Observations made on length-weight relationship for adult milkfish, ova-diameter frequency distribution,

relationship between fecundity and total length, fecundity and standard length; and weight and

fecundity are presented. The regression lines for 17 morphometric characters in relation to the standard

length were worked out. Snout to anal origin grows faster than snout to ventral origin. Head length; shows

faster rate of growth than head depth. The stomach content revealed the presence of diatoms predominantly.

Fecundity varied between 1424 and 5321 thousands in the fish in the size range of 1,100 - 1,340 mm

Gandhi, V

Mohanraj, G

Thiagarajan, R

ABSTRACT Observations made on length-weight relationship for adult milkfish, ova-diameter frequency distribution, relationship between fecundity and total length, fecundity and standard length; and weight and fecundity are presented. The regression lines for 17 morphometric characters in relation to the standard length were worked out. Snout to anal origin grows faster than snout to ventral origin. Head length; shows faster rate of growth than head depth. The stomach content revealed the presence of diatoms predominantly. Fecundity varied between 1424 and 5321 thousands in the fish in the size range of 1,100 -1,340 mm

V Gandhi

G Mohanraj

R Thiagarajan

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BIOLOGY AND BIOMETRY OF MILKFISH CHANOS CHANOS (FORSSKAL)

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J. mar. biol. Ass. India, 1986, 28 (1 & 2) : 1 6 9 - 1 7 / BIOLOGY AND BIOMETRY OF MILKFISH CHANOS CHANOS (FORSSKAL) V. G A N D H I , G . MOHANRAJ* AND R . THIAGARAJAN* Central Marine Fisheries Research Institute, Cochin-6^2 031 ABSTRACT Observations made on length-weight relationship for adult milkfish, ova-diameter frequency dis-tribution, relationship between fecundity and total length, fecundity and standard length; and weight and fecundity are presented. The regression lines for 17 morphometric characters in relation to the standard length were worked out. Snout to anal origin grows faster than snout to ventral origin. Head length; shows faster rate of growth than head depth. The stomach content revealed the presence of diatoms predominantly. Fecundity varied between 1424 and 5321 thousands in the fish in the size range of 1,100 - 1,340 mm. INTRODUCTION ALTHOUGH the milkfish Chanos chanos (Forss-kkl), is one of the most important cultivable species of finfishes in various culture systems in Philippines, Indonesia, Taiwan. Hawaii, etc. 1951, 1952 and 1955), Chacko et al. (1953), Devanesan and Chidambaram (1953), Chacko and Mahadevan (1956), Tampi (1957), Pani-kkar et al. (1952) and Chacko and Thomas (1962) have recorded adult milkfish from Coro-mand^l Coast, Palk Bay, Gulf of Mannar and I4O0O tzooo KMOO tooo «000 • • • • •^ • IIOO • • • 1190 • • • I 2 0 0 • ^^ • i2fln • • > ooo • ' TOTAL LENGTH (rr™, Fig. 1. Total length-weight relationship of milkfish. catches of this species from the sea are negligible throughout the world. In India Chacko (1950, •Present address : Madras Research Centre oi CMFRI, 29 Commander-in-Chief Road, Madras - 600 105. Malabar Coasts. Valuable contributions have been made regarding several aspects of milk-fish, such as spawning, occurrence of fry and fingerlings, food and feeding habits, etc. by Chacko (1945, 1955), Tampi (1957, 1958), 170 V. GANDHI AND OTHERS Silas et al. (1980), Dorairaj et al. (1984), Mammen (1965), Mohapatra (1966) and Rangirajan and Ganapathy (1949). Tampi and Bensan (1976) have reviewed the work pro-grammes on the biology of this fish carried out in India. Senta and Kumagai (1977) have studied the vertebral variation of the milkfish from various localities of the Indo-Pacific. From these it may be seen that no work has been carried out on the biometry of adult MATERIALS AND METHODS Surveys have been conducted in Theedai and Ariyankundu in the Palk Bay, and Pudu-madam and Appatheevu in the Gulf of Mannar areas to locate suitable centre for adult milkfish collection. At Ariyankundu, bottom set nylon gill nets with a mesh size of 13 to 17 cm are being oper-ated with the help of dugout canoes or small Tte * --rtr Tjte- •M Fig. 2. Standard length-weight relationship of milkfish. milkfish in India. Liao (1971) has given meristic and mdrphometric characters of nine adult specimens. In the present study, the authors have worked out the biometry, length-weight relationship and fecundity of milkfish. The authors wish to express their gratitude to: Shfi. C. Mukundan, Head of Demersal Fisheries Division and Dr. P. Bensam for critically reading the paper and suggesting improvements. plank-built boats for catcjiiiig adult milkfish. The sizes of the ..boats abe 4 to 5 metres in length and 1.0 to 1.5 in width. Only one or two fishermen per , boat used to go for the operation of the net. They operate the nets in the evenings and clear the catches in the following morning. Twenty one adult milkfish were examined, which is the largest number of fish ever analy-sed from the wild from a particular centre in BIOLOGY AND BIOMETRY OF MILKFISH 171 India. Twenty fishes were collected from Ariyankundu and one from Appatheevu near Kilakkarai during the years 1979 to 1982. After the fishes were weighed, meristic and morphometric characters were taken. All the 21 fishes were analysed for sex and stage of maturity. The weight of the internal organs such as gonads, heart, liver, stomach, gizzard, spleen and weight and length of intestine were quantitatively giving percentage to each food item of the total food content of the stomach of the each fish. In order to find out the rela-tionship between standard length and other morphometric characters and weight-fecundity, the general equation Y=a+bx was employed whereas to find out the relationship between the length and weight, the total length and the fecundity and standard length and the fecun-dity, the curvilinear regression equation Y= a+X^ was used. MO Fig. 3. Relationship between standard length and other morphometric characters of milkfish. recorded from 8 fishes, in fresh condition. Fecundity estimation of the ova in the II and III stage fishes, was also done in fresh con-dition, counting the eggs in a portion of known weight and thereby calculating the total num-ber from the total weight of the ovaries. The ovaries were preserved in 10% formalin for ova diameter study. For ova diameter frequ-ency, 100 ova from the ovary of each fish were measured. Similariy the anterior spiral por-tion of the oesophagus region was analysed RESULTS Ariyankundu is identified as the best collection centre where about 100 numbers of adult milkfish are caught every year. The peak period for the catch of milkfish is January to April with a secondary period in October to December. At Ariyankundu, the sea forms a shallow bay with a stretch of coral and sand rocks with a depth of 4 to 6 metres. The adult fish were obtained during January to April, October and December. Out of 21 adult milkfishes, 16 fishes were females and 5 were males. Data on the date of capture, place, total length of fish, weight, sex, weight of gonad, gonadosometic index (GSI) values, average ova diameter, maturity stage and fecundity are presented in Table 1. It was observed that scales on lateral line ranged from 79 to 88 in number. Rows of scales above lateral line varied between 12 and 14 whereas the rows below lateral line were 12 or 13. The total length, standard length and weight of the fishes were from 1042 to 1340 mm, 800 to 1059 mm 7 to 15 kg respectively. The total length and weight and standard length and weight relationship in its logarithmic form are as follows. Log W = -5.9042+ 3.2304 Log. tL . Log W = -4.4502 + 2.8636 Log. SL. TABLE 1. Gonad weight, GSl and fecundity of adult milkfish M Date of catch Place 10. 4.1978 Ariyankundu 25. 1.1979 29. 1.1979 30. 1.1979 9. 2.1979 14. 2.1979 17. 2.1979 18. 2.1979 22. 2.1979 23. 2.1979 26. 2.1979 4.10.1980 13.10.1980 15.10.1980 15.12.1980 14.03.1982 Appa Island (Kilakarai) Ariyankundu Total length (mm) Body weight (kg) Sex Gonad weight (gm) GSl Ova diameter Maturity stage Fecundity according to (Total No. Tampi (1957) of eggs*) 1161 1113 1075 1290 1270 1175 1^0 1055 1235 1340 1152 1294 1042 1145 1186 1120 1069 1092 1170 1247 1100 9.0 7.0 7.0 15.0 15.0 9.5 14.5 7.5 14.0 13.5 11.4 14.0 9.0 10.5 12.0 9.0 7.0 8.0 8.0 12.0 8.0 Female Male Male Female Male Female Male Female Male Fsmale 909 73 20 310 1257 147 355 19 235 330 920 1170 275 965 1090 35 14 11 52 125 815 10.10 1.04 0.29 2.07 8.85 1.55 2.45 0.25 1.68 2.44 8.07 8.36 3.06 9.10 9.08 3.90 2.00 1.38 6.50 1.04 10.18 0.67 0.37 0.80 0.42 0.29 0.32 0.37 0.71 0.71 0.74 0.76 0.62 III II I II III II II I II II III III III III III I I I I I III 3453047 5321043 1424486 3516391 1777745 3420837 3571939 4450348 3896879 3087744 (230) (355) (150) (243) (127) (253) (313) (318) (371) (257) < > 2; D X > Z D 0 3; Vi 3291146 (411) No. of eggs per gram body weight of fish in parenthesis. BIOLOGY AND BIOMETRY OF MILKFISH 173 The correlation coefficient was calculated to be 0.887 and 0.867, indicating a high degree of correlation between total length and weight and standard length and weight (Fig. 1 and 2). The regression lines of morphometric cha-racters in relation to the standard length are presented in Fig. 3 and 4, based on the follow-ing equations. Snout length -19.8748 + 0.0644x Anal ray length 16.3441 + 0.0356x Eye diameter 0.3227 + 0.0586x Depth at caudal 38.7325 + 0.2I05x Post-orbital length 69.8354 4--0.0215x Inter-orbital space 12.2713 H- 0.078Ix Ventral fin length 47.4345 + 0.0498x Pectoral fin length 50.8509 -4- 0.0933x Dorsal ray length 837.8567 + 0.1073x Head depth 3.6488 + 0.1568x Head length 21.4988 -j- 0.183Ix Maximum body depth 57.5448 + 0.1515x Snout to dorsal origin -15.9901 + 0.4884x Snout to Ventral origin 6.2156 -f 0.5242x Snout to anal origin 62.1698 -^  0.8759x Fork length 133.2105 + 0.8992x Total length 324.4190 -r 0.941x The regression lines reveal that snout to anal origin grows faster than snout to ventral origin and snout to dorsal origin. Maximum body depth stands in the 6th place in growth rate among the above mentioned characters. Head length grows faster than the head depth. A comparison of the relative growth of fin rays shows that the dorsal ray length grows faster than the pectoral, the ventral fin and the anal ray length. Interorbital space grows better •00 STANOAflO LENGTH Imm) Fig. 4. Relationship between standard length and other morphometric characters of milkfish. Fig. 5. Percentage frequency of ova diameter for 10 Chanos chanos with date of capture and maturing stage. than postorbital length. Snout length, eye diameter and depth at caudal are having slower growth rate, when compared with other mor-phometric characters. The weight of heart, liver, stomach, gizkard, spleen and intestine ranged from 10 to 30, 45 174 V. GANDHI AND OTHERS to 190, 25 to 90, 44 to 215, 10 to 30 and 113 to to 250 g respectively. The length of the intes-tine varied between 2620 and 5350 mm (Table 2). Analysis of stomach contents of adult milk-fish (1069 - 1290 mm) revealed the presence predominantly of diatoms such as Coscinodis-cus, Thalassiothrix, Nitszchia, Navicula and matters ranged from 5 to 15, 5 to 10, 4 to 10, 4 to 10 and 5 to 35% respectively (Table 2). The sizes of the female fishes varied between 1069 and 1340 mm in total length and 7 and 15 kg in weight. Among the 16 females, 5 fishes attained stage II of sexual maturity, whereas 7 fishes were in stage III. The length TABLE 2. Weight {g) of internal organs and food items (% volume) of 8 adult milkfish Total length (mm) Weight of fish heart " liver " stomach " gizzard " spleen " intestine Length of intestine (mm) Diatoms Gastropods Copepods Foraminifera Mysids Digested matter 1 1290 14500 25 45 50 215 15 245 4240 50 10 5 10 5 20 2 1055 7500 10 100 25 70 13 85 2620 75 5 10 5 -5 3 1235 1400C 30 105 40 125 30 140 4200 80 -5 5 5 5 Fish No. 4 1120 9000 18 52 58 44 16 113 5350 75 5 10 --10 5 1069 7000 !5 60 60 40 13 150 4201 50 5 -5 5 35 6 1092 8000 15 63 90 45 10 165 4800 75 --5 10 10 7 1170 8000 20 70 90 45 10 230 4795 75 15 5 --5 8 1247 12000 25 190 70 240 20 250 5000 50 10 10 5 5 20 Average 1160 10000 20 86 60 103 17 172 4400 66 6 6 4 4 14 Pleurosigma along with other food items such as gastropods, copepods, foraminifera, mysids and digested matters. The percentage of dia-toms in the stomach content varied from 50 to 80%, whereas the percentage of gastropods, copepods, foraminifera, mysids and digested of ovaries ranged from 370 to 461 mm and the weight from 14 to 1257 g. The GSI values for stages I and II of maturity of fishes were between 1.04 and 6.50, and 1.55 and 2.45 res-pectively and that of fishes in stage III were between 8.07 and 10.18. The average diameter BIOLOGY AND BIOMETRY OF MILKFISH 175 of the ova ranged from 0.29 to 0.80 ram. The ova of the fish in stage II form a mode mainly at 0.37 mm in the range of 0.27 to 0.42 mm. On the other hand, ova of fishes in stage III showed a mode mainly at 0.78 mm in the range of 0.62 to 0.80 mm (Fig. 5). Further progres-sion in the ova diameter modes could not be traced due to lack of matured speciemns beyond the stage III. The sizes of male fishes ranged from 1042 to 1113 mm in the total length and 7 to 9 kg in length and log standard length have been plotted against log fecundity (Fig. 6 and 7). The relationship has been expressed as Log Fecundity = 2.0694+1.4364 Log Total Length (r^0.2407) and Log Fecundity = -0.4172+ 2.3289 Log Standard Length (r = 0.4693). The relationship of fecundity with weight of fish can be expressed as Fecundity = 1242 + 171.39 Weight of fish (Fig. 8). The occurrence of spawning population of milkfish and fry in the Gulf of Mannar and Fig. 6. Total length and fecundity relationship. weight. The length of testes varied between 173 and 489 mm and that of weight 11 and 275 g. The GSI values were 0.25 to 1.38, 1.04 and 3.06 for the I, II and III stage of maturity respectively. It has been observed from the fecundity estimation of ovaries of 11 fishes (1100 to 1340 mm), the maximum number of ova was 5321 thousand for the fish of total length 1270 mm and the minimum was 1424 thousand for the fish of total length 1175 mm. A linear rela-tionships has been shown when the log total Palk Bay during January - April (the primary spawning season) and October - December (the secondary spawning season) indicates the existence of two spawning seasons of milkfish. DISCUSSION It was observed that scales on lateral line, scales above lateral line and scales below lateral line varied between 79 and 88, 12 and 14 and 12 and 13 respectively whereas Liao (1971) accounted 83 to 95 scales on the lateral line, 12 to 15 above the lateral line and 14 to 17 176 V. GANDHI AND OTHERS below the lateral line while he analysed nine adult milkfishes (778 to 1040 mm in total length and 4.02 to 10.6 kg in weight). The maximum length and weight of fish dur-ing the present study were 1340 mm and 15 kg. Liao (1971) reported that the heaviest milkfish weighed 10.6 kg and the longest one measured 1040 mm whereas Tampi (1957) recorded the maximum length of 1260 mm and the maximum weight of 15.51 kg. It was observed that the maximum length and weight of ovaries were 461 mm and 1257g TB a——I z ar Fig. 7. Standard length and fecundity relationship. Biometrical study reveals that the total length has the fastest rate of growth and the snout has the slowest rate of growth when compared to other morphometric characters. It was found that the weight of the intestine was more than the weight of other internal organs. The present findings on food may be compared with the findings of Chacko (1945) who also reported the presence of Fragillaria, Rhizosolenia and Trichodesmium along with fish-eggs and larvae in the stomach content of milkfish. Tampi (1958) has recorded the food items of Hypinia, Gracilaria, Polysiphonia, Nitszchia, Pleurosigma and Grainmatophora along with spats of Pteria, small gastropods, copepods, crustacean larvae and nematodes in adult Chanos. t»9C « M M ' i i !><» i •OOB V \ • « • * 9 )0 • • 1 12 , ^--^ « .'• !t • • « • Fig. 8. Weight and fecundity relationship. with GSl of 8.85 and the average diameter of the ova ranged from 0.29 to 0.80 mm whereas Liao (1971) mentioned that the largest pair of ovaries weighed 2,64 with GSI of 24.91 and the dark yellow eggs were quite separate and mature with the average diameter of 1.12 x 1.23 mm. Tampi (1957) reported that the maximum length and weight of ovary were 438 mm and 1405 g. During the present study it was recorded that the maximum length and weight of the testes were 489 mm and 275 g with GSI of 3.06 whereas Liao (1971) had stated in his note that there was only one male fish among the nine adult milkfish and the greyish white gonad weighed only 18.1 g and was not mature at all. It was seen fro:-;-! the fecundity estimation of the ovaries of 11 fishes that the maximum and the minimum number of ova were 5321 and 1424 thousands as against tiie observation of Liao (1971) that the least number was 1319 thousand and the most was 3288 thousand eggs. Tampi (1957) recorded a maximum of 4896 and a minimum of 2118 thousand eggs. BIOLOGY AND BIOMETRY OF MILKFISH REFERENCES 177 CHACKO, P . I. 1945. On the food and alimentary canal of the milkfish Chanos chanos (Forsskal). Curr. Sci., 14: 242-243. 1950. Marine zooplankton from the waters around Kurusadi Island. Proc. Indian Acad. Sci. 31 (3): 162-174. • 1951. Survey of Pulicat Lake with special reference to availability of Chanos chanos. Prog. Rep. Madras Rural Piscicultural Scheme, 1950-51, pp. 33. 1952. Further investigations on the breeding habits and availability of spawner and young stages of milkfish Chanos chanos. Prog. Rep. Madras Rural Piscicultural Scheme 1951 - 52. pp 2-3. 1955. Spawning habits of the milkfish Chanos chanos (Forsskal) in coastal waters of Madras State, India. Proc. 42nd Ind. Sci. Congr. Part III Sect. VII. Page 307. (Abstract). , J. C. ABRAHAM AND R . ANDAL 1953. Report on a survey of the flora, fauna and fisheries of the Pulicat Lake, Madras State, India 1951-52. Centre Fresh Water Fish Biol. Station. Madras, 8: 1-8. AND M. S. MAHADEVAN 1956. Collection and culture of the milkfish CItanos chanos (Forsskal) in and around Krusadai Islands, with notes on its bio-logy. Govt. Madras Fish Statistics Report Year Book. 1954 - 55: 145 - 154. AND S. D. THOMAS 1962. Further obser-vations on the breeding of milkfish Chanos chanos in the inshore waters of Rameswaram. Proc. 49th Indian Sci. Congr. (Cuttack). Pt. 3, Abstract 390. LiAO, I. C. 1971. Notes on some adult milkfish from the coast of Southern Taiwan. Aquaculture, 1 (3): 1-10. MAMMEN, T . A . 1965. Transport of the fry and fin-gerlings of the milkfish Chanos chanos (Forsskal). J. Bombay Not. Hist., 63: 298-314. MoHAPATRA, P. 1966. On the occurrence of Clianos fry in the Mahanadhi Estuary. Bull. Orissa Fish. Res. Invest.. 1: l - I l . PANIKKAR, N . K . , P . R . S. TAMPI AND R . VISWANA-THAN 1952. On the fry of milkfish Chanos chanos (Forsskal). Curr. Sci., 21 (1): 18-19. RANGARAJAN, V. AND S. V. GANAPATHI 1949. Col-lection, acclimatization and transport of the fry and fingerlines of mi\k(hh Chanos chanos. Indian Fmg., 10: 368-374. SENTA, T . AND S. KUMAGAI 1977. Variation in ver-tebral number of the milkfish Chanos chanos collected from various localities. Bull. Fac. Fish., Nagasaki Univ., 43: 35-40. SILAS, E . G . , G . MOHANRAJ, V. GANDHI AND A. R. THIRUNAVUKKARASU 1980. Spawning ground of the milkfish and seasonal abundance of the fry along the east and southwest coasts of India. Proc. Symp. Coastal Aquaculture, MBAI, 3 : 916-932. TAMPI, P. R. S. 1957. Some observations on the reproduction of the milkfish Chanos chanos (Forsskal). Proc. Indian Acad. Sci., 46 (B): 254-273. 1958. On the food of Chanos chanos. Indian J. Fish., 5 : 107-117. DORAIRAJ, K . , G . MOHANRAJ, V. GANDHI, A. RAJU, V. S. RENGASWAMY AND J. X. RODRIGO 1984. On a potentially rich milkfish seed collection ground near Mandapam along with the methods of collection and transportation. Indian J. Fish., 2\ (2): 257-271. AND P . BENSAM 1976. Review of work programmes carried out in India on the biology of the milkfish Chanos chanos. Inter. Milkfish Work-shop Conference, May 19-22, 1976. Tigbauan, llloilo. Philippines. 

Biology and biometry of milkfish Chanos chanos (Forsskal)

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Biology and biometry of milkfish Chanos chanos (Forsskal)

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