Species Synopsis No, 29FAO Fisheries Biology Synopsis No. 72 Frb/S72(Distribution restricted) SAST - Tuna

SYNOPSIS OF BIOLOGICAL DATA ON DOUBLE-LINED MACKERELGrammatorcynus bicarinatus (Quoy and Gaimard) (INDO-PACIFIC)

Exposé synoptique sur la biologie du Grammatorcynus bicarinatus(Quoy et Gaimard)(Indo-Pacifique)

Sinopsis sobre la biología del Grammatorcynus bicarinatus(Quoy y Gaimard) (Lndo-Pacifiqe)

Prepared byE, G, SILAS

Central Marine Fisheries Research InstituteMandapam Camp, India

FISHERIES DIVISION, BIOLOGY BRANCHFOOD AND AGRICULTURE ORGANIZATION OF THE UNITED NATIONSRome, 1963

811

FIb/S72 Mackerel 1:1

1 IDENTITY

1,1 Taxonomy

1, 1,]. Definition

Phylum VERTEBRATASubphylum Craniata

Superclass GnathostomataSeries PiscesClass Teleostomi

Subclass ActinopterygiiOrder Perciformes

Suborder ScombroideiFamily Scombridae

Subfamily ScombrinaeGenus Grammatorcynus

Gill; 1862Species Grammatorcynus bicarthatus(Quoy and Gaimard)1824

1.1.2 DescriptionGenus Grammatorcynus Gill,1862

Type: Thynnus bilineatus Rtippell (=Thynnusbicarinatus Quoy and Gairnard); Type locality ofT, bicarinatus - Sharks Bay, Western Australia.

(Syn. Nesogrammus Evermann and Seale1907: type - Nesogrammus piersoni Evermannand Seale)

Body elongate, fusiform; size relativelysmall, generally not exceeding one meter; bodycovered with cycloid deciduous scales; cheeksscaled; corselet indistinct; lateral lines, two,first commencing from upper angle of operculuniand running along upper half of body to almostcommencementof caudal keel, while secondbranches off from former below vertical fromthird dorsal spine, descending to lower half ofbody to join first lateral line in a vertical belowpenultimate dorsal finlet; caudal peduncularkeel on each side not very prominent and coveredwith a row of pored scales along ridge; pair oflateral keels at base of caudal much smaller;mouth relatively small, maxillary not surpassingvertical below middle of eye; teeth in jaws pointed,villiform on vomer, palatines and upper surfaceof broad tongue; two dorsal fins more or lesscontiguous; first dorsal with XI-XII strongspines; dorsal and anal finlets six or seven;

812

pectorals relatively short; interpelvic pro-cess short, triangular, not reaching beyondhalf length of innermost pelvic fin ray (Fig. 1);caudal deeply forked; gill-rakers welldeveloped; gill membranes free; opercleslightly notched at hind margin; vertebrae 31(13+18).

- Grammatorcynus bicarinatus (Quoyand Galmard) 1824

Body proportions expressed as percentagesof fork length (method as given by Marr andSchaefer 1949) for specimens from the AndamanSea and Western Marshall Island are givenbelow,

Head 18,1 to 22, 3; first predorsal distance29, 2 to 31, 3; second predorsal distance 53, 3to 57, 0; preanal distance 59, 6 to 63, 6; pre-pelvic distance 25, 7 to 27, 0; greatest depth ofbody 18, 2 to 20, 7; length of pectoral 11, 7 to14,3; length of second dorsal 8,1 to ll. 4; lengthof anal 8, 0 to 10,1 and diameter of iris 4, 3 to5, 9 percent in fork length,

Fig, 2 shows the disposition of the differentorgans of the viscera in adult male and female,

The stomach is relatively small and heart-shaped, In normal position it is almostentirely covered by the two lateral lobes of theliver, Internally there are about nine irregularridges at the oesophageal end which graduallypeter out towards the middle of the stomach,The stomach region appears to be distensible(Fig. 1), The ridges again appear in the lowerthird of the stomach and converge prominentlyat the blind end, The pylorus, which is at theupper lateral side of the stomach, is thick-walled and has about five thick longitudinalfolds extending into the short pyloric sac, fromwhich the duodenal part of the intestine abruptlycurves down along the postero-lateral side ofthe stomach, from the end of which the intestineruns as a straight narrow tube to the vent. Thepyloric caecae are not so numerous as in someother scombroids (e, g. Thunnus), but arebranched and in many clusters, mainly confinedto between the upper one-third of the laterallobes of the liver, covering only a little partof the surface of the stomach, The liver is tri-lòbed, the middle lobe being greatly reducedin comparison to the large lateral lobe, of whichthe right one is the longest, The airbladder is

¡I t.

;,L4

Fig,

1G

ram

mat

orcy

nus

bica

rina

tus

(a)

Out

er g

ill-a

rch

of r

ight

sid

e sh

owin

gna

ture

of

gill-

rake

rs; (

b) U

pper

jaw

s an

d ro

of o

f m

outh

sho

win

gco

nica

l tee

th o

n ja

w a

nd v

illif

orus

teet

h or

vom

er a

nd p

alat

ines

;(c

) In

ter-

pelv

ic p

roce

ss a

nd p

elvi

c fi

n on

one

sid

e; (

d) I

nner

view

of s

tom

ach

show

ing

natu

re o

f m

ucou

s fo

lds,

GR

- s

patu

late

gill

-rak

er; I

PP -

inte

r pe

lvic

pro

cess

; OF

-'O

ssif

ied'

gill-

fila

men

ts; P

B -

pal

atin

e ba

nd o

f vi

llifo

rus

teet

h; P

Y-

pylo

ric

open

ing

of s

tom

ach;

VB

- v

omer

ine

band

of

villi

foru

s te

eth.

PC

LVST

G

T

IN

8l

Fig, 2 Grammatorcynus bicarinatus - Disposition of the visceral organs inmature (a) male (431 mm) and (b) female (445 mm) Left testes andleft ovary are slightly drawn towards one side,GB - gall-bladder; IN - intestine; LV - liver; 0V - ovary;PC - pyloric caeca; SP - spleen; ST - stomach; T - testes;TGR - longitudinal groove along inner side of testes,

FIb/572 Mackerel 1:3

1:4 FIb/S72 Mackerel

ovate, thin walled and extends to about theposterior end of the visceral cavity.

Color in freshly-caught fish: The upperbody, especially the dorsum of the head andthe region above the upper lateral line, isbluish green with a metalic lustre. The bellyand the underside of the body are silvery-white. The interspinous membranes of thefirst dorsal and the fins are tinged light blue,while the inner edge, the tips and the innerray of the caudal fin are tinged yellowish.There is a patch of light red in the region ofthe chin, below the eye, The iris surround-ing the pupil is conspicuously whitish.

On preservation in formalin, the headturns dark grey superiorly, The upper halfof the body is greyish with a tinge of yellow.A slightly darker band, about one cm thickpasses from the upper angle of the operculumalong the mid-lateral side of the body to thebase of the caudal, The central rays of thecaudal beyond the hypural and the tip of thecaudal are whitish, The lower half of the body,including the abdomen, is yellowish-white.The interspinous membrane of the first dorsalis greyish between the first four anteriorspines and along the upper half of the remain-ing rays. The outer margins of the seconddorsal and anal fins are tinged dark-greyishalong their anterior margins, The pelvicsare dusky, and so are the pectorals, whichhave a basal scaly whitish area, Scattereddark spots are present on the side of the body,especially along the upper half, and there areirregular rows of small greyish blotches onthe abdomen between the pelvic and anal fins,Dorsal finlets are greyish basally and lighteralong margin,

Scales are small, From the commence -ment of the lateral line at the upper angle ofthe operculum to the bifurcation of it thereare about 21 to 28 perforated scales; upperlateral line with about 130 to 138 scales frombifurcation to peduncular keel; about 140 to170 scales on lower lateral line from bifur-cation to peduncular keel; about 23 scalespresent from where the lateral lines meetposteriorly, to hypural along edge of peduncularkeel; 12 to 14 rows of scales are presentbetween origin of the first dorsal and lateralline and about 13 rows between origin of thesecond dorsal and lateral line, The laterallines are mostly separated below the 8th and

815

9th dorsal spines, separated by about 28 rowsof scales at this point. However, abnormalitiesin the nature of the lateral line may be seen asshown (Fig. 3 a, b) for two specimens from theAndaman Sea

Teeth on the upper and lower jaw are uni-serially arranged, relatively small, conical,pointed or with slightly blunt tips, there beingabout 30 in the upper and about 40 in the lowerjaw (Fig, lb), Minute closely set villiformteeth are presest in patches on the vomer,palatines and the exposed surface of the tongue,

The longest gill-raker is about as long asthe longest gill-filament, The four rakers onthe upper limb of the gil) arch are shorter thanthe first seven on the lower limb, On theouter gill-arch of both sides, one or two of therakers may often be spatuJ. ate and directedtowards the basc of the gill-filaments (Fig. la).Between the gill-filaments a few 'ossified fila-ments faintly resembling rakers are present,the significance of which is not known,

For meristic characters see section 1, 3. 1.

1. 2 Nomenclature

1. 2,1 Valid scientific name

Grammatorcynus bicarinatus (Quoy andGaimard).

L 2.2 Synonyms

Thynnus bicarinatus Quoy and Gaimard 1824,

Thynnus bilineatus Riippell 1835; Gunther1860; Klunzinger 1871,

Grammatorcynus bilineatus Gill 1862;Kishinouye 1915, 1923; Hardenberg 1935.

Nesorammus plersoni Evermann andSeale 1907,

Grammatorcynus bicarinatus McCulloch1922; Herre 1953; Roxas and Martin 1937,

Grammatorcynus bicarinatus Umali 1950;Warfel 1950; Wade 1951; Sette 1952; Dung andRoyce 1953; Ogilby and Marshall 1954; Roux-Estevi and Fourmanoir 1955; Munro 1958 a, b;Schultz 1960; Jones, Silas and Dawson,1960,

FIb/S72 Mackerel

UL---------------------------

LL----

p,--- LL

816

UL

'ig, 3 Grammatorcynus bicarinatus - a and b showing abnormalities in thenature of the lateral line0A - anal fin; D1 - first dorsal; D2 - second dorsal; LL - lower lateralline; UL - upper lateral line,

1:5

Grammatorcynus bicarinatus (in part)Fraser-Brunner 1950; de Beaufort 1951.

Nicholls and La Monte (1954) in describinga large Xenogramma from Peru, erxoneouslyconsidered it to represent the adult ofGrammatorcynus and this consequently resul-ted in NesogrammuS thompsoni Fowler fromHawaii, which is identical with Xenogrammacarinatus Waite being treated as a synonymyof Grammatorcynus bicarinatus by Fraser-Brunner (1950), and de Beaufort (1951), Munro(1949) clarified the position relegatingXenogramma carinatus to the synonymy of thelittle known gempylid Lepidocybium flavo-brunneum (Smith),

1, 2 3 Standard common names,vernacular names

(See Table I below,)

1, 3 General variability

1, 3, 1 Subspecific fragmentation (races,varieties, hybrids)

* Meristic counts

For 13 specimens ranging in length from 405to 452 mm from the Andaman Sea the meristiccounts are as shown in Table II,

Both GUnther (1860) and Kluzinger (1871)have followed Rdppell' s (1835) description ofThynnus bilineatus and it is therefore evident

Table I

Common and vernacular names

Country

Australia

India

Japan

Standard common name

Double-lined mackerel

Double-lined mackerel

Vernacular name

Shark mackerel (N, Queensland);Large-scaled tuimy(Queensland);Salmon; Salmon mackerel(Moreton Bay); Large scaledtuna

Kusarah (Ryukyu

817

that the 17 branched anal rays given by GUntheris an error, as the range for this character inthe species does not exceed 12.

Wade' s mention of 13 dorsal spines isinteresting, Perhaps the last dorsal spineseen in the larvae is not exposed being com-pletely covered by the skin in adults,

The range of meristic characters for thespecies may be stated as:

D1 XI-XII; D2+ finlets i-iii, 6-11 + 6-7;

P1i-ii, 21-24; P2I, 5; A + finlets i-iii,8-11 + 6-7;

Gill-rakers 19-21 (2-4 + 1 15-16);

Vertebrae 31(13 ± 18).

Morphometric data given by earlier authorshardly throws any light on variations of specificnature in this species as will be seen from thescant data available presented in Table IV.

- Varieties

There can be hardly any doubt that only asingle species is represented in the Indo-Pacific. However, a comparison of themorphometric data for specimens from theAndaman Sea with that given by Dung and Royce(1953) for 15 specimens from Marshall Islandsindicates certain trends of variations, as willbe evident from Figs. 4, 5 and 6. The datasuggest that, size for size, the first predorsal

1:6 FIb/372 Mackerel

Tab

le I

I

Mer

istic

cou

nts

for

spec

imen

s fr

om A

ndam

an S

ea

6+1

indi

cate

s in

stan

ces

whe

re th

e la

st r

ay o

f th

e se

cond

dor

sal a

nd a

nal f

ins

wou

ldap

pear

to b

eal

mos

t com

plet

ely

deta

ched

to f

orm

fin

let.

Hen

ce f

or c

alcu

latin

g m

ean

(M)

this

is tr

eate

d as

7.

Cha

ract

ers

Dor

sal

spin

es

Seco

nd d

orsa

lra

ys(i

-ii,

9-10

=10

-12)

Dor

sal

finl

ets

Pect

oral

rays

Ana

l ray

s(i

-ii,

10-1

1=11

--12

)A

nal

finl

ets

Gill

rak

ers

Tot

alU

pper

limb

Mid

dle

Low

erlim

b

Ran

ge11

1210

1112

66+

l7

2324

25

li12

6 6+

l7

23

41

1516

1920

21

Num

ber

ofsp

ecim

ens

112

111

17

24

16

62

109

13

15

612

210

25

5

N=

l3N

=13

N=

13N

=13

N=

12N

=l3

N=

12N

=12

N=

l2N

12M

=ll.

92M

=ll

M=

6.46

M=

24.3

8M

=1l

.83

M=

6.30

M3.

4l-

M=

15.8

3M

=20

.25

Tab

le I

II

Mer

istic

cou

nts

in G

rani

mat

orcy

nus

bica

rina

tus

from

. var

ious

par

ts o

f th

e In

do-P

acif

ic

Aut

hor

Loc

ality

DV

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2+F

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P2A

+fi

nlet

sG

ill r

aker

s

Giin

ther

Red

Sea

XII

i10+

6i,1

7+6

(186

0)

Klu

nzin

ger

Red

Sea

XII

i10+

61,

11+

6(1

871)

Kis

hino

uye

Ryu

kyu

Isla

nds

and

31(1

3±18

)X

II?,

9+7

?, 9

+7

5+16

(192

3)M

arsh

all I

slan

ds

Har

denb

erg

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t Jav

a Se

asX

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721

I, 5

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(193

5)

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lO+

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16(1

950)

Bea

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Java

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711

23-2

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(195

1)

Wad

eS.

E. S

ulu

Sea

and

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1+(i

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And

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1:12 FIbIS72 Mackerel

distance, second predorsal distance, preanal dis-tance and length of second dorsal in total lengthare slightly greater for the specimens from theAndaman Sea. In characters such as head length;prepelvic distance; greatest height of body; lengthof pectoral fins and diameter of iris, there is con-siderable overlap. It is not known whether thetrends of differences noted reflect the occurrenceof distinct breeding populations in the two areas.

It has been found that in specimens fromAndamans, irrespective of sex, there is some

823

difference in the decurved position of thesecond lateral line, In some specimens(Fig. 7a) the pectoral fin hardly reaches thesaid lateral line, while in others (Fig. 3b)it overlaps the lateral line by about half itslength. The latter condition is also seen inspecimens from Australia (Fig. 7b).

Albinism, melanism or rubisrn have notbeen observed, Nor has natural hybridiza-tion ever been noted,

FIb/S72 Mackerel 1:13

Fig. 7. Grammatorcynus bicarinatus:

824

Female 449 mm from Andamans;

Specimen from Eastern Australia (after Ogilby andMarshall 1954).

2 DISTRIBUTION

, I Delimitation of the total area of dis-Wtribution and ecological characteri-zation of this area

As shown in Fig, 8, the areas of occurrenceare:

Red Sea; Andaman Sea; coasts ofAustralia; Java Sea; New Guinea; NorthCelebes; Philippines; MarshaU Islands; andthe Ryukyu Islands south of Japan,

According to this information,0 geographicaldistribution ranges from about 40 E to about

o o o170 E, and from 30 N to 37 S, This areacovers parts of the tropic and subtropic areasof the Indian and Pacific oceans,

2, 2 Differential distribution

The presence of live coral reefs is verycharacteristic of most of the areas where thespecies occurs, suggesting its reef-dwellinghabit,

2, 2,1 Areas occupied by eggs, larvaeand other junior stages: annualvariations in these patterns, andseasonal variations for stagespersisting over two ¿r moreseasons, Areas occupied byadult stages; season6l andannual variations of thes e

Eggs

Exact information is lacking, However,Wade' s (1951) collection of larvae from North

Table V

825

of Celebes (Sulu Sea) would indicate that itis one spawning area, Gonadial studies ofthis species from the Andaman Sea (Silas, inthis synopsis) suggest that the reefs offcentral and southern Andamans could beanother spawning area, (See section 3,1, 7),

- Larval stages

The only available information is thatgiven by Wade (1951) (Fig, 9 a), The larvaecan be easily distinguished from those ofother tunas by the fewer vertebrae (31 insteadof 38, or more in the other species) while thislow vertebral count is also characteristic ofthe mackerel genus Rastrelliger, but thelatter is typified by only five detached dorsaland anal finlets respectively instead of six orseven seen in Grammatorcynus,

Wade' s collections of larval and post-larvalG, bicarinatus are from the following areas(Table V),

The 8,5 mm larva (Fig, 9a) shows thefollowing characteristic features: dorsal pro-file almost horizontal from occiput to posteriorthird of length; abdominal sac large, somewhatlonger than deep; and opening at about mid-length of body; head relatively large, dorsalprofile rounded; snout bluntly rounded, three-fourth diameter of eye; mouth slightly oblique,maxillary extending to vertical below middleof eye; eyes large, about 2, 5 times in headlength; eight or nine teeth on each side of bothjaws, short, heavy, bluntly pointed spines,about seven along edge of preoperculum, thatat the angle being the largest; an additionalsmall spine present on the faintly-markedcrest on surface of preoperculum; vertebrae

(after Wade, 1951)

Station Date Latitude LongitudeSpecimens

Number Size (mm)

B-29 12 October 1947 6°57 N l20°l5 E 1 8, 6

B-339 1 August 1948 l°N 119°0 8 E i 12, 9

B-345 3 August 1948 4°05'N 120°59'E 1 8,5

G-65 3 May 1948 e6° 04. 2 N 120°45. 5E 4 10-11, 5

G-68 6 May 1948 6° 43. 6' N ll9°l2 E 1 l7,.5

FIb/572 Mackerel 2:1

Fig, 8 Geographical distribution of Grammatorcynus bicarinatus in the Indo-Pacific. The black circles indicate locations of collection or reportedoccurrence; the two square patches indicate likely spawning areas0

826

60'--

80

20

o'i

:

60'

30' 60' 50' 120' 1500

'"

--.

180'

i'

150'

'

+

r'

'-

120',ver90'

-

-

j:i

60'

80

20

/

/,

30']O. 60' 90' 1200 150'E. 180' 150'W 120' 90'

2:2 FIb/s72 Mackerel

Fig. 9. Gramrnatorcynus bicarinatus:

&2 7

Larvae 8.5 mm;Post larva 17. 5 mm from Sulu Sea of Philippines(after Wade 1951).

Flb/S72 Mackerel 2:3

31 (13 -F 18); first dorsal with 13 spines, shortand weakly developed last spine "almost unitedwith first ray of second dorsal". Second dorsalwith 9 rays and 7 finlets; anal with 11 rays and7 finlets (after Wade 1951).

specimens are light cream incolour, with a scattered pattern of small blackpigment spots. The dorsal aspect of the headfrom the nape anteriorly to above the eye isslightly pigmented with small black chrornato-phores; while laterally, below the nape andbehind the eye, there are several scatteredareas of similar pigment. There is scattereddark pigmentation on the tip of the snout andimmediately posterior to the angle of the jaws.The base of the first dorsal and of both dorsaland anal finlets have a narrow line of dark pig-ment, A lightly pigmented area extends overthe side of the body between the dorsal and analfinlets, There are a few scattered pigment spotsat the base of the caudal fin. The abdominal sacis darkly and heavily pigmented dorsally and an-teriorly, and the colour pattern also extendsdownward laterally on the posterior portion ofthe sac" (Wade 1951),

- Postlarvae and juveniles

To this may be referred the 17, 5 mm speci-men described and figured by Wade (1951)(Fig. 9h). At this stage, as seen in the accom-panying figure, a characteristic color pattern isseen, The preopercular spines number 10 andare in the form of short blunt projections, 6along the horizontal edge, one at the angle and3 on the vertical edge. The second spine ofthe first dorsal is the longest. Wade has drawnattention to the error in regard to both dorsal

828

and anal finlets in his drawing of the specimen -(reproduced here as Fig. 9b) - where the lastray of the second dorsal and anal represent thefirst dorsal and anal finlets respectively, thespecimen having a second dorsal fin ray countof 10 rays plus 7 finlets and an anal count of12 rays plus 7 finlets,

Most of the larvae and postlarvae werecollected under a light at night.

- Adults

Capture of adult Grammatorcynus wouldindicate its occurrence close to reefs in waters20 fathoms in depth. There is no regularfishing for this species anywhere in its distri-bution range, but stray catches are made atPort Blair, Andamans (January to March);Philippines (off Zamboanga, Mindanao and Job,Sulu Archipelago) and off New South Wales andQueensland, East Australia, while its occur-rence in other areas is only sporadic or rare,

Off Port Blair, Andamans,, the fish iscaught using handlines with Sardinella spp, aschief bait.

2, 3 Behavioristic and ecological determi-nants of the general limits of distribu-tion and of the variations of theselimits and of differential distribution

No definite information except what has al-ready been mentioned under section 2. 2. 1.Temperature would appear to be a factor limi-ting the occurrence of the species to areas wherecoral reefs occur. If so, its non-occurrence inthe Central Pacific, in Hawaiian waters, ispuzzling.

2:4 Fib! S72 Mackerel

FIb/S72 Mackerel

3 BIONOMICS AND LIFE HISTORY

3,1 Reproduction

3,1,1 Sexuality (hermaphroditLsm,heterosexuality, intersexuality),

Grammatorcynus is heterosexual, Noexternally observable characters are known todistinguish males and females,

3, 1, 2 Maturity (age and size)

Preliminary observations made here onspecimens from Andaman waters would indicatethat the fish is mature at about 420 mm, Asmaller mature female, 416 mm was found tocontain transparent ova while a specimen 449 mmtaken in February 1960 had recovering ovarieswith a few unshed degenerate eggs of an earlierbatch, Two males 405 and 431 mm had welldeveloped testes (Fig, 2a), No information isavailable about the age of the investigated maturespecimens,

3,1, 3 Mating (monogamous, polygamous,promìscuous)

Should be polygamous. No information isavailable about prespawning or spawningbehavior,

3,1, 4 Fertilization (internal, external)

External, As in the case of other tunas,eggs should be pelagic.

3. 1. 5 Fecundity

Estimates of the larger maturing ova withdiameter of 0. 4 mm and more for ovary weightof 34,40 g was found to be about 93, 100. Thenumber of such maturing ova in the right and leftlobes of the ovaries per gram was more or lessthe same.

3.1.6 Spawning- Spawñing season (beginning,

end, peak)

The occurrence of mature ovaries with trans-parent eggs and spent and recovering ovariesfrom January to March in the Andaman Sea indi-cates that this period is one spawning period.The data are too meagre to comment on season,

829

extent, peak spawning period, etc. Ova dia-meter frequency (Fig. 10) indicates two dis-tìnct size groups of maturing eggs in the recove-ring ovary; one with the mode of 9,43 mm andthe other with the mode at 0, 81 mm,

- Number of spawnings per year,frequency

No definite information for any area. How-ever, from Fig, 10 for specimens from theAndaman Sea it would appear that spawning maybe over an extended period and fractional spawn-ning is suggested.

Collateral data from the occurrence ofvarious sizes of larvae ranging between 8. 5 mmand 17. 5 mm during the months of May, Augustand October in the Sulu Sea (see section 2. 2, 1)(Wade 1951) could also suggest intermittentspawning over an extended period.

3.1.7 Spawning grounds

Unlike skipjack, yellowfin and the albacore,which may migrate over long distances, G.bicarinatus would appear to be more 'sedentary'in habit and as such it wil], not be surprising ifeventually the fish is found to breed near thereefs where they occur. At present, informa'-tion is available only for two areas: the Anda-man Sea, where specimens with ripe ovariesand recovering ovaries have been collected, andthe Sulu Sea south of the Philippines, where lar-vae and postlarvae have been collected (Fig. 8).

3. 2. Larval history

3:1

3. 2, 1 Account of embryonic and juve-nile life (prelarva, larva, post-larva, juvenile).

Only information is that given by Wade (1951).The smallest larva described is 8, 5 mm (Fig. 9a)and thç largest postlarva 17. 5 mm (Fig. 9b).

3. 3 Adult history3.3.6 Gieatest size

By far the largest size of G. bicarinatus onrecord is that from Java Sea given by de Beau-fort (1951) as 963 mm. Ogilby and Marshall(1954) remark that in Queensland waters thespecies attains about 36 inches (914 mm), whileWhitley (1962) remarks that it may attain

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FIb! S72 Mackerel 3:3

48 inches (about 122 cm) and a weight of 25 lb(11,3 kg) in Australian waters. Hardenberg(1935) refers to a 500 mm specimen caught fromthe reefs off west Java, while Kishinouye (1926)remarks that most specimens caight at MarshallIslands and Ryukyu Islands are about 3 00 mm intotal length. Dung and Royce (1953) have givenmorphometric data for 8 females ranging from408 to 580 mm and 7 males ranging from 425 to467 mm from Western Marshall Islands,Klunzinger (187],) refers to this species attain-ing about 500 mm in the Red Sea, while the speci-mens from Port Blair, Andamans are from 405to 452 mm. Apparently the species may beexpected to attain slightly over 100 cm but allindications are that breeding size is attained atmuch less than half this length, and generallyfish between 300 and 600 mm are taken.

3, 3.4 Competitors

Observations made at Port Blair, Andamansindicate that among predaceous reef-dwellingspecies, most prominently Gymno sarda unicolorand Sphyraena spp. are taken from the same habi-tat as G. bicarinatus, But no information is avai-lable about the nature of competition, if any,

3.4 Nutrition and growth

3.4. 1 Feeding (time, place, manner,season)

No precise information. However, for foodof fish taken on hand lines see section 3.4.2.

Table VI

Dietary items of Grammatorcynus bicarinatus from Andamans

831

3.4.2 Food (type, volume)

Results of examinations of the food of G.bicarinatus caught at Port Blair, Andamans inFebruary 1960 and February to March 1961shows that crustacean (stomatopod larvae),Squilla sp; Megalopa; Peneid larvae and Mysis,form the most important food of the specieswhile fishes come second in importance.Strangely, no remains of squids of any otherorganisms were present as food. Fishes inthe food have been identified as Sardinella sp,,Thrissocles sp., Sphyraena sp., and Balistessp. The percentage composition of the fooditems both volume-wise as well as number-wise are given in Table VI,

3. 5 Behavior

3.5,2 Schooling

There is nowhere any reference to .bicarinatus having been encountered in largeschools, Its habit may be more akin to that ofthe dog-tooth tuna Gymnosarda unicolor, whichmay be seen in small packs, close to reefs, oreven solitary,

3. 5. 3 Reproductive habits

See sections 3.1.5, 3,1.6, Itis probablethat the spawning period may be an extended onewhen eggs may be shed in more than one batch.There is no information as to whether therecould be two spawning seasons in the same year.

! Unrecognisable semidigested remains of crustacea have not been taken into account

Food itemsPercentage

compositionby volume

Percentagecomposition1by numbers-

Fish 32, 7 6 6Crustacea

Stomatopoda (Stomatopodlarvae, Squilla, etc)

13, 0 21, 8

Penaeid larvae,, Mysis etc, 3, 5 30 6Megalopa 3 O 40, 9Semidigested. remains ofcrustacea 47, 8

POPULATION

4,1 Structure

4. 1, 1 Sex ratio

No definIte information, Of 15 specimenslisted by Dung and Royce (1953) from WesternMarshall Island, 8 were females and 7 males,In 13 specimens the author examined fromAndamans 8 were females, 2 males, while theviscera of 3 were too badly damaged to aid insex determination,

832

FIb/S72 acl:erel 4:1

FIb/S72 Mackerel 5:1

5 EXPLOITATION

5. 1 Fishing equipment

5. 1. 1 Fishing gear

Adult G, bicarinatus are caught off PortBlair, Andamans using hand lines in watersaround 20 fathoms or more deep. There is noinformation about capture methods for otherareas,

5, 2 Fishing areas

There are no areas in which a specific fisheryfor this specie s exists except perhaps off northQueensland, Australia from where "it is receivedinto Brisbane market with the mackerel catch andduring the height of the season sometimes reachesas high as ten percent of the mackerel catchlanded there" (Ogilby and Marshall 1954),

833

5, 2. 1 General geographical distribu-tion

See section 2. 1

5, 2. 2 Geographical ranges (latitudes,distances from coast, etc.)

See section 2, 1

5.3 Fishing seasons

5 . 3. 1 General pattern of fishingseason

In Andamans the fish is caught mainly fromJanuary to March. Whitley (1962) remarks that"the fish has been found in February and Junein New South Wales, and in winter months inQueensland",