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 83'4
Transcript
Species Synopsis No, 30FAO Fisheries Biology Synopsis No, 73 FIb/S73(Distribution restricted) SAST - Tuna
SYNOPSIS OF BIOLOGICAL DATA ON ORIENTAL BONITOSarda orientalis (Temminck and Schlegel) 1842 (INDIAN OCEAN)
Exposé synôptique sur la biologie de la pélamideSarda orientalis (Temminck et Schlegel) 1842 (Océan Indien)
Sinopsis sobre la biologra del bonitoSarda orientalis (Temminck y Schlegel 1842 (Océano Indico)
Prepared byE, G. SILAS
Central Marine Fisheries Re,search InstituteMandapam Camp, India
FISHERIES DIVISION, BIOLOGY BRANCHFOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSRome, 1963
Palamita Bonaparte, 1831,1ype: Scomber sarda Linnaeus(Type designation by Jordan,1919)
Creotroctes Gistel, 1848.Type: Scorñber sarda Linnaeus(Genus proposed to replaceSarda Cuvier)
"Body elongate, but rather shortand compressed in young specimens.Scales minute, and a small corselet moreor less distine1 The caudal keel isthick and naked, Teeth in both jaws arelarge, compressed, strongly curved in-ward but not trenchant. Near the anter.orend of the lower jaw, the row of teeth isis bent inwards and approaches the sym-physis. The vomer is toothless, but asingle.. row of rather strong curved teethon the palatines. Tongue also toothless.Many dark longitudinal more or lessoblique stripes are found in the dorsalpart of the body. Verbetrae of thecaudal peduncle have lateral keels..,,"(Kishinouye, 1923).
The genus has been placed under thefamily Cybiìdae by Kishìnouye (1923);under family Thunnidae, subfamily Sardi-nae by Fowler (1949); and under family
Body proportions expressed as thow-sandths of total length (measured as sug.-gested by Marr and Schaefer, 1949) for 45specimens ranging in ength from 80 mm to497 mm collected from Vizhingam from thesouth west coast of India are given inTable I.
The disposition of the differentorgans of the vis cera in an adult male497 mm long is shown in Figure la, Thereis hardly any difference between thìs andthose given for the ty.pical specimen ofS. orientalis from Japan by Godsil (1955)except that part of the gall-bladder lyingalongsìde the intestine ìs also clearlyseen, The right lobe of the liver isslightly longer than the left. (Figurelb latter viewed from dorsally with lobesdetached). The stomach is hidden fromview, but is an elongate organ.
Silas (1962) has drawn attention tochanges in the shape and disposition ofthe visceral organs in specimens ofS. orientalis ranging from 80 mm to about1400 mm, Air-bladder is wanting.
There are marked differences betweenjuvenile and adult body colourations.According to Jones (1960) in the smallestjuvenile - 80 inni long - "The body bearstwelve transverse bands which are broadat the dorsal aspect and taper laterallyto become imperceptible on reaching thesides of the abdomen and above the anal,One of the larger juvenile specimensmeasuring 158 mm in standard length and174 mm in total length collected fromVizh,ngam.,.., The transverse bandsreferred to the previous stage have sub-.divided ìnto more or less hoizonta1streaks, which ultimately unite to giverìse to the lines so characteristic inthe adult, In a specìmen 262 mm in totallength all the lines immediately above thepectoral fins have a1redy been formed asin the adult!!. (Figures 2a d 2'b),In specimens between 250 nun and 300 mmexamined by the author from Vizhìngam onthe south west coast of India., the sìdesof the body are characterised with 5 to 7
Table I
Body measurements expressed in thousandths of total length in differentsize groups of Sarda orientalis (Temminck and Schlegel)
(After Silas, 1962)
In each column the number of specimens is given followed by range and themean is indicated in prenthesis,
836
Size groups(mm)
Characters 50 loo iso 200 201 250 251 300 351 - 400 451 500
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 ofiris i : 56 24:39-56 3:43-50 13:43-49 2:49-61 2:41-42
(43) (46) (46) (50) (41,5)
1:2 FIb/S73 Bonito
FIb/S73 Bonito 1:3
837
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; LVliver; PC z caecal mass; RT right testes; SP z spleen.)
Dorsal view of liver of same with right lobe detached showingrelative lengths of the three lobes,
Figure 2.
Sarda orientalis (Temminck and Schlegel)
a) and b) Lateral view of specimen 80 mm and 158 mm showing
variation in early
juvenile colouration (after Jones, 1960).
longitudinal stripes along the upper halfrunning horizontally. Below the stripes,in the lower half of the body the inter-rupted bars are still evident, The tipsof the second dorsal, dorsal finlets,anal and anal finlets are whitish,The interspinous membrane of D1 is black-ish throughout except for the narrowbasal area between the first eight spineswhich is light dusky. The outer marginof the pectoral is also whitish whilethe pelvics are colourless, In formalin,dorsally the body is blackish while later-ally it is dusky and ventrally yellowishbrown which in life appears more or lesssilvery. According to Day (1878) "Theupper half of the body with about eightbroad, straight, blue lines passing back-wards and a little upwards, silvery belowthe lateral-line where, however, thereare similar lines but very faint,"
The corselet is not prominent, butwell formed, its posterior extensionreaching to below tip of pectorals. Thelateral line takes a loop above level ofmid-pectoral from which it gently slopesto the caudal keel slightly undulating.
Posterior teeth on each side of thelower jaw are more prominent than thosetowards the symphysis as well as thoseon each side of the upper jaw. However,more teeth appear to be present in theupper jaw (lo - 14 on each side) than inthe lower jaw (7 - 12 on each side),
The gill rakers are small, thelongest being only about half the lengthof the longest gill filament,
For osteological characters as wellas other anatomical features of S. orient-aus, reference may be made to KrshinouyeÇTWT3) and Godsil (1955).
For meristjc characters see section1.3.1
1,2 Nomenclature
12,l Valid scientific name
Sarda orientalis (Temminck andSchlegel)
1,2,2 Synonyms
Pelamy.s orientalis Schlegel, 1850GUnther, 1860
839
FIb/S73 Bonito 1:5
Scarda chilensis war, orientalisSteindachner and Doderlein, 1885(* Typographic error for Sarda)
Sarda orientalis Kishinouye, 1923Fraser-Brunner, 1950Godsil, 1955Smith, 1961Jones and Silas,
1960, 1962Talbot, 1962
Sarda velox Meek and I-Iildebrand,l923
Sarda orientalis serventyiWhitley, l9'45, 1962
The species S. chilensis and S.orientalis have been confounded by someworkers, but now it is quite clear thatthroughout the Indo-Pacific only twospecies, or two species complexes - nanielythe S. orientalis complex and the S.chilensis complex - exist while a thirdspecies, S. sarda is known only from theAtlantic and Mediterranean. S. orientalismay easily be distinguished from S.chilensis by the fewer gill rakers (total8 - 13 versus 20 - 27) the absence of gillteeth (versus present in S. chilensis) andother anatomical differences drawn 'atten-tion to by Godsil (1955). But for thedisjunct distribution, the available datais insufficient to consider the WesternAustralian representatives of the speciesas distinct, although Whitley (1945) hasused the subspecific naine S.o. serventyito denote the same. Godsil's (1955) workthrows more light on the clos0e affinitybetween S. orientalis as well as S. veloxand it is highly doubtful whether both'are not conspecific, We consider thelatter a synonym of S. orientalis,
Variability in meristic counts inspecimens ranging in length from 80 nunto 497 mm from Vizhingam on the southwest coast of India is given in TablesIII, IV and V.
The meristic characters given abovehardly throw any light on infra-specificvariations. The only noteworthy dif-ference appears to be the higher analfinlet counts for the South African speci-inns (6 - 9) while in both Indian andWestern Australian specimens it rangesfrom 5 - 7. The meristic data given forthe typical S. orientalis from Japanesewaters by Kihinouye (1923) (D.l9, 15,7-8. A.15, 5-6, Gill rakers 4+9:Vertebrae 25+20) and Godsil (1955)(D.l8, 15-16, 9.A.15, 6-7, gill rakers2-3+1+8-9) (total 11-13 or 14) drawattention to the absence of any markeddeviations from the typical forni from
841
Japanese waters, except that mentionedabove for South Africa. Hardly anydifference in the modal count of gillrakers is seen, Godsil (1955) mentions3+1+8 12 as the modal count for the fivespecimens from Japanese waters examinedby hirn. As will be seen from Table IV,the modal count of this character forspecimens from Indian seas appears tobe 3+9 12.
Differences in body colouration areattributable to the different growthstages, Some of the changes from juvenileto adult may be seen in Figures, 2a, Zb,and 3.
Albinism, melanism or rubism havenot been observed, nor has natur.alhybridization ever been noted.
- Abnormalities
Only two types of abnormalities weremet with namely, the occasional absenceof a finlet (Figure 4a) or the markedshortening of the pectoral fins (Figure4b). The latter may be compared with thenormal condition as shown in Figure 4e.
1:7
Characters
range
Dorsal
Second
Dorsal
Pectoral
Anal rays
Anal finlets
spines
dorsal rays
finlets
rays
17 18 19
Number of
specimens
237
7
Meristic counts for specimens from Indian seas
(After Silas, l962)/
14 15 16
20
73
144
114.43
7 7+1 8 8+1
75
31
1
44 7.86
Table III 23 214 25
3 28 13
4424.2
13 14 15 16
4 18
6
N29
M14,13
1/
For calculating mean, when dorsal and anal finlet counts are
given as 5+1, 6+1, 7+1 and 8+1, these are treated as 6, 7, 8
and 9 respectively.
5 5+1 6 6+1 7
23 36
21
446,02
Table IV
Gill raker count for Sarda orientalis from three centres
along the south west coast of India
(After Silas, 1962)
A
Locality
Gill rakers on upper and lower limbs of outer gill arch
Meristic counts in Sarda orientalis from various parts
of the Indian Ocean
Author and Area
D1
D2
D2 filets
P1
AA fIlets
Gill rakers
Smith, 19'48
(South Africa)
XVII-XIX
l-l6
6-9
-ii-iìi,
10-12
69
- + 8
Munro, 1958
XVII-XIX
15
7-8
22-27
15
5-6
2-4+7-9
(V/est Australia)
Silas, 1962
XVII-XIX
1'-l6
7-8
23-25
1316
5'7
24+610
(South west coast
of India)
(exception-
ally 9)
I2tì,
111
___%_'
-na.
s-
V-
-'_
i'?
'-
/\--
1-'
ec-
V::
: :.
.
A
,-
ICB
Figure
Sarda orientalis (Temminck and Schlegel)
Juvenile 2'45 mm long (after Jones and Silas
l96O)
Adult showing difference in colour pattern on side of body
(after Fraser-Brunner
l95O)
8
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 finwhich may be compared with normal condition seen in (C)
1: 1+ FIb/S73 Bonito
2 DISTRIBUTION
2,1 Delimitation of the total areaof distribution and ecologicalcharacterization of this area
As shown in Figure 5 the areas ofoccurrence are: east coast of SouthAfrica; Seychelles; Somali and Gulf ofAden; west coast of India and southwest coast of Australia. Surprisinglythe species has not been reported fromthe British East African coast nor fromIndonesian waters. More information isneeded about the spatial distribution ofthis spec:es, of which large schools ofjuveniles and adults enter coastal watersseasonally.
2,2 Differential distribution
2,2.1 Areas occupied by eggslarvae and other junior stages;annual variations for stages per-sisting over two or more seasons.Areas occupied by adult stages:seasonal and annual variations ofthese
- Eggs
Eggs of S. orientalis have not beenidentified from the plankton from anyarea although from the available mf orma-tion on spawning of this species (Silas,1962; Rao, 1962) it is likely that eggsmay be encountered in the plankton ofthe coastal waters off south west India,especially during the months June-August.See under 3.1,6 and 3,1,7,
- Larvae and other juniorstages
No information regarding larvae fromthe Indian Ocean.
Juveniles 80 mm and òver have beenreported on by Jones (1960), and Silas(1962) from Cape Comorin, Vizhingam andCalicut on the south west coast of India.Available data indicate that juvenilesare caught with shore seines in placesalong the south west coast of India eachyear mainly during October and November
- areas occupied by adult stagesseasonal and annual variationsof these
See under 2.1
8'49
In south western Australia, Whitley(1962) remarks that it is found from"Rottnest Island in the north to as fareast as Doubtful Island Bay. The normalnorthern limit appears to be Busselton"Further, speaking of the distributionalpatterns of S. orientalis and S,chilensis,Whitley (l96) remarks that:
"Only one occurs in the Indian Ocean,but both are found in the Pacific, In thePacific Ocean S. chilensis is a temperateto warm-temperate species which exhibitsthe phenomenon of bipolarity or antitro-phicality (vide Hubbs), The northern andsouthern hemisphere populations are separ.-ated by S. orientalis (Syn, velox) whichin this ocean has a pantropical distribu-tion, Walford (1937 Marine Game Fishesof the Pacific Cvast, p.21) believed thatthe various forms were limited by physicalfactors and that th tropical form couldnot stand cool waters. That this is by nmeans the whole story is evident from thedistribution pattern in the Indian Ocean,There are no forms of the chilensiscomplex and inste°ad of being confined tothe tropical belt as it is in the Pacific,S, orientalis extends both north andsouth into more temperate waters - intowaters where in corresponding parts of thePacific, a form of chilensis might beexpected to occur, This indicates thattemperature limitations need not preventthe occurrence of S. orientalis in anyparticular habitat and that biologicalcompetition from similar species has to breckoned with, It is clear that theoptimum environment of S. orientalisis the region of the tropics, from whichit can exclude the penetration of itsallies of the chilensis complex. On theother hand they can successfully resistthe entry of orientalis into their optimumenvironment, where S. orientalis aloneoccurs, it inhabits alike tropical andtemperate water".
Distributional data would indicatethe occurrence of S. orientalis at leastfor a part of the year in coastal waters,when a seasonal fishery for it may exist,as along the south west coast of Indiabut to a lesser extent along the Somaliacoast, Its occurrence in other areas isapparently sporadic or rare.
FIb/S73 Bonito 2:1
C
20
o20
SA
RD
A O
RIE
NT
ALI
S (
TE
rUN
cK A
ND
SC
t-:L
EG
EL)
.. F
ISH
ING
AR
EA
SP
OR
AD
IC O
R R
EG
ULA
R 0
CC
UR
EN
CE
400
60
F
120'
pp.
S..,
.
Figure 5.
Map showing the distribution of Sarda onientalis in the Indian Ocean.
140°
o
-20 20
o o
680
100V
0010
0012
00
2,3 Behaviouristic and ecologicaldeterminants of the generallimits of distribution and ofthe variations of these limitsand of differential distribu-t ion
The temperature spectra for bonitosare given by Rosa and Leavastu (1962) asranging between 12°C and 25°C nd byKishinouye (1933) (for S, orientalis) asbetween 13.5°C and 23°C, From Figure 5,as well as the information given undersection 2,2,1 it will be seen that iñ theIndian Ocean S, orientalis is found inthe northern hemisphere between O°N andca 37°S which means that it is found intemperate waters in the southern hemi-sphere. Ori the south west coast ofIndia, the occurrence of fully matureadults (June-September) precedes theappearance of juveniles and half-growns(October-November) and it is likely thatthese incursions could be both for feed-ing as well as spawning (Silas, 1962).
S, orien-talis is heterosexual, Noexteral1y observable characters areknown to help distinguish males andfemales.
3.1.2 Maturity (age and size)
Silas (1962) reports that maturingovaries containing transparent ova wereseen in specimens above 386 mm while betwe-n 480 mm and 605 mm most of the speci-
mens collected in August-September 1960and 1961, were in ripe running conditionor had already spawned, some showingsigns of recovering. However, the age ofthe investigated mature specimens is notknown.
Polygamous. No information is avail-able about prespawning or spawningbehaviour.
3.1.4 Fertilizatipn (internal,external)
External. As in the case of otherscombroids, the eggs should be pelagic.
3.1.5 Fecundity
Two attempts (Silas, 1962 and Rao,1962) have been made in estimating thefecundity of the oriental bonito fromIndian seas, and the data are summarisedin Tables VI and VII. The fish is saidto attain at least a metre in length butthe estLnates are only of smaller sizesranging from 386 mm - 605 mm; a largernumber of eggs may be expected in stilllarger specimens. The number of ova perspawning in two specimens with ripeovaries is estimated by Silas (1962) as0.08 - 0,15 million while Rao (1962)found this to vary from 0.21 - 0,28million in four specimens. The totalnumber of ova produced during the breed-ing season has been estimated by theseworkers as 0,24 to 0.64 million and0,91 to 1.15 million respectively,See Figures 6a to 6e for illustrationsof ripe ovary.
852
- Relation of gonad size andegg number to body size andto age
Available data are summarised inTables VI and VII, Total number of ovaproduced during the breeding season wasfound to show an increase with the sizeof the fish by Rao (1962), When evalu-ated in terms of number of eggs per 1,000g of body weight, (Table VI) this wasnot found to be the case for the specimensexamined by Silas (1962).
3.1,6 Spawning
- Spawning seasons (beginning,end, peak)
Among several ovaries of S. orient-alis examined by Rao (1962) from Vizhingamduring 1959-1960, only four were in riperunning condition, The definite durationof the spawning season is not yet fullyknown, although Rao (1962) opines thatlike Euthynnus affinis and Auxis thazardthe oriental bohito also spawns in thelocalwaters (off Vizhingarn, south westcoast of India) "from April to Septemberand possibly in other months of the yearwith a peak in July - August". Supportingevidence is also given by Silas (1962) bythe collection of fish with ripe ovariesor partly spent ovaries from the same areain 1960 and 1961 during the months ofAugust - September. Larval collectionsare wanting. However, the occurrence ofearly juveniles in this area duringOctober - November reported on byJones (1960) and Silas (1962) is alsointeresting.
- Number of spawning per year,frequency
"The study of ova diameter frequencypolygons of ripe spawning (or rJpe run-ning) and recovering ovaries indicatesthat in the most advanced stage (ripe -stage V (Figure 7, I) the most advancedmode containing ripe ova is the mostprominent, while more than one mode isseen for the maturing ova. In the riperunning condition (spawning - stage VI)(Figure 7, II and III) the most advancedmode is seen to be completely separatedfrom the maturing eggs which in turn showtwo or more modes, Three recoveringovaries (stage VII) (Figure 7, IV, V andVI) in which there are indications ofprevious spawning by the presence ofdegenerate large eggs also showthe most
Table VI
Counts of ovarial eggs in five mature specimens of Sarda orientalis
from Vizliingam, south west coast of India
(After Silas, 1962)
N)
Date of collection
13-9-61
20-8-60
8-9-60
l-8-60
25-8-60
Total length (mm)
Body weight (g)
Weight of ovaries (g)
No. of countable ovaria].
eggs in gram of roe
No. of eggs in ovaries
(in thousands) to be
spawned in a season
No. of eggs per 100 g of
body weight (in thousands)
No. of eggs of the most
advanced mode in gram of
roe
No. of eggs of the most
advanced mode in ovaries
Remarks
386
899
53.650
4533
2432
2705
- -
spent-
recovering?
490
1LI'+6
85.720
4525
3879
2682
- -
maturing
- -
89,140
7550
5126
-
990
88248
ripe
running?
545.
-
72.750
8900
6475
-
2131
155030
ripe
running
605
-
84.400
4890
3980
-
160
1.3024
pawning
(partially
spent?)
Table VII
Estimated number of ova produced per spawning and during the
breeding season by individual fish of Sarda orientalis
(After Rao, 1962)
ing season (fecundity)
(millions)
Fish Number
SO, 10
SO, 13
So. 16
So, 11
Fish length (m)
51.0
54.0
55.0
Fish weight (g)
1.
l'41.37
L 83
2 06
Number of ova produced
per spawning (millions)
0.21
0.23
0.25
0,28
Total number of ova
produced during the breed-
0.91
0.93
1,03
1.15
Figure 6. Sarda orientalis (Temminck and Schleì)
(A) and (B) Cross section of ovaries of specimens 368 mm and L9O mmrespectively showing distribution of larger transparent ova thròugh-out the ovary and the formation of the central lumen into which theripe eggs migrate.
Cross section of ovary of specimen 605 mm showing central lumen fromwhich ripe ova have been removed,
Sanie before removal of ripe ova,
() Ovary of same specimen (part of right ovary removed for showing crosssections (C) and (D).
855
3:4 FIb/S73 Bonito
to
>00020
Iow
30
w 20Q<IzwoC-,
40
30
20
to
30
20
to
w 20
20
IO 20 30 40 50 60 70MICROMETER DIVISIONS
856
80 90 lOO
17644 88 13MILL 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 specimens col-lected at Vizhingam. (The combined frequency is also shown). (After Silas, 1962)
FIb/S73 Bonito 3:5
advanced mode as the most prominent one 318 Egg structures sizeas seen in stage V (Figure 7 I). The hatching types parasitescombined frequency (Figure 7 VII) shows and predatorsthe most advanced mode containing theripe ova to be well demarcated from matur "The ripe ovum of S orientalis isIng batches, which in turn show several very large, In fresh condition they aremodes. If it were to be presumed that spherical, more or less transparent withduring 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 andmature 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 conditiononeTime, 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 haspreliminary 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 of ma11the ova diameter frequency of ripe run- oil globules at one of the poles (Figuresning ovaries of two specimens of S. 8B and 8C) their number varying between 3orientalis from Vizhingam, and 14 with an average of about 8 and rang-
ing 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 indica1earlier 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 foundsequent 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 mayattains maturity and is ready for spawn-. indicate that they are eggs retained overing even before attaining 386 mm, The a longer period and are próbably in theripe running specimens examined were 49 early stages of resorption. Eggs partlycm 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 notAccording to Silas (1962) the spent discernible is shown in Figure 8A,
and recovering ovaries had very few largedegenerate eggs of the last spawned batch, 3,2 Larval history
3,1,7 Spawning grounds 3.2,1 Account of embryonic andjuvenile life (prelarva,
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 mmsouth west coast of India (Trivandrum to (total length including caudal 8) mm) fiCape Comorin) indicates that the sea off ured and described by Jones (1960) (Figurethis 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 juvenileavailable 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 shorecoastal to oceanic situation, and it may seines along the south west coast of Indianot be wrong to ¿enote the species as a range between 150 mm to 290 mm,neritic pelagic spawner,
857
3:6 FIb/S73 Bonito
i
858
H
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 ofthe ovary showing cluster of oil globules (each about 0,15 mmin diameter) at one pole (stage VI) (after Silas, 1962)
FIb/S73 Bonito 37
Jones (1960) remarks that the food ofthe juvenile S, orientalis consists of lar-val and juvenfleTcrustaceans.Kumaran (l962Y found that Anchoviella triwas the most common fish that occurred'ithe stomach contents of juveniles, whilestomatopod larvae were present as a minoritem.
Parental care
The species as other scömbroids maynot exhibit any parantal care,
- Parasites and predators
See undr 3,3,5 for parasites collect-ed from juveniles and adults, No informa-tion is'available on predators.
3,3 Adult history
3,3,3 Competitors
During the season when juveniles arecaught along the south west coast of Indialarge numbers of juveniles of the littletunny, Euthynnus a, affinis are alsocaught along with them in shore seines,Adult S. orientalis are very often caughtin this area along with adult E, affinis,Auxis thazard, Kishinoella tonggol andScomberornorus spp. in shore seines as wellas gill nets, A certain amount of competi-tion for food may be expected between thesespecies,
3,3,5 Parasites and diseases
Silas (1962) records a species ofmonogenetic trematode (Capsala sp,) fromthe gills, palate and inner wall of theoperculum of juvenile and adult S,orientalis collected from Vizhingam, southwest coast of India. Silas and Ummerkutty(l962) have recorded the parasitic copepodsCaligus bonito Wilson (adults and chalimusstages), and Parapetalus sp. from the gillsand buccal cavity of juveniles and adultscollected from the same area,
Information is not available ondiseases,
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Large specimens caught in shore seinesand drift nets off south west coast ofIndia are less than 700 mm, However, thefish is said to attain a larger size asSmith (l9B) mentions under S, chilensis( S, orientalis) "Attains at least 10inc1es",
Regarding Japanese specimensKishinouye (1923) mentions "Grow to alength of about 80 cm and to a weight of1,5 g to 3,0 g."
3. Nitrition and growth
3,t.2 Food (type, volume)
Jones (1960) remarks that adults feedon young and small sized fishes, crusta-ceans and squids.
3.5 Behaviour
3,5,1 Migration and localmovements
Information is wanting, See under3,5.2,
3,5,2 Schooling
Schools of adults and young appearalong the south west coast of India,between Trivandrum and Cape Comorin fromabout July to December, the schools ofjuveniles appearing especially in October-November when they enter bays and inshoreareas and are caught in shore seines,More information is needed.
3,5,3, Reproductive habits
No information except data givenunder 3,1,6,
- Feeding 3.3,6 Greatest size
3:8 FIb/S73 Bonito
FIb/S73 Bonito 4:1
'4 POPULATION (STOCK)
'4.2 Size and density
L1.,2l Average size
Average size of adults caught atVizhingam and other centres along thesouth west coast of India is about 1+5 cm.More information is wanting.
4.6 Relation of population to com-munity and ecosystem, biologi-cal production, etc.
The term neritic-pelagic may be applied to the habitat of S orientaliseWithin this realm, it may be said tobelong to the surface and mid-water com-munity as most other scombroìds Thearea of occurrence of S orientalis offsouth west coast of India is an area ofhigh productivity In this area, thefishery for this species also coincideswith that for the little tunny Euthynnusaffinis affinis (Cantor), the northernbluefin or Indian longtailed tunnyKishinoella tongo1, and few other scorn-broids, especially Scombromorus sppMost of these prey on smaller tishes andas such it is likely that a certainamount of competition may exist betweenthese species More information is ned-ed,
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FIb/S73 Bonito 5:1
S EXPLOITATION
5,1 Fishing equipment
5,1,1 Fishing gear
Adult orientalis are usuallycaught in drift nets (gill nets) andalso shore seines when schools enterbays along the south west coast ofIndia, Juveniles are also caught inshore seines and gill nets, Along theSouth African coast, where this isregarded as a sport fish, Smith (198-1961) remarks that the fish "fightswell when hooked", The species hasalso been taken by trolling (Wheelerand Ommanney, l953)
5,1,2 Fishing boats
No special boats appear to be inuse for fishing for the orientalbonito,
5,2 Fishing areas
5,2,1 General geographicdistribution
See under 2,1, The only areaswhere the oriental bonito forms a seasonal minor fishery is along the southwest coast of India and as indicated byRosa and Laevastu (1961) along theSomali coast of Africa,
Along the west coast of India,stray catches of S, orientalis may bemade from various localities from asfar north as Ratnagiri, but regularcatches are only made south of Trivandrsim to Cape Comorin (Ca,77°E 775O'E; 8°N to Ca, 8°5B) where fishirg iscarried out as far as 20 km from thecoast, Information is not availableabout the other areas,
5,2,3 Depth ranges
Along the south west coast ofIndia fishing is carried out inwaters less than 200 m deep,
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5,3 Fìshing seasons
53,l General pattern of fish-ing season
Along the south west coast of Indiathe available information points to thefishing season for adult S. orientalisto be from about July to epte]iber,although stray specimens may be caughtduring the months of April, May and June,It is likely that there may be changes inthe pattern of the fishing season fromyear to year within this period,
