NOAA Technical Report NMFS Circular 429 

Synopsis of Biological Data 

on Tunas of the Genus 

Euthynnus 

Howard O. Yoshida 

October 1979 

FAO Fisheries Synopsis No. 122 

u.S. DEPARTMENT OF COMMERCE 

Juanita M. Kreps, Secretary 

National Oceanic and Atmospheric Administration 

Richard A. Frank, Administrator 

National Marine Fisheries Service 

Terry L. Leitzeli, Assistant Administrator for Fisheries 
The National Marine Fisheries Service (NMFS) does not approve, recommend or endorse any proprietary product or proprietary material 

mentioned in this publication. No reference shall be made to NMFS, or 

to this publication furnished by NMFS, in any advertising or sales promotion which would indicate or imply that NMFS approves, recommends 

or endorses any proprietary product or proprietary material mentioned 

herein, or which has as its purpose an intent to cause directly or indirectly 

the advertised product to be used or purchased because of this NMFS 

publication. 
CONTENTS 

Introduction ........................................................................ . 

1 Identity ......................................................................... . 

1.1 Nomenclature .............................................................. . 

1.11 Valid name ......... ... .............................. ... .............. . . 

1.12 Synonymy .................................................... .. .... .. . 

1.2 Taxonomy . .................... . ........................................... . 

1.21 Affinities ...................................................... ..... .. . 

1.22 Taxonomic status . .... ..... .......... ..... ............................. . 

1.23 Subspecies ............................................................ . 

1.24 Standard common names, vernacular names ................................. . 

1.3 Morphology ..................... ................. .......................... . 

1.31 External morphology ....................................... ...... ...... . 

*1.32 Cytomorphology 

1.33 Protein specificity ................................... .... ............... . 

2 Distribution ...................................................................... . 

2.1 Total area ....................................... .. ......................... . 

2.2 Differential distribution ....................................................... . 

2.21 Spawn, larvae, and juveniles .............................................. . 

2.22 Adults ............................................................... . 

2.3 Determinants of distribution changes 

*2.4 Hybridization 

3 Bionomics and life history ........................................................... . 

3.1 Reproduction ............................................................... . 

3.11 Sexuality .......................... . .......... .. ...................... . 

3.12 Maturity ....... ...................................................... . 

3.13 Mating ........... ...... . ............... .. .......... ..... ............. . 

3.14 Fertilization ..... ....... ... ............. ..... .. ..... ................... . 

3.15 Gonads ....................................... ... ..................... . 

3.16 Spawning ...................................... . ...................... . 

3.17 Spawn ............................................................... . 

3.2 Preadult phase .............................................................. . 

3.21 Embryonic phase ..................... ....... . .......... ............. ... . 

3.22 Larvae and adolescent phases .................... .. . .. ......... .... ....... . 

3.3 Adult phase ........................................... .. ................... . 

3.31 Longevity ............................................................. . 

3.32 Hardiness ..... ............ .... ............ ........ ........... ......... . 

3.33 Competitors ........................................................... . 

3.34 Predators ................................. . ........................... . 

3.35 Parasites, diseases, injuries, and abnormalities .. .. .......... ...... ........... . 

3.36 Physiology, biochemistry, etc ........................................... ... . 

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3.4 Nutrition and growth .......................................................... 35 

3.41 Feeding ............................................................... 35 

3.42 Food ....................................... · ..................... ·.... 36 

3.43 Growth rate ............................................................ 36 

3.44 Metabolism ............................................................ 38 

3.5 Behavior ................................................... ···· .. · ..... ···· . 38 

3.51 Migrations and local movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 

3.52 Schooling .................. .. ............................. ·.······· .. ·. 39 

3.53 Responses to stimuli ..................................................... 39 

4 Population .................................... .. ...... · .. ·.·· .. · ... ··· .··········· 41 

4.1 Structure ........................... · .. ···· ..... · .. ························· 41 

4.11 Sex ratio. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 

4.12 Age composition. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41 

4.13 Size composition .......... .. .................. ...... ...... .. ............ 41 

4.14 Subpopulations....................................................... .. 46 

III 

Synopsis of Biological Data on Tunas of 

the Genus Euthynnus 

HOWARD O. YOSHIDA1 

ABSTRACT 

Biological and fisheries data on Euthynnus affinis, E. alletteratu8, and E. lineatus from published 

and unpublished sources were compiled, synthesized, and summarized following the FAO species synopsis outline. 

INTRODUCTION 

The fishes of the genus Euthynnus are widely distributed in the warm and tropical waters of the world's 

oceans. In some localities they appear to be the dominant scombrid in the coastal, nearshore waters. Euthynnus alletteratus is one of the commonest scombrids in the 

western North Atlantic (Rivas 1951). In trolling surveys 

off the southeastern coast of the United States this species was caught most often (Anderson2

). Ben-Tuvia 

(1957) stated that E. alletteratus seemed to be the only 

common scombrid along the coast of Israel in the Mediterranean. In Hawaiian waters E. affinis was one of the 

more common species taken by trolling (Welsh 1949; 

Tester and Nakamura 1957). Walford (1937) stated that 

I

E. lineatus was very abundant in the eastern tropical 

Pacific. 

Although the species of Euthynnus are widely distributed and apparently abundant in some localities, generally the group as a whole is not commercially as important as the other tunas, e.g., skipjack tuna, Katsuwonus 

pelamis. Calkins and Klawe (1963) stated that E. lineatus was of no commercial value and Kikawa and staff 

(1963) noted that consumer demand for E. affinis was not 

very great in Japan. The world landings of Euthynnus 

ranged from 80,350 to 87,735 metric tons (t) and averaged about 84,674 t during the period from 1973 to 1976 

(FAO 1977). 

Because the world demand for tuna is steadily growing 

and since several of the commercially important tunas 

are at or near the level of maximum sustainable yield, 

the underexploited and presently commercially unimportant tuna and tunalike species are likely to attract 

more attention. Therefore it is important that the life 

history and biology of these species, including Euthynnus, be elucidated. 

The purpose of this report is to collate and update all 

the information presently available on Euthynnus. All 

'Southwest Fisheries Center Honolulu Laboratory, National Marine 

Fisheries Service, NOAA, Honolulu, HI 96812. 

2 Anderson, W. W. 1954. Progress report, South Atlantic Fishery 

Investigations, Appendix SA-2. In Atlantic States Marine Fisheries 

Commission, 13th Annu. Meet., Baltimore, Part 2, p. 211-213. 

1 

papers on Euthynnus published in the F AO Species 

Synopsis series (Calkins and Klawe 1963; Kikawa and 

staff 1963; Marchal 1963; Williams 1963) were relied on 

heavily in preparing this report. 

1 IDENTITY 

1.1 Nomenclature 

1.11 Valid name 

Collette (1978) discussed the relationships of the 

groups of fishes in the subfamily Scombrinae, including 

Euthynnus. He pointed out that some workers (FraserBrunner 1950; Collette and Gibbs 1963) placed the 

mon typic Katsuwonus in synonymy with Euthynnus, 

which he thought obscured the relationships of Euthynnus (sensu stricto) with Auxis and of Katsuwonus with 

Thunnus. 

The status of the species within Euthynnus is clear; 

there are three allopatric species of Euthynnus throughout the world: E. affinis (Cantor) of the Indo-West Pacific, including Hawaii and the Red Sea; E. alletteratus 

(Rafinesque) of the Atlantic Ocean (including the Mediterranean Sea, the Caribbean Sea, and the Gulf of Mexico); and E. lineatus Kishinouye of the eastern Pacific. 

Euthynnus affinis was originally described as Thynnus 

affinis Cantor 1850. The holotype was from Penang, most 

likely from the Strait of Malacca. It was 536 mm (FL) 

long and is preserved as a dried skin in the British 

Museum as BMNH 1860.3.19.214 (Collette3

). 

The little tuna from the eastern Pacific was originally 

described as Euthynnus lineatus Kishinouye 1920 and 

still retains that name. 

Euthynnus alletteratus has long been accepted as the 

valid name of the Atlantic little tuna. It was first described as Scomber alletteratus Rafinesque 1810. It was 

claimed recently by Postel (1973), however, that the fish 

described and figured by Rafinesque is actually Auxis 

rochei and that the specific name for the Atlantic little 

tuna should be Euthynnus quadripunctatus of Geoffroy 

3B. B. Collette, Systematics Laboratory, National Marine Fisheries 

Service, NOAA, Washington, DC 20560, pers. commun. March 1978. 
Saint Hilaire (1817). However, Tortonese (1975) argued 

for the retention of the name alletteratus. It was also 

pointed out that Rafinesque (1810) described Sarda 

sarda (as Scomber palamitus), Auxis rochei (as S. bisus), 

and E. alletteratus (as S. alletteratus) and that he could 

not have confused " bisu" (Auxis) with "alletterata" 

(Euthynnus) (Tortonese 1976). Thus Scomber quadripunctatus of Geoffroy Saint Hilaire (1817) is listed herein as a junior synonym of Euthynnus alletteratus. 

1.12 Synonymy 

The synonymies given below make no distinction between objective and subjective synonyms. The synonymies for Euthynnus affinis and E. alletteratus are based 

on synonymies given by Jones and Silas (1964) and 

Fraser-Brunner (1949), respectively. There are no synonyms for E. lineatus. 

Euthynnus affinis 

Thynnus affinis Cantor 1850 (Penang). 

Thynnus thunnina. Temminck and Schlegel 1850 

(Japan). 

Auxis taso (not of Cuvier) Bleeker 1850 (Java). 

Euthynnus alletteratus. Jordan, Tanaka, and Snyder 

1913 (Japan). 

Euthynnus yaito Kishinouye 1923 (Japan). 

Gymnosarda alletteratus. Meek and Hildebrand 1923 

(Panama). 

Wanderer wallisi Whitley 1937 (New South Wales, 

Australia) . 

Euthynnus affinis affinis. Fraser-Brunner 1949 (Aden, 

Seychelles, Thailand). 

Euthynnus affinis yaito. Fraser-Brunner 1949 (Japan, 

Hawaii, Pacific islands). 

Euthynnus affinis. Rosa 1950 (in part). 

Euthynnus alletteratus affinis. de Beaufort 1951 (in part) 

(Indo-Pacific). 

Euthynnus wallisi. Whitley 1964 (Australia). 

Euthynnus alletteratus 

Scomber alletteratus Rafinesque 1810 (Sicily) . 

Scomber quadripunctatus Geoffroy Saint Hilaire 1817 

(Egypt). 

Thynnus leachianus Risso 1827 (Nice). 

Thynnus thunnina Cuvier 1829 (Mediterranean). 

Thynnus brevipinnis Cuvier in Cuvier and Valenciennes 

1831 (Mediterranean). 

Thynnus brasiliensis Cuvier in Cuvier and Valenciennes 

1831 (Brazil). 

Euthynnus alletteratus. Jordan, Evermann, and Clark 

1930 (western Atlantic). 

Euthynnus thunnina. Nobre 1935 (Portugal). 

Euthynnus alletteratus alletteratus. Fraser-Brunner 

1949 (North Atlantic). 

Euthynnus alletteratus aurolitoralis. Fraser-Brunner 

1949 (Gold Coast). 

2 

1.2 Taxonomy 

1.21 Mfinities 

- Suprageneric 

Phylum Chordata 

Subphylum Vertebrata 

Superclass Gnathostomata 

Class Osteichthyes 

Subclass Actinopterygii 

Order Perciformes 

Suborder Scombroidei 

Family Scombridae 

Subfamily Scombrinae 

Tribe Thunnini 

- Generic 

Genus Euthynnus Jordan and Gilbert 1882. 

The generic concept of Euthynnus as given below follows that of Godsil (1954a) and Collette (1978). 

The species of Euthynnus are fusiform, streamlined, 

and have a lunate caudal fin similar to all tunalike 

fishes. The body is naked except for the scaly corselet. A 

series of oblique or longitudinal black markings above 

the lateral line distinguishes Euthynnus from Katsuwonus, which has black longitudinal stripes on the belly. 

The contiguous or nearly contiguous dorsal fins distinguishes Euthynnus from Auxis, which has widely separated dorsal fins. The concave distal margin of the first 

dorsal fin separates Euthynnus from Sarda, which has a 

nearly straight first dorsal margin. The species of 

Euthynnus usually have eight dorsal and seven anal 

finlets. Palatine teeth are present in all and vomerine 

teeth in two of the species. The intestine is straight. 

There are 37-39 vertebrae. Godsil (1954a) gave a detailed description of the generic skeletal characters. 

Unlike Auxis, Euthynnus has a common trunk for the 

dorsal and ventral branches of the cutaneous artery. 

However, Euthynnus is more primitive than Katsuwonus in that the cutaneous artery's ventral branch is 

short and dendritic (Godsil 1954a) and much less developed than the dorsal branch. Euthynnus also differs 

from Auxis wherein the dorsal cutaneous artery lies dorsal to the corresponding vein and not ventral. In Euthynnus the aorta is moved ventrally a distance greater than 

the depth of the centrum owing to the development of the 

trelliswork, a distance less than in Auxis and more than 

in Katsuwonus (Collette 1978). 

- Specific 

Euthynnus affinis (Cantor) (Fig. 1). 

The folowing description is based on that given by 

Godsil (1954a). 

The dorsal black markings that are superimposed over 

a blue to indigo background are most accentuated in the 
Figure 1.- Variations in the ma rkings of three Eu lhy nnus affinis. 

(From Godsil 1954a, fi g. 65.) 

anterior region and are more oblique in E. affinis than in 

the other two species. Black or dusky spots are sca ttered 

over a relatively wide area on the belly below t he pectoral. These spots are variable and cannot be regarded as a 

specific character. 

The crest or rise of the lateral line above the pectoral 

fi n is minimal. The crest or rise, when present, is always 

gentle at its anterior lope . In many specimens the lateral 

line is almost horizontal from the opercular margin over 

the anterior third of the pectoral fin, from where it slopes 

gently downward . 

The caudal keels are not conspicuously developed and 

are evident externally only by a dorsoventral flattenmg 

f the peduncle. 

The operculum i relatively traight at the po terior 

margin and a mall dark or black elongated pot i generally pre ent at the dor al extremity of thi margin. The 

posterior outline of t he preoperculum i gently and 

moothly rounded . A small irregular dark pot or area i 

pre ent below the po teroventral margin of the eye. 

The maxillary extend to or lightly beyond the vertial through the middle of the eye and, depending on the 

ize of the pecimen , 24 to 35 teeth are on each ide of the 

lower jaw. \ omerine teeth are pres nt but palatine te th, 

though alway pr -ent. rna) not be a, pr minent . 

Th dorsal fin i - contiguou., i. about t\\ i e t h htl ht 

of the e ond dorsal fin. and i rou hi) half the head 

length ; it dorsal outline is tron Iy c ncave. Th in rtion of the anal fi n i on a vertical thr u h tht ri in 

the first d rsa l finlet, or bet\\ t' n thi and the end 0 th 

Euth)nnus alletteratu (Rafine qu 2). 

The following de criptlOn i 

Euth)nnu., aUell ralu i. di 

and E. 1m atu, by the ab enc of vom rin t th nd b 

the do al markmg . . The pattern of dor al mar In in -

clude broken, longitudinal black or dar har runnln 

irregularly from the co elet toward th audal r n 

and are more continuou. and regular po teriorl) . Ant 'norl}, hort irregularly curved line , blot he • or J 

place the bars. 

The marking are sup rimpo ed ov r a backgr und of 

blue which hade dor. ally into the deep hlue and bla 

of the middorsallme . The blu fad inw. Ij..:er b I) th 

lateral line and the entire bell) i 

irregular number of black or dark po ar pr 

tween \-entral and pectoral fin ,and hghtl'i po ten r to 

the pectoral . 

The ventral projection of the c()~ let i varlabl hut 

generally short, extending po teriOT the tiP of th 

toral, a di -tance not exceeding one ·tourth or 0 a I n 

ly more) the length of the p ct ral In In m t I 

men The maxillary extend po t nod) t) 8 

dravm through the middle 01 the '. 

The posterior margin 01 the operculum l r letl\ d 

treight and the preopHculum m thl ' r und d In 

teeth are moderate. individually di Inct, nd num r 

from approximateh 25 to 35 on ch Id f th I 

jaw The palatine te th an harp and n pi u u 
Euthynnus lineatus Kishinouye (Fig. 3). 

The following description is also based on Godsil 

(1954a). 

This species can in most instances be readily identified by the dorsal markings, which generally consist of a 

series of three, four, or five broad continuous black 

stripes running horizontally on the back from the corselet 

to the caudal fin. The most ventral stripe starts anteriorly below the lateral line and generally crosses it in its 

path to the caudal region. Variations in the pattern consist mainly of interruptions in the continuity of the 

~ Il('un 3.-\'orilllion' In thl' dorsal markings of Eulh),nnu8 linealus. 

l pPt'r fil(urt' r~pr("('nl' lhl' typical pattl'rn a nd lhl' lowest figure 

ho an,' lrl'mt' 'ariant. (From Godsil 195.ja. fig . 56.) 

4 

stripes, or branching of individual stripes including 

supplementary short irregular markings between. 

The black dorsal stripes are superimposed over a background of blue that deepens into black dorsally and 

shades into grey and silver below. The belly is dusky or 

silvery; an irregular number (usually from two to six) of 

black spots are present between the pectoral and pelvic 

fins. 

Palatine teeth are present in all specimens; vomerine 

teeth are present although difficult to discern in some 

specimens. 

The posterior margin of the operculum is straight and 

the free margin of the preoperculum is smoothly 

rounded. The maxillary extends to a vertical drawn 

through the center of the eye. 

A key for the separation of the species of Euthynnus, as 

adapted from Godsil (1954a), is given below. 

A. Specimens having 37 (36-38) vertebrae, 

with four lobes or protuberances on each 

of two vertebrae, predominantly the 31st 

and 32d. (Invariably has vomerine teeth; 

usually has about five continuous, horizontal black dorsal stripes; 33 to 39 gill 

rakers and 29 to 31 gill teeth.) ......... E. lineatus 

B. Specimens having 39 vertebrae. 

1. Vomerine teeth present. No indication 

of lobes on 33d or 34th vertebrae. 

(Usually has oblique broken dorsal 

markings; from 29 to 33 gill rakers and 

28 or 29 gill teeth.) ................ . E. affinis 

2. Vomerine teeth absent, although a 

longitudinal bony ridge can be felt in 

this area . Incipient lobes or protuberances occur on the 32d and 34th vertebrae. (Usually has broken horizontal 

dorsal markings; from 37 to 40 gill 

rakers and 31 or 32 gill teeth; width of 

snout between anterior margin of eyes 

less than distance of this plane from tip 

of upper jaw.) ............... E. alletteratus 

1.22 Taxonomic status 

See also section 1.11. 

Godsil (1954a) made a detailed comparison of the 

three species of Euthynnus (Table 1). He indicated that 

while the specific identity of E. affinis, E. alletteratus, 

and E. lineatus appeared to be well established, most of 

the differences that distinguish each species were relative. He noted that all the characters that positively separate the species were skeletal and that only the absence 

of the dentigerous vomerine plate in E. alletteratus could 

be used for superficial identification. However, it should 

be pointed out that E. alletteratus (37-40) is separable 

from E. a/finis (29-33) on the basis of gill raker counts. 

Euthynnus lineatus is clearly separated from E. affinis 

and E. alletteratus by having 37 (36-38) vertebrae as op-
Character 

ternal 

Dorsal markings 

Color 

Belly spots 

Lateral line 

Vomerine teeth 

Maxillary extent 

Proportions: 

Head length 

insertion 

1st dorsal 

2d dorsal 

anal fin 

ventral fin 

Ventral insertion to vent 

Width between 

anterior margin of eye 

Gill rakers 

Gill teeth 

Anal rays 

ternal 

Ventral view of 

viscera 

1. Mosaic 

2. Right lobe of 

liver 

3. Fat organ 

Ureter 

1. Branches 

keleton 

Vertebral column 

Protu berances 

E. ltn.l!atzu 

Continuous, horizontal bar 

Darker or deeper hued than In 

alletteratus or a{{inl!> 

Larger than in afftn.is 

a. DIp below second dOl1lal 

b. Relatively steep rise above 

pectoral 

Present 

To vertical through center of 

eye 

3.13 to 3.62, as in affinis, 

longer than alletteratus 

2.82 to 3.33, more posterior 

than alletteratus, as in 

affims 

1.51 to 1.79, includes affinis 

and alletteratus 

1.37 to 1.55, as in affims, 

more posterior than in 

alletteratus 

2.76 to 3.25, as in affims, 

more posterior than in 

alletteratus 

2.62 to 3.01, includes afftn.1S 

and overlaps alletteratus 

Less than distance from tip 

of upper Jaw to plane 

through anterior margin of 

eye 

7tolO +1 +24 to 28 

Total count 33 to 39 

8 to 10 +21 to 23 

Total count 29 to 31 

11 to 12 

Absent 

Lateral, as In afflnis 

Absent 

Large, straight, few collecting 

tubule as m afftn.is 

37 vertebrae 

4 large lobe on each, 31st 

and 32d ,ertebrat' 

E ol/f'llcralu 

Broken hOrizontal ba 

As in afflnt 

ot record d 

No dip below econd dorsal 

Gentle rise above pectoral 

Absent 

As m laneatus 

3.65 to 3.89, shorter than 

afftn.1S and ltn.eatus 

3.37 to 3.55, more anterior 

than m affinis and laneatau 

1.72 to 1.77, as in linealau. 

more anterior than in afftn.1.I 

1.57 to 1.61. more anterior 

than in arrim8 and hnea/au 

3.27 to 3.46. more anterior 

than m afftn.is and Itn.eatw 

2.57 to 3.12, overlap linea/au 

less than arrlms 

Less than distance from tiP of 

upper Jaw to plane through 

anterior margtn of ey~ 

10 to 11 + 1 + 26 to 28 

Total count 37 to 40 

9 +22 to 23 

Total count 31 to 32 

11 to 15 

Ab ent 

ie lal 

Absent 

GeneralJ) email, erratic, 

numerou coliKtan tubul 

9 vertebra 

incipient lobe- on 3d and 

th vertebrae 

d to 39. It i further differentiated by the pre ence of 

Our characteri tic lobe on each of the 31 t and 32d 

'ertebrae and by having the major portion of the caudal 

ony keel on the e tw vertebrae . The major portion 0 

he caudal bony keel are on the 33d and 34th \'ertebrae 

In E. affims and E . alletteratu" . 

Euth.\nn.u$ affinis and E. alleN raW, ar pe lfi ally 

different in several structural feature, : the ab enc 0 \0-

merine teeth in E. alletteratu , the pr _ nc I)f in ipi nt 

5 

E a{/lnu 

maller than tn 

(enterof en' 

3 11 to 3 ~3, Ill! tn llnt'O/u , 

more postenor han In 

allttt. ratu 

1.65 to 1 70. In 1111. a/cu, 

more po4!tenor thlln In 

011"1/. ratu. 

148 to 1 52. 118 In Ian lu 

mor po4!tenor than In 

allctt ratu 

3.07 to 3.24. a In Iln atu , 

more po4!ten r than tn 

allctl,'ralu, 

2.75 to 2 '. a, tn lin alu 

gr~alt'r than 01 .. tl(fat 

h 

Gr~at r than dl lane from lip 

01 upper )a\lo to plan thr u h 

antenor mar nn of e) 

.. to .. 1 22 to ~~ 

Total count to 

+~ t021 

Total count ~ 

13 to 14 

Pr nt, 

17 

Indl 811\ 

&.1\ 

II 

Indl all\ 

HI m t.rI 8\ 

Hlom tn .1 

HI mIn .1 

HI Inca I 

81 m lr a 

B 

H m n.1 

H 

Ind • 
length (fork length) in each case by the head length, first 

dorsal insertion, second dorsal insertion, anal insertion, 

and ventral insertion, he obtained figures ranging from 

12.86 to 13.23 for E. affinis (eight specimens 378-643 mm 

Table 2.-Common and vernacular names of Euthynnus affinia, 

E. alletteratus, and E. lineatus. 

Country 

Australia 

Sri Lanka 

China 

Comoro Island 

East Africa 

Hawaii, U.S.A. 

India 

Indochina 

Indonesia 

Japan 

Madagascar 

Malaysia 

MauritiLis 

Mirjurtein coast 

Mogadiscio 

New Guinea 

Pakistan (West) 

Philippines 

Seychelles 

Somalia 

Abidjan 

Angola 

France 

Ghana 

Guinea 

Ivory Coast 

Mauritania 

Portugal 

Senegal 

South Africa 

Spain 

Tunisia 

United States 

Ecuador 

Mexico 

Peru 

United States 

Standard common 

name(s) Vernacular name(s) 

Euthynnus afflnls 

Mackerel tuna, 

little tuna 

Les er bonito, 

mackerel tuna 

Bonito 

Bonito, 

little tuna 

Little tuna 

Yaito 

Bonite 

Bonito 

Kababida 

Dwarf bonito 

Oceanic bonito 

Little tunny, 

bonito 

Atavalla, Ragodura, ureya 

(Sinhalese ), hural (Tamil) 

Tow chung 

Mibassi, Mpassi 

ehewa (Kiswahili)-also 

refers to A UXIS spp and 

Katsuwonus pelamlS 

Bonito, kawakawa 

Choori min, suraly (Tamil), 

ohaman, chuki (Marathi) 

Cangu 

Tongkol, diverg-bonito, tongkol 

komo, poetilal 

uma, hiragatsu'vo, oboeogatsuwo 

segatsuwo, sumagatsuwo, 

watanabe 

Thonnine 

Tongkol; Ikanayer, embak, 

Choreng, Kemoel-mas, 

Tombal-mas (Malay) 

Bonite 

Shirwa, shirwl (Arabic) 

Maba'adi (Somali), Jeidha 

(Somali), also refers to small 

Thunnus alba cares and 

M egalaspis cordyla 

Dawan, Chooki, Jukko 

Katsanta, turingan, yaito bomto 

Bonite 

Euthynnus alieLteratus 

Bonita 

Merma 

Thonine 

El'la (Apollonien), Poponkou 

(Keta) 

Makreni 

Klewe (Kru), bokou-bokou 

(A1ladian) 

Corrinelo (Vermeulen) 

Atun Fule-fule 

Walaz (OuoloO, dolo-dolo 

(Lebau) 

Little tunny, Merma 

little tuna, 

mackerel tuna 

Bacoreta 

R'zem 

Little tunny False albacore 

Euthynnus lineatus 

Negra, bonito negro 

Barrilete negro 

Barrilete negro 

Black skipjack Cross-bred mackerel 

6 

FL) and 13.64 to 14.19 for E. alletteratus (seven specimens 503-763 mm FL). He found that these values were 

independent of fish size for both species so that mean 

values, 13.046 for E. affinis and 13.996 for E. alletteratUb, 

could be used to define the species. The head of E. affini, 

wa proportionately larger and the fins were more paste 

riorly inserted . 

1.23 ub pecies 

No sub pecies are recognized . 

1.24 tandard common names, vernacular 

name 

The common and vernacular name of the three specie of Euthynnus are given in Table 2. 

1.3 Morphology 

1.31 External morphology 

The pattern of markmg may vary, ometime considerably, III the three pecie of Euthy nnus (FraserBrunner 1949; God il 1954a). ( ee Fig . 1-3.) 

Euthynnus affmis 

God !I (1954b) made morphological studies on E affim from Hawaii and Japan (Table 3). He found several 

minor difference in the body proportions of fish from the 

two area but concluded that the e differences merely 

indicated population differences. 

Meristic data on E. affini from various areas are give 

in Table 4. 

Table 3.-Bod} proportions of Euthynnus affinia from Japan 

and Hawaii. (From God il 1954b, table I.) 

Range In ratl 

Proportions Japan Hawaii 

Head length 3.66-3.72 3.«-3.60 

1st dorsal insertion 3.07-3.27 3.11-3.23 

2d dorsal insertion 1.54-1.67 1.65-1.70 

Anal insertion 1.53-1.54 1.48-1.52 

Ventral insertion 3.33-3.43 3.07-3.24 

Greatest body length 3.55-3.99 

Dorsal-ventral distance 3.97-4.18 3.86-4.18 

Dorsal-anal distance 2.31-2.37 2.28-2.38 

Ventral insertion to vent 2.75-2.86 2.75-2.95 

Length of 1st dorsal base 3.24-3.41 3.23-3.53 

Length of 2d dorsal base 14.07-15.96 14.29-15.53 

Length of anal base 13.76-14.46 14.02-17.38 

Pectoral length 6.23-6.88 5.54-6.05 

Height of 1st dorsal 6.86-7.00 6.41-7.00 

Height of 2d dorsal 13.83-14.78 12.10-14.15 

Height of anal 13.83-15.00 11.91-14.15 

Diameter of iris' 7.27-7.82 6.06-8.00 

Maxillary length ' 2.49-2.53 2.31-2.51 

Snout to posterior margin of eye ' 2.35-2.38 2.14-2.34 

'Ratio of this measurement is to head length. All other measurements 

are related to fork length. 
Table 4.-Enumerative data on Euthynnu8 affinis. 

First Second 

dorsal dorsal Dorsal Anal Anal Pectoral Gill 

Area fi n fi n fi nl ets 

Sri Lanka 

Deraniyagala (1952) 14-15 12 

Munro (1955) 15 20 

East Africa 

Morrow (1954) 14-15 11-12 

Will iams (1956, 1964) 15-16 11-13 

India 

8 

8 

8 

8 

Jones and Silas (1964) 14 11-14 8-9 

Indonesia 

De Beaufort and 

Chapman (1951) 15 13 

Indo-Pacific 

Fraser-Brunner 

(1949, 1950) 

Madagascar 

Fourmanoir (1957) 

[Pakistan.] (west) 

Central Fish 

Department (1955) 

Red Sea 

15 11-13 

15 13-14 

8 

8 

8 

Steinitz and BenTuvia (1955) 

15-16 8-9 

Reunion 

Blanc and Postel 

(1958) 

South Africa 

Smith (1961) 

Japan 

Godsil (1954b) 

Hawaii 

Godsi I (1954 b) 

15-16 11-13 

15 12-13 

14-15 12-13 

Euthynnus alletteratus 

Based on body proportions of E. alletteratus taken 

along the eastern Atlantic, Marchal (1963) indicated 

that there were no noteworthy differences in the samples 

from Cap Vert, Senegal, to Ghana. 

Postel (1956) compared body proportions and meristic 

data of E. alletteratus from the Mediterranean Sea 

(Tunisia) and the eastern Atlantic Ocean (Senegal). He 

noted that the Tunisian sample was characterized by a 

shorter head and a shorter predorsal (snout to insertion 

of first dorsal) and preventral (snout to insertion of ventral) distance (Table 5). The Tunisian specimens also 

had a smaller number of gill rakers (36-41) than the 

Senegalese specimens «38-47). 

Body proportions of E. alletteratus from the U.S. 

Atlantic coast are given by Godsil (1954a) (Table 6). He 

also presented meristic data from these fish, which are 

shown below. 

Meristic character 

First dorsal spines 

Second dorsal rays 

Counts 

10-15 

12-13 

8 

8 

8 

7 

fin finl ets fin 

14-15 7 28 

14 7 26 

12-14 6-7 

13-14 6-7 

12-15 6-8 24-28' 

14 7 24 

13-15 7-8 

14 8 26 

7 

12-15 6-8 

14 7 

13-14 7 

rakers 

22-24 (lower 

arch) 

24 (lower arch) 

(7-10) + (22-23) 

= 29-33 

(7-10) + (22-25) 

= 29-35 

24 (lower arch) 

(7 -10) + (22-23) 

= 29-33 

25 (lower arch) 

23-24 (lower 

a rch) 

8+1+24 = 33 

25 (lower arch) 

8+1+(22-24) 

= 31 -33 

(7-9)+1+(22-24) 

= 29-34 

8 

11-15 

7 

Dorsal fin lets 

Anal rays 

Anal finlets 

Gill rakers (10-11) + (0-1) 

+ (26-28) = 37-40 

Mansueti and Mansueti (1962) prepared a "topographic" osteology of a specimen captured in Chesapeake Bay (Fig. 4). 

Euthynnus lineatus 

Body proportions of E. lineatus are given in Table 7. 

Meristic data, from Godsil (1954a), are given below. 

Meristic character 

First dorsal spines 

Second dorsal rays 

Dorsal finlets 

Anal rays 

Anal finlets 

Gill rakers 

Counts 

13-15 

11-12 

8-9 

11-13 

7-8 

(7-11) + 1 

+ (23-29) = 31-41 
Table 5.- Body proportions of Euthynnus alletteratus from 

Tunisia and Senegal (Postel 1955b: 132-133; 1956: 54). Ratios 

indicate fork length divided by length of body parts. 

Ratios Length 

class Head First dorsal Ventral Pectoral 

(em) N length insertion insertion length 

Tunisia 

40-45 1 4.27 3.40 3.40 7.06 

45-50 2 4.21 3.57 3.48 6.99 

50-55 11 4.22 3.50 3.46 6.99 

55-60 30 4.24 3.55 3.50 6.95 

60-65 10 4.29 3.56 3.53 6.90 

65-70 16 4.28 3.53 3.53 6.70 

70-75 13 4.29 3.55 3.53 6.82 

75-80 3 4.21 3.59 3.55 6.86 

80-85 5 4.29 3.60 3.57 6.88 

85-90 5 4.33 3.58 3.55 6.88 

90-95 3 4.40 3.67 3.59 6.81 

95-100 4.37 3.65 3.62 7.06 

Senegal (Males) 

30-35 3.82 3.25 3.15 

35-40 7 3.84 3.28 3.18 6.12 

40-45 81 3.85 3.30 3.20 6.08 

45-50 62 3.85 3.30 3.22 6. 14 

50-55 13 3.87 3.33 3.24 6.31 

55-60 0 

1.33 Protein specificity 

The erythrocytes of two E. lineatus were tested with a 

series of 540 bean extracts as part of a preliminary work 

on a program for typing fish blood. On the basis of agglutinations, it was determined that the blood of E. lineatus can be differentiated from that of six other scombrids in the eastern tropical Pacific (Calkins and Klawe 

1963). 

Table 6.-Body proportions of seven Euthynnus alletteratus from the western Atlantic (Atlantic 

coast of United States). Fork length the numerator 

except those indicated by an asterisk, where head 

length is the numerator. (From Godsil 1954a, 

table 15.) 

Proportions Ratios 

Head length 3.65-3.89 

1st dorsal insertion 3.37-3.55 

2d dorsal insertion 1.72-1.77 

Anal in ertion 1.57-1'.61 

Ventral insertion 3.27-3.46 

Greatest body depth 3.91-4.16 

Greatest body width 6.07-6.12 

Dorsal-ventral distance 4.08-4.36 

Dorsal-anal distance 2.37-2.50 

Ventral insertion to vent 2.87-3.12 

Length of first dorsal base 3.30-3.57 

Length of second dorsal base 14.16-17.25 

Length of anal base 13.80-16.05 

Pectoral length 5.89-6.50 

Height of 1st dorsal 6.90-7.74 

Height of 2d dorsal 10.78-13.55 

Height of anal 10.78-12.74 

Diameter of iris *7 .81-8.35 

Maxillary length *2.54-2.74 

nout to posterior margin of eye *2.43-2.45 

2 DISTRIBUTION 

2.1 Total area 

In general the species of Euthynnus are coastal fishes 

found in tropical and subtropical waters of the world. Of 

the three species, E. lineatus has the most restricted 

distribution, occurring only in the eastern tropical Pacific Ocean. Euthynnus affinis and E. al!etteratus are 

Table 7.-Measurements (millimeters) and proportions of Euthynnus lineatus. Fork length the numerator except those 

indicated by an asterisk, where head length is the numerator. (From Godsil 1954a, table 10.) 

Fish number 

Proportions 19 20 24 26 28 29 30 31 32 33 34 35 36 37 38 Ratios 

Body length 520 574 5 3 492 472 446 427 613 514 432 476 455 484 ca . 443 462 

Head length 150 167 170 157 137 13 123 176 148 116 136 132 137 132 134 3.13- 3.72 

1st dorsal Insertion 165 1 6 1 3 Broken 150 158 133 197 160 129 146 142 145 145 143 2.82- 3.35 

2d dorsal insertion 306 345 340 326 283 293 252 367 299 249 278 267 280 ca . 269 272 1.51- 1.79 

Anal insertion 336 3 4 3 6 359 308 315 281 408 339 280 305 295 316 292 302 1.37- 1.56 

\'entral insertion 164 1 2 178 154 153 137 198 167 132 153 146 168 147 154 2.76- 3.27 

Greatest body depth 132 157 148 ca . 123 131 128 3.32- 4.58 

Greatest body width ca.85 ca . 79 ca. 85 5.93- 6.17 

Dor.al-\'entral dIstance 128 147 116 127 120 3.51- 4.55 

Dorsal-anal distance 210 241 192 204 210 2.19- 2.50 

\'entral In>ertion to vent 180 206 187 157 170 144 205 175 147 149 153 153 143 150 2.62- 3.19 

Length I>t dorsal base 146 1 Broken 137 143 145 3.12- 3.86 

Length 2d dorsal base 32 33 30 34 31 13.12-18.84 

Lengt h of a nal base 31 31 24 30 31 14.87-20.10 

Pectorallen!(th 4 8 89 78 84 87 5.31- 6.99 

HeIght of 1st dorsal 66 72 Broken 64 71 76 6.28- 7.97 

Height of 2d dorsal 33 Broken 33 35 36 12.74-16.63 

Hel!(ht of anal 34 ca.45 36 35 35 12.74-18.29 

Diameter olm> 23 ca 20 20 20 19.5- • 6.00- 7. 5 

:\laxIliary length 59 65 57 53 52 57 • 2.48- 2.75 

"nollt to postenor 

margin 01 eye ca. 58 62 * 1.97- 2.39 

8 
~ 

First DorsaL Fin 

SYNCRANIw,r 

ATLANTIC LITTLE TUNA 

Euthynnus alletteratus (Rafinesque) 

injerwr foramen 

Fin 

NEUROCRANIUM 

8 v:::;e....-~ pLerotic ~exocc!Pltal - atlas 

centrum 

transversapophysis 

prehaemapophysis 

( haernaL prezygapophysis) 

prehaemapophyseal spur 'it 1 I posthaemapophyseal spur 

,,1,&ce. Ja/}~I/Wall5(/~I;" D VERTEBRA 2 3 

PECTORAL GIRDLE 

Figure 4.-Topographic osteology of Euthynnus alletteratus. A. Syncranium, axial, and appendicular skeleton. B. Neurocranium. C. Pectoral girdle. D. Parts of vertebra 23 and its 

unique trellis. (From Mansueti and Mansueti 1962, fig. 2.) 
n rthea tern area, 130 ea. tern central 

y Republic. 

central area; 430 ~ uthea~tern area; 440 

1m mland); 5Oea.ternareali .). 

nt 10 Au tralta, 640 ea. tern Oceania; 660 

II , 70 Pacific I .; ~ central group. 

n the di tribuhon ot E affini is e~­

al n th entire ea t frican coa.t 

nd the ulf of den, along the 

nd both coa of lndia, Burma, 

" c" 

MalaJia . and Indone'ia. and to the we t coa t of 

u..,tnida It occur: around ~ladaga~car (:\lalaga y RepublIc' ~n Lan 'a (Ceylon). and the off hore islands and 

ar hipt'lligl • ot • lauritius. Reunion, Comoro, the eychelles including Aldabra, Laccadlve, Maldives, and 

.o\ndaman and 'icobar \\ illiam' 1963; Jone and "'ila 

1 ~ ). 

Euth) nnu~ alletteratus 

Al\W (Atlantic. NW) 

A .., \\' (Atlantic. SW) 

A. 'E (AtlantiC, J. E) 

A "'E (Atlantic, SE) 

100 :Vrica 110 northwe tern area; 140 we tern central 

area; 150 'outhern area. 

200 :\ Irth America. 236 ew Englad; 237 Middle 

AtlantiC tates; 235 southern tate; 238 southern Atlantic states 

3 Latin America. 311 Mexico; :320 Caribbean Is.; 351 

Brazil; 352 Uruguay, 353 Argentina . 

500 Europe. 510 Scandinavia; 520 western area 

(mainland); 530 British I Ie ; 540 outhern area; 550 

. outheastern area. 

Euthynnu.\ alletteratus i found along both coast of 

the Atlantic Ocean and in the Mediterranean 'ea. It is 

also found in the Sea of Marmara and it occurs po. 

radically in the Black Sea (Demir 1961.1963) (Fig. 6) . 

In the eastern Atlantic Ocean, Laeva tu and Rosa 

(1963), in their di tributional chart of E a II ett era tus. 

indicate that the limits of the "regular" di tribution of 

t his species are from off the coa t of Morocco to the coa t 

of northwest Atrica. Marchal (1963) listed the following 

areas along the west African coast from which E. alletteratu~ has been recorded: unier Bay. Mauritania 

(Po-tel 19S0); ape Verde blands and Gambia (Cadenat 

19."0; Postel 1950); off the Bi -ago. GUinea, and ierra 

Leone (!\1archal 1961; Po tel 1962); the length of the 

PACIFIC OCEAN 

fr m Kl ft an larr 
o· 

! -----L 

_ F+----j .............. UNCERTAIN, ASSUMED BOUNDARY t-40' 

-----SPORADIC OCCURRENCE 

I --LIMIT OF REGULAR DISTRIBUTION 

, I I I 

80· 40· 20· o· 20· 

Figure 6,-Distribution of Euthynnus alletteratus. (Adapted from 

Laevastu and Rosa 1963, fig. 4.) 

coast of Liberia, the Ivory Coast and Ghana; St. Thomas 

an? Principe Islands (da Costa and Frade 1958); and 

Pomte-Noire (Roux 1957). 

The distributional chart of E. alletteratus in the western Atlantic given by Laevastu and Rosa (1963) shows 

the limits of its distribution from the coast of Maine to 

the northern boundary of Brazil. Briggs (1958) stated 

that in the western Atlantic E. alletteratus is distributed from "Bermuda and the Gulf of Maine to Ilha Victoria, Brazil, and the northern and eastern Gulf of Mexico." Fraser-Brunner (1949) also recorded the species 

from Rio de Janeiro, Brazil. 

Euthynnus lineatus 

ISE (Pacific, SE) 

200 North America. 232 southwestern states (California), 

300 Latin America. 310 Central America (mainland); 

340 western South America. 

Euthynnus lineatus is found in the tropical coastal 

waters of the eastern Pacific from about lat. 35°N to 12°S 

(Fig. 7). Calkins and Klawe (1963) constructed this figure from records of E. lineatus reported in the literature, 

tuna vessel logbooks, scientific logs of oceanographic 

cruises by ships of the Scripps Institution of Oceanography and the National Marine Fisheries Service, and 

field-book notes of C. L. Hubbs, Scripps Institution of 

Oceanography, and D. P. de Sylva, University of Miami. 

Records of E. lineatus in the literature include the northernmost record from off San Simeon, Calif. (lat. 35 °20'N, 

long. 120 0 40'W) (Nowell 1961), specimens from California waters (Roedel 1948; Fitch 1952), Baja California 

11 

(Godsil 1954a), the Tres Marias Islands (Fowler 1944), 

Acapulco, Mexico (Mais and Jow 1960), Costa Rica 

(Schaefer and Marr 1948), Colombia Bank (lat. 2°N, ' 

long. 79°W), Guayaquil Bank (lat. 3°35'S, long. 80° 

55'W) (GodsiI1954a; Clemens 1957), and from the Galapagos Islands (Fowler 1938, 1944; Schmitt and Schultz 

1940; Seale 1940; GodsiI1954a). Logbooks of commercial 

tuna vessels indicate that E. lineatus has been encountered nearly everywhere along the coastline from 

about halfway down the coast of Baja California to 

northern Peru. They have been frequently encountered 

in the Gulf of California, the Revillagigedo Islands, all 

along the coast of Mexico and Central America, and the 

Galapagos Islands. There have been occasional reports of 

this species from Clipperton and Cocos Islands and there 

is a single report of its occurrence from Shimada Bank 

(lat. 16°52'N, long. 117°30'W) (Calkins and Klawe 1963). 

More recently, they have been recorded as far as 2,000 mi 

(3,200 km) off the coast in the eastern Pacific (Klawe 4). 

In addition there are two records of E. lineatus from the 

Hawaiian Islands (Matsumoto and Kang 1967; Matsumoto 1976). 

2.2 Differential distribution 

From all indications it appears that the distribution of 

all the different life stages of E. affinis and the other two 

species of Euthynnus appears to be similar. As noted 

earlier the adults are generally coastal fishes and judging 

from the distribution of the various life stages of these 

species, the entire life cycle is completed within the 

coastal province. 

2.21 Spawn, larvae, and juveniles 

Euthynnus affinis 

Larval and juvenile E. affinis are widely distributed in 

the Indo-Pacific area (Fig. 8). As many investigators 

have observed in the past, e.g., Matusmoto (1959), it appears that larval and juvenile E. affinis are generally 

taken close to iand masses and less frequently around 

oceanic islands. There also are a few captures of larval 

fishes in midocean localities but chances are these were 

carried away from coastal areas by the prevailing currents. 

In the coastal waters of southern Japan Yabe et al. 

(1953) indicate that preadults ranging in length from 150 

to 250 mm are taken from August to October near 

Aburatsu, Kyushu. Preadults also constitute a regular 

part of the commercial catch in other areas. In the fishery for E. affinis off the southwest coast of Sri Lanka, fish 

smaller than 240 mm appear regularly in the commercial 

landings (Sivasubramaniam 1970). In the Philippines 

Wade (1950a) obtained many of his juvenile and preadult E. affinis from various fish markets. 

4 W. L. Klawe, Inter-American Tropical Tuna Commission, Scripps 

Institution of Oceanography, La Jolla, CA 92037, pers. commun. to 

Tamio Otsu, National Marine Fisheries Service, Southwest Fisheries 

Center, Honolulu, HI 96812, November 1977. 
~'" 120· 115· 110· 105· 100° 95· 90· 85· 80· 7S· 

3S· • 35" 

• lit ~;~~~~ 

I\~ 30° 30· '( 

':)0.,. GULF OF 

• \..~ CAlIFORMA 

• I~ 25· .: .'It ~ 25G 

.r.~ 

• • • .1'1. TRes AlAIIIAS I 

• • [ <,. ISL ANOS 

20G 20° .ft' REVJLLA(il(iEOO • .i! j ISLANDS • .t4I tiUlFOF J. 

'<It. rEHUANrCPEc SHIMADA >I • 15° BANK • • •• -\>. 15· 

•• •• • •• • • 

10° CL IPPER rON IS. Iii • • ~~ PANAMA 

• ..... ~~ •• • ~ 05° coco IS • •• 05· ~ J PAR AMOiJN' • .) BANK • 

O· • GALAPAGOS ......... 0° ISlANOS 

• GutJ OF 

~"IIArAOCAf( 

05° ... OS· 

10° 

10· 

15° 1 

15° 

200 

1250 1200 1150 110· lOS· 100· 95,· 90· 

Figure 7.-Distribution of Euthynnus lineatus in the eastern Pacific Ocean. (From Calkins and Klawe 1963. 

fig. 2.) 

Euthynnus alletteratus 

The distribution of larval and juvenile E. alletteratus 

is shown in Figure 8. They have been recorded from both 

sides of the Atlantic Ocean, the Mediterranean Sea including the Black Sea and Sea of Marmara, and from the 

Gulf of Mexico. In the eastern Atlantic along the west 

African coast, the northernmost record of larval E. alletteratus is from off the northern coast of Morocco. There 

are numerous records of larval E. alletteratus from the 

Gulf of Guinea. The absence of records from farther 

south along the coast of Africa may merely reflect lack of 

sampling effort. In the western Atlantic, larval E. alletteratus has been collected as far north as lat. 35°42'N off 

the North Carolina coast of the United States and as far 

south as lat. 100 S off the coast of Brazil. Although most 

of the larvae have been 'collected relatively close to shore, 

there are a few midocean records of E. alletteratus larvae. 

Richards and Simmons (1971) suggested some sort of 

vertical stratification in the distribution of larval E. alletteratus. They noted that the larvae were collected 

more often at the surface at night. They also tentatively 

concluded that there was greater net avoidance by larval 

E. alletteratus during the day. However, they attributed 

the higher frequency of capture at night to vertical migration. 

Marchal (1963) stated that along the coasts of the 

Ivory Coast and Ghana postlarval and juvenile E. alletteratus were found at the surface from 2 mi (3.2 km) to 

around 100 mi (160 km) off the coast. Marchal made the 

observation that those postlarval and juvenile fish,found 

out to 100 mi (160 km) offshore were probably taken out 

by the currents because no adults were found beyond the 

12 
~ I A ~ E4thy""US offl"ls I 

w 

40· 

20· 

/---1----20· 

20 · o· 60· E 

Figure S.-Distribution of larval and juvenile Euthynnus spp. (See Tables 9-11.) 

continental shelf. He stated that these young forms of all 

sizes were taken from October to July and that they may 

be present all year. Marchal observed that preadult E. 

alletteratus appeared to be closer to the coast than the 

adults. He indicated that the beach seines did not catch 

fish over 40 cm long. 

In the Mediterranean Sea in Haifa Bay, Oren et a1. 

(1959) captured preadults 80 to 240 mm long from the 

end of June to the middle of August. Also in the Mediterranean area, Demir (1963) reported the catch of preadult E. alletteratus ranging from 145 to 220 mm long in 

the Sea of Marmara during the period from the last week 

of August to the second half of September. He also reported 180 to 250 mm long preadults in the Dardanelles 

from the middle of August to the end of the first week in 

October. 

I,n the Gulf of Mexico juvenile and preadult E. alletteratus 15 to 172 mm long have been commonly found beyond the edge of the continental shelf throughout the 

summer months (Bullis 1955). 

Euthynnus lineatus 

Larval and postlarval E. lineatus are almost as widely 

distributed as the adults in the eastern tropical Pacific 

Ocean (Fig. 8). They have been recorded as far north as 

lat. 29°45'N (Point Antonio, Baja California) and south 

13 

to lat. 04°()()'N, long. 81 °35'W (the vicinity of Malpelo 

Island) (Calkins and Klawe 1963). The larvae were also 

collected near the head and entrance of the Gulf of California . Except for one specimen caught near Malpelo 

Island, all the larval and juvenile E. lineatus have been 

collected within about 150 mi (240 km) of the mainland. 

2.22 Adults 

See section 5.3. 

2.3 Determinants of distribution changes 

The three species of Euthynnus seldom occur more 

than a few hundred miles from land. They are usually 

found around land masses and island chains generally 

between lat. 35 °N and 35°S (Blackburn 1965). Godsil 

(1954a) noted that E. lineatus along the west coasts of 

Baja California and Central America appeared to be localized in distribution and confined to certain inshore 

areas. He also noted that E. affinis in the Hawaiian 

Islands were confined within the 20 or 30 fathom (36.5 or 

54.8 m) contour. In the western Pacific near New Guinea 

E. affinis were abundant and distributed in inshore 

waters throughout the area (Mori et a1. 1969). Around 

the Maldive Islands in the Indian Ocean E. affinis are 

found close to the islands and they often venture into 
shallow water in pursuit of bait (Jonklaas 1967). In this 

respect the species of Euthynnus generally appear to be 

similar to some species of Sarda which are also inhabitants of the coastal or neritic, pelagic province. Sverdrup et al. (1942) characterized the neritic province as 

one where the environment is more variable than in the 

oceanic. In the neritic province the chemical constituents of the seawater are more variable: salinities are 

usually lower and some of the inhabitants may be more 

or less euryhaline. 

The species of Euthynnus, particularly E. affinis, are 

also found in waters around oceanic islands and archipelagos although here too they are found close to shore. 

The following example illustrates the type of habitat occupied by the species of Euthynnus. 

Off the coast of Japan E. affinis may occur in waters 

with salinities ranging from 31.22 to 33.80%. (Yabe et al. 

1953). Yabe et al. (1953) also noted that near Aburatsu, 

Japan, heavy autumnal rains make the water turbid 1 or 

2 mi (1.6 or 3.2 km) from shore and cause a considerable 

lowering of the salinity in the surface water. However, 

these conditions did not seem to affect the catches of E. 

affinis. Kishinouye (1923) noted that E. affinis in 

Japanese coastal waters are found in waters ranging from 

18° to 28°C. 

Williamson (1970) described the coastal environment 

of E. affinis around Hong Kong. The coast is composed of 

steep, rocky headlands and islands and the 50 m contour 

lies about 25 mi (40 km) offshore. The surface water 

temperature ranges from 14° to 29°C annually. The west 

side of Hong Kong is greatly influenced by the estuary 

waters fed by the West River. The bottom in this area is 

muddy and the water turbid and brackish (surface 

salinity, 33%. in February and 6%. in July). On the east 

side of Hong Kong more oceanic conditions prevail: the 

surface salinity is 34%. in February and 26%. around July, which is the height of the summer rainy season. 

In the Indian Ocean the tropical and subtropical 

waters are generally characterized by a scarcity of 

plankton offshore except in areas where vertical mixing 

of water masses occurs, e.g., off Somalia, where upwelling takes place. Strong development of phytoplankton and the ensuing zooplankton is confined to the 

immediate coastal areas (Williams 1963). 

Along the Atlantic coast of the United States most of 

the E. alletteratus are taken in "green water" and are 

seldom taken in the "blue water," or slope water of the 

Florida Current (de Sylva and Rathjen 1961). As de 

Sylva and Rathjen pointed out, E. alletteratus typically 

occupy the inshore turbid waters. Morice and Cadenat 

(1952) made a similar observation in Guadeloupe, and 

Whiteleather and Brown (1945) noted that this species 

appeared to be a coastal fish in areas around Trinidad, 

Tobago, and Guyana. 

Calkins and Klawe (1963) characterized the general 

habitats of E. lineatus based on published studies 

(Holmes et al. 1957; Brandhorst 1958; Cromwell 1958; 

Cromwell and Bennett 1959; Sund and Renner 1959). 

Calkins and Klawe (1963) noted that E. lineatus occurs 

in the equatorial Pacific water mass which extends 

14 

approximately from lat. 23° or 24 ON to northern Peru 

and the Galapagos Islands. There are transition zones to 

the north and south of the tropical water mass which are 

influenced by the cold California Current and the Peru 

Current in the north and south, respectively. The principal warm currents influencing the tropical water mass 

are the North Equatorial, the Equatorial Countercurrent, and the South Equatorial Current. Where E. lineatus is most frequently found near the coast, these currents are usually weak and variable and the thermocline 

is relatively shallow (10-50 m) which allows the exchange 

of nutrients between the deep layer and the surface 

waters. In a thermal dome located off Central America 

(lat. 9°N, long. 900 W) the thermocline is frequently less 

than 10 m and sometimes reaches the surface. In the Gulf 

of Panama, the Gulf of Tehuantepec, the Gulf of California, and the inshore waters of Baja California, upwelling enriches the inshore waters. 

3 BIONOMICS AND LIFE HISTORY 

3.1 Reproduction 

3.11 Sexuality 

All of the species of Euthynnus are heterosexual, males 

and females do not differ in external appearance, and 

there is no record in the literature of hermaphroditism in 

these fishes. However, it would not be surprising if 

hermaphroditic specimens were to occur since cases have 

been discovered in closely related species, e.g., Katsuwonus pelamis (Uchida 1961). 

3.12 Maturity 

Euthynnus affinis 

Euthynnus affinis apparently attains sexual maturity 

at a relatively small size, at least in certain areas of its 

distributional range. Buiiag (1958) examined a total of 30 

E. affinis 44.4 to 62.2 cm long in Philippine waters and 

found that the smallest female with mature gonads was a 

specimen 49 cm long. A 47.7 cm female was found to have 

spent ovaries. In an earlier study in Philippine waters, a 

sample of 205 females included a ripe specimen between 

40 and 40.9 cm long that was determined to be spent. In 

yet another study comprising a sample of 144 fish 33.4 to 

50.8 cm long, it was found that the smallest mature female was around 38.5 cm long (Ronquillo 1963). 

Euthynnus affinis in the Indian Ocean appears to 

reach sexual maturity later than those occurring in the 

Philippines. Based on a sample of 75 specimens taken 

near the Seychelles, Ommanney (1953) reported that E. 

affinis attained sexual maturity between 50 and 65 cm 

TL (total length), probably in the third year of life. Williams (1956, 1963) examined 37 specimens from east 

Africa and noted that fish there attained sexual maturity 

between 55 and 60 cm TL. In Mauritius waters E. affinis 
55 cm long are mature (Bai. ac'). Off the uthwe t 

coast of India near Vizhingam (lat. 0 °22', " long. 

76°59'E) the mallest female with ripe ovarie wa found 

to be 48 cm (Rao 1964). 

In the outh China ea off Kwangtung, hina, E af· 

flnt!> pre umably attain exual maturity at around 50 

cm (William on 1970) EI ewhere in thi paper \ dliam· 

son also noted that two dlstmctize·group of fi h made 

up the pawning school and that the mailer of the ize 

group wa made up of fish with a mean ize of 44 cm 

which were probably a year old. Around Hawaii, Te ter 

and akamura (1957) determined the ex and maturity 

of 93 E affims caught by trolling. However, they did not 

relate the sexual maturity of the fi h to it ize. They 

found that five female in their ample were ripe. 

Euthynnu . alletteratus 

In the eastern Atlantic m the area off Dakar, ' enegal, 

Postel (1955b) determined the size of first matuntj of E. 

alletteratus a 39.7 cm for the male and 3 .6 cm for the 

female . Po tel considered that E alletteratu.s were ex· 

ually mature when the gonado omatic index reached 3 to 

4cc, which wa related to the time when the exual 

product could be expre sed by a lIght pres urI.' on the 

body walls. Marchal (1963) tated the smallest E allet· 

teratus he ob erved in pawning condition were 44.2 to 

·14.7 cm long off the coast of Guinea. 

In the western Atlantic Ocean off the coa t of Flonda, 

de Sylva and Rathjen (1961) observed that the malle t 

fi h in ripe condition was a female 27.2 cm long. How· 

ever, they also noted that mo t fish In their ample were 

n t in pawning conditIOn until thej were 35 cm long. 

And in the pan ish fi hery for E. alletteratu ba ed at 

the southern ports of Barbate and Tarifa, it wa found 

that the ize at first pawning wa 56.5 cm for the male 

and 57.0 cm for the females (Hodnguez·Roda 19 ). 

Euth.vnnus lineatu 

The ize at first pawning for E. lineatu.., i not known . 

There are nly fragmentary ob 'ervation on the gonadal 

development of this species in the eatern tropical Pacif· 

ic where it occun,. Mead (1951) reported two female 54,4 

Imd 55.0 cm long, which had wollen and tur id ovarie , 

from the waten, off entral America . chaefer and Man 

(194 ) r ported two adult. from the Gull 01 ,'I ya, 

Co ta JUca, in an advan ed ~tage of maturit . but did not 

glv their size. 

3.1'~ ~1at ing 

15 

3. 14 fertilization 

Fertilization I m 

nus. 

3. 1;' (ronad 

Euth nnu If I II 

I shitOn'dn on \ "tllnl{ m. IndlJl (I r um Itao I 

for 

I ngth 

(em) 

fecund It} 

!l~ al. 

Th undlt of E II 

d 

3 1 

th n· 
(9) 

16 

FO) NUMBER OF FISH l ! M'~ ~,~ ; ,~, L 

14 

12 

(10) 

(9) (7) 

(2) (6) 

(27) I 1 I (I) 

0 (2) 

0 

(I) 

6 

4 

0 (28) 

(3) I 0 

2 

o MAR. APR. MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 9.-Seasonal distribution of Euthynnus affinis gonad index in 

the Philippines. (From Ronquillo 1963, table 16.) Gonad index 

= iJo X 10', where Wo is the weight of the paired ovaries in grams and 

L is fork length in millimeters. 

Philippine waters to define the spawning season (Fig. 9). 

His results were essentially the same as those obtained 

by Wade (1950b) and Buiiag (1958) in that no clear 

seasonality in spawning was evident. Ronquillo (1963), 

however, noted that the highest gonad indices were found 

from March to May. Based on the development of 

ovarian ova, Buiiag (1958) concluded that E. affinis in 

the Philippines spawns more than one batch of eggs during a spawning season (Fig. 10). Although he did not encounter any fully ripe ovaries in his samples, Buiiag 

(1958) speculated that ripe eggs of E. affinis would probably be between 0.8775 and 1.1050 mm in diameter. 

On the basis of the distribution of larval E. affinis in 

Philippine waters, Wade (1951) indicated t hat spawning 

may have seasonal peaks. Matsumoto (1959), however, 

indicated that Wade may have misidentified the larvae 

and that what Wade identified as E. affinis were more 

likely Auxis. Based on an earlier study reporting the capture of juveniles, Wade (1950a) stated that E. affinis 

spawn in the vicinity of Manado, Celebes, East Indies; 

near Marigabato Point, Cotabato Province, Mindanao; 

and Batangas and Balayan Bays, Luzon, Philippines. 

In the western Indian Ocean near the Seychelles, the 

spawning season for E. affinis is during the period of the 

northwest monsoon, from October-November to AprilMay including a peak from J anuary to March (Ommanney 1953). Off the coast of east Africa the spawning 

season extends from January to J uly, the middle of the 

northwest monsoon to the beginning of the southeast 

monsoon (Williams 1963). The capture oflarval E. affinis 

in the western Indian Ocean during the months of December and January (Jones and Kumaran 1964) corrobo16 

STAGE I 

0 I 

~ 

I STAGE" 50 I 

I 

o I 

/ STAGE III 50/ 

(/) I C> 0 C> 

w i ... 100 I STAGE IV 0 I a: 

w / al 50/ :=; 

;:) I z 0 i 100 I 

I 

/ 

50/ 

/ 

0 r 

/ 100 I 

/ 

50/ 

I 

o T 

STAGE V-A 

A 

/ 

50 STAGE VI 

/ 

0 

0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 

DIAMETER IN MICROMETEN UNITS 

Figure 10.-Ova diameter frequency polygons of EuthynnuB affinis 

showing the va rious sta ges of development of the ova to maturity: 

I, Immature; II, early ma turing; !II, la te maturing; TV . V, V·A, 

mature; VI. ripe; VII, spen t. (Fr om Buila g 195 , fig. 3.) 

rates the a bove observations. In other close-by areas in 

the western Indian Ocean, fish in spawning condition 

were taken in November and December around Madagascar (Fourmanoir 1957) and in December around 

Ma uri ti us (Baissac see footnote 5) . 

Off the southwest coast of India near Vizhangam, Rao 

(1964) indicated that E. affinis spawns from April to 

September. He did not discount spawning also in other 

months of the year and noted the possibility that individual fish may mature and spawn several batches of ova 

during the spawning season. The capture of juveniles up 

to 200 mm in the months of January, May, June, 

September, October, and November near Vizhingam and 

Cali cut, India (Jones 1960; Table 9) suggests a rather 

lengthy spawning season for E. affinis in these waters. 

In the eastern equatorial Indian Ocean, larval E. affinis have been captured from August to October in Indonesian waters (Matsumoto 1959; see Table 8) which suggested spawning during these months. 

Larval and juvenile E. affinis have been recorded from 

many other areas in the Indo-Pacific (Table 9; see also 
Table 9.- Records of larval and juvenile Euthynnus aftinia in the Indo-Pacific. 

Marine area 

Locality code [see Number Length 

Date Lat. Long. Rosa (1965)) Larvae Juveniles (mm) Reference Remark 

Apr. 1929 04°03'N 123°26'E I8EW 1 Matsumoto (1959) 

04°03'N 123°26'E 3 Matsumoto (1959) 

06°55'N 114°02'E 18EW 15 Matsumoto (1959) 

06°55'N 114°02'E 23 Matsumoto (1959) 

06°55'N 114°02'E 25 Matsumoto (1959) 

08°02'N 109°36.5'E I8EW 1 Matsumoto (1959) 

08°02'N 109°36.5'E 2 Matsumoto (1959) 

08°02'N 109°36.5'E 42 Matsumoto (1959) 

May 1929 12°15'N 109°26'E 18EW 1 Matsumoto (1959) 

20030.5'N 125°28'E 18EW 2 Matsumoto (l959) 

20030.5'N 125°28'E 2 Matsumoto (1959) 

June 1929 14°37'N 119°52'E 18EW Matsumoto (1959) 

July 1929 ob°41.5'8 134°14.5'E 18EW 1 Matsumoto (1959) 

00°41.5'8 134°14.5'E 3 Matsumoto (1959) 

00°41.5'8 134°14.5'E 2 Matsumoto (1959) 

00°40.5'8 134°15'E 18EW 7 Matsumoto (1959) 

00°40.5'8 134°15'E 3 Matsumoto (1959) 

00 °40.5'8 134°15'E lO(?) Matsumoto (1959) 

00°40.5'8 134°15'E 4 Matsumoto (1959) 

00°40.5'8 134°15'E 4 Matsumoto (1959) 

00°33'8 134°00'E 18EW 11 Matsumoto (1959) 

00°33'8 134°00'E 3 Matsumoto (1959) 

00°33'8 134°00'E 1(?) Matsumoto (1959) 

01 °01'8 137°20'E 18EW 2 ,Matsumoto (1959) 

01 °01'8 137°20'E 3 Matsumoto (1959) 

01 °20'8 138°42'E 18EW Matsumoto (1959) 

01 °20'8 138°42'E 1 Matsumoto (1959) 

Aug. 1929 07°53'8 116°18'E 18EW 1 Matsumoto (1959) 

07°53'8 116°18'E 2(?) Matsumoto (1959) 

09°09'8 114°47'E 18EW 2 Matsumoto (1959) 

8ept. 1929 06°22'8 105°12'E 18EW 7(?) Matsumoto (1959) 

06°22'8 105°12'E 13(?) Matsumoto (1959) 

04°38'8 99°24'E 18W 1 Matsumoto (1959) 

02°00'8 98°59'E 18W Matsumoto (1959) 

02°00'8 98°59'E 1 Matsumoto (1959) 

02°00'8 98°59'E 2 Matsumoto (1959) 

02°07'8 99°53'E 18W 1 Matsumoto (1959) 

01 °29'8 l00007'E 18W 2 Matsumoto (1959) 

01 °29'8 100007'E 10 Matsumoto (1959) 

00°52'8 99°25'E 18W 1 Matsumoto (1959) 

00°52'8 99°25'E 1l Matsumoto (1959) 

00°52'8 99°25'E 7 Matsumoto (1959) 

Oct. 1929 02°57'8 99°36'E 18W 1 Matsumoto (1959) 

03°12'8 99°26'E 18W Matsumoto (1959) 

Dec . 1929 01°45'N 71 °05'E 18W 1 7.08 Jones and Kumaran (1963) Length not defined 

00035'N 66°09'E 18W 1 Jones and Kumaran (1963) Length not defined 

03°45'8 56°33'E 18W 2 6.05,7.14 Jones and Kumaran (1963) Length not defined 

05°01'8 54°46'E 18W 5.94 Jones and Kumaran (l963) Length not defined 

08°27'8 50054'E 18W 1 5.59 Jones and Kumaran (l963) Length not defined 

1l °55'8 49°55'E 18W 2 4.7 Jones and Kumaran (1963) Length not defined 

12°09'8 49°34'E 18W 8 6.62-12.72 Jones and Kumaran (1963) Length not defined 

09°10'8 45°17 'E 18W 1 6.58 Jones and Kumaran (1963) Length not defined 

08°24'8 42°54'E 18W 3 5.14·7.94 Jones and Kumaran (1963) Length not defined 

07°24'8 41"51'E 18W 56 4.68-8.75 Jones and Kumaran (1963) Length not defined 

04°45'8 40010'E 18W 15 5.42·12.16 Jones and Kumaran (1963) Length not defined 

Jan. 1930 03°26'8 42°58'E 18W 34 4.74-8.69 Jones and Kumaran (1963) Length not defined 

04 °21 '8 42°56'E 18W 2 6.1l Jones and Kumaran (1963) Length not defined 

14°16'8 41°48'E 18W 3 6.79 Jones and Kumaran (1963) Length not defined 

16°12'8 42°04'E 18W 14 4.79-9.14 Jones and Kumaran (1963) Length not defined 

18°30'8 42°18'E 18W 1 Jones and Kumaran (1963) Lengt h not d fined 

21 °13'8 42°26'E 18W 3 5.69-5.88 Jones and Kumaran (l963) Length not defUied 

23°1l'8 42°54'E 18W 2 7.08-8.39 Jones and Kumaran (963) Length not defmed 

25°14'8 36°21'E 18W 29 4.62-7.42 Jones and Kumaran (l~ ) Lenl("th not defmed 

Mar. 1948 Manado, Celebes, 18EW 115 Wade (l950a) For len 

Netherlands, East 

Indies 

17 
Table 9.- Continued . 

Manne area 

Loca it~ code [see Numbe r Length 

Date Lat. Long. Rosa (1965) I Larvae .Ju venile (mm) H.eferente k.emarlu 

Apr. 1948 Batanga ,Luzon, I 'EW 7 141.178 Wade (1 :iI)a) Fork length 

Philtpplnes 

May 1948 7°02' 124°12'E [ EW 2 3:1.oS,3;; Wade (1950a) Fork len h 

Taal, Batangas Province, [SEW 4 127 170S Wade (J 5Oa) f ()rk length 

Luzon, Philippines 

Batangas, Luzon, ISEW 2 40,44 Wade ()950a) Fork lengt h 

Philippines 

Mar 1949 Batangas, Luzon, '2 40, I)H I Wilde (19508) Fork lengt h 

Philippines 

Batangas, Luzon, !!O Wade (1 5Oa) f ork length 

Philtpplnes 

Apr. 1949 Batangas, Luzon, 76.5 \\'ade (l :,Oa) Fork lenmh 

Philippines 

Batanga , Luzon , 73·11'2 Wade (1 5011) f ork length 

PhIlippines 

Batangas, Luzon, '2 117.5· 131 Wade (1 .'j()a) f ork len h 

Philippines 

Aug.-Oct. Oft southern Kyushu, EW • umerou" 1502SO Vabe et al (1 5.1) fork len h 

1950 Japan 

Sept 1956 Calicut, l.ndla W 

Oct 1956 Vizhlngam, l.ndia 1'\V 

Nov 1956 Vizhingam, l.ndla 

Jan. 1957 Vizhingam, l.ndla 

May 1958 Vizhingam, l.ndla 

June 1958 Vizhlngam, l.ndia 

Aug 1956 00°01' 133°02'W l'EW 

12°31 ' 132°Q4 'W lEV,. 

Jan. 1957 07°55' 1100 02'W ! E\\ 

Feb. 1957 02°58' 129°55'W lEW 

14°57' 146°20'W !'EW 

Mar. 1957 08°12'S 145°12'W ! EW 

June 1957 21° 11 'N 158°17.S'W I E\\ 

21°2S'N 157°21'W I'E\\ 

21°24.SN 159°00'W [ EW 1 

Dec. 1957 09°34' 139°SO'W ! E\\ 2 

Oct.1960 12°29'N 43 °03'E EW 215 

July-Aug. Gulf of Tonkin EW 22 

1960-61 

JUly-Sept. Hawaii ISEW 

1967 

July-Sept. 

[ 21·30' 24 ·"l ! EW 24 

1968-71 119°28' -121 °30'E 

03°30' - 12°00'N 

102°45' -115°1S'E 

Fig. 8). Larvae and juveniles have been reported from 

Hawaii (Strasburg 1960; Higgins 1970), near the Marquesas and Tuamotus and surrounding areas (Strasburg 

1960; Nakamura and Matsumoto 1967), in the Gulf of 

Tonkin (Gorbunova 1965a), in the Gulf of Aden (Gorbunova 1965b; Parin 1967), around Taiwan and adjacent waters (Matsumoto 1959; Chen and Tan 1973), and 

off the coast of southern Japan (Yabe et al. 1953) . These 

records suggest t hat E. affinis probably spawns throughout its range, 

Euthynnus alletteratus 

Based on the records of occurrence of postlarval and 

juvenile E. alletteratus, Padoa (1956) indicated that 

spawning in the Mediterranean occurred in the springtime and in the summer. The summer spawning con6 

2 

2 

2 

25 

18 

,2.0·1400 LenlCth gl~en b ,Jone 

1165 I tandArd length 

162.0 

.3·,5.0 

245,406 

".0 here 

3.5-60 Gorbunova 1 1965a) Length not defi ned 

HIggins (1970) 

Chen and Tan (19,3) 

elusion wa based on po tlarval material reported on by 

Ehrenbaum (1924); however, Matsumoto (1959) indicated tha t the identification of E. alletteratus by Ehrenbaum was erroneous. On the other hand, Belloc (1955) 

noted that spawning takes place in different parts of the 

Mediterranean chiefly in July-August. Ben-Tuvia (1957) 

indicated that young E. alletteratus 8 to 16 cm long are 

taken by " light fishing" from June to September along 

the Mediterranean coast of Israel, which, according to 

him, suggested summer spawning. Postel (1964) also indicated that the spawning season for E. alletteratus in 

the Mediterranean is in the summer (June-July-August), 

In the eastern Atlantic, Postel (1950) noted that the 

spawning season was from April to November, including 

a peak from June to September along the coast of Dakar, 

Senegal. Further south along the coast of western Africa, 

Marchal (1963) indicated that peak spawning took place 
in October and November. Along the Ivory Coast, Marchal (1963) indicated that the spawning season is very 

extended, at least from October to June. He noted an interruption of spawning during July to September coinciding witb a cooling of the sea in the Ivory Coast area. 

Of interest is the series of larval tuna surveys conducted 

'n the northwestern Gulf of Guinea in 1964 and 1965 by 

he Miami Laboratory, NMFS (National Marine Fisheries Service) (Richards et a1. 1969a, 1969b, 1970). The 

cruises were made in the winter-spring "warm season" in 

the Gulf of Guinea (February-April 1964 and MarchApril 1965) and in the summer-fall "cool season" 

(August-October 1964). Larval E. alletteratus were 

caught during the cool season as well as the warm season 

(Table 10). Although the surveys did not cover all the 

months of the year, the results, together with observations made by Marchal (1963), suggest year-round 

spawning in the northwestern Gulf of Guinea. Around 

Sao Tome and Principe the spawning season extends 

from October to December (Frade and Postel 1955; da 

Costa and Frade 1958). 

The development of E. alletteratus gonads indicates 

an extended spawning season beginning in March and 

continuing to about November off the coast of Florida 

(de Sylva and Rathjen 1961). Potthoff and Richards 

(1970) also concluded that E. alletteratu pawn over a 

long period in Florida waters. They ba ed their conclusion on the occurrence of juveniles in the regurgitated 

food of seabirds in the Dry Tortugas, Fla. 

Klawe and Shimada (1959) reported the capture of 

juvenile E. alletteratus during the month of March, 

April, June, July, and August m the Gulf of Mexico 

(Table 11) and suggested reproductive activity at lea t 

during these months if not also in other months of the 

year. The records of other larval and juvenile E. alletteratus shown in Table 11 suggest spawnmg in tho e 

areas also. 

Marchal (1963) concluded that in the Mediterranean 

and along the west coast of Africa, E. alletteratus spawn 

during periods of the year when the water is warmest and 

that this species apparently reproduces throughout Its 

range. 

Euthynnus lineatus 

Klawe (1963) found that E. lineatus spawning in the 

northern part of its distribution is limited to the summer 

months. He also noted that farther south, E. lineatus 

spawns throughout the year including a possible peak in 

early spring (Table 12). 

Table 10.-Records of larval Euthynnu8 alletteratu8 in the northwestern Gulf of Guinea 

and off Sierra Leone (ASE' ). (From Richards et a l. 1969a , 1969b. 1970.) 

Locality No , of Locality No, of 

Date Lat, Long, larvae Date Lat, Long. larvae 

February 1964 04 °20'N 08°09'W 78 October 1964 04°23'N 01°04'E 3 

04 °51'N 05°30'W 1 02°53'N 01°02'W 

05 °02' 03°53'W 2 03°38'N 02°()()'W 

04 ° 15'N 01 °32'W 1 04°()()'N 02°38'W 4 

02 °45'N 01 °30'W 4 04°09'N 03°1O'W 5 

02°51'N 01°25 'W Fe bruary 1965 07°57' • 16°53'W 1 

04°20'N 01 °30'W 1 06°29'N 16°28'W 5 

04 °30'N ()() 054'W 5 06°l5'N 16°29'W 

04 °34'N ()()049'W 1 09°()()'N 16°02'W 

05°3 l 'N ()()OlO'E 2 06°1 N 15°30'W 1 

05°28'N ()()OlO'E 2 07°30'N 15°()()'W 2 

04°48'N ()()OOI'E 4 February 1965 08°30'N 15°2?'W 

04°59'N Ol O()()'E 15 08°14'~ 15°()()'W 7 

04°30'N 01°30'E 3 07°26':-'; 15°01'\\' 

March 1964 04 °31'N 01°55'E 2 07°()()'t-, 14°29'W 

05°01'N 03°58'W 1 07°01'N 14°28'W 

April 1964 04°32'N 05°01'W 5 March 1965 07°08'N 13°30'W 

04°56'N 01°11 'W 11 07°03'N 13°06'\\ 

04 °54' ()()030'W 33 06°49'N 13°04W 4 

04°15'N ()()033'W 04°35':-; 02°32 W 3 

03°52'N 01°03W 04°06', • 02°33 W 

02°55'N 02°04'W 10 04°20'; • 01"59'\\ 

03°31'N 02°04 \\ 10 04°08' •• 01 °28 \\ 

August 1964 04°20'N 06°59'\\ 2 04 °10' •• ()()'2~ W 1 

04°32'N 06°19 'W 04°22' •• wo06'W 9 

05 o()() 'N 04°30',," 05035'.1. r ()()032 E 3 

04 °21'. . 02°02'W 05°05, ()()025 E 1 

04°18'N 01 °09'\\ 05°59. Ul 30 E 2 

04°27':-; 01°44'W 05°4,5 . 01 30 I=- I 

06 O()() ':-'; 01°39'E 05°5J. U! E 

06°09'N 02°37'E 1 04°15 0'2 30 E 

September 1964 02°30''\ 07°57"W 1 

03°50':\ 06°·11 \\' 5 

Man ne area code, , 

ee Rosa (1965), 

19 
Ta ble I I.-Record s of la r va l nnd juvenile Ellthynnus ullett eratll8 in the Atl a n tic nnd Medite rra nea n . 

Date 

June 1920 

July 1920 

May 1921 

Nov. 1921 

May 1922 

June 1953 

Jul} 1954 

Aug 1954 

June 1955 

Aug. 1955 

Sept. 1955 

Aug. 1956 

Oct. 1957 } 

Dec. 1958 

July 19GO 

Aug.- ept.} 

1964 

Feb.-Mar. 

1963 

Apr.-July 

1960-67 

oct.} 1964-

Dec. 66 

Feb. 

Aug.-Oct. 

1964 

Throughout 

the year 

June-Aug. 

Aug.-Oct. 

1959 

Aug.-Sept. 

1959 

Locality 

Lat. Long. 

18°()()'N 

33°07'N 

33°07'N 

17°55'N 

07°22'N 

05°35'N 

05°35'N 

05°35' 

05°06' 

05°06'N 

05°06 N 

35°42'N 

25°35'N 

34°35'N 

2 °59' 

28°36'N 

29°05'N 

27°34' 

27°58']\i 

29°2 ' 

2 59',' 

28°46N 

29°12'\ 

2 °40'~ 

2 °50':\ 

28°50':\ 

28°47 N 

2 °45'N 

28°55 ]\i 

28°55'N 

29°01'N 

2 °12'N 

28°17'N 

29°27 N 

64°14'W 

77°()()'W 

77°()()'W 

64°48'W 

46°51'W 

51°08'W 

51°08'W 

51°08'W 

51°35'V> 

51°35'W 

51°35 'W 

73°43'V> 

79°25'\\ 

75° 15'V> 

°O,' \\, 

87 °5 '\\' 

8°IO'W 

9°()()'\\' 

&l003'W 

7°30'\\, 

°02'\\, 

°40' \\' 

°34'W 

°5 'W 

7°57\\' 

8io56'W 

O()()'\\' 

7°57'W 

7°4 'W 

°43'\1>' 

Gulf of Mexico 

28°50'N 7°50'W 

OffTakoradl, Ghana 

Off Dakar, Senegal 

Around Cuba 

06°18'N 

04°40' 

100()()'S 

03°()()'N 

03°37'S 

24°30'N 

07°S 

05°N 

04°30'N 

09°20'N 

23°20'W 

24°28'W 

34°33'W 

300 ()()'W 

300 04'W 

82°50'W 

12°E } 

04°30'W 

04°30'W 

19°41 'W 

Ivory Coast and 

Ghana 

Haifa Bay 

Dardanelles 

Sea of Marmara 

Marine area 

code [see 

&lsa (1965) J 

AW 

AW 

AW 

A W 

A W 

A 'W 

A \\-

A '\\ 

A ' \\ 

A E 

ASE 

AW 

A E 

ASE 

AW 

ASW 

A W 

ASW 

ASE 

ASE 

ASE 

ASE 

ASE 

ASE 

umber 

Larvae J uventleH 

4 

5 

1 

1 

2 

10 

1 

14 

2 

5(?) 

{ lOgle } specimen 

p toGO 

specimens 

per catch 

20 

2 

4 

No numbers 

given 

2 

-I 

tl6 

3 

4 

5 

29 

10 

16 

4 

90 

116 

GO 

11 

12 

52 

33 

47 

Numerous 

umerous 

Numerous 

Numerous 

'Total length measured from tip of snout to shortest median ray of caudal fin . 

20 

Length 

(mm) 

25.35 

2,-41 

2 ·33 

21·44 

26· 

76-

11-47 

5 ·1 

4· 6 

22-174 

21-31 

3.0-0.3 

3 -53 

31-55 

6, -

29·65 

4-

17-

49-

32-94 

24-49 

19-29 

1- 2 

4 14-610 

3 0-5.4 

3. ,3.7 

4.4 

8.7 

4.2 

4.4 

29-135 

4.2-10.2 

80-240 

145-220 

180-250 

IWference 

Mau.um(lto (1959) 

Malllumol/l (19:;9) 

Mat.umolo (1959) 

MtllRUrnOlo (1959) 

Mat urnolo (1959) 

Mau.urn(lt{J (19:;9) 

Mal,urnot" (1959) 

:\lst8urnoto (1 :;9) 

Mil urnOlo (I 5 1 

:\lal,urnolo (1959) 

,\18 um(Jto (1 59) 

Mal urnoto \1 591 

Kla"c (19601 

Klawe (J 1) 

RPmarlu 

( ) 

(I) From LOrnach of 

Euth}1UlW 

Klaw~ and _ hlmada (1 ')9~ (I) 

Kla"eand t.lrnada(95) (1) 

Klawe and Shimada (1 .591 ( 1 

Kla"c and hlmada (19:;9) (I) 

Klawe and ) 

Kla"e and hlmada II ;) ) ( 1 

Kla"c and hlrnllda (J~,- ) ( 1 

Kla\\e and hlmada (1 59) (II 

Kla"c and hlmada (1 • .) 1 ( I 

Kla .... e and hlrnada (I - ) ( I 

Klawe and hlmada (1.5 ) I 

Kla"'c and ... hlrnada (l!;l59) ( I 

Kla"'cand ~h.mada (19591 (I 

Kla",e lind hlmada (19') 1 ) 

Kla .... e and hlmada (l ,591 ( ) 

Klawe and hlrnada (1 59) ( ) 

Klawe ann 'himada (1959) ( ) 

Kla",e and ' himada 1959) I 1 

KIa .... " and hlmada (1.59) ( ) 

Kla .... e and hlmada (959) ( ) 

Klav.e and hlmada (1959) ( ) 

Klaweandhimada(l95) (I) 

Kazano\,a (1962) Length not defined 

Kazano\,a (1 '21 Length not defUled 

Gorbuno\'a and 

Length not defined ala barr! (1 "j ) 

Zharo\ and Zhudo\'a (1969) Length not defined 

Zharo\ and Zhudova (1969) Length not defined 

Zharov and Zhudo"a (1969) Length not defined 

Zharov and Zhudova (1969) Length not defined 

Zharov and Zhudova (1969) Length not defined 

Potthoff and 

Richards (1970) 

Zhudova (1969a) 

Zhudova (l969b) 

Marchal (1963) 

Ben-Tuvia (1957) 

Demir (1963) 

Demir (1963) 

tandard length 

Approximate locations 

Length not defined 

Length not defined 

Fork length 

Fork length 
Table 12.-Average numbers of Euthynnus 

lineatus larvae caught per hour of surface 

plankton tow off Cape Blance, Costa Rica. 

(From KJawe 1963:465.) 

No. of No. of 

Month larvae Month larvae 

January 1.5 July 0.1 

February 0.1 August 0.2 

March 3.2 September 1.4 

April 14.9 October 0.0 

May 0.6 November 0.2 

June 0.0 December 0.7 

Records of larval and juvenile E. lineatus from the 

eastern Pacific and from near Costa Rica are shown in 

Tables 13 and 14, respectively. The records indicate the 

probable spawning periods and localities in the eastern 

tropical Pacific Ocean. 

3.17 Spawn 

There is very little information on the fertilized eggs of 

Euthynnus in the literature. Delsman (1931) described 

the eggs of Thynnus thunnina (= E. affinis) which he 

had earlier identified as eggs of Scomber (= RastrelliTable 13.-Records of larval and juvenile Euthynnus lineatus in the eastern tropical Pacific Ocean (ISE'). 

The lengths of the specimens were given as total or fork length in the various references listed in the table; 

however, both were taken in the same manner, i.e., from the tip of the snout to the shortest median ray in the 

caudal fin. 

Total or Collector 

Locality Number fork length or 

Date Lat. Long. Larvae Juveniles (mm) reference 

Jan. 1922 06°49'N soo25'W 4 Matsumoto (1959) 

06°49'N soo25'W Matsumoto (1959) 

06°49'N soo25'W 1 Matsumoto (1959) 

06°49'N soo25'W 13 Matsumoto (1959) 

06°40'N soo47'W 4 Matsumoto (1959) 

06°40'N 800 47'W Matsumoto (1959) 

06°40'N soo47'W Matsumoto (1959) 

06°40'N soo47'W 2 Matsumoto (1959) 

06°40'N soo47'W 2 Matsumoto (1959) 

06°40'N soo47'W 58 Matsumoto (1959) 

06°48'N soo33'W 1 Matsumoto (1959) 

06°48'N 800 33'W 2 Matsumoto (1959) 

06°48'N 800 33'W 2 Matsumoto (1959) 

06°48'N soo33'W Matsumoto (1959) 

06°48'N soo33'W 1 Matsumoto (1959) 

08°24'N 79°23'W 13 Matsumoto (1959) 

08°40'N 79°23'W 25 Matsumoto (1959) 

Sept. 1928 07°06'N 79°55'W 2 Matsumoto (1959) 

07°16'N 78°30'W Matsumoto (1959) 

07°55'N 79°02'W Matsumoto (1959) 

Mar. 1947 08°20'N 84°lO'W 8 48-86 Schaefer and Man (1948) 

09°20'N 85°20'W 10 29-56 Schaefer and Man (1948) 

09°10'N 85°20'W 1 61 Schaefer and Man (1948) 

May 1949 lOo58'N 89°56'W 2 7.5,10.5 Mead (1951) 

11 °20'N 87°20'W 23 14-18 Mead (1951) 

12°50'N 89°40'W 2 18,24 Mead (1951) 

Oct. 1951 24°35'N 112°05'W 9.7 Sefton, Jr.' 

Jan. 1955 12°34'N 89°50'W 8 25 (mean) Clemens (1956) 

08°43'N 84°11'W 34 17-38 Clemens (1956) 

Nov. 1955 07°42'N 79°20'W 1 30 Eastropac Expedition' 

03°01'N 82°15'W 6 27-38 Eastropac Expedition' 

Dec. 1955 11 °48'N 88°25'W 46 Eastropac Expedition' 

Nov. 1955 08°31.3'N 79°32'W 2 Klawe (1963) 

Aug. 1956 26°04.5'N 112°48'W 7.0 La Jolla Lab., NMFS' 

Sept. 1956 15°05'N 93°54'W 3 15-27 KJawe (1963) 

Oct. 1956 12°51'N 93°05'W 51 KJawe (1963) 

Nov. 1956 14°00'N 96°11'W 30 Schaefer and Shimada' 

Feb. 1957 17°24'N 102°04'W 1 21 Renner and Hark' 

Aug. 1957 29°12'N 115°39'W 1 La Jolla Lab., NMFS' 

31°11'N 114°15'W 2 29.5,353 La Jolla Lab., NMFS' 

May 1958 05°34'N 81°29'W 60 KJawe (1963) 

08°28'N 84°21'W Klawe (1963) 

15°15'N 95°23'W 11 Klawe (1963) 

June 1958 18°44'N 104°21'W 5 20-27 Klawe (1963) 

17°49'N 103°38.5'W 99 7.5-45 Klawe (1963) 

21°36'N l06°44'W 3 18-48 KJawe (1963) 

16°39'N 1000 05'W 1 Klawe (1963) 

17°24'N 101°25'W 6 Klawe (1963) 

18°44'N 104°21'W Klawe (1963) 

21 
Table 13.-Continued. 

Locallty 

Date Lat Long . Larvae 

Nov. 1958 14 °56.5'N 93 °06.5'W II 

15°39' 93 °59.5'W 1 

14 °1 ' 95 °02. 'W 1 

15 '02' 95'07.5'W I 

14 °2 1'N 97 °01'W 3 

14°21'N 97 °01'W 24 

15°31 N 97°44'\\ 5 

Dec 195 15·31':-'; 97·44'W 15 

15°36'N 99°235'W 

Jan. 1959 15°29.5'N 9 °325'W 

15°29.5' • 9 ·32.5' v,; 4 

Feb. 1959 19°46',\ 105·H'\\' 5 

Apr 1959 OS·12'N 

OS·12'N ' ·17'\ .... 

osol5'N 3·23'W 

ept 1959 15°39'~ 97°00'\\ 2 

14 20':-' 95°.~9'W 6 

14°20'''- 95°59W 6 

14°54. 'N 95'07.1'\\ 36 

14·21.5'\1 94°01'W 5 

16 2 ':-' 99°32.5'\\ 2 

Feb 1961 12 35', 9.3°40W 

Oct. 1966 Entrance. Gulf of 2 

California 

Nov 1966 Entrance. Gull of 3 

California 

Ot"fTres l\larlas Is. 

Dec 1966 Entrance, Gulf of 

California 

Manne area code. ee Ro a (1965). 

'As reported in KJawe (I ) 

ger) kanagurta. Delsman noted that the egg diameters 

were 0.85 to 0.95 mm and that the diameter of the oil 

globule ranged from 0.21 to 0.24 mm. Sanzo (1932) described some fertilized eggs which he tentatively identi· 

fied as belonging to Euthynnus alletteratus. The egg 

were buoyant, spherical, and transparent, and were 

about 1.08 mm in diameter with an oil globule 0.28 mm 

in diameter. The dimensions of the fertilized eggs were 

very similar to that of Auxis and Thunnus eggs, but the 

embryos did not show yellow pigmentation as in those 

species. The yolk sac was rich in black pigment. 

Houde and Richards (1969) reported on the collection 

of some fertilized eggs which were later determined to be 

from E. alletteratus, The eggs were collected from May 

through August 1969 in the Straits of Florida off Miami 

and returned to the laboratory for incubation. In a 

successful attempt at hatching some of the fertilized 

eggs, examination of the resulting larvae reared to 12 

days past hatching revealed that the larvae were those of 

E. alletteratus. They noted that the larvae hatched 

within 12 h of collection and probably within 24 h after 

the eggs were fertilized. They did not include a description of the fertilized eggs. 

Calkins and Klawe (1963) stated that the fertilized 

eggs of E. lineatus are pelagic but they had never been 

specifically identified in plankton collections. 

22 

Total or C'Allector 

fork length or 

(mm) 

6 12·1 Broadhead and ChAt n ' 

1 76 Brolldh ad and hatWln' 

6 13·28 halWln' 

3 75·95 Vann 

Kla"'e et al. (1 70J 

KlalO.e et al WiO) 

KlalO.e et al (19'70) 

Kla",e et al. (1970) 

3.2 Preadult pha e 

3,21 Embryonic pha e 

Euthynnus affinis 

Del man (1926), a tated earlier, de cribed orne fer· 

tilized eggs of comber (= RastrellLger) kanagurta which 

he later reidentified as Thynnus thunmna (= E. affmLS} , 

He noted that the eggs took Ie s than 24 h to hatch. Delsman's drawing of a newly hatched larva indicate a size 

of approximately 2.1 mm at hatching. He counted a total 

of 39-41 "myotomes" in larvae of various stages of development (Fig. 11). Whether these were actually larvae 

of E. affinis has not been verified. 

Euthynnus alletteratus 

Houde and Richards (1969) collected the fertilized eggs 

of E. alletteratus and were successful in hatching the 

eggs and rearing the larvae up to 18 days past hatching. 

The larvae were slightly less than 3 mm long at hatching. 

The newly hatched larvae had a large yolk sac that contained a single prominent oil globule, the eyes were unpigmented, and the mouth and gut were not functional. 

The yolk was absorbed, the eyes became pigmented, and 
Table 14.-Larval and juvenile Euthynnu8 lineatu8 captured 

off Cape Blanco, Costa Rica (ISE'). (From Klawe 1963, 

table 5.) 

Location Number Total 

from length 

Date Cape Blanco Larvae Juveniles (mm) 

Nov. 1958 20mi S 6.5 

20mi S 9.0 

20mi SSW 1 6.0 

20mi SSW 2 5.0 

Jan. 1959 20 mi S 8 21·39 

20miS 43 14-25 

Feb. 1959 20mi S 8 25-50 

20mi S 1 5.0 

Mar. 1959 20mi S 3 5.1-6.7 

20mi S 6.7 

5 miSE 2 6.2,8.2 

5 miSE 6 5.2-9.2 

5 miSE 5.3 

Apr. 1959 20mi S 4 11-25 

5 miSE 77 16-25 

20mi S 2 6.5-7.7 

20miS 7 5.0-8.2 

20miSE 12 4.1-7.1 

5 miSE 23 4.5-7.5 

5 miSE 25 4.4-7.5 

5 miSE 12 4.4-7.2 

5 miSE 88 4.4-14.2 

May 1959 lOmiSE 11 16-25 

10 mi SE 5 5.5-8.0 

10miSE 1 8.5 

10mi SE 2 6.0-13.0 

June 1959 lOmiW 2 ca.17 

Aug. 1959 12 mi SE 3 4.6-8.8 

6 miSE 3 15-17 

Sept. 1959 20miS 4 4.8-5.7 

10mi S 5 6.1-7.4 

10mi S 4 5.0-7.3 

lOmi S 5 4.4-7.5 

Nov. 1959 20mi S 4 11.5-53 

20mi S 1 4.4 

Jan . 1960 10mi S 9 4.1-5.5 

10mi S 2 4.6-4.8 

Feb. 1960 20mi SSW 18 

Mar. 1960 10mi S 12 15-28 

20mi S 6 3.3-6.3 

20mi S 19 4.3-8.6 

10miS 6 3.7-6.7 

lOmi S 4 6.6-8.3 

May 1960 20mi S 14 13-21 

10mi S 6 9.5-24 

10mi S 6.5 

July 1960 10mi S 4 13-17 

10mi S 62 10-24 

10mi S 7.0 

Aug. 1960 10mi S 6.0 

20mi S 1 19 

10mi S 3 12-18 

Sept. 1960 10mi S 51 12.5-24 

Oct. 1960 10miS 7.5 

' Marine area code . See Rosa 1965. 

the mouth and gut were functional within 48 h after 

hatching. 

Euthynnus lineatus 

No information. 

23 

3.22 Larvae and adolescent phases 

The larvae and juveniles of all three species of Euthynnus have been described in detail (e.g., Schaefer and 

Marr 1948; Wade 1950a; Mead 1951; Matsumoto 1958, 

1959; Jones 1960). The following descriptions of young 

Euthynnus are taken primarily from the above references. 

Euthynnus affinis 

The smallest specimen identified by Matsumoto 

(1958) as E. affinis measured 4.6 mm TL (Fig. 12a). The 

head length is moderate (33.9% TL), there are 40 myomeres, and the abdominal sac is nearly triangular. The 

mouth is fairly large (about 71.9% of the head length) 

and contains 12 teeth on the upper jaw and 9 teeth on the 

lower jaw. The distance from the tip of the snout to the 

anterior edge of the orbit is almost equal to the orbit 

diameter. Three long spines are present on the posterior 

edge of the preopercle; the longest spine is the one at the 

angle. Generally, a single chromatophore is found at the 

middle of the lower jaw and at the symphysis of the pectoral girdle. 

The median fins show very little development; there 

are 4 or 5 rays in the caudal fin and only strong striations 

representing rays in the incipient anal and dorsal fins. 

The pelvic fins are undeveloped and the pectoral fins 

show only striations. 

There are 13 and 15 teeth in the upper and lower jaws, 

respectively, and the preopercular spines have increased 

to 6 in a 5.5 mm TL specimen (Fig. 12b). 

FIve short spines are present in the first dorsal fin and 

about nine rays in the caudal; the other median fins and 

the pectorals still show only strong striations and the 

pelvic fins are just emerging as small buds. 

The single chromatophore at the middle of the mandible and that at the pectoral symphysis are still evident. 

A 7.6 mm TL specimen exhibits some striking changes, 

particularly in pigmentation. A series of four or five chromatophores is present on the anterior half of the mandible and the first dorsal fin is almost completely 

pigmented. 

The head comprises 39.8% of the total length and the 

snout length is much greater than the diameter of the orbit. About 16 teeth are present on both the upper and 

lower jaws, and 7 spines are noticeable on the posterior 

edge of the preopercle. 

There are 8 spines in the first dorsal fin; the length of 

the longest spine is less than half the distance between 

the dorsal fin insertions. The second dorsal and anal fin 

rays are further developed and, although the rays are not 

clearly evident, about 11 radials in the second dorsal and 

12 in the anal are present. The first 7 dorsal and 6 anal 

finlet radials are also evident. There are 9 + 9 rays in the 

caudal fin and the pelvic fins are complete with 1 spine 

and 5 rays; about 5 rays are noticeable in the pectoral 

fins. 
12+28 

Newly hatched larva, X 40. 

10+00 

~--------

Larva of the n('xt mornin g, X 40. 

10+29 

Larva of the Accond night, X 40. 

Larva of the seclJod morning, with yolk eQrnpletely 

absorbed and eyell black, X 40. 

Figure Il.-Larva e of Euthynnus affinis. (From Delsman 1926, figs. 3-6.) 

The first dorsal fin is heavily pigmented, and the 

pigmentation at the tip of the snout is more extensive in 

a 9.6 mm TL specimen (Fig. 12d). Chromatophores now 

extend over two-thirds of the length of the mandible and 

the chromatophore at the symphysis of the pectoral girdle still persists. 

The first dorsal fin now has 13 spines and the length of 

the longest spine is greater than half the distance be24 

tween the dorsal fin insertions. There are 13 rays in the 

secon<;l dorsal and anal fins. 

Figure 12.-Euthynnus affinis larvae: (a) 4.6 mm; (b) 5.5 mm; (c) 7.6 

mm ; (d) 9.6 mm. (From Matsumoto 1958, figs. 15-17.) The body 

length, total or fork length, was measured from the tip of the , snout to 

the fork of the tail when the tail was forked, and to the tip of the 

longest ray when the tail was not forked. 
-- ~' .. 

1;.." . 

," t' 

..... 

• ,J 

, 

{ , 

) , ' .' 

I MM 

t 

(0 ) 

(b) 

" -

(c) 

"1 , 

I 

(d) 

25 
Figure 13.-Juvenile Euthynnus amnis: (a ) 24.5 mm SL; (b) 33.5 mm FL; (c) 56.6 mm SL; (d) 67 mm FL; (e) 96.0 mm 

SL; (f) 110 mm FL; (g) 156 mm FL. (From Wade 1950a, fi gs. 10-1 3; Jones 1960, figs. 1-3.) 

Wade (1950a) and Jones (1960) described juvenile E. 

affinis ranging in length from 24.5 mm SL (standard 

length) to 156 mm FL (Fig. 13). In the 24.5 mm SL specimen (Fig. 13a). all the larval characters are lost except 

for the vestiges of the preopercular spines (Jones 1960). 

The color of the body in the 24.5 mm SL and in the 33.5 

mm FL (Fig. 13b) specimens is light brown dorsally and 

become paler toward the midline. A dark longitudinal 

26 

band is present along the lateral midline and ventrally 

the body is pale. 

According to Wade (1950a) the color of the body and 

the head darkens as the fish grows larger and about 9 to 

13 darker vertical bars begin to develop above the lateral 

midline on specimens about 60 mm FL. 

The first dorsal has 16 spines and the posterior spine 

nearly reaches the base of the second dorsal. There are 12 
to 14 rays (mostly 13) in the second dorsal and 13 or 14 

rays in the anal fin. There are 8 dorsal and 7 anal finlets. 

The gill raker count on a 35 mm FL specimen was 4 + 1 

+ 20 and increased to (7-8) + 1 + (22-23) in specimens of 

127 to 175 mm FL (Wade 1950a). 

Euthynnus alletteratus 

See section 3.2l. 

In a 4.6 mm TL specimen of E. alletteratus (not figured), no visible indication of spine or ray development is 

evident in the unpaired fins. The future fins are represented by a continuous membrane which starts near the 

nape and extends around the caudal end to the anal 

opening. There are 40 myomeres including the urll ty Ie; 

the urostyle is incompletely developed and e ·tend poteriorly in line with the longitudinal ax! at the bod) 

Chromatophores are pre ent at the pectoral gIrdle 

symphysis and immediately antenor to the anal openIng 

along the midventral line. There are about 3 hroma -

phares over the forebrain and about 12 0\ er the mid 

brain and a row of 3 or 4 well- paced chromatophor I 

evident over the middle two-third of the len h a thE 

lower jaw (:\olat umoto 19"9) 

A 5.5 mm TL specimen (Fi 14a) hoy. th I pment of four hart. pine in th 

paired tin~ are beg-inning to de\ elop. and th u 

turned upward. hromatophore- al n th mar In 
. ,r 

~ ~/ ," > 

(0 ) I MM. 

Fil(ure ll.- Futhynnus alletteratus larvae: (a) 5.5 mm ; (b) 7.5 mm ; (e) 9.3 mm . (From Matsumoto 1959, figs. 8-10.) (See Fig. 12 

for definition of body length.) 

Inw r jaw have increa ed and cover the anterior twothird. pt the jaw length . .l ine chromatophores are present on the midventrallme from the anal fin origin to the 

cfiudnl peduncle (~lat~umoto 1959). 

28 

A 7.5 mm TL specimen (Fig. 14b) has 9 very long 

spines in the first dorsal fin. There are 12 or 13 rays in the 

second dorsal, 14 rays in the anal, and about 17 rays in 

the caudal fin. 
Pigmentation is increased on the first dorsal fin and 

about 13 well-scattered chromatophores are present on 

the outer two-thirds of the fin between the first and 

seventh spines. The chromatophores along the lower jaw 

have increased and now appear closer together. The 

pigmentation along the mid ventral edge of the body consists of about 11 regularly spaced chromatophores 

although some specimens may have as many as 15 

(Matsumoto 1959). 

The most noticeable change in a 9.3 mm TL specimen 

(Fig. 14c) is the extremely long spines in the first dorsal 

fin. Similar to E. lineatus of comparable size, the length 

of the longest spine is about equal to the body depth 

measured at the origin of the second dorsal fin. The second dorsal and anal fins have 13 rays. The posterior edge 

of the caudal fin now shows signs of becoming forked and 

the ventral fins are beginning to enlarge. Pigmentation 

on the outer half of the first dorsal fin membrane has increased; there are 22 chromatophores extending over 8 

interspinous membranes (Matsumoto 1959). 

Matsumoto (1959) noted many changes in a 10.6 mm 

TL and a 11.5 mm TL specimen (not figured). Both 

specimens have completely developed dorsal and anal 

fins including 16 spines and 13 rays in the dorsal, followed by 8 finlets, and 14 rays in the anal followed by 7 

finlets. The caudal fin is more clearly forked and the 

pelvic fins are longer. The 11.5 mm TL specimen has 20 

+ 19 vertebrae. An increase in pigmentation is evident in 

several places. The lower jaw bears two rows of chromatophores (the larger specimen has a third row) and the 

upper jaw has a single row of chromatophores along twothirds of its length. 

Matsumoto (1959) also described postlarval and juvenile E. alletteratus ranging in length from 12.0 to 58.0 

mm TL (Fig. 15). The pigmeTltation along the dorsal and 

ventral edges of the body and along the midlateral line 

noted in the 10.6 and 11.5 mm TL specimens was also 

evident in the 12.0 mm TL specimen (Fig. 15a). Distinctive changes occurred between the 12.0 and 18.5 mm TL 

specimens (Fig. 15b). The abdominal sac was more 

elongate and the anus was more posteriorly placed in the 

larger specimen. The head parts, particularly the mouth, 

appeared smaller in relation to the total length and the 

fins and finlets were more clearly defined. The outline of 

the dorsal fin in the 26.0 mm TL specimen (Fig. 15c) 

resembles that of an adult and the body is narrower, relative to the total length than in the 18.5 mm TL specimen. For specimens larger than 26.0 mm TL the only 

noticeable change is in the increased pigmentation on 

the body. At about 40 mm TL one to three very faint 

spots or ventral bars appear along the dorsal third of the 

body. The number of bars increases to about 10 in a 58.0 

mm TL specimen (Fig. 15d) and to 13 on a 94.3 mm TL 

fish (not figured) . 

Richards and Dove (1971) described in detail the internal development of young E. alletteratus ranging in standard length from 3.5 to 24.0 mm. Anatomical features of 

E. alletteratus were described and compared with those 

of K. pelamis, Thunnus albacares, T. obesus, T. thynnus, T. alalunga, T. atlanticus, and Auxis spp. The fol29 

lowing anatomical features were examined: the sensory 

organs including the eyes, olfactory organs and 

acoustico-Iateralis systems, the nervous system (brain), 

swim bladder, kidney, gonads, liver, pancreas, spleen, 

digestive system, cardiovascular system, gills, skeleton, 

musculature, and pigmentation. Potthoff and Richards 

(1970) also made observations on the development of the 

axial skeleton of E. alletteratus and also computed a regression equation to estimate the standard length of a 

specimen based on the length of the vertebral column. 

The equation is, SL = 3.66 + 1.22 VL, where SL is standard length in millimeters, and VL is vertebral column 

length in millimeters. 

Euthynnus lineatus 

The smallest larval E. lineatus identified by Matsumoto (1959) measured 5.0 mm TL (Fig. 16a). The head is 

relatively large (about 37% TL) and the mouth is also 

large and contains about eight teeth on each side of both 

jaws. 

As in the other species of Euthynnus at the same stage, 

the abdominal sac is short and triangular, and the anus 

is located near the middle of the body. Spines and rays 

are undeveloped in all the fins. There are 38 or 39 myomeres including the urostyle. 

Chromatophores are present at the symphysis of the 

pectoral girdle and anterior to the anal opening. There is 

no pigment on the lower jaw at this stage of development (Matsumoto 1959). 

There are 5 short spines in the region of the first dorsal 

fin and posterior to these, 2 more are beginning to develop in a 6.0 mm TL specimen (Fig. 16b). The second 

dorsal and anal fin rays are still poorly developed and are 

difficult to distinguish; there are 17 rays in the caudal 

fin . Three or four chromatophores can be seen near the 

middle of the lower jaw (Matsumoto 1959). 

In a 7.1 mm TL specimen (Fig. 16c) the first dorsal fin 

has 7 definite spines, of which the 6 anterior ones are 

slightly greater in length. Three additional weak spines 

are beginning to develop but the fin rays are poorly 

formed. The caudal fin is beginning to fork and has 18 

well-developed rays. 

There are some striking changes in pigmentation in 

this specimen. The first dorsal fin between the second 

and sixth spines now has six large chromatophores. Chromatophores are present at the tips of the upper and lower 

jaws and seven more are found along the anterior twothirds of the lower jaw (Matsumoto 1959). 

Compared with the 7.1 mm TL specimen, a 9.3 mm TL 

specimen (Fig. 16d) has a well-developed dorsal fin. It 

has 12 well-developed spines of which the longe t is 

about 78% of the body depth at the origin of the second 

dorsal fin. The second dorsal fin consists of 11 ray and 

the anal fin 12 rays. The pelvic fins are nearly complete 

in development and the pectorals have about 14 distinct 

rays. The first dorsal fin is pigmented over the first eight 

interspinal membranes; the pigmentation is generally 

concentrated on the outer two-thirds of the fin (Matsumoto 1959). 
',", .. •• r" •• 

I MY 

-

~. 

;/ 

\ .... 

30 

2 MM 

. ./ 

-'~ / .. -"" 

(a) .," 

(b) 

(c) 

(d) 
The abdominal sac is more elongate and the anal opening only slightly anterior to the anal fin origin in a 10.6 

mm TL postlarval E. lineatus (Fig. 17a). The dorsal fin 

consists of 15 spines and 12 rays, and there are 8 dorsal 

finlets; the fmal fin consists of H rays and there are 7 

anal finlets (Matsumoto 1959). 

The 18.6 mm TL juvenile (Fig. 17b) is already similar 

in body shape to larger juveniles due mostly to a gradual 

reduction in the head depth relative to body length and 

to the elongation of the abdominal sac, wherein the anal 

opening is closer to the anal fin origin. 

The fins and finlets are more clearly defined in the 18.6 

mm TL specimen. The dorsal fins have the full adult 

complement of 15 spines and 12 rays, followed by 8 

finlets. The anal fin also has the full adult complement of 

12 rays followed by 7 finlets. The caudal fin is well developed and more deeply forked, the pelvic fins are 

longer, and the pectorals have 24 completely formed rays 

which are comparable to the fully developed fins (24-26 

rays) of the adults (Matsumoto 1959). 

In the 21.0 mm TL specimen (Fig. 17c), except along 

the area of the lower jaw, the pigmented areas are more 

widespread (Matsumoto 1959). 

3.3 Adult phase 

3.31 Longevity 

See sections 3.43 and 4.13. 

The maximum size and longevity of E. affinis are not 

well defined. Kishinouye (1923) stated that E. affinis 

from Japanese waters grow to be 60 cm and 3.5 kg, and 

that on rare occasions, specimens over 100 cm long and 

10 kg in weight are found. Ommanney (1953) reported 

that the largest E. affinis caught during a survey in the 

Mauritius-Seychelles area was a specimen 87 cm long, 

which weighed 8.6 kg (19 lb). Around the Marquesas 

Islands" E. affinis as large as 79 cm have been taken on 

surveys conducted by the NMFS Honolulu Laboratory. 

Landau (1965) estimated the age of the oldest fish from a 

sample collected in the Red Sea as 6 yr old. The fish was 

62 cm SL and weighed a little over 5 kg (Hlb). 

Fowler (1936) indicated that E. alletteratus from the 

West Indies grow to 122 cm. The largest specimen 

measured by Postel (1956) in the Mediterranean Sea off 

Tunisia was 101.5 cm, but he noted seeing many exceeding a meter in lengt.h. In the tropical eastern Atlantic, the largest specimen measured by Postel (1955a) in 

Senegal was 94.6 cm. Landau (1965) noted that the 

oldest E. alletteratus in her Mediterranean samples belonged to age group X and was estimated to be about 86 

cm SL (defined as the distance from snout to insertion of 

caudal fin). The world record sport catch for E. alletteratus is a specimen 92.07 cm long and weighing 12.24 

kg (20 lb) (International Game Fish Association undated). 

Figure 15.-Postlarvae and juvenile Euthynnus alletteratus: (a) 12.0 

mm (b) 18.5 mm ; (c) 26.0 mm; (d) 58.0 mm. (From Matsumoto 1959. 

figs. 11-14 .) (See Fig. 12 for definition of bod) length.) 

31 

There is no information on the longevity of E. lineatus. 

3.32 Hardiness 

Not much is known on the hardine of the three species of Euthynnus. In establishing tunas in tanks and 

ponds for experimental purposes, Te ter (1952a) noted 

that small E. affinis 0.4 to 1.4 kg (1-3 lb) became established in these enclosures more readily than yellowfin tuna, T . albacares. Once a school of E. affinis became established, newly introduced fish started to feed 

during the second day of confinement. In the experimental tanks maintained by MF in Honolulu, E affinis have survived for more than 14 mo (Magnu on 

1965). Stevens and Fry (1971) took body temperature of 

E. affinis that had been in captivity for 2 yr. Calkin and 

Klawe (1963) stated that the hardines of E. lineatus i 

similar to that of other tunalike fishes and that "They 

are hardy enough to be successful in their natural 

environment, but they can only stand a minimum of 

handling." 

3.33 Competitors 

The competitors of E. affinis in east African water include skipjack tuna, small yellowfin tuna, Auxis thazard, 

and a carangid, Megalaspis cordyla (Williams 1963). 

These fishes school together with E. affinis off ea t Africa 

in the Indian Ocean. In waters around Sri Lanka, E affinis are found in schools together with A. thazard, and 

presumably these two species are direct competitor for 

food (Williams 1963). 

Marchal (1963) stated the E. alletteratus compete 

with species with which it is found uch a A thazard 

and S. sarda. He also suggests the dolphins (Delphmus) 

and other cetaceans, Grampus and Globicephala, a 

probable competitors. 

In the eastern tropical Pacific, E. lineatu 1 found in 

close association with yellowfin tuna, kipJack tuna, and 

dolphin fish (Coryphaena) that undoubtedly compete 

with it for food (Calkins and Klawe 1963). 

3.34 Predators 

In east Africa, E. affinis have been found in the tomachs of longline-caught striped marlin, Tetraptur 

audax, and sharks, Carcharhmw> pp. (William. 1 '3). 

Predators of E. alletteratus include variou. pecie 01 

sharks, Carcharhinus spp. and Galeocerdo pp., large 

yellowfin tuna, and I twphoru pp. (i\.1archall 

Euthynnus lineatus have been found in the toma h 

of yellowfin tuna (Alverson 1 ). alkin and Kla .... e 

(1963) stated that the large billfi he undoub edl pre) 

on E. lmeatus 

3.35 Para ite, di ease., inJune, and sbn r· 

malitle 

ila (1 'ia) and lia and mmer -utt) 1 7) m de 

detailed urvey on para~iti m III Euth~ nnu and oth I 
1 MM. 

32 
",. ... ,' .... 

. 0 V 

t. 

~ I ur. 17. I' _II nal and IU\ 

• 

· · 

, 

(0 ) 

(b) 

(c) 
Tnhl(' I:;. Parll,ill" of !l ulh.\'flIlUH. (Modltil'" from Silll 1%711 : ~tI." IIl1d I mmf'rkull~ l'I4.i,1 

HIlst 

Euth nllIl.' ,,/lI'II,'rotu., 

D"ubllul r~l'l)rd 

____ ('_t):IJl' pod 

CO/lgU' hUll II;) 

CUll1/1i C(J"pJIIJI {WI 

I'" uduC\cnus app.·"ulculatu 

( ,milieu/ax ,uthl/IIII 

H"mo/orhu" {J II (,It \ m JU 

Table 16. Para,ite, of Euth,nnu, alit'll '"/U. (I rom 1' .. ,lf'l 1\';/, 

tubk 2.1 

Locallond 

ParaSIte L,t" IOgl' In:., laUon 

Ca/htctrarh) nthus graCllt Pier <erLold lana" Bod, ca"l) 

Otobothrudae Plerco"erLold Id" ae p) 1 CI caeca 

Rod florh) fichu prL"n, Adult toma h 

Sterrhuru" sp. Adult "tomaLh 

Hlrudrnella clal'ata Adull torna h 

Hex').,toma thunfllnae Adult G,ll. 

Hex,).,toma macrocanlhum Adult ("il 

Semci/a orb,gn,\I Adult \ enlral hnletform macu/ata 

3.36 Physiology, biochemi try, etc. 

Carey et a!. (1971) tated that the tunas, including E. 

alletteratus, have evolved a countercurrent heatexchange mechanism for conserving metabolic heat and 

raising body temperature . They determined that the 

temperature of one specimen of E. alletteratus was 

31.2°C. The surface water temperature was 19.9°C, thus, 

the body temperature of the fish wa 11.3°C higher than 

the surrounding water temperature. 

Stevens and Fry (1971) determined the body temperatures of two E. affinis held in captivity for 2 yr. They 

found that captivity reduced the excess temperature (defined as the body temperature minus ambient water 

temperature) of E. affinis. Graham (1973) determined 

the thermal profile of E. lineatus, which uses a centrally 

located vascular heat-exchange mechanism similar to 

that of E. alletteratus to maintain core body temperatures warmer than ambient temperature of seawater. He 

also described the structure of the central heat-exchange 

mechanism and the effect of temperature changes in 

blood-gas relationships in E. lineatus. Graham found 

that a warm central core in E. lineatus was related to the 

distribution of red muscle. The warmest body temperatures occurred along t he vertebral column between the 

34 

( .,psala mant, rI 

/I.'l U IDOla macracanthum 

('up ola aufl 

/71( ' a mllllma, 

//.1 0 toma • uth 111\1 

l ltop rudaxll1 at UU flU 

"I up • udax In ma rova 

/lLt t"ma ,uth fin! 

lhfluflu .combn 

1."ClthochlrUm 1 ... ;rJflUm 

Hhipluocul I Capltalum 

Rh'/Jld'Jcolyl nn fJl) I 

lerrhuru. montlC 1/1 

J "liP 111.1 /nw:nU., 

Hiupldf)c<tt Ie plapapillata 

/,I'Cllho hlrum m naporum 

I/' IIho h"um mlCf tomum 

HIrudin 11£1 marIna 

I ... IIlao hlrum ma rwporum 

1 lila hlrum 011 ra t 01"01 

lir t and ond dor I In . 'I h h at·exrh ng m chanI"m In}, ilneotu wa com d of the dor al aona. the 

po tenor c r IIn81 in. and a I rge "ertical ret . The dor-

... al Hurta .... u mbedded In th po. rior cardinal vein 

and wa thu ompl t Iy bath d in venou- blood. 

(,rahllm 1 und that imlla r to the ilua ion In bluefin 

tuna . T lh)nnu , th u ygen·carrYlng capacJt) 01 hemogluhin .... a unall cted by han ing blood temperature, 

Graham (1 1 75' cli. u. ed the adaptive "igmficance of 

el .... ated body temperature in ombrid fi. he He reiterated the ob. enation made by arey e( al. (1971) that 

the pnncipal ad\'antage 01 a high and airl)' con tant 

body tern ratur i facilitation ofcontinuou wimming 

by increa Ing the frequency of mu cular contraction, 

thu. increa. ing available wimming po .... er. Graham 

(1975) al 0 ob. en'ed that .... arm-bodied fi he probably 

achieve a marked independence from em'ironmental 

temperature thal permit them to make rapid horizontal and vertical migration without the nece ity of 

thermal acclimation. 

Aspect of ga exchange in E. affinis have al 0 been determined ( teven 1972). The perfu ion rate of the gill 

wa determined to be 1.77 liter min per kg (mean) and 

ranged from 1.55 to 1.88 liter/min per kg in three trials on 

a 2.26 kg specimen . The head 10 s in centimeter of water 

averaged 1.8. The calculated re istance to water flow offered by the gIlls averaged 1.03 cm of water/min per kg 

per liter and ranged from 0.90 to 1.20. Oxygen uptake 

was determined to be 503 mg/h per kg (mean) and ranged 

from 400 to 643. The calculated utilization (fraction of 

oxygen removed from the water) averaged 0.79 and 

ranged from 0.69 to 0.95. 

Rivas (1953) determined that scombrid fishes, including Euthynnus, possessed a pineal apparatus. He 

gave a description of the pineal apparatus and hypothesized that it might function as a light receptor to control 

phototactic movements of the fish. Support for Rivas' 

hypothesis was provided by Murphy (1971) who investi-
gated the pineal organ in bluefin tuna and found that the 

bluefin tuna's pineal organ had sensory cells possessing 

the structural characteristics of vertebrate retinal photoreceptor cells. He concluded that the pineal organ in 

bluefin tuna 'serves as a photoreceptor which receives external light stimuli and that such stimuli may travel 

from the pineal organ to a site of action via an apocrine 

secretion moving through capillaries or more likely by 

impulses transmitted by the pineal nerve. 

Magnuson (1970) made a detailed study of the hydrostatic equilibrium of E. affinis. This study was based on 

morphometric and body density measurements of fish 

31.6 to 67.8 cm long and from observations on the swimming behavior of fish about 42 cm long held in tanks. 

Variations in required lift under various conditions of 

seawater density, density of fish, and amount of food in 

the gut were evaluated. Magnuson (1970) also estimated 

the effectiveness of each lifting hydrofoil on E. affinis in 

terms of the percentage of the total lift it produced, its 

surface loading, and its coefficient of lift. He used all 

these parameters to develop a model which predicted the 

minimum speed required for hydrostatic equilibrium. In 

a later paper Magnuson (1973) tested this model to see if 

it predicted the swimming speeds of a large number of 

scombroid fishes, including E. affinis; considered the 

"adaptive radiation in the morphology especially of 

the gas bladder and pectoral fins which together with 

swimming speed contribute to the mechanism by which 

scombroids maintain hydrostatic equilibrium"; and considered problems associated with maintaining hydrostatic equilibrium by large body size. 

3.4 Nutrition and growth 

3.41 Feeding 

Observations on various aspects of feeding and related 

observations have been made on Euthynnus. Bullis and 

Juhl (1967) observed what they called "phalanx orientation" in the feeding behavior of E. alletteratus near the 

Grenadine Islands in the Lesser Antilles. This pattern of 

orientation was observed as the E. alletteratus were 

apparently feeding on a large group of dwarf herring, 

Jenkinsia lamprotaenia, which had collected directly under a floating night light. The phalanx developed by a 

single fish being joined by another and then by a third 

fish . This phalanx took the form of a tightly packed 

three-fish aggregation evenly aligned side by side. The 

phalanx attacked the ball of dwarf herring without altering formation. The observers noted that the attack on the 

dwarf herring did not start until the phalanx had been 

formed. During the course of feeding, additional E. alletteratus were seen to join the phalanx until it was estimated that the phalanx contained 14 or 15 fish of about 

the same size. 

Wicklund (1968) reported on daylight feeding patterns 

of E. alletteratus in Florida waters. He observed a school 

of 20 and a group of 4 fish feeding on bigeye scad, Selar 

crumenophthalmus, and herring, Clupea sp. Wicklund 

35 

observed E. alletteratus moving toward the herring at 

which time the herring moved to the bottom and mixed 

with the scad. The E. alletteratus attacked when all the 

herring and scad were tightly packed against the bottom. 

In their attacking maneuver, the fish swam downward 

toward their prey with a great burst of speed and in the 

instant before reaching bottom they turned harply 

parallel to the bottom, stirring up clouds of sediment. 

Wicklund noted that the E. alletteratus took their prey 

at this point or a fraction of a second later, and noted 

that the fish's jaws could be heard snapping audibly. The 

feeding continued all day, presumably in the same manner. The E. alletteratus left the area in the evening at 

1800 and returned at 1030 the next day. 

Wicklund's (1968) observations have similarities and 

differences from observations made by Hiatt and Brock 

(1948). The latter observed a group of three E. affinis 

herding a closely packed school of several hundred scads, 

Decapterus sanctaehelenae, over a large coral head in 

Rongerik lagoon in the northern Marshall Islands. They 

noted that the three E. affinis " ... usually followed the 

school of scads rather closely, with one tuna at each rear 

flank of the school and the third lagging behind them . 

Now and then the scads would turn off to one side, at 

which time the tuna on that side could move forward 

swiftly and herd them back into line." On one occasion, 

Hiatt and Brock (1948) saw a stray scad eaten by the 

rearmost E. affinis. Except for this incident, the E. 

affinis did not make any attempt to prey on the scads 

during the 3-h observational period. Wicklund's observations were similar to Hiatt and Brock's in that in both instances the Euthynnus forced the prey into tightly 

packed schools. However, the E. alletteratus observed by 

Wicklund (1968) aggressively attacked their prey 

whereas the E. affinis observed by Hiatt and Brock 

(1948) merely picked off the stragglers. In this regard, 

Wicklund's observations are more similar to those made 

by Kishinouye (1923). Kishinouye (1923) noted that E 

affinis were voracious feeders, and de cribed their 

feeding method as darting swiftly into a school of small 

fish and scattering them. As Kishinouye (1923) stated 

however, the feeding habit of E. affim may vary 

throughout the year. Presumably, this could also be true 

for the other species of Euthynnus 

Walters (1966) studied the filter feedmg of E. affmi by 

means of high-speed motion pictures. He howed that E. 

affinis traveled an average of 5.9 body length / while 

feeding and observed a maximum speed of 10.0 bod ' 

lengths/so He found no change in speed and no mcrea. e 

in swimming effort as the fish opened it mouth and dJ -

tended the orobranchial chamber to engulf it prey 

Walters (1966) observed that the feeding mecham m I 

drag free and that E affims feed by wimming over 1 

prey rather than by sucking it mto it mouth . He al 

pointed out that E. affini , and combrid Ii. he m neral, are facultative filter-feeders in that the ' are able to 

feed in open water upon wimmmg organi m that are 

minute in compari on to the ~lze of the predator, and 

noted the high gill-raker count in the p Cle upport hi tatement. 
Magnuson and Heitz (1971) determined thut the mean 

gill-raker gap for E alfmis wa~ 1 4 mm and the f1l((·ring 

area of the first gill arch wa 61)0 mm~. Th y not d thut in 

terms of gill-raker gap, K affifll.\ waH interm('dlate 

(ranked fifth. gomg from small to large) compar -d with 

Kati;ull'onu peianlls. Auxi.\ rcJchci. A thazard,. 'con/· 

ber japvnlcu~, Thunnw albacaff'.\, T. alalLln~a, T. 

obesui;, 'arda chilil'nsis, S. url('ntah." ('(}ryplto{'/w 

eqUlsel!s, and C hlppuru.\, ranked from !nIdI to laq(e, 

re pectively. Magnu<;on and Hill (1971) r ·Iat d the gill. 

raker apparatu~ to food seledlvily amung th I h 

and noted that despite the varil'd diet 01 "combnd Ii hl' , 

electi\'it~ .. in terms of size doe e i I in the lI11nhnd. 

They ob'erved that within a spene , larger fi h t d on 

relatively fewer crustaleans and mm !l he , 

3..1:2 Food 

Ob erv tion on the diet of f.'uth..,nnu. trom variull lu. 

calitiesuggest that th e fishe~ teed primllrily Oil what· 

ever I available at any particular plan~ and tim. an 

example R nquillo (1 .')'3) f lund that E afiLn~ fed I ut 

equall ' on crustacean (;6.2 c b~ numb rand fi he 

(43. °c by numberl in Philippine .... at r. Ronquill) 

(19;)3) lound no quids in the tomllch . Ar Illd Ha 

Te ter and 1 ' akamura (1 57) al. olund that quid 

negligible in the diet 01 E. aiillll', but unhke th Phlhp· 

pine area, fi he" were much more 1m )rt.ant 1. b ' 

volume than crustacean" (.2 by volum ) 1n th In· 

dian Ocean, Kumaran 1 ) f(lund 

by volume) were mll.t important, 

(38.3'(' b) volume), and cru ta an 

were the lea t important. 

For E. alletteratu. in the ;>'ledilt'rranean a, Urtn et 

al. (1959) found that crustacean" (1)3 c b . number ""er 

mo, t important followed by Ii hes 1_2 c b) number) and 

squid (lF~ by number). Heterop d and tunicatemade up 4 C c by number of the diet. 

Small fi h; quid; Auxi thazard: a pelagiC rab, 

Pleuroncodes planipe : and ierra mackerel, umblro· 

morus I; ierra , have been found in the tomach of E lineatus (Calkins and Klawe 1963). 

Table 17 pre ent example of lood item, found in 

stomachs of Euth) nnu~ from .. adou area . It can be een 

in Table 17 that Postel (1954) Ii ted E. alletteratul;, prt!-

sumably a juvenile, from the tomach of an adult E. 01-

letteratus. 

3.43 Growth rate 

Euthynnus affinis 

The available information on the age and growth of E. 

affinis is sketchy and fragmentary. 0 data are available on the growth of the larvae. On the juveniles, Ki hinouye (1923) suggested that a ll5 mm specimen caught 

off Port Keelung in August may have been about 3 mo 

old. Wade (1950a) speculated that a 115 mm long specimen from the Celebes Sea was 3 or 4 mo old, and that a 

175 mm specimen may have been spawned as long as 6 

36 

Cro. tacea 

PlanktoniC cru,tace8 

Euph8U,18Ci'ae 

er~f'lId8e 

Parapeneu., Ionlllru,trLs 

Bryozoan, 

Madrepora)re, 

Green algaf 

7 

17 

1 

I 

1 I 

• 

14 

27 

20 

07 

6.b 

6.6 

14 

07 

7 

.. 1 

07 

U 

[, 

07 

07 

07 

tab e I ) 

01 

01 

01 

01 

1 1 

07 

10 

• 0.6 

01 

o 

o 

01 

02 

.6 

rno before it capture. The e observations suggest a 

growth rate of 1.0 to 1.3 mm/day. 

Yabe et al. (1953) pre ented length data of preadult E. 

affini landed at the port of Aburatsu, Japan, during 
August-October 1950 (Table 18; Fig. 18). Yabe et al. 

indicated that E. affinis between 150 and 250 mm were in 

their first year of life. Figure 18 suggests an average 

growth rate of 1.5 mm/day. This growth rate is not very 

different from that suggested for E. affinis juveniles in 

the Philippines. 

Ommanney (1953) observed the age-size relationship 

of E. affinis caught near the Seychelles. Although the 

basis for determining the age-size relationship is not 

made clear, he suggested that postlarval to 25 cm fish 

Table 18.-Average size of Euthynnus affinis 

landed at Aburatsu, Japan. (From Yabe et aJ. 

1953, table 5.) 

No. of 

fish Fork length (mm) 

Month measured Range Mean 

Aug. 26 107 183-240 200 

30 51 201-225 213 

31 98 203-239 217 

Sept. I 53 194-240 214 

2 19 199-268 218 

4 92 209-245 225 

5 78 204-290 224 

6 91 200-309 221 

7 79 203-307 235 

8 132 196-325 234 

9 149 200-271 222 

20 115 213-274 236 

25 13 223-255 236 

Oct. 6 5 230-295 241 

l1 9 252-278 262 

13 24 254-286 265 

16 138 244-313 270 

17 III 220-332 272 

oL-------------------------~----------~ _" _______ )~l ______ _,,-------)l~-------.,---

AUG. SEPT. OCT. 

Figure 18.-Growth of preadult Euthynnus affinis off the southern 

coast of Japan. (Data from Yabe et al. 1953.) 

37 

were in their first year of life, 25 to 45 cm fish in their second year, 45 to 65 cm fish in their third year, and 65 cm 

and larger fish in their fourth year and over. 

Landau (1965) determined the ages of E. affinis from 

the southern Red Sea based on the annular marks on the 

vertebral centra. The age-size relationships are given in 

Table 19. Landau, using the graphical method, estimated that the L", for E. affinis in the Red Sea was 580 

mm SL. 

Table 19.-Age-size relationships of Euthynnus affinis from 

the Red Sea. (From Landau 1965, tables 2, 3.) 

Age 

I 

II 

III 

IV 

V 

I 

II 

No. of 

fish 

28 

11 

18 

25 

10 

78 

2 

Length (SL)' in mm 

Range Mean 

Approximate mean 

weight (kg) 

Southern Red Sea (April-June 1964) 

310-430 345 0.9 

370-520 456 2.1 

470-560 511 2.8 

520-590 544 3.3 

520-600 554 3.5 

Bay of Eilat, Red Sea (May 1964) 

320-340 370 1.0 

505 and 525 3.0 

'SL is standard length defined by the author as the distance 

from the snout to the insertion of the caudal fin . 

On the basis of annular marks on the first dorsal spine 

of E. affinis, Shabotinets (1968) determined the age-size 

relationship of fish taken in the Gulf of Aden as shown 

below. 

Age 

3 

4 

5 

6 

Size (em) 

50-65 

55-75 

65-80 

86 

Euthynnus alletteratus 

Houde and Richards (1969) observed the growth of larval E. alletteratus under laboratory conditions. They collected fertilized eggs in the western edge of the Gulf 

Stream near Miami, Fla., and incubated and hatched 

the eggs in 20- and 140-gal (75.5- and 530-liter) aquaria. 

The growth in length of the larvae in one of their rearing 

experiments is shown in Figure 19. As can be seen the larval fish grew from approximately 2.5 mm to a little less 

than 8.5 mm in 18 days. Houde and Richards noted that 

the growth of the larvae was probably not as fast as in the 

natural environment. 

Based on modal groups in length-frequency distributions Postel (1955b) presented the following age-length 

relationships for E. alletteratus off Dakar in the eastern 

Atlantic: 

Less than 1 yr (Group 0) 

1 to 2 yr (Group 1) 

2 to 3 yr (Group 2) 

3 to 4 yr (Group 3) 

Over 4 yr 

<30cm 

30-45 cm 

45-60 cm 

60-75 cm 

>75cm 
9 I 

0 

8 

7 

6 

E 

E 0 

:I: 5 ~ 

(!) 0 z 

w 0 

..J 4 8 ..J 

~ 0 8 § 9 0 ~ 3 - 6 

§ 

2 -

o 2 4 6 8 10 12 14 16 18 20 

DAYS AFTER HATCHING 

Figure 19.-Growth in length of Euthynnus alletteratu8 larvae 

orea red in the laboratory. (From Houde and Richards 1969, fig. 3.) 

Landau (1965) determined the ages of E. alletteratus 

in the Mediterranean Sea by reading marks on the vertebral centra . Lengths of fish at various ages were backcalculated by relating the radius of annular marks on the 

vertebrae to the length by the regression: 

LS = 45.85 V + 72.62 

where LS is standard length defined as distance from 

snout to insertion of caudal fin, and V is vertebral radius. 

The age-size relations determined by Landau are given 

in Table 20. Landau also estimated Lao for E. alletteratus 

as 840 mm, using the graphical method on size obtained 

by back-calculations. 

Euthynnus lineatus 

Except for some observations on the growth of juvenile E. lineatus there is nothing in the literature on the 

growth of this species. Clemens (1956) was able to rear 

juvenile E. lineatus for up to 10 days in shipboard 

aquaria. From the beginning of the holding experiment 

to the end 10 days later, the average weight of the juveniles increased 11 times and the average length increased approximately 1.4 times (Table 21). 

Table 20.-Age-length and age-weight relationships for EuthynnuB alletteratus in the Mediterranean Sea. (From Landau 1965, table I.) 

Length (SL) , 

inmm Approximate mean 

Age Range Mean weight (kg) 

I 28-49 358.4 0.8 

II 46-68 539.1 2.8 

III 54-75 637.2 4.5 

IV 61·79 701.9 6.0 

V 65-84 755.0 7.5 

V1 74 -86 801.5 8.5 

VII 75-84 810 9.0 

'SL is standard length defined by the author as 

the distance from the snout to the insertion of the 

caudal fin . 

3.44 Metabolism 

Malvin and Vander (1967) determined the plasma 

renin activity in E. affinis. They pointed out that there is 

general agreement that freshwater fishes contain renin in 

their kidneys but that this problem had not been resolved in marine fishes; furthermore, plasma renin had 

not been measured for marine species. Their results 

showed that certain characteristics in the plasma renin 

activity of E. affinis and K. pelamis were identical to 

that of the mammalian renin-angiotensin system which 

strongly indicated to them that the material being evaluated was angiotensin generated by the enzymatic action 

of renin. It was determined that the renin activity, expressed 8S angiotensin-equivalents, was 23.3 and 15.8 

ng/ml of plasma for two specimens of E. affinis. 

Klawe et a1. (1963) determined the hemoglobin content of the blood of E. lineatus. They noted that the 

hemoglobin content of the blood of fishes is generally related to the level of activity of the species. The hemoglobin concentration of E. lineatus blood ranged from 

16.9 to 19.9 g/l00 ml for five fish measuring 427 to 657 

mm. This level of hemoglobin concentration was higher 

than for Scomber japonicus and Sarda chiliensis. They 

speculated that the higher hemoglobin content of the 

blood of E. lineatus was somehow related to its complex 

cutaneous vascular system which S. japonicus and S. 

chiliensis lack. 

3.5 Behavior 

For feeding behavior, see section 3.4; for reproductive 

behavior, see section 3.13. 

Table 21.-Growth of postlarval Euthynnus lineatus. (From Clemens 1956, table 1.) 

Number 

Hours' Standard length (mm) Fork length (mm) Weight (g) 

of fish Range Average Range Average Range Average Range Average 

23 0 0 17.0-37.5 26.8 18.5-40.0 28.3 0.10-0.57 0.29 

3 171-175 173 48.0-52.0 49.3 51.0-55.0 52.0 1.51-1.91 1.70 

3 194-200 197 54.0-55.0 54.3 58.0 58.0 1.94-2.37 2.14 

4 244-248 246 59.0-71.5 63.6 63.0-75.0 67.5 2.61-4.72 3.46 

'Hours of growth computed from time fish started feeding, 42 h after capture. 

38 
3.51 Migrations and local movements 

See section 5.3. 

3.52 Schooling 

Aspects of the schooling behavior of Euthynnus relative to feeding have been discussed in section 3.41. Other 

observations on the schooling behavior of Euthynnus 

indicate that these species tend to school with other species. In the Indian Ocean off the east Mrican coast, E. affinis were found in schools with small T. albacares, K. 

pelamis, Auxis sp., and a carangid, Megalaspis cordyla 

(Williams 1963). Williams noted, however, that all individuals in the schools were of much the same size. He 

also found that with small E. affinis "the schooling is 

strong and disciplined." 

Elsewhere in the Indian Ocean, Williams (1963) noted 

that in waters around Sri Lanka, mixed schools of Auxis 

spp. and E. affinis are common. Sivasubramaniam 

(1970) stated that K. pelamis, Auxis spp., and young T. 

albacares occur together with E. affinis and that the 

catches are almost always mixed. Fourmanoir (1957) 

observed that around Madagascar, schools of E. affinis 

were almost always distinct from that of other species of 

tuna, except in June to the east of Nosy-Be, where T. 

albacares were taken at the same time as E. affinis. 

Williams (1963) noted that in east Mrica, schools of E. 

affinis were composed of 100 to 1,000 or more individuals, and in Sri Lanka as many as 5,000 individuals 

(mixed E. affinis and Auxis spp.) may be taken in one 

haul of a beach seine. 

Cahn (1972) investigated side-to-side spacing and 

positional orientation of E. affinis during schooling in 

experimental tanks. The study was designed to demonstrate the role of the lateral line sensory system in the 

schooling of E. affinis. Euthynnus affinis, in the experimental tanks, significantly increased their side-to-side 

spacing and altered their diagonal to abeam position 

ratios so that the abeam orientation assumed increased 

importance when the hydrodynamic field between orienting fish was blocked by a transparent partition. She 

concluded that hydrodynamic contact is essential for the 

typical spacing and positional orientation in schooling, 

and that the lateral line plays a prime regulatory role as 

the water turbulence detector. 

Although E. alletteratus are found in schools most of 

the time, they have a tendency to scatter during certain 

periods of the year (Marchal 1963). Marchal further 

noted that E. alletteratus schools have an elliptical 

shape of variable size and may be as long as 30 m along 

the long axis. Like E. affinis, E. alletteratus often school 

with other species, including Auxis sp., Sarda sarda, and 

Selar crumenophthalmus. All the individuals in these 

mixed schools tend to be of the same size {Marchal 1963). 

Euthynnus lineatus in Peruvian waters are frequently 

found in schools with T. albacares and K. pelamis of the 

same size (Bini 1952). The number of individuals in the 

school, however, was not as great as the commercially 

important species. Calkins and Klawe (1963) reported 

that commercial tuna fishermen have observed that E. 

39 

lineatus will frequently collect around drifting or 

anchored tuna boats. They noted that T. albacares and 

K. pelamis also exhibit this type of behavior but believed this behavior pattern was more pronounced with 

E. lineatus. Hunter and Mitchell (1967) observed schools 

of E. lineatus beneath flotsam or drifting objects. However, these schools remained near the floating objects 

only for short periods and they did not swim as close to 

the objects as did other small fishes. They could not 

ascertain whether the schools of E. lineatus were truly associated with a particular object. 

3.53 Responses to stimuli 

Tester (1959) summarized the various experiments on 

the response of E. affinis and other tunas to stimuli 

(Hsiao 1952; Miyake 1952; Tester 1952a, 1952b; Van 

Weel 1952; Tester et a1. 1954; Hsiao and Tester 1955; 

Tester et a1. 1955; Miyake and Steiger 1957). It was 

found that E. affinis were attracted to continuous white 

light over a range of moderate intensity (about 70 to 450 

fc). Euthynnus affinis were not attracted to a light of 

weaker intensity, and were repelled by a light of stronger 

intensity (Hsiao 1952). In experiments testing the reaction of E. affinis to moving objects of various colors, it 

was found that white lures were slightly more attractive 

than red, black, or silver (Hsiao and Tester 1955). Hsiao 

and Tester (1956) noted, however, that this may have 

been associated with greater visibility than color preference . Experiments on the chemoreception of E. affinis 

indicated that this species had a well-developed sense of 

smell or taste in that they were strongly attracted to clear 

colo?less extracts of tuna flesh. It was further found that 

the attractant was contained in the protein rather than 

the fat fraction of the clear extract (Van Weel 1952; 

Tester et a1. 1955). It was also determined that E. affinis 

became conditioned to the smell of juices exuded from 

the food which presumably contained common or similar substances which stimulated the feeding response 

(Tester et a1. 1954). 

Nakamura (1968) determined the visual acuity of E. 

affinis. Visual acuity was defined as the ability to see 

clearly the fine details of objects, especially as the objects 

become smaller and closer together. To determine the 

visual acuity, E. affinis were trained to discriminate between vertically and horizontally striped images that 

were projected on an opal glass plate in an experimental 

tank. The visual acuity of two E. affinis, 36.4 cm (0.9 kg) 

and 43.4 cm (1.6 kg), were determined at various levels of 

luminance (Fig. 20) . Nakamura (1968) also conducted 

these experiments on K. pelamis and noted that at lower 

luminances the visual acuity of the two species were 

similar. At higher luminances, however, K. pelamis had 

a greater visual acuity than E. affinis. 

Experiments have also been conducted to describe the 

hearing thresholds and frequencies audible to E. affinis 

(Iversen 1969). Based on experiments with two specimens, Iversen determined a threshold curve for acoustic 

sound pressure for E. affinis which showed that the fish 

perceived sounds from 100 to 1,100 Hz (Fig. 21). The 
. 16 1 1 

. 14 

.12 -

/,,~H0/0 0 0 

.10 I- ll~lJ II 

>-

t-

:5 O/ 

-

'-' ..: ;::0 .081- ...J II it. 4 6

..: 6.6 

:::l 

oOOiO rn 

;; .06 00) ! . 04 o 0 0 o 0 0 .02 00 -

-

-

-

OL-~~~~~--~ -2.5 -2.0 -1 .5 -10 ~~~-0.5 ~~~~~~~~ 0 to.5 +1.0 tl.5 

LOG OF LUMINANCE OF WHITE STRIPES (FOOT-LAMBERTS) 

Figure 20.-Visual acuity curve of Euthynnu8 affinis at adaptive 

illumination of 170 luxes. Curve fitted by eye. (From Nakamura 

1968, fig. 3.) (Although not explicitly stated, it is believed that 

visual acuity is plotted against log. of luminance.) 

lowest mean threshold was 7 dB/mbar at 500 Hz. At 100 

Hz the threshold was 30 dB/mbar higher than at 500 Hz, 

and at 1,100 Hz it was 23 dB/mbar higher. The mean 

thresholds for E. affinis were consistently higher than 

those for T. albacares (Iversen 1967). Iversen (1969) 

noted that this difference could have resulted in part 

from the lack of a gas bladder in E. affinis. 

Steffel et al. (1976) conducted experiments on captive 

E. affinis to determine their ability to discriminate 

temperature gradients. Tests on two fish yielded a discrimination threshold of 0.10° to 0.15°C. Their experiments indicated that the thermal sensitivity of E. affinis 

is no more acute than that of inshore fishes and appeared 

inadequate for direct sensing of weak horizontal temperature gradients at sea. 

Walters (1966) determined the swimming speed of E. 

affinis by high-speed motion pictures. He observed that 

E. affinis traveled an average of 5.9 body lengths/s while 

feeding and a maximum of 10.0 body lengths/so The nonfeeding swimming speed, with food present, averaged 4.5 

body lengths/s and ranged from 2.9 to 12.5 body lengths/so 

Magnuson (1969) investigated the swimming activity 

of captive E. affinis as related to their search for food in 

outdoor tanks. He determined that the average swimming speed of E. affinis, averaging about 35 cm long, was 

80 cm/s during the day and 83 cm/s at night in tanks containing no food. These fish had been in captivity for less 

than a month. Swimming speed measurements made 

after the fish had been in captivity for 5 to 6 and 8 mo 

showed that the speed was lower than that of fish held 

less than a month, but no marked difference was 

observed between the mean speed during the day (74 

cm/s) and the mean speed during the night (72 cm/s). 

Magnuson (1969) also measured the swimming speed of 

40 

50 

.1 

a:: d I d 44 em Euthynnus offinia 

..: 40 

A 

° 54 em Euthynnua offinia ID I 0 

a:: 

'-' t : j 

.... 30 ID 

0 4 

...J 

I 

~ + b w 

> 20 ~ 

w ~ a:: b :::l 

rn 

rn ] w 

a:: 

Cl. 

0 

t t z 

:::l + '- .;. 0 6 rn 

-10 200 300 400 500 1000 

FREQUENCY (Hz) 

Figure 21.- Acoustic sound pressure thresholds of two Euthynnu8 

af{inis. (From Iversen 19G9, fig.!.) 

E. affinis in tanks containing several thousand live prey 

fish. They appeared to swim faster than those without 

food, averaging 108 cm/s during the day and 92 cm/s at 

night. He noted that the higher day speeds were cl;lused 

from intermittent high-speed pursuit of the prey. 

Euthynnus affinis did not prey on the baitfish at night. 

Magnuson (1969) found that swimming speed was 

highest after a meal and decreased when the fish were deprived of food . He argued that if the level of swimming 

activity is regulated by search for food, swimming speed 

should be higher when motivation to feed is increased by 

deprivation of food . Because swimming speed decreased 

during deprivation, he concluded that swimming activity 

must be regulated in response to some biological need 

other than food search. He further concluded that swimming activity appeared to be more closely related to the 

requirements for maintaining hydrostatic equilibrium 

and gill ventilation, than for food search. 

Inoue et al. (1970) also made observations on the swimming speed of E. affinis. They found that E. affinis swam 

at a speed of 0.30-1.27 m/s during the day and 0.33-0.75 

m/s under artificial lights in their experimental tanks 4 

m in diameter and 0.6 m deep. 

Nakamura and Magnuson (1965) gave a detailed 

description of the coloration of living E. affinis. In addition to the permanent coloration, E. affinis exhibited 

three transient color patterns or markings that were related to feeding. These patterns or markings were black 

spots ventral to the pectoral fins, faint vertical bars on 

the flanks, and a yellowish middorsal stripe. These three 

color patterns were observed when E. affinis were 

feeding. Nakamura and Magnuson (1965) suggested that 

these transient color patterns may act as "social releasers" to signal the presence of food to other members 

of the school. 

Wickham et al. (1973) investigated the efficlicy of 

mid water artificial structures for attracting pelagic sport 

fishes in the Gulf of Mexico near Panama City, Fla. With 
equal experimental fishing effort they obtained signifi- ' 

cantly greater catches of E . alletteratus around the artificial structures than in adjacent control areas. However, they noted that E . alletteratus were seldom 

observed or captured at the structures unless baitfish 

were present. They concluded that E. alletteratus apparently were not attracted by the structures per se, but 

rather by the presence of the baitfishes that were attracted to the structures. 

4 POPULATION 

4.1 Structure 

4.11 Sex ratio 

The sex ratios of E. affinis in various localities are 

given in Table 22. Williamson (1970) estimated the sex 

ratio of E. affinis by size near Hong Kong. He found that 

for fish from 38 to 49 cm the sexes appeared to be represented in equal numbers but for fish from 50 to 73 cm, 

67% of the fish were males. 

The sex ratio of E. alletteratus in various localities is 

given in Table 23. 

No information is available on the sex ratio of E. 

lineatus. 

Table 22.-Sex ratio of Euthynnu8 affinis. 

Sample 

Number (percent) 

Locality size Males Females Source 

East Africa (western 11 6(54.5) 5(45.4) Morrow (1954) 

Indian Ocean) 

East Africa (western 37 22(59.4) 15(40.5) Williams (1964) 

Indian Ocean) 

Hawaii 93 45(48.4) 48(51.6) Tester and 

Nakamura (1957) 

Philippines 456 243(53.3) 213(46.7) Wade (1950b) 

Table 23.-Sex ratio of Euthynnus alletteratus. 

Sample 

Number (percent) 

Locality size Males Females Source 

Between North Carolina 227 121(53.3) 106(46.7) de Sylva and 

and northern Florida Rathjen (1961) 

Miami, Fla . 550 261(47.5) 289(52.5) de Sylva and 

Rathjen (1961) 

Barbate and Tarifa, 378 198(52.4) 180(47.6) Rodriguez-Roda 

Spain (1966) 

Senegal 866 432(49.9) 434(50.1) Postel (19Mb) 

4.12 Age composition 

See section 4.13. 

4.13 Size composition 

Euthynnus affinis 

The length-frequency distribution of E . affinis caught 

by trolling and drift nets in the southwest region of the 

Sri Lanka fishery is shown in Figure 22. The E . affinis 

41 

70 

60 

>- u 50 z 

W 

::::l 

0 

w 40 a:: 

lJ.. 

fz 30 w 

u 

a:: 

w 20 (l. 

161 

20 

24.1 

28 

32.1 

36 

40.1 

44 

DRIFT NET (4'-6' MESH) 

N=740 

48.1 

52 

56.1 

60 

64.1 

68 

FORK LENGTH (em) 

Figure 22.-Length frequencies of Euthynnus affinis caught by 

drift nets and troll lines in the southwest regions of Sri Lanka. 

(From Sivasubramaniam 1970, fig. 3.) 

taken by the commercial fishery ranges from 20 to 65 cm. 

Occasionally fish in the 15 to 20 cm and 65 to 68 cm 

groups are also taken (Sivasubramaniam 1970). Sivasubramaniam discussed the size selectivity of the various 

gear used in the Sri Lanka fishery . He noted that the 

trolling gear sampled a wide range of sizes of E. affinis. 

However, he also stated that trolling gear selected a 

larger proportion of smaller sizes of fish in the stock. 

Although drift nets are highly selective, the use of a wider 

range of mesh sizes from 10.2 to 15.2 cm (4-6 in) in Sri 

Lanka made these nets less selective. He indicated that 

the use of 10.2 to 15.2 cm mesh nets resulted in the capture of a fairly wide size range of E. affinis. Since the 

pole-and-line fishing method is directed primarily at K. 

pelamis which range from 40 to 55 cm, this fishing 

method tends to select E. affinis of the same size range 

which are found together with K. pelamis. Finally, Sivasubramaniam (1970) pointed out that the selectivity of 

longline gear relative to the size and behavior of E. affinis 

eliminated this species from longline catches. It appears 

that in general all the various life stages of E. affinis occupy the same habitat, and the size of fish taken is primarily dictated by the gear used. This probably holds 

true for the other two species of Euthynnus which are 

also coastal fishes. 

The length-frequency distribution of E. affinis caught 

by trolling along the southeast coast of India is shown in 

Figure 23. The E. affinis caught during July 1960 in this 

area ranged from about 42 to 68 cm. No modes were discernible in the length distribution. The August 1961 sample showed a mode at around 46 cm and the September 

1961 sample at around 52 cm. As noted earlier, other fishing 

gear in addition to trolling gear are used to catch E. affinis 

along the southeast coast of India. Presumably, the 

length-frequency distribution of E. affinis caught by 

other gear would differ from that of fish caught by trolling. 

The length range of E. affinis caught along the southwest coast of India is given by Bennet (1964) (Table 24). 

The gear used in this fishery includes drift nets and hook 

and line (presumably trolling gear). Shore seines are oc-
JULY 1960 (N-15) 

15 

10 

5 

oL-~~-L-L~ __ L-L-~-L-L~ __ L-L-~-L~~~ 

40,-,-,--,-,-,--,-,-,--,-,-,--,-,-,--,-,-,-, 

35 

t; 30 z 

ILl 

::> 

~ 25 a:: 

~ 

~ 20 z 

ILl 

() 

ffi 15 Cl. 

10 

5 

AUG. 1961 (N·32) 

oL-L-~-L-L~~L-L-~-L-L~~ __ L-~-L-L~~ 

20.-.-.--.-.--.-.--.-.--.-.-.--.-.--.-.--.-.-. 

SEPT. 1961(N'16) 15 

10 

5 

OL-~40~0-L~--L-~~50LO~--L-~~-L~--L-~-L~7~00~ 

TOTAL LENGTH (mm) 

Figure 23.-Length frequencies of Euthynnus affinis caught by 

trolling off the southeast coast of India . (From Silas 1967b, 

fig. 15.) 

Table 24.-Size composition of Euthynnu8 affinis from the southwest 

coast of India. (From Bennet 1965, table 3.) 

Minimum Maximum Minimum Maximum 

length length length length 

Month (em) (em) Month (em) (em) 

1960 1961 

July 45.0 60.5 January 30.5 62.8 

August 43.5 64.0 February 31.7 58.5 

September 43.0 60.0 March 24.3 62.3 

October 15.0 62.3 April 30.1 70.1 

November 24.7 55.0 May 42.5 67.3 

December 26.3 62.7 June 42.5 63.7 

July 48.2 66.1 

August 41.6 67.3 

September 42.2 61.0 

October 20.3 59.0 

casionally used. The fish caught during the sampling period measured from 15 to 70 cm. Bennet (1964) noted 

that the smallest fish were taken in October 1960 by 

shore seine. He further stated that the smaller sizes are 

not represented in the commercial catches. The size 

range and the modal groups of E. affinis caught in vari .. 

ous other localities in the Indian Ocean as summarized 

by Williams (1963) are shown in Table 25. 

42 

Length-frequency data on E. affinis caught in 

Japanese waters are scanty. Yabe et al. (1953) presented 

size data on young E. affinis landed at Aburatsu, Kyushu, Japan, in 1950 (Fig. 24). 

During a fishing and marketing experiment (see section 5), E. affinis measuring 23 to 73 cm were taken by a 

Table 25.-Size composition of catches of Euthynns affinis in various areas of the Indian Ocean. (From Williams 1963, table 3.) 

Area and author 

Australia 

Roughley (1951) 

East Africa 

Morrow (1954) 

Williams (1964) 

Madagascar 

Fourmanoir (1955) 

Seychelles 

Ommanney (1953) 

Somalia 

Ogilvie et al. 

(1954) 

>-

() 

Z 

ILl 

::> 

~ a:: 

~ 

~ 

Z 

ILl 

() 

a:: 

ILl 

Cl. 

200 

I 

205 

Main size groups 

2.2-4.1 kg 

5.4-6.6 kg 

1.0-2.2 kg 

3.6-5.4 kg 

45-65 em 

Over 65 em 

50 em at 3-4 kg 

Overall size 

Up to 76 em and 8.2 kg 

51-71 em at 1.9-5.2 kg 

40-78 em at 1.0-7.3 kg 

Up to BO em 

43-87 em at 1.0-8.6 kg 

Up to 79 em and 6 kg 

AUG . 26 

AUG. 30 

AUG. 31 

SEPT. I 

SEPT. 2 

SEPT. 3 

SEPT. 5 

SEPT. 6 

SEPT. 7 

SEPT. S 

SEPT. 9 

SEPT. 20 

300 

I· 305 

Figure 24.-Length frequencies of Euthynnus affinis laitded at 

Aburatsu, Kyushu, Japan, in 1950. (From Yabe et aJ. 1953, fig. I.) 
modified purse seiner off Hong Kong. Two size groups 

were represented in the landings. The dominant group 

included fish from 50 to 73 cm long (2.5-7.0 kg) and the 

other less numerous group was composed of fish 38 to 44 

cm long (1.2-2.5 kg) (Williamson 1970). 

In the Philippines, the size of E. affinis taken by trollng by research vessels is shown in Figure 25. The fish 

ranged from about 30 to 80 cm and the length-frequency 

!:Iistribution showed a prominent mode at about 50 cm. 

Other commercial fishing methods capture much smaller 

E. affinis. Wade (1950a) reported finding E. affinis as 

50 

45 

I I I I T 

S. F. BAIRD a T.N. GILL 

40 

35 r-

:r: 30 

~ 

... 

... 

0 25 II: 

ILl 

m 

~ 

::> 20 z -

f15 -

10 f5 f0 ~r lh l-, 

300 400 500 600 700 600 

TOTAL LE.NGTH (mm) 

Figure 25.-Length frequency of Euthynnu8 affinis taken by 

trolling in Philippine waters, 1947-49. (From Ronquillo 1963, 

fig. 16.) 

small as 40 mm in the fish markets in the Philippines. 

The length-frequency distribution of E. affinis taken in 

recent purse seine surveys near the Philippines (Rosenberg and Simpson6

) is given below. 

Length (cm) Number Percent 

30 1 0.3 

35 79 25.2 

40 228 72.6 

45 6 1.9 

50 

Elsewhere in the Pacific, size distribution of E. affinis 

taken by trolling around Hawaii and the Marquesas is 

shown in Figures 26 and 27, respectively. Length-weight 

relationships have been determined for E. affinis from 

various locations in the Indo-Pacific (Table 26). 

' Rosenberg, K. J. , and A. C. Simpson. 1975. Pelagic fisheries 

development - trip reports chartered purse seine vessels. Regional. 9 

February 1975 to 26 March 1975, voyage 3, 28 p. South China Sea Fisheries Development and Coordinating Programme. 

43 

4 MAY 

JUNE 

12 JULY 

6 

II: 

ILl 

m 

~ 

::> 

z 

6 SEPTEMBER 

4 

0 

24 OCTOBER 

20 

16 

12 

6 

4 

0 

4 NOVEMBER 

0 2 3 4 5 6 7 6 9 10 II 12 13 14 15 

WE I GHT ( POUNDS) 

0.4 0.9 1.4 1.6 2.2 2.7 3.2 3.6 4.1 4.5 5.0 5.4 5.7 6.3 6.6 

WEIGHT (kg) 

Figure 26.-Weight composition of Euthynnus affinis captured off 

Kaneohe, Oahu, Hawaii, by months, 1951-55. (From Tester and 

Nakamura 1957, fig . 6.) 

6 

5 

4 

II: 

ILl 

m 3 :;: 

::> 

z 

2 

fIf- r 

o 

r-"'rr.o 

b-n50 

I 

51 

"":' 

~ 

F'f""T: 

c: 

;"""' 

60 

I 

61 

I 

'"'l 

.;, 

~ 

" 

LENGTH (em) 

n 70 

I 

71 

I""" 

I I 

.",..,0; 

"7' 

-

-j 

60 

I 

61 

Figure 27.-Length frequency of Euthynnus affinis taken by trolling around the Marquesas Islands. (Data from files of Southwest 

Fisheries Center, National Marine Fisheries Service, NOAA, 

Honolulu, HI 96812.) 
Table 26.-Length-weight relations W = aL b of E uthynnu8. Predictive equations were fit throught logarithmic tran -

formation of data (see Ricker 1973). 

No.of 

Size range of fish 

Species and locality fish Weight Fork length 

E. affinis 10 1.81-5.22 kg 52-71 em 

(Indian Ocean) (4-11.5Ib) 

E. affmis 201 12-58 em 

(Indian Ocean ) 

E. affinis 

(Indian Ocean) 

E. affinis 226 

(South China Sea) 

E. afftms 101 0.45-6.80 kg 

(Hawaii) (1-15 Ib) 

E. affmis (males) 203 34.4·81.0 em 

(Philippines) 

E affim (females) 165 33.1·652 em 

(Philippines) 

E. alletteratus 325 

(western Mediterranean ) 

E. alletteratus 

(eastern Atlantic) 

E. alletteratus 100 1.35-13.9 kg 473-1,015 mm 

(Tunisia) 

E. alletteratus 343 0.23-8.39 kg 23.1-85.8 em 

(Florida) 

E. lmeatus 109 0.91-6.?6 kg 365-667 mm 

(eastern Pacific) (2-13Ib 

130z) 

Euthynnus alletteratus 

Juvenile E. alletteratus caught in the Sea of Marmara 

(from last week in August to mid-September) and the 

Dardanelles (mid-August to first week in October) in 

1959 apparently were the first records of juveniles in 

Turkish waters (Demir 1963). The juveniles caught in the 

Sea of Marmara were slightly smaller (mode at 20 cm) 

than those taken in the Dardanelles (mode at 23 cm) 

(Fig. 28). 

Rodriguez-Roda (1966) presented length-frequency 

distributions of E. alletteratus landed at Barbate and 

Tarifa, Spain, in 1963 and 1964 (Fig. 29). He smoothed 

the percentage frequency of the various length classes by 

the formula, f = fn - l +2fn + fn+l. The length distribu4 

tions of the males and females were the same for both 

years. However, the length-frequency distribution in 

1963 showed a single strong mode at 60 cm whereas the 

1964 distribution showed two strong modes at 45 and 60 

cm and a lesser mode at about 85 cm. It is of interest that 

the weight-frequency distribution , also smoothed by the 

formula given above, showed a single prominent mode at 

4 kg in 1963 but in 1964 showed a mode at about 2 kg and 

another at about 9 kg (Fig. 30). Thus, in 1963 both the 

length- and weight-frequency distributions indicated 

only a single size group in the fishery but in 1964, three 

size groups were represented in the landings in terms of 

length, and only two size groups in terms of weight. 

Postel (1955b) presented the length-frequency distribution of E. alletteratus taken in the eastern Atlantic off 

Senegal (Fig. 31). He stated that the length group from 

30 to 45 cm were 1 to 2 yr old fish and those from 60 to 75 

44 

Weight Length 

a b unit unit 

0.0166 2.963 g em 

0.0137 3.0249 g em 

0.0138 3.0287 g em 

0.08853 2.5649 g cm 

0.0108 3.1544 g em 

0.0334 2.83768 g em 

0.0211 2.94854 g em 

0.0222 2.914 97 g em 

0.0152 3.0 g em 

0.0163 3.0 g em 

0.00496 3.2631 4 g em 

0.01327 3.0817 g em 

2O.--~----~-----~ 

tZ 

W 

u 

a: 

w 

a.. 

15 

10 

5 

SEA OF MARMARA 

Source 

Morrow (1954) 

ivasubramaniam 

(1966) 

ilas (1967b) 

Williamson 

(1970) 

Tester and aka· 

mura (1957) 

RonqUillo 

(1963) 

RonqUillo 

(1963) 

Rodriguez. 

Roda (1966) 

Postel (950) 

Postel (1956) 

Beardsley and 

Richards 

(1970) 

Klawe and 

Calkins 

(l965) 

o DARDANELLES 

,'\ 

1\ 

I 

I 

I 

, 

I 

, 

, 

, 

I 

~ 

I 

I \ 

, \ 

1 \ I \ 

I \ , \ 

I \ , 0 

, \ 

, \ 

, \ , I , I , I , I 

I I 

I I 

I I 

I I ~ I , I 

I ~ , I 

I I 

I I 

I I 

I I , I 

I I 

I I 

I I o I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

o 

\ 

\ 

If' 

/ OL--L __ L--L __ L--L-~~--L-~A-L __ L--L~L--L~~-L~ 

14 15 16 17 18 19 20 21 22 23 24 25 26 

LENGTH (em) 

Figure 28.-Length frequencies of juvenile Euthynnus aUetteratu8 

from the Sea of Marmara and the Dardanelles. (From Demir 

1963, fig. 2.) 
. 30 

20 

10 

f1963 

/ 

/ 

/. 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

I 

) 

--MALES (N'91) 

---- FEMALES (N-74) 

~ OL-~~--=-~--L--L~ __ ~~~~ __ ~ 

~ 30r--'-'--r--.-'--r--.-'--r--'-'-~ 

20 1964 --MALES (N =107) 

---- FEMALES (N = 106) 

10 

LENGTH (em) 

Figure 29.-Length frequencies of Euthynnus alletteratuB landed 

at Barbate and Tarifa, Spain, in 1963 and 1964. (From RodrlguezRoda 1966, fig. 6.) 

-

z 

~ 

1963 

30 

", / , / 

20 / 

I 

I 

I 

I 

I 

10 I 

I 

I 

I 

I 

°0~~-2~-73-4~~5-~6-~~~~9--~10~~1=' ~'2~~'3 

WEIGHT (kg) 

igure 30.-Weight frequencies of EuthynnuB alletteratus landed 

t Barbate and Tarifa, Spain, in 1963 and 1964. (From Rodrlguez-

. oda 1966, fig. 7.) 

em were 3 to 4 yr old. He noted that fish 45 to 60 cm long 

(2-3 yr old) were not found in the area off Cap Vert, Senegal. However, Marchal (1963) stated that E. alletteratus 

from 50 to 70 em were found in normal proportions off the 

coast of Guinea. 

The length-frequency distribution of E. alletteratus 

caught by sport fishermen on charter boats off Miami, 

Fla., is shown in Figure 32. In Figure 33 is shown the 

length-frequency distribution of E. alletteratus taken by 

commercial trolling between North Carolina and northern Florida. The length range of fish generally landed by 

the Miami sport fishery (Fig. 32) was from about 500 to 

750 mm (de Sylva and Rathjen 1961). de Sylva and Rathjen noted that only a very few large or very small fish 

were taken and that fish larger than 620 mm were pre45 

30 

25 

20 

IZ 

W 

u 15 !r 

W 

a.. 

10 

5 

0 

20 

I 

24 

55 60 65 70 75 60 65 90 I I I I I I I I 

59 64 69 74 79 64 69 94 

LENGTH (em) 

Figure 31.-Length frequency of Euthynnus alletteratus from 

Senegal. (Data from Postel 1955b.) 

35~--'---'--r--'--_--'-----, 

:r 

Ul 

30 

25 

;;: 20 .... 

o 

!r 

W 

~ 15 

::J 

Z 

10 

5 

1\ 

FEMALES I ~ (N=242)~ \ 

I I 

I 

I 

I 

I 

I 

I 

I 

,~ 1\ 

\ 

, 

, 

, 

\ 

\ 

MALES 

(N=295) 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\ 

\,', '\ 

260 340 420 500 560 660 740 620 900 

FORK LENGTH (mm) 

Figure 32.-Length frequencies of male and female Euthynnus 

alletteratus caught by anglers off Miami, Fla .. September 1952 to 

August 1953. (From de Sylva and Rathjen 1961, fig. I.) 

dominantly males, possibly suggesting either a differential growth rate or mortality beginning at that size between the sexes. They also found that the E. alletteratus 

taken by commercial trolling between North Carolina 

and northern Florida were of similar size as those taken 

off Miami. However, they pointed out that the lengthfrequency distribution of the Miami sample showed a 

more even distribution of sizes while that of North 

Carolina-northern Florida was markedly leptokurtlc. 

They suggested several causes for the disparity in the 

length-frequency distributions from the two areas, including the fact that the commercial trolling gear possibly selected a certain size range of fish by the use of 

only a certain range of hook sizes, as also suggested by 

Carlson (1952). Carlson indicated that the selectivity was 

possibly due to the loss of maller fish caused by the 

hooks pulling free more easily de Sylva and Rathjen 
ro,-----__ ----__ ----~------~----------_. 

:r 

en 

lL: 

u. 

o 

15 

a: 10 w 

m 

::;;; 

::> 

z 

FORK LENGTH (mm) 

Figure 33.-Length frl'Quenc) of 217 Eu/hynnllH olle//ero/II caught 

by commercial trolling gear between North Carolana and north rn 

Florida, Jui) 1951. (From de )ha and Rathjen 1961, lig. 2.1 

(1961) also suggested that in the Miami port fi her), the 

anglers use a wider a ortment of bait and artificial 

lures and becau e the angler i more careful in landing 

the fish, the hook 1 less apt to pull free . 

Beardsley and Richards (1970) also pre ented lengthfrequency data of E. alletteratus caught in the port fi hery in southern Florida (Fig. 34). The e fi h were 

sampled at a Florida taxidermy firm during a period 

from September 1967 to September 1968. They indicated that because the fish was sampled at a taxidermy 

company the length-frequency distribution may be 

biased because usually only the largest fish caught are 

preserved and mounted. A comparison of the lengthfrequency data presented by de Sylva and Rathjen (1961) 

(Fig. 32) with that of Beardsley and Richards (1970) (Fig. 

34), however, does not clearly indicate that larger fish 

were being selected. 

The length-weight relationships determined for E. alletteratus from various localities are given in Table 26. 

Euthynnus lineatus 

The length-frequency distribution of E. lineatus taken 

between June 1972 and August 1975 in the Gulf of California and from Baja California to Ecuador is shown in 

Figure 35. 

The length-weight relationship for E. lineatus computed by Klawe and Calkins (1965) is given in Table 26. 

The largest E. lineatus collected by Calkins and Klawe 

was a male 636 mm long which weighed 4.8 kg (10.5 lb). 

4.14 Subpopulations 

For various reasons, probably including the fact that 1) 

Euthynnus in general are commercially not very impor46 

10,,----~----.----.----,-----~--_,----~1 

o 

10 

5 

o ~ 

20 

1:1 

o 

OCT - DEC Jfhn1, nm. ,,,.,,, 

JTTIfh-fl 

FOR LENGTH (em 1 

JAN-MAR 

( 'IO!.I 

APR-JU .E 

( '331 

n 

JULY - SEPT 

( • • 48 \ 

Figure .'l~.- Length frequen ie b) Quarter of the \ ear for Eulh)nnU$ ollet/era/u ample<! from a ta iderm) plant in outh Florida 

from ' ptember 196; through, ptember 1 . (From Beard Ie) 

and Richard, 19;0. lig. 2.\ 

12r-------------------------------------~ 

.... 

z 

10 

8 

W 6 u 

a: 

W 

Cl. 

4 

35 40 45 50 55 60 65 

LENGTH (em) 

Figure 35.-Length frequency of Eu/h y nnlUl lineatlUl. (Data 

courtesy of W. Klawe, Inter-Am. Trop. Tuna C~mm., La Jolla, 

Calif.) 

tant and 2) investigators had been concerned primarily 

with clarifying the species status in the genus, very little 

has been done to investigate the subpopulation problem 

within this group. Based on various published works on 
meristic and morphometric characters of E. alletteratus 

in the Mediterranean and eastern Atlantic, Marchal 

(1963) concluded that two subpopulations existed in this 

area. He stated that the Senegal population extended at 

least from 'Cap Vert, Senegal, to Ghana and probably 

well beyond the tropical coast of west Africa. The Mediterranean subpopulation, which can be differentiated 

from the subpopulation off Senegal by meristic and morphometric characters, extends into the Atlantic south to 

Morocco and perhaps to as far north as the Bay of Biscay, 

France. In an earlier work Postel (1953) attempted to determine if the E. alletteratus that appeared in the cold 

season and the warm season off Cap Vert belonged to 

separate subpopulations on the basis of the number of 

spots on the pectoral region of the two groups of fish. Because of the wide variability of the number of spots the 

results were not conclusive. 

In a preliminary study of the serology of tunas including E. affinis, Cushing (1956) indicated that it was 

probable that serological techniques could be applied 

profitably to the study of racial and specific variation in 

tunas. He stated that species differences existed among 

several species of tunas tested including E. affinis. In 

some preliminary experiments on two E. lineatus, it was 

found that the blood of this species could be differentiated from that of six other scombroids from the eastern 

tropical Pacific (Calkins and Klawe 1963). Other than 

these preliminary studies nothing has been done on 

subpopulation determination by serological methods. 

4.2 Abundance and density (of population) 

Probably because of the relative commercial unimportance of the species of Euthynnus, very few detailed 

studies have been made on the relative abundance of 

these fishes. Sivasubramaniarn (1970) investigated the 

exploited stock of E. affinis along the southwest coast of 

Sri Lanka. He found a high degree of variability in catch 

rates of E. affinis within four subareas along the southwest coast which he attributed to seasonal changes in occurrence and to the schooling behavior of this species. He 

concluded that the best index of the relative density of E. 

affinis was an average taken from the mean catch rates 

obtained in the four subareas. The catch rate was given 

as the catch in pounds per operation or trip not exceeding 

24 h. Sivasubramaniam (1970) found that the index of 

relative density was higher (35.3) in 1968 than in 1969 

(31.1). tIe also indicated that the mean value of relative 

density obtained for the southwest subarea could indicate the relative strength of recruitment of E. affinis 

along the whole southwest coast. He noted that E. affinis 

are first recruited into the troll fishery in the southwest 

subarea along the southwest coast. 

Sivasubramaniam (1970) estimated that a little over 

600 tons of E. affims were landed in 1969 on the southwest coast of Sri Lanka. These landings did not include 

those made by the non mechanized boats. He noted that 

there is evidence of differential spatial distribution of E. 

affinis by size and that it could be possible to avoid capturing small fish by avoiding areas occupied by them. He 

4, 

indicated that the annual yield of the fi her}' could be 

considerably increased by doing thi . 

EI ewhere in the Indian Ocean it ha been recorded 

that E. affims occurred in commercial quanti tie in 

Australian water (Roughley 1951) and around omalia 

(Ogilvie et a!. 1954). Williams (1964) noted that there are 

large unexploited schools of E. affinis in ea t African 

waters and Morgan (1956) e timated that Euthynnus 

and Sarda represented about 0.5('c of all fish by weight in 

the Indian Ocean. 

Marchal (1963) reported that the manner of fi hing 

and total catches of E. alletteratus have had no effect on 

the populations of this species. Rodnguez-Roda (1966) 

presented long-term landings data of E. alletteratus in 

the Spanish fishery covering the period from 1929 to 

1964. The landings were given m number of fish and 

show wide annual fluctuations but no significant trend 

4.3 Natality and recruitment 

4.31 Reproduction rates 

See section 3.1. 

5 EXPLOITATION 

It was noted earlier that Euthynnus generally has little 

or no commercial value. In many localities it appear 

that the typical fishery for Euthynnus is a multi pecle 

fishery. It is not very clear whether the Eulhynnw, or the 

other species of tunas are the main target of the e fi heries. Euthynnus usually schools together with other pecies of tunas, and sometimes nontllna , and the u e of 

nonselective gear and fishing method probably account 

for the mixed catches. However, there i some evidence of 

size-differentiated schooling habits in Euth}·nnus. In the 

Indian Ocean, it was found that small E. affinis tended 

to be found in pure schools but the larger fish were found 

to school with other species (William 1963) William 

also noted that in Madagascar, ' omalia, eycheJle, 

Pakistan, Sri Lanka, and the west coa t of India, E affinis is the prime objective of fi herie and _ pecific attempts are made to catch thi spelie· . 

The FAO Yearbook of Fi hery Statio tic_ (FAO 1977) 

indicate that nine countries had landing 01 E afflnL 

between 1973 and 1976. In the Indian Ocean, the follo",-

ing countries showed landing . :\.laldi\'e., Paki tan , e) -

cheJle , Yemen (Arab Republic), and Indone la; in the 

western Pacific; Indone ia, l\lalay, ia, Papua ey, 

Guinea, and Philippines; and in the central Paclfi . 

United tates. Other ource (FAO 1974a, 19i4b howed 

that Banglade. h, India, Israel, and ~ n Lan a al 0 at on 

time had landmg. of E. afflnL.. ... 

In the Atlantic Ocean and the Medlt rranean a, lh 

followmg countrie:- had landm of E all tt ratu between 19i3 and 19-6: Angola, Bul ana , ) pru , 

I\'ory Coast, Mauritania, . loro c , Pol nd, Romam 

~pain, Cnited 'tate, Venezuela, and \ u la\la FA 

197,). An earher Itt F 0 1 i a) h y, d that I r I, 
Liberia, and Turkey also at one time had landing of E. 

alletteratus. 

Euthynnus lineatus landings for Panama and the 

United States between 1973 and 1976 are shown in the 

FAO Yearbook of Fishery Statistic (FAO 1977). 

5.1 Fishing equipment 

Silas (1967b) described the "multiple trolling" tuna 

fishery off the southeast coast of India (Gulf of Mannar). 

This is a multispecies fishery and in addition to E affinis, a number of other species are taken. The ve el 

used in the fishery are known a Tubconn-type boat 

which are small sailboats ranging in length from .2 to 

10.4 m (27-34 ft). These ves el troll even or nine line 

and carl") a crew of six or seven fi hermen on the mailer 

boats and seven to nine fishermen on the larger boat 

Brined Sardinella ( . albela, S. gibbo a, and ' Irm) are 

used almost exclu ivelya bait and only rarely are artificial lures used. 

Other methods of fishing for E affim' in the Gulf of 

Mannar indude bottom-set nylon net (150 mm me h), 

shore seines, drift nets (pachuvalai) of 130-150 mm me h, 

and longline (Chacko et a!. 1967). In the southern ector 

of the Gulf of Mannar, the drift nets are et In depth of 

about 30 m. The longline et i compo ed of up to 400 

hooks baited with quid and the gear i et In depth of 25 

to 40 m. 

Off the southwest coast of IndIa at Vizhingam, a tuna 

fishery is conducted almost exclu ively by dugout canoe 

and catamarans (Bennet 1964). Including E. affLnIS, 

seven species of tunas are taken in thl fi hery. The other 

species are Auxis rochei, A thazard, 'arda orientaLLs, 

Thunnus tonggol, T albacare, and Katsuu'onu 

pelamis Bennet (1964) stated that E. affLnI is one of the 

most important commercial specie at Vizhingam. The 

principal fishing gears include cotton and nylon drift 

nets, hook and line, and occasionally shore eine . From 

July 1960 to October 1961, he noted that 71.4£'[ of the 

landings of E. affinis were made by drift nets, 24.3 CC by 

hook and line, and only 4.3 CO by shore seines. 

In the coastal waters of Sri Lanka, mechanized boat 

of 3.5-ton class and H-ton class, in addition to the traditional outrigger canoes, are engaged in the mixed tuna 

fishery (Sivasubramaniam 1970). The fishing gear used 

includes drift nets, trolling lines, pole and line, longline, 

and beach seines (Sivasubramaniam 1966, 1970). In 

Pakistan the fishing gear or methods used are trolling, 

longlines, handlines, and beach seines (Qureshi 1952). In 

the Malagasy Republic, Comoro Island, east Africa, 

Somalia, Seychelles, and Australia the commonest 

fishing method for E. affinis is trolling with either 

natural bait or artificial lures. Handlines and longlines 

are also used in Somalia (Williams 1963). 

In Japan no specialized fishery for E. affinis exists, 

apparently because consumer demand for this species is 

not great (Kikawa and staff 1963). Presumably, most of 

the E. affinis caught in Japan are taken incidentally with 

other species. Kikawa and staff (1963) stated that E. affinis are taken together with Auxis, juvenile K. pelamis, 

48 

T. albacare8, and T thynnus In the coastal waters of 

Japan , E affLnls are taken mainly from mall sailing and 

motorized ve elll They are al 0 taken by pole and line. 

In an attempt to develop a tuna fi hery In Hong Kong, 

the Hong Kong Fi h Marketing OrgaDlzatlon offered to 

buy E. afflfll8 at a pedal high price ID 1967 and 1968. 

Two boat WItched to tuna fishing u ing a modified 

purse IDe method About 16 t of E af/LflIs were landed 

in the 2 yr but the fi h could not be marketed at a profit 

and th project wa abandoned (William on 1970). 

Warfel (1950) tated that the mo. t productive method 

of catching tuna in the Philippine i the fi h trap, called 

corral., or in Tagalog, baklad. The beach eine i the 

next mo. t productive. Other method u ed are a Philippine version of a pur e eine called a talakop, trolling 

(ibid-. ibid), and occa. ionally a drive-in net. 

In Hawaii, E. affLni 1. taken incidentally in the livebait pole-and-hne Kabuuonu. pelami fi hery and 

reer alional troll fihery. 

Euth) nnu alletteratu. 

Li ke many of t he Ii herie for E. affLni , the Ii herie 

for E. allt'tteratu appear to be multi pecie fi herie . 

Along the coa t of Tuni ia in the MedIterranean, for example, Po. tel (195 ) li,t T. th)nnu .. arda arda, Auxi 

p .. and E. allett ratu, a pecie taken in pecialized 

trap. called madrague . ~ladrague are al 0 u ed in the 

Moroccan Ii her) (~1archal 1 ). The Tun i ian fi he 1")' 

lands 400 to 5 ton' and the Moroccan fi he 1")' to 3 

ton of E. all tteratu~ per year (Po tel 1964)_ 

Fi"herie for E alletteratu along the ea t coa t of 

Africa are apparently not well developed (Marchal 1 63). 

They are caught ID beach eine ID enegal, the 1\'01")' 

oa't, Ghana. and Angola. Off the Ivory Coa t, E alletteratw. are al a taken In ardine purse eme and in 

Angola they are al 0 taken in trap imilar to the 

madrague (Marchal 1963). On the i land of ao Tome 

and Principe, E alletteratus are taken by a type of encircling gill net (Frade and Po tel 1955). 

In the we tern Atlantic and adjacent a.rea , Riva 

(1951) tated that the fle h of E. alletteratus is good and 

of commercial importance throughout the We t Indie . 

Chilton (1949) reported that for many years E. alletteratu ha been caught in varying amount along the 

Atlantic coa t of the United tate and along the coa t of 

the Gulf of Mexico. Chilton's account of thi species 

along the Atlantic and Gulf of Mexico coasts indicates 

that although E. alletteratus is frequently taken, and 

sometimes in fair amounts, no large-scale sustained fishery exists for this species in these areas. Mansueti and 

Mansueti (1962) reported on this species in Chesapeake 

Bay and stated that during 1951-61, E. alletteratus had 

been harvested commercially in pound nets and hand 

seines. However, the annual landings were minimal (less 

than 6 t per year). In addi tion to pound nets and hand 

seines, E. alletteratus in the western Atlantic has been 

taken by menhaden purse seines and trolling with artificial lures (Chilton 1949; de Sylva and Rathjen 1961). 
Euthynnu [meatus 

Euthynnus lineatus were not fished commercially in 

the eastern tropical Pacific before 1972 except for the 

small numbers that were taken and sold fresh in the local 

markets of Latin American countries. This species is 

taken incidentally by gear used to catch other species of 

fish. They have been taken by tuna purse seines, by livebait pole-and-line fishing, commercial and sport trolling, 

and by trolled handlines. They are taken by commercial 

tuna vessels of all sizes, from small albacore trollers to 

large purse seiners and by bait boats, and by Ecuadorian and Peruvian canoe and raft fishermen (Calkins 

and Klawe 1963). Since 1972 the following commercial 

catches of E. lineatus have been reported in the InterAmerican Tropical Tuna Commission's yellowfin tuna 

regulatory area (data courtesy of Calkins 7): 

Year 

1972 

1973 

1974 

1975 

1976 

1977 

5.2 Fishing areas 

See section 5.3. 

5.3 Fishing seasons 

Catch (tons) 

660 

1,845 

4,043 

582 

1,673 

1,195 

Euthynnus affinis 

Off the coast of South Mrica and southwest Australia, 

E. affinis occur and are fished during the southern sum- , 

mer when surface water temperatures are at a maximum (Williams 1963). In the Seychelles, the fishery is 

highly seasonal and takes place during the northwest 

monsoon (October-November to April-May), when the 

surface water temperature is highest (29°-30°C). In 

northern Somalia, the fishery is conducted during the 

northeast monsoon at the time of minimum sea-surface 

temperature . In Pakistan, west coast of India, and Sn 

Lanka, E. affinis is taken throughout the year with slight 

local seasonal variations (Williams 1963). Bennet (1964) 

found that good landings of E. affinis occur during the 8 

mo from October to May and the period of low catches is 

from June to September (Table 27) in the Vizhmgam 

fi hery-(southwest coa t of India). Bennet observed that 

the period of low catches coincides with the southwest 

monsoon when the seas are rough and very little fi hing 

effort is expended . In contrast to the generalized tatement made by Williams (1963) on the sea onal nature of 

the E . affinis fishery in Sn Lanka, Ivasubramaniam 

(1970) described a omewhat more complex situation of 

the sea onality of the E affinis fishery (Fig. 36). The 

easonal picture around ri Lanka i complicated by two 

-T P. Calkins, Int~r-American Tropical Tuna mml klon, ~cnpps 

Institution of Oceanography, La Jolla, CA 9203" pen! rommun ,1u'h 

19, . 

49 

Table Zi.-'Ionlhh landln (kilo rom) of f lAth nnu 

affini al \ 'ilhlngam, Indl (~rom B nn I I I. I I I' 

;\tonlh 

.Janual1 

Febru IJ ..,~ 

• • 1 

March 6.1 

April ,4-1-1 

May 6.151 

June 

.July 

August 

eptember 

October 

November 

December 

Total 

factor: the differential selectivity of the gear u ed (tr II, 

ing and drift net) and vanatlOn in recruitment by lZ in 

the various areas around , n Lanka . 

Off east Mnca, around the omOTO Island And th· 

Malaga y Republic, E. affinis IS taken thr ughout th 

year (Wilham 1963). Euth.\nnu, affml' 1 pre nt 

around the Philippine throughout the year but t ht' 

highest catche are made from October through D -

cember and April through ~1ay (Warfel 19-0). r und 

Japan, E. afflnL i taken near the lzu I land Ir m 1\18) 

to November (Kikawa and taff 1 63). Young E afillu , 

<J) 

o 

z 

is 

Cl. 

w 

~ a: 

:r 

u 

~ u 

WEST zss ,"''* 120 1968 1 

':1 / 

60 

4Q 

20 

o 

~jJ N. WEST 

1969 

'I /, 

. \ ! \ 
15 to 25 cm long, have been caught near Aburatsu in 

southern Kyushu from August to October (Yabe et al. 

1953). 

The mean monthly landings of E. affinis at two ports 

in Kochi Prefecture, Japan, in 1973 and 1974 (Fig. 37) 

indicate that E. affinis are present throughout the year 

near Kochi. Because of the sparse data, the significance 

of the three peaks in January, May, and September is 

not clear. 

In troll fishing conducted off the northeast coast of 

Oahu, Hawaii, from 1951 to 1955, Tester and Nakamura 

(1957) reported that no E. affinis were taken between De1200 

10 00 

~ 800 z 

o 

z 

< ..J 

~ 600 I 

f-

~ ~ 

:i 400 w 

~ 

200 

+--f----+-+-- ... 

W-~~WL~U-~L-~-LU-~L-~-L~~L-~-U 

APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 37.-Mean monthly landings of Euthynnus affinia in Kochi , 

Japan, 1973-74. (Data courtesy of T. Koto, Nansei Reg. Fish. 

Res. Lab., and S. Kikawa , Far Seas Fish. Res. Lab., Japan.) 

2.0 , 

I I - I 

r- I I ,..r-i+ f+ 1 I - I _ I 

I I 

CJ') 

z 

0 

f- 1.5 

u 

ii 

fW 

~ 

r+ f+ !--l- + I ~ 

CJ') 

'" Z 1.0 0 

Z 

< - ..J - ,-

~ I 

f- ri-' f+ f+ 

T -t-r- t- 1+ ! ~ 

I ! 

Z 

0 

~ .5 

z 

< w 

~ 

0 I I I I 

JAN FE8 MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 38.- Mean monthly landings of Euthynnus affinia in 

Hawaii, 1964 -74 . (Data from files of Southwest Fisheries Center, 

a tional Marine Fis heries Service, NOAA, Honolulu, HI 96812.) 

50 

cember and April. Their data showed a peak in the catch 

rate (catch per hour) in October. However, they 

cautioned that the fact that no E. affinis were taken from 

December to April cannot be regarded as significant 

since only a small number of hours were expended in 

fishing during that period. Welsh (1949) reported good 

catches of E. affinis during March, April, and May 1948 

and during February and April 1949 in Hawaiian waters, 

including the same area fished by Tester and Nakamura 

(1957). The mean monthly landings of E. affinis in 

Hawaii from 1964 to 1974 indicate higher landings from 

October to April (Fig. 38). The results obtained by Tester 

and Nakamura (1957) and Welsh (1949) are not inconsistent with those shown in Figure 38. Thus it appears that 

around Hawaii, E. affinis may be less available from 

May to September and more available from October to 

April. 

Euthynnus alletteratus 

In the Gulf of Gabes, Tunisia, E. alletteratus is found 

sporadically throughout the year. Off the northern coast 

of Tunisia, it appears in the spring and disappears in the 

autumn (Postel 1964). In Morocco, Postel stated that E. 

alletteratus appears in May and disappears at the end of 

November. Data presented by Ben-Tuvia (1957) on the 

mean monthly landings of E. alletteratus during 1~50 to 

1955 in Israel (Fig. 39) indicate this species is caught 

throughout the year and that the landings peak in May 

and October. Rodriguez-Roda (1966) gave a summary of 

the fishing seasons and the months of peak catches for E. 

alletteratus in the various Spanish fisheries in the Mediterranean and the Atlantic (Table 28). The various 

seasonal peaks in the Mediterranean fisheries suggest 

that this species may make seasonal migratory movements. 

Off the coast of Senegal in the eastern Atlantic, E. alletteratus arrive in large numbers in January-February 

5 

I I I I rI r- I 

I I I 4 r- + 

I I 1 ,- -L +- -+------- r- I I I r-

-l. ~ I 

-I- + T 

~ r- -

r- I i 

~ -

1+ ...l- i-'- r+ ~ 1 1+ f+ 

I I I 

CJ') 

z 

0 

fCJ') 

'" 3 z 

0 

z 

< 

..J 

~ I 2 fZ 

0 

~ 

z 

< 

w 

~ 

o I I I II JAN FEB MAR APR MAY JUNE JULY AUG SEPT OCT NOV DEC 

Figure 39.-Mean monthly landings of Euthynnus alletteratu8 

from 1950 to 1955 in Israel. (From Ben-Tuvia 1957, table 3.) 
Table 28.-Fishing seasons for Euthynnus alletteratus in Spain. 

(From Rodrlguez-Roda 1966, table 3.) 

Months of 

Region Fishing season peak catches 

N,,'h ",,' } Jan. to Dec. Sept. and Oct. 

Northwest coast Atlantic June to Dec. Oct. 

Southwest coast Ocean Feb. to Dec. Aug. to Oct. 

Canary Islands Jan. to Dec. Dec. to Mar. 

S",h,m ",,' } Jan. to Dec. Sept. and Oct. 

Southeast coast Mediterranean Jan. to Dec. Sept. and Oct. 

Eastern coast Sea Apr. to Dec. July to Oct. 

Balearic Islands Jan. to Dec. May to July 

and May-June (Postel 1955b). They are present all year 

in the region of Cap Vert (Marchal 1963). Off the Ivory 

Coast, Marchal (1963) stated that E. alletteratus are 

found throughout the year along the coastline but that 

th~ catches peak in February. He stated that E. alletteratus are caught in Angola starting in October, the 

catches peak in February and March, and become nonexistent in May-June. 

In the western Atlantic, Chilton (1949) suggested that 

E. alletteratus make seasonal migrations along the U.S. 

coast. In May and June they have been reported moving 

north to North and South Carolina and in August and 

September they have been caught along the coasts of 

New Jersey and New York. Observations made from 

September 1952 to August 1953 on anglers' catches 

landed at Miami, Fla., indicate that 87% of the catches 

were made from March through August including a peak 

in July (de Sylva and Rathjen 1961). de Sylva and Rathjen stated that there is evidence of a general drift of E .. alletteratus out of the Miami area toward the south durmg 

the winter and that they occur further north along the 

coast during the summer. 

Euthynnus lineatus 

Euthynnus lineatus is taken throughout the year in all 

areas of its distributional range. Although information on 

the seasonal abundance is not very clear, Calkins and 

Klawe (1963) cited an Ecuadorian census of fishermen 

which indicated that E. lineatus was most abundant 

from May to September in the open coastal ar~as and 

from January to March in the Gulf of GuayaqUil. 

5.4 Fishing operations and results 

5.42 Selectivity 

The beach seines, principally used in the Sri Lanka 

fishery for E. affinis, are not size selective. ~urface tr~lling, handlines, and longlines that are used m the Indian 

Ocean are also not selective (Williams 1963). 

Calkins and Klawe (1963) stated that E. lineatus are 

taken by nonselective gear. 

de Sylva and Rathjen (1961) suggested that the commercial trolling gear used to catch E. alletteratus may 

possibly be selective for a certain size range of fish (see 

section 4.13). 

51 

5.43 Catches 

With the exception of the Philippines and Indonesia 

where a fair amount of E. affinis is landed, the species of 

Euthynnus are nowhere the basis of important large 

commercial fisheries. To illustrate the magnitude of the 

fisheries for Euthynnus, from 1965 to 1976 the total world 

landings for all the species fluctuated from 37,000 to 

88,000 t (Fig. 40). In comparison, the annual world production of K. pelamis has ranged from 300,000 to 350,000 

tin 1966-71 (Matsumoto 1974). 

In Figure 40 is also plotted the total world production 

of E. affinis and E. alletteratus from 1965 to 1976. The 

world landings of E. affinis varied from 29,900 to 84,800 t 

annually and that of E. alletteratus from 4,600 to 9,500 t. 

Euthynnus affinis constituted 77.1 to 97.0% of the total 

for Euthynnus during this period. Only small amounts of 

E. lineatus have been reported in the statistics. It should 

be pointed out, however, that the world production of 

Euthynnus, as indicated by the statistics given above, is 

probably underestimated. It may happen that because 

only small amounts of Euthynnus are taken, they are 

lumped together with other species of tunas, or together 

with other miscellaneous species. Other problems associated with collecting catch statistics in the Indian 

Ocean are discussed in FAO (1973). Thus the figures for 

Euthynnus are probably not only underestimated but are 

also subject to inaccuracies. 

The production of E. affinis from 1973 to 1976 in the 

Pacific and Indian Oceans is given in Table 29. As noted 

earlier, the Philippines and Indonesia have comparatively large fisheries for Euthynnus. The Philippines 

landings of E. affinis fluctuated from 9,447 to 24,000 t be100 

90 

TOTAL Euth nnus 

80 

en 

z 70 

~ 

~ 

a:: 60 Iw 

:. I 0 

z 

<t 50 en 

=> 

0 

P • . . I E. cfflnls I - I 

I I 

I- 40 

en 

I /°--_0 __ -0_ II 

---0 

(!) 

z 

0 30 z 

<t 

..J 

20 

E. clletterctus 

10 - --_ x, E.linectus x--X- x-x ............ - -r-

~ "---· ___ l_' 

OLI ~-~1 6-:::7---:1~96;:;9;---::19;:;7::-' --;C19'ri. - 0 - ·its·- 6 -' 

Figure 40.-World Ian dmgs · 0 f E u)n th nu • (D la from f ,,0 

1974a. 1976. 19;;.) 
tween 197a and 1976. The landlnR in lndon ' in l1u('lu -

ated between :H,600 and 41.616 t (paei Ie O('!'un) und 

5,200 and 8,609 t (indian Ocean) during the arne p'riod. Although the FAU Yearbook of Fi hcr)-' Stutl tic 

doe. not ~how any landings of g affifll.~ In Indill from 

19n to 1976, according to Ht.'nnet (1 G·I), fi .7 tn20fl. l 

were produced in Vizhll1gam, lndia. bet~et'n I !) lund 

1960 ( ee Table 26). In Hawaii, where E. afflnl i tukl'n 

incidentally in the pole·and.line Ii. hery lor K pl'/Onll\. 

between .0 and 4:L9 t were r('cord d dunn' the II-)-r lX'-

Tiod from 1964 to 1977. In .Japan. production liKur tor 

E afflnis are not readily available b '('uu e they IIr (,m· 

bined with thos of oth r pel'! (Kikawa and luI! 

1963), 

The world landing" of E allelt r(llu, from 1973 to 1'1 I 

are ::;hown in Table :m. It can b s en thut onl . r lllll\ l ' 

mall quallt iut's (If this spel it''> af' tu en In an ' I th 

fisheries. During the p 'rind trom 1~7 . til 1 7b, the t<)t I 

annual pwd u tion of E. all tt,'rolll In th ~ ,( TIl 

Atlantic amounted to . lightly 0\ r : ) l. In th tern 

AtlantIC', during the same period, the tolltl Elnnual 

Ta bl,' _. I ndinl/:' of Fulh nnu aI/1m In on,lri It,n 

~ \() I~;; . 

re 

Pacific 0 e n t lal 

lndone'ls 

\ \sI8) .Ia 

Papua. C''' GUinea 

PhlllppmeL'nltt-d, tale 

Indian Olean to1.lll 

lndonbl 

-"l aldIH. 

I ~ 

( I r m 

Ta ble :lO.-Landing, of Euth) nltu. all,' tlt ratu in mt'tro(" tun, 

(f rom lAO IY i 7.) 

Area 

Western Atlanlll Ocean tutal 

Poland 

Cnited ,tate, () 

Venezuela 300 

Eastern Atlantic total ~ .. OCiO 

Angola 900 

Buigaiia 0 

Y 

37J 

4 ., - ~ 

1 ., - • ~ I 

~ 

\ 

3.57 

2.5 \5 

449 

5 

- 1 

1. ., 

H9 

lundillK l1uctulttl'f1 between 1,!*i7 and ,~ 5 t. and 10 the 

Ml'dltt'rrUIH an '/I t I Y did IlI)t eJI( d 70() t during the 

Lltl H,, 1 t Hf. (' n ED 

I' T h rap ~n F 

HI G 

IG 2 

o tunas (keanoltT. ~Iar . 

Ghana 66 13 ,6 HL..A 

Ivory Coa t 0 1.5 . 

Mauritama 1,000 '1,000 

Morocco 0 46 

Poland 6 

RDmama 100 297 

Spain 

Mediterranean ea total 700 13 

Cypru 0 5 

Morocco 0 5 

Spain 700 

Yugoslavia 0 3 

Total landings 3,000 '4,680 

'Estimated . 

50 

' 1,000 

14 

46 

27 

7 

0 

20 

'2.902 

400 

1.000 

32 

\0 

'2, 1 

52 

, ur une petite c \Ie. t. 'n de pOi , n, de la ~umon . \Iem 

In,t SCI .\!adaglbcar. ~er F. Ocean ~ -,-37 . 

BRA;\OHURsT. \\ . 

Hj,5.~ Thermocltne tOJ)OltTaph). zooplankton ,tandmg crop. and 

methani,m, 01 fertilization in the eastern t pical Pacific J 

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