SYNOPSIS of BIOLOGICAL DATA on ORIENTAL BONITO Sarda Orientalis (Temminck and Schlegel) 1842 (INDIAN OCEAN)

Home , Sarda (fish)

Species Synopsis No, 30 FAO Fisheries Biology Synopsis No, 73 FIb/S73 (Distribution restricted) SAST - Tuna

SYNOPSIS OF BIOLOGICAL DATA ON ORIENTAL BONITO Sarda orientalis (Temminck and Schlegel) 1842 (INDIAN OCEAN)

Exposé synôptique sur la biologie de la pélamide Sarda orientalis (Temminck et Schlegel) 1842 (Océan Indien)

Sinopsis sobre la biologra del bonito Sarda orientalis (Temminck y Schlegel 1842 (Océano Indico)

Prepared by E, G. SILAS Central Marine Fisheries Re,search Institute Mandapam Camp, India

FISHERIES DIVISION, BIOLOGY BRANCH FOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONS Rome, 1963

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1 IDENTITY Scombrìdae subfamily Scombrìnae, by Fraser-Brunner (1950'). 1.1 Taxonomy Species Sarda orientalis 1,1,1 Definition (Temminck and Schlegel)

Phylum VERTEBRATA Body proportions expressed as thow- Subphylum Craniata sandths of total length (measured as sug.- Superclass Gnathostomata gested by Marr and Schaefer, 1949) for 45 Series Pisces specimens ranging in ength from 80 mm to Class Teleostomi 497 mm collected from Vizhingam from the Subclass Actinopterygii south west coast of India are given in Suborder Scombroidea Table I. Subfamily Thunninae Genus Sarda Cuvier The disposition of the different Species Sarda orientalis organs of the vis cera in an adult male (Temminck and Schlegel) 1842 497 mm long is shown in Figure la, There is hardly any difference between thìs and those given for the ty.pical specimen of 1,1,2 Description S. orientalis from Japan by Godsil (1955) except that part of the gall-bladder lying Genus Sarda Cuvier 1829 alongsìde the intestine ìs also clearly seen, The right lobe of the liver is (Tautotype: Sconther sarda Linnaeus) slightly longer than the left. (Figure lb latter viewed from dorsally with lobes Synonyms: Pelamys Cuvier detached). The stomach is hidden from view, but is an elongate organ. Palamita Bonaparte, 1831, 1ype: Scomber sarda Linnaeus Silas (1962) has drawn attention to (Type designation by Jordan, changes in the shape and disposition of 1919) the visceral organs in specimens of S. orientalis ranging from 80 mm to about Creotroctes Gistel, 1848. 1400 mm, Air-bladder is wanting. Type: Scorñber sarda Linnaeus (Genus proposed to replace There are marked differences between Sarda Cuvier) juvenile and adult body colourations. According to Jones (1960) in the smallest "Body elongate, but rather short juvenile - 80 inni long - "The body bears and compressed in young specimens. twelve transverse bands which are broad Scales minute, and a small corselet more at the dorsal aspect and taper laterally or less distine1 The caudal keel is to become imperceptible on reaching the thick and naked, Teeth in both jaws are sides of the abdomen and above the anal, large, compressed, strongly curved in- One of the larger juvenile specimens ward but not trenchant. Near the anter.or measuring 158 mm in standard length and end of the lower jaw, the row of teeth is 174 mm in total length collected from is bent inwards and approaches the sym- Vizh,ngam.,.., The transverse bands physis. The vomer is toothless, but a referred to the previous stage have sub-. single.. row of rather strong curved teeth divided ìnto more or less hoizonta1 on the palatines. Tongue also toothless. streaks, which ultimately unite to give Many dark longitudinal more or less rìse to the lines so characteristic in oblique stripes are found in the dorsal the adult, In a specìmen 262 mm in total part of the body. Verbetrae of the length all the lines immediately above the caudal peduncle have lateral keels..,," pectoral fins have a1redy been formed as (Kishinouye, 1923). in the adult!!. (Figures 2a d 2'b), In specimens between 250 nun and 300mm The genus has been placed under the examined by the author from Vizhìngamon family Cybiìdae by Kishìnouye (1923); the south west coast of India., the sìdes under family Thunnidae, subfamily Sardi- of the body are characterised with 5to 7 nae by Fowler (1949); and under family

835 1:2 FIb/S73 Bonito

Table I

Body measurements expressed in thousandths of total length in different size groups of Sarda orientalis (Temminck and Schlegel) (After Silas, 1962)

Size groups (mm)

Characters 50 loo iso 200 201 250 251 300 351 - 400 451 500

Head Length 1 : 319 24:275-319 3:291-307 13:288-306 2:295312 2:294-299 (299) (299) (302) (303) f296) Snout to

origin of D1 1 : 310 23:271-315 3:291-311 13:300-311 2:298-312 2:294-310 (297) (300) (306) (305) (302) Snout to

origin of D2 1 : 610 24:532-619 3:569-599 13:593-626 2:588-604 2:590-608 (586) (587) (604) (596) (599) Snout to

origin of A 1 : 709 24:623-721 3:688-698 13:686-710 2:688-710 2:688-694 (684) (692) (699) (699) (691) Snout to

origin of P2 1 : 341 23:302-350 3:318-354 13:311-339 2:311-337 2:322-336 (330) (334) (328) (324) (329) Greatest depth.

of body 1 : 225 24:204-233 3:213-240 13:214-234 1:215 2:204-209 (218) (226) (224) (206,5)

Length of pl 1 : 101 24:67-121 3:103-124 13:115-126 2:127-131 2:124-137 (107) (112) (129) (129) (130,5)

Height of D2 i : 73 24:51-80 3:64-80 13:54-86 2:82-84 2:86-87 (64) (73) (70) (83) (86,5)

Height of A 1 : 78 23:58-81 3:60-71 13:64-79 2:80-87 2:86-91 (64) (66) (71) (83,5) (88,5) Diameter of iris i : 56 24:39-56 3:43-50 13:43-49 2:49-61 2:41-42 (43) (46) (46) (50) (41,5)

In each column the number of specimens is given followed byrange and the mean is indicated in prenthesis,

836 FIb/S73 Bonito 1:3

Figure 1, Sarda orientalis (Temminck and Schlegel)

Ventral view of Viscera in situ in a specimen 97 mm, (GB z gall-bladder; IN z intestine; LT left testes; LV liver; PC z caecal mass; RT right testes; SP z spleen.) Dorsal view of liver of same with right lobe detached showing relative lengths of the three lobes,

837 a) and b) Lateral view of specimen 80 mm and 158 mm showing Figure 2. juvenile colouration (after Jones, 1960). Sarda orientalis (Temminck and Schlegel) variation in early FIb/S73 Bonito 1:5

longitudinal stripes along the upper half Scarda chilensis war, orientalis running horizontally. Below the stripes, Steindachner and Doderlein, 1885 in the lower half of the body the inter- (* Typographic error for Sarda) rupted bars are still evident, The tips of the second dorsal, dorsal finlets, Pelamys chilensis (nec Cuvier) anal and anal finlets are whitish, Day, 1878,1889 The interspinous membrane of D1 is blackish throughout except for the narrow Sarda chilensis (Partim) basal area between the first eight spines Chabanaud, 1944; Barnard, 1927 which is light dusky. The outer margin of the pectoral is also whitish while Sarda chilensis (nec Cuvier) the pelvics are colourless, In formalin, Smith, 1949 dorsally the body is blackish while laterally it is dusky and ventrally yellowish Sarda orientalis Kishinouye, 1923 brown which in life appears more or less Fraser-Brunner, 1950 silvery. According to Day (1878) "The Godsil, 1955 upper half of the body with about eight Smith, 1961 broad, straight, blue lines passing back- Jones and Silas, wards and a little upwards, silvery below 1960, 1962 the lateral-line where, however, there Talbot, 1962 are similar lines but very faint," Sarda velox Meek and I-Iildebrand,l923 The corselet is not prominent, but well formed, its posterior extension Sarda orientalis serventyi reaching to below tip of pectorals. The Whitley, l9'45, 1962 lateral line takes a loop above level of mid-pectoral from which it gently slopes The species S. chilensis and S. to the caudal keel slightly undulating. orientalis have been confounded by some workers, but now it is quite clear that Posterior teeth on each side of the throughout the Indo-Pacific only two lower jaw are more prominent than those species, or two species complexes - naniely towards the symphysis as well as those the S. orientalis complex and the S. on each side of the upper jaw. However, chilensis complex - exist while a third more teeth appear to be present in the species, S. sarda is known only from the upper jaw (lo - 14 on each side) than in Atlantic and Mediterranean. S. orientalis the lower jaw (7 - 12 on each side), may easily bedistinguished from S. chilensis by the fewer gill rakers (total The gill rakers are small, the 8 - 13 versus 20 - 27) the absence of gill longest being only about half the length teeth (versus present in S. chilensis) and of the longest gill filament, other anatomical differences drawn 'attention to by Godsil (1955). But for the For osteological characters as well disjunct distribution, the available data as other anatomical features of S. orient-is insufficient to consider the Western aus, reference may be made to Krshinouye Australian representatives of the species ÇTWT3) and Godsil (1955). as distinct, although Whitley (1945) has used the subspecific naine S.o. serventyi For meristjc characters see section to denote the same. Godsil's (1955) work 1.3.1 throws more light on the clos0e affinity between S. orientalis as well as S. velox 1,2 Nomenclature and it is highly doubtful whether both' are not conspecific, We consider the 12,l Valid scientific name latter a synonym of S. orientalis,

Sarda orientalis (Temminck and 1,2.3 Standard common names, Schlegel) vernacular names

1,2,2 Synonyms See Table II

Pelamy.s orientalis Schlegel, 1850 GUnther, 1860

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Table II

Common and vernacular names

Country Standard Vernacular name(s) cOmmofl name

Australia (Western) Oriental bonito

India Oriental bonito Vari choora (Malayalam)

Mauritius - Seychelles Brasse-a-dents (Creole name)

Somali Sinufa

South Africa, Republic Bonito of

840 FIb/S73 Bonito 1:7

1.3 General variability Japanese waters, except that mentioned above for South Africa. Hardly any 1.3,1 Subspecific fragmenta- difference in the modal count of gill tion (races9 varieties9 rakers is seen, Godsil (1955) mentions hybrids) 3+1+8 12 as the modal count for the five specimens from Japanese waters examined Meristic counts by hirn. As will be seen from Table IV, the modal count of this character for Variability in meristic counts in specimens from Indian seas appears to specimens ranging in length from 80 nun be 3+9 12. to 497 mm from Vizhingam on the south west coast of India is given in Tables Differences in body colouration are III, IV and V. attributable to the different growth stages, Some of the changes from juvenile The meristic characters given above to adult may be seen in Figures, 2a, Zb, hardly throw any light on infra-specific and 3. variations. The only noteworthy difference appears to be the higher anal Albinism, melanism or rubism have finlet counts for the South African speci-not been observed, nor has natur.al inns (6 - 9) while in both Indian and hybridization ever been noted. Western Australian specimens it ranges from 5 - 7. The meristic data given for - Abnormalities the typical S. orientalis from Japanese waters by Kihinouye (1923) (D.l9, 15, Only two types of abnormalities were 7-8. A.15, 5-6, Gill rakers 4+9: met with namely, the occasional absence Vertebrae 25+20) and Godsil (1955) of a finlet (Figure 4a) or the marked (D.l8, 15-16, 9.A.15, 6-7, gill rakers shortening of the pectoral fins (Figure 2-3+1+8-9) (total 11-13 or 14) draw 4b). The latter may be compared with the attention to the absence of any marked normal condition as shown in Figure 4e. deviations from the typical forni from

841 Characters Meristic counts for specimens from Indian seas (After Silas, l962)/ Dorsal Second Dorsal Pectoral Anal rays Anal finlets range 17 18 19spines dorsal rays14 15 16 finlets rays Numberspecimens of 2 37 7

20 7 3 144 7 7+1 8 8+1 114.43

Table III 23 214 25 7 5 31 1 3 28 13 44 44 13 14 15 16 7.86 4 18 6 24.2 MN 2914,13 1/ For calculating mean, when dorsal and anal finlet counts are 5 5+1 6 6+1 7 given as 5+1, 6+1, 7+1 and 8+1, these are treated as 6, 7, 8 and 9 respectively.

2 3 36 2 1 44 6,02 Table IV Gill raker count for Sarda orientalis from three centres along the south west coast of India (After Silas, 1962) A No, of Locality Gill rakers on upper 1+8and 2+8lower 3+8 limbs L+8 1+9of outer2+9 3+9 gill L+9 arch 1+10 2+10 3+10 4+l0 specimens Cape Comorin ------2 1 - - - - 3 VizhingamCalicut -1 -2 -3 - 3 -6 1' 2 -2 -- -1 - -1 37 2 No, of specimens 1 2 3 - 3 6 18 3 1 4 1 42 Table IV (continued) B Locality Upper limb Gill rakers Lower limb VizhingamCalicutCape Comorin -1 2 3 8 9 10

- 9 - 21 2 -13 - 6 25 23 6

No of specìmens 9 25 6 -6 N 2 M 2,7 N 30 2 M 9 Table IV (continued) C Locality 9 10 Total No. of gill rakers 11 12 13 14 Cape Comorin - - 2 - Vi zhingarn i -S 9 15 2 16 -1 No.Calicut of specimens 1 5 9- 19 7 1 N : M 11.7 Meristic counts in Sarda orientalis from various parts of the Indian Ocean Table V Author and Area D1 D2 D2 filets P1 A A fIlets Gill rakers Munro,Smith,(South 19'481958 Africa) XVII-XIXXVII-XIX l-l6 15 6-97-8 22-27 - ii-iìi, 10-12 15 5-669 2-4+7-9 - + 8 ofSilas, India)(South(V/est 1962 Australia)west coast XVII-XIX 1'-l6 (exception-ally 9) 7-8 23-25 1316 5'7 24+610 ___%_' -na.s - V- I2tì,111 - ec- '_i '?' - . /\V -- 1-' :: : : . A ,B - AdultJuvenile showing 2'45 mmdifference long Figure(after in colourJones and pattern Silas on side of body Sarda orientalis (Temminck and Schlegel) IC l96O) (after Fraser-Brunner l95O) 1: 1+ FIb/S73 Bonito

Figure 'Sarda orientalis (Temrninck and ch1egel) Abncrinaìites:

Post anal part of body showing absence of dorsal finlet

Head and anterior part of body showing markedly short pectoral fin which may be compared with normal condition seen in (C)

8 FIb/S73 Bonito 2:1

2 DISTRIBUTION In south western Australia, Whitley 2,1 Delimitation of the total area (1962) remarks that it is found from of distribution and ecological "Rottnest Island in the north to as far characterization of this area east as Doubtful Island Bay. The normal northern limit appears to be Busselton" As shown in Figure 5 the areas of Further, speaking of the distributional occurrence are: east coast of South patterns of S. orientalis and S,chilensis, Africa; Seychelles; Somali and Gulf of Whitley (l96) remarks that: Aden; west coast of India and south west coast of Australia. Surprisingly "Only one occurs in the Indian Ocean, the species has not been reported from but both are found in the Pacific, In the the British East African coast nor from Pacific Ocean S. chilensis is a temperate Indonesian waters. More information is to warm-temperate species which exhibits needed about the spatial distribution of the phenomenon of bipolarity or antitro- this spec:es, of which large schools of phicality (vide Hubbs), The northern and juveniles and adults enter coastal waterssouthern hemisphere populations are separ.- seasonally. ated by S. orientalis (Syn, velox) which in this ocean has a pantropical distribu- 2,2 Differential distribution tion, Walford (1937Marine Game Fishes of the Pacific Cvast, p.21) believed that 2,2.1 Areas occupied by eggs the various forms were limited by physical larvae and other junior stages; factors and that th tropical form could annual variations for stages per- not stand cool waters. That this is by n sisting over two or more seasons. means the whole story is evident from the Areas occupied by adult stages: distribution pattern in the Indian Ocean, seasonal and annual variations of There are no forms of the chilensis these complex and inste°ad of being confined to the tropical belt as it is in the Pacific, - Eggs S, orientalis extends both north and south into more temperate waters - into Eggs of S. orientalis have not been waters where in corresponding parts of the identified from the plankton from any Pacific, a form of chilensis might be area although from the available mf orma-expected to occur, This indicates that tion on spawning of this species (Silas, temperature limitations need not prevent 1962; Rao, 1962) it is likely that eggs the occurrence of S. orientalis in any may be encountered in the plankton of particular habitat and that biological the coastal waters off south west India, competition from similar species has to b especially during the months June-August.reckoned with, It is clear that the See under 3.1,6 and 3,1,7, optimum environment of S. orientalis is the region of the tropics, from which - Larvae and other junior it can exclude the penetration of its stages allies of the chilensis complex. On the other hand they can successfully resist No information regarding larvae fromthe entry of orientalis into their optimum the Indian Ocean. environment, where S. orientalis alone occurs, it inhabits alike tropical and Juveniles 80 mm and òver have been temperate water". reported on by Jones (1960), and Silas (1962) from Cape Comorin, Vizhingam and Distributional data would indicate Calicut on the south west coast of India.the occurrence of S. orientalis at least Available data indicate that juveniles for a part of the year in coastal waters, are caught with shore seines in places when a seasonal fishery for it may exist, along the south west coast of India each as along the south west coast of India year mainly during October and November but to a lesser extent along the Somalia coast, Its occurrence in other areas is - areas occupied by adult stagesapparently sporadic or rare. seasonal and annual variations of these See under 2.1

8'49 20 o 6 80 100V 120' 140° C o 20 S..,. pp. -20 F 20 SARDA ORIENTALIS (TErUNcK AND SCt-:LEGEL) SPORADIC OR REGULAR 0CCURENCE .. FISHING AREA o o 400 Figure 5. 60 Map showing the distribution of Sarda onientalis in the Indian Ocean. 00 1000 1200 FIb/S73 Bonito 2:3

2,3 Behaviouristic and ecological determinants of the general limits of distribution and of the variations of these limits and of differential distribu- t ion

The temperature spectra for bonitos are given by Rosa and Leavastu (1962) as ranging between 12°C and 25°C nd by Kishinouye (1933) (for S, orientalis) as between 13.5°C and 23°C, From Figure 5, as well as the information given under section 2,2,1 it will be seen that iñ the Indian Ocean S, orientalis is found in the northern hemisphere between O°N and ca 37°S which means that it is found in temperatewaters in the southern hemisphere. Ori the south west coast of India, the occurrence of fully mature adults (June-September) precedes the appearance of juveniles and half-growns (October-November) and it is likely that these incursions could be both for feeding as well as spawning (Silas, 1962).

851 FIb/S73 Bonito 3:1

3 BIONOMICS - Relation of gonad size and egg number to body size and 3.1 Reproduction to age

3.1,1 Sexuality (hermaphroditism Available data are summarised in heterosexuality, inter- Tables VI and VII, Total number of ova sexuality) produced during the breeding season was found to show an increase with the size S, orien-talis is heterosexual, No of the fish by Rao (1962), When evalu- exteral1y observable characters are ated in terms of number of eggs per 1,000 known to help distinguish males and g of body weight, (Table VI) this was females. not found to be the case for the specimens examined by Silas (1962). 3.1.2 Maturity (age and size) 3.1,6 Spawning Silas (1962) reports that maturing ovaries containing transparent ova were - Spawning seasons (beginning, seen in specimens above 386 mm while betwe- end, peak) n 480 mm and 605 mm most of the specimens collected in August-September 1960 Among several ovaries of S. orient- and 1961, were in ripe running condition alis examined by Rao (1962) from Vizhingam or had already spawned, some showing during 1959-1960, only four were in ripe signs of recovering. However, the age of running condition, The definite duration the investigated mature specimens is not of the spawning season is not yet fully known. known, although Rao (1962) opines that like Euthynnus affinis and Auxis thazard 3.1.3 Mating (monogamous, poly- the oriental bohito also spawns in the gamous, promis cuou&) localwaters (off Vizhingarn, south west coast of India) "from April to September Polygamous. No information is avail-and possibly in other months of the year able about prespawning or spawning with a peak in July - August". Supporting behaviour. evidence is also given by Silas (1962) by the collection of fish with ripe ovaries 3.1.4 Fertilizatipn (internal, or partly spent ovaries from the same area external) in 1960 and 1961 during the months of August - September. Larval collections External. As in the case of other are wanting. However, the occurrence of scombroids, the eggs should be pelagic. early juveniles in this area during October - November reported on by 3.1.5 Fecundity Jones (1960) and Silas (1962) is also interesting. Two attempts (Silas, 1962 and Rao, 1962) have been made in estimating the - Number of spawning per year, fecundity of the oriental bonito from frequency Indian seas, and the data are summarised in Tables VI and VII. The fish is said "The study of ova diameter frequency to attain at least a metre in length but polygons of ripe spawning (or rJpe run- the estLnates are only of smaller sizes ning) and recovering ovaries indicates ranging from 386 mm - 605 mm; a larger that in the most advanced stage (ripe - number of eggs may be expected in still stage V (Figure 7, I) the most advanced larger specimens. The number of ova per mode containing ripe ova is the most spawning in two specimens with ripe prominent, while more than one mode is ovaries is estimated by Silas (1962) as seen for the maturing ova. In the ripe 0.08 - 0,15 million while Rao (1962) running condition (spawning - stage VI) found this to vary from 0.21 - 0,28 (Figure 7, II and III) the most advanced million in four specimens. The total mode is seen to be completely separated number of ova produced during the breed- from the maturing eggs which in turn show ing season has been estimated by these two or more modes, Three recovering workers as 0,24 to 0.64 million and ovaries (stage VII) (Figure 7, IV, V and 0,91 to 1.15 million respectively, VI) in which there are indications of See Figures 6a to 6e for illustrations previous spawning by the presence of of ripe ovary. degenerate large eggs also showthe most

852 Counts of ovarial eggs in five mature specimens of Sarda orientalis from Vizliingam, south west coast of India (After Silas, 1962) Table VI N) TotalDate oflength collection (mm) 13-9-61 20-8-60 8-9-60 l-8-60 25-8-60

Body weight (g)

No.eggsWeight of incountable of gram ovaries of ovaria]. roe (g) No.spawned (inof eggsthousands) in inpera seasonovaries 100 to gbe of body weight (in thousands)

No.advanced of eggs mode of thein grammost of No.advancedroe of eggs mode of thein ovariesmost 386

Remarks 53.650 899

4533

2432 2705 -

1LI'+6 490 spent- - recovering? 85.720

45253879 2682 -

maturing - 89,1407550 -

5126 - 88248 990 545. 890072.750 - ripe running?

6475 - 155030 2131 84.400 605 - ripe running 4890

3980 160 - spent?)(partiallypawning 1.3024 Fish Number SO, 10 SO, 13 So. 16 So, 11 Fish lengthweight (m)(g) 1. l'4 51.0 1.37 54.0 L 83 55.0 2 06 TotalNumberper spawningnumber of ova of produced(millions) ova 0.21 0.23 0.25 0,28 produced during the breed- 0.91 0.93 1,03 1.15

Estimated number of ova producedbreeding per spawning season andby individualduring the fish of Sarda orientalis (After Rao, 1962) Table VII ing(millions) season (fecundity) 3:4 FIb/S73 Bonito

Figure 6. Sarda orientalis (Temminck and Schleì)

(A) and (B) Cross section of ovaries of specimens 368 mm and L9O mm respectively showing distribution of larger transparent ova thròugh- out the ovary and the formation of the central lumen into which the ripe eggs migrate. Cross section of ovary of specimen 605 mm showing central lumen from which ripe ova have been removed,

Sanie before removal of ripe ova, () Ovary of same specimen (part of right ovary removed for showing cross sections (C) and (D).

855 FIb/S73 Bonito 3:5

40 30

to 00> 020 Io w

w 20 Q

IO 20 30 40 50 60 70 80 90 lOO MICROMETER DIVISIONS

44 88 13 176 MILL IME TE R S DIAMETER OF OVA

Figure 7. Sarda orientalis (Temminck and Schlegel)

Frequency polygons of diameters of the eggs in the ovary of 6 mature specimenscol- lected at Vizhingam. (The combined frequency is also shown). (After Silas, 1962) 856 3:6 FIb/S73 Bonito

advanced mode as the most prominent one 318 Egg structures size as seen in stage V (Figure 7 I). The hatching types parasites combined frequency (Figure 7 VII) shows and predators the most advanced mode containing the ripe ova to be well demarcated from matur "The ripe ovum of S orientalis is Ing batches, which in turn show several very large, In fresh condition they are modes. If it were to be presumed that spherical, more or less transparent with during a spawning season the ova over 5 homogenous yolk while in preserved mater. microdjvjsions or about 0.11 mm are to ial the ovum appeared translucent and mature and spawn, it is clear that in slightly pale yellow in colour, Its dia- S, orientalis all the ova do not ripen at meter in fresh and preserved condition oneTime, but as seen by the number of averaged 1,13 mm and 1,04 mm respectively, modes, mature in batches, Spawning Each ripe ovum contained a single, spheri- season may be an extended one and the cal and colourless oil globule whiöh has preliminary data suggest fractional an average diameter of 0.29mm," (Rao, spawning during a season", (Silas, 1962). 1962). Silas (1962) found ripe ova with 1,33 ¡mn diameter which had burst from fol- Fao (1962) has also arrived at some- lides and were lying loose in the lumen what similar conclusions after studying of the ovary to have a cluster ofma11 the ova diameter frequency of ripe run- oil globules at one of the poles (Figures ning ovaries of two specimens of S. 8B and 8C) their number varying between 3 orientalis from Vizhingam, and 14 with an average of about 8 and ranging in diameter from 0,06 mm to 0,23 mm, The smallest specimen in the sample Several eggs had oil globules of the same examined by Silas (1962) which had a few size as those shown in the above figures, large eggs, probably remenants of an The structure of the eggs does not indica1 earlier batch of eggs spawned was 386 mm.that they are degenerate, but their dia- This would need confirmation, but if sub- meters were slightly more than that found sequent observations could corroborate for ripe eggs by Rao (1962) and this coin- this then it is likely that the species bined with the number of oil globules may attains maturity and is ready for spawn-. indicate that they are eggs retained over ing even before attaining 386 mm, The a longer period and are próbably in the ripe running specimens examined were 49 early stages of resorption. Eggs partly cm to 60,5 cm (Silas, 1962), Four speci-. degenerate collected from recovering ovar- mens examined by Rao (1962) were between ies show scattered oil globules of differ- 48 cm to 55 cm, ent sizes. An early ripe ovum (diámeter 0,9 inni)in which the oil globule is not According to Silas (1962) the spent discernible is shown in Figure 8A, and recovering ovaries had very few large degenerate eggs of the last spawned batch, 3,2 Larval history

3,1,7 Spawning grounds 3.2,1 Account of embryonic and juvenile life (prelarva, - Coastal (surface, vegetation, larva, postlarva, shore, shoal, sand, shelter); juvenile) bottom No information is available about - Oceanic (surface, bottom) embryonic life, nor on prelarva, larva and post larva, Capture of females wìth ripe, ripe running and recovering ovaries along the Earliest juvenile on record is 80 mm south west coast of India (Trivandrum to (total length including caudal 8) mm) fi Cape Comorin) indicates that the sea off ured and described by Jones (1960) (Figure this coast is one of the spawning grounds 2a). For colouration see under 1,1,2, of this species, No information is Variations in body colour in the juvenile available from other areas of the Indian are indicated in Figures 2a, 2b and 3a, Ocean, Spawning grounds may extend from Most of the juveniles caught in shore coastal to oceanic situation, and it may seines along the south west coast of India not be wrong to ¿enote the species as a range between 150 mm to 290 mm, neritic pelagic spawner,

857 FIb/S73 Bonito 37

Figure 8. Sarda orientalis (Temminck and Schlegel) Mature ovum with diameter of 0,9 mm (Stage V).

and (C) Ripe ova, diameter 1.3 mm lying loose in the kumen of the ovary showing cluster of oil globules (each about 0,15 mm in diameter) at one pole (stage VI) (after Silas, 1962)

858 3:8 FIb/S73 Bonito

- Feeding 3.3,6 Greatest size

Jones (1960) remarks that the food of Large specimens caught in shore seines the juvenile S, orientalis consists of lar-and drift nets off south west coast of val and juvenfleTcrustaceans. India are less than 700 mm, However, the Kumaran (l962Y found that Anchoviella tri fish is said to attain a larger size as was the most common fish that occurred'i Smith (l9B) mentions under S, chilensis the stomach contents of juveniles, while ( S, orientalis) "Attains at least 10 stomatopod larvae were present as a minor inc1es", item. Regarding Japanese specimens Parental care Kishinouye (1923) mentions "Grow to a length of about 80 cm and to a weight of The species as other scömbroids may 1,5 g to 3,0 g." not exhibit any parantal care,

- Parasites and predators 3. Nitrition and growth See undr 3,3,5 for parasites collected from juveniles and adults, No informa- 3,t.2 Food (type, volume) tion is'available on predators. Jones (1960) remarks that adults feed 3,3 on young and small sized fishes, crusta- Adult history ceans and squids. 3,3,3 Competitors 3.5 Behaviour During the season when juveniles are caught along the south west coast of India 3,5,1 Migration and local large numbers of juveniles of the little movements tunny, Euthynnus a, affinis are also See under caught along with them in shore seines, Information is wanting, Adult S. orientalis are very often caught 3,5.2, in this area along with adult E, affinis, 3,5,2 Schooling Auxis thazard, Kishinoella tonggol and Scomberornorus spp. in shore seines as well as gill nets, Schools of adults and young appear A certain amount of competi-along the south west coast of India, tion for food may be expected between these species, between Trivandrum and Cape Comorin from about July to December, the schools of juveniles appearing especially in October- 3,3,5 Parasites and diseases November when they enter bays and inshore areas and are caught in shore seines, Silas (1962) records a species of monogenetic trematode (Capsala sp,) from More information is needed. the gills, palate and inner wall of the operculum of juvenile and adult S, 3,5,3, Reproductive habits orientalis collected from Vizhingam, south west coast of India. Silas and Ummerkutty No information except data given (l962) have recorded the parasitic copepodsunder 3,1,6, Caligus bonito Wilson (adults and chalimus stages), and Parapetalus sp. from the gills and buccal cavity of juveniles and adults collected from the same area,

Information is not available on diseases,

859 FIb/S73 Bonito 4:1

'4 POPULATION (STOCK)

'4.2 Size and density

L1.,2l Average size

Average size of adults caught at Vizhingam and other centres along the south west coast of India is about 1+5 cm. More information is wanting.

4.6 Relation of population to com- munity and ecosystem, biological production, etc.

The term neritic-pelagicmay beap plied to the habitat of Sorientalise Within this realm, it may be said to belong to the surface and mid-water com- munity as most other scombroìds The area of occurrence of S orientalisoff south west coast of India is an area of high productivity Inthis area, the fishery for this species also coincides with that for the little tunny Euthynnus affinis affinis (Cantor), the northern bluefin or Indian longtailed tunny Kishinoella tongo1, and few other scorn- broids, especially Scombromorus spp Most of these prey on smaller tishes and as such it is likely that a certain amount of competition may exist between these species More information is ned- ed,

860 FIb/S73 Bonito 5:1

S EXPLOITATION 5,3 Fìshing seasons

5,1 Fishing equipment 53,lGeneral pattern of fishing season 5,1,1 Fishing gear Along the south west coast of India Adult orientalis are usually the available information points to the caught in drift nets (gill nets) and fishing season for adult S. orientalis also shore seines when schools enter to be from about July to epte]iber, bays along the south west coast of although stray specimens may be caught India, Juveniles are also caught in during the months of April, May and June, shore seines and gill nets, Along the It is likely that there may be changes in South African coast, where this is the pattern of the fishing season from regarded as a sport fish, Smith (198- year to year within this period, 1961) remarks that the fish "fights well when hooked", The species has 5,3,2 Duration of fishing also been taken by trolling (Wheeler season and Ommanney, l953) Se under 5,3,1, 5,1,2 Fishing boats

No special boats appear to be in use for fishing for the oriental bonito,

5,2 Fishing areas 5,2,1 General geographic distribution

See under 2,1, The only areas where the oriental bonito forms a seas onal minor fishery is along the south west coast of India and as indicated by Rosa and Laevastu (1961) along the Somali coast of Africa,

5,2,2 Geographic ranges (latitudes, distances from coast etc,)

Along the west coast of India, stray catches of S, orientalis may be made from various localities from as far north as Ratnagiri, but regular catches are only made south of Trivan drsim to Cape Comorin (Ca,77°E 775O' E; 8°N to Ca, 8°5B) where fishirg is carried out as far as 20 km from the coast, Information is not available about the other areas,

5,2,3 Depth ranges

Along the south west coast of India fishing is carried out in waters less than 200 m deep,

861