDAPAM AREA BY P. SAM BENNET (Central Marine Fisheries Research Institute) INTRODUCTION THE sardines, locally called Choodai, constitute one of the important groups of fishes supporting the fisheries of the Mandapam area. Sardinella albella and Sardinella gibbosa are the two important species forming the fishery. Previous studies on sardines in the area include observations made by Devanesan (1932) on the food and feeding habits and Chacko (1946) on the bionomics of S. gibbosa. Investigations have been in progress since 1952 at the Central Marine Fisheries Research Station (Sekharan, 1955 and 1959) on the Choodai fishery. The present study was undertaken from May 1958 to March 1960 as a continuation of the work. MATERIAL AND METHODS Random samples of Choodai from commercial catches were obtained from PuUamadam, Thangachimadam and Dhanushkodi in the Palk Bay and from Rameswaram Road and C.M.F.R.S. area in the Gulf of Mannar. It may be pointed out here that " torch fishing " with handnets were sparingly operated in the fishing centres during the period of study and the gillnets accounted for a very insignificant proportion of the total catch. Bulk of the sardine catch were landed by shore seines operating within two miles from shore. The fishery usually starts in April in the Palk Bay and lasts till October. From November to March it is continued in the Gulf of Mannar coast. All random samples taken from the commercial catches were measured for length frequency observations and detailed study was done only on selected samples. The standard length, i.e., the length from the tip of the snout to the end of the silvery area on the caudal peduncle was recorded in millimetres. Head length was measured from the tip of the snout to the posterior edge of the operculum. In many cases the fishermen's records of catch have been used while calculating the monthly landings. Gut contents of 580 specimens preserved in 5% formalin as soon as they were landed were studied. After 

Scales and otoliths of the 'Koth'Otolithoides brunneus (Day)as age indicators

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Scales and otoliths of the 'Koth'Otolithoides brunneus (Day)as age indicators

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