\

c THE SPECIES OF RASTRELLIGER IN THE JAVA SEA, THEIR TAXONOMY, MORPHOMETRY AND POPULATION DYNAMICS

by

TATANG SUDJASTANI

B.Sc. Academy of Agriculture Bogor, Indonesia, 1962

A THESIS SUBMITTED IN PARTIAL FULFILMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE

in the Department

of

Zoology

We accept this thesis as conforming to the required standard

The University of British Columbia April, 1974 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study.

I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission.

Department of ZOOLOGY

The University of British Columbia Vancouver 8, Canada

Date 9 APRIL 1974 ABSTRACT

Rastrelliger is a mackerel genus which inhabits the Indo- Pacific Regions. This genus is characterized by long, numerous and featherlike gill rakers, and anal fin without spines. Two species, Rastrelliger braahysoma and R. kanagurta, are recognized. These are identified by the differences in the ratios of the greatest body depth and the length of intestine to fork length, and the appearance of the cephalic lateral line canal systems. Synonymies, descriptions and morphometric ranges are given. The morphometric characters of the two species exhibit some intraspecific differences due to sexual dimorphism and strong allo- metric growth, R. braahysoma exhibits intraspecific geographical variation in its dorsoventral depth, greatest body depth, and inter- orbital distance; while R. kanagurta exhibits variation only in its dorsoventral depth and head depth. Both speci.es attain their maximum growth increments before they reach sexual maturity. The vital parameters for yield prediction are as follows: the coefficient of growth rate K=0.19, 0.23; the length-weight exponent b=2.88, 3.19; the maximum length 1.^=22.92 cm, 23.89 cm; the natural mortality coefficient M=0.38, 0.37; and the total mortality coefficient Z=0.82, 1.20 fori?, braahysoma and R. kanagurta respectively. Rastrelliger fisheries in the Java Sea have not yet ii

reached maximum exploitation which suggests the possibility of increas• ing production by increasing fishing intensity. iii

TABLE OF CONTENTS Page ABSTRACT i TABLE OF CONTENTS iii LIST OF FIGURES v LIST OF TABLES vii ACKNOWLEDGMENTS ..... x

I. INTRODUCTION 1 II. MATERIALS AND METHODS 2 III. RESULTS AND DISCUSSIONS 7 1. Systematics Study 7 Description of the genus Rastrelliger ... 7 Key to the species of Rastrelliger .... 8 Specific Descriptions 8 Rastrelliger braahysoma 8

Rastrelliger kanagurta 9 Nomenclature 12 Diagnostic Characters 23 2. Morphometric Study 25 Sexual Dimorphism 30 Allometrie Growth 30 Geographic Variations . 33 3. Meristic Characters 45 4. Qualitative Characters ...... 49 5. Population Study Rastrelliger Fisheries . . . Population Parameters . . . Sexual Conditions .... Longevity Environmental Tolerance Competitor and Predator . Parasites Growth Behaviour Age Length-weight Relationships Recruitment Survival Rates ' Mortalities . Dynamics of Populations . . Beverton and Holt Model Ricker Model , IV. GENERAL DISCUSSIONS V. CONCLUSIONS

LITERATURE CITED APPENDICES . . . V LIST OF FIGURES Figure Page

1. Bathymetric Chart of the Java Sea 3 2. Ratio of Body Parts to Fork Length 16 3. Ratio of Fork Length to Body Depth 17 4. Sexual Dimorphisms of Rastvelligev bvachysoma 32 5. Geographical Variations in R. bvachysoma 32 6. Geographical Variations in R. kanaguvta 44 7. First Occurrence of Haemal Brace 47 8. Cephalic Lateral Line Canal System of Rastvelligev . . 52 9. Digestive Tracts of Rastvelligev 53 10. Sexual Maturity Stages Composition of R. kanagurta . . 61 11. Sexual Maturity Stages Composition of R. bvachysoma . . 62 12. Growth Curve of R. bvachysoma 69 13. Growth Curve of R. kanaguvta 70 14. Relation Between Total Effort and Catch Per Unit of Effort of Rastvelligev kanaguvta 75 15. Length Frequency Distribution of R. kanaguvta 86 16. Length Frequency Distribution of R. bvachysoma .... 87 17. Catch Curve of R. kanaguvta 97 18. Catch Curve of R. bvachysoma 98 19. Yield Isopleth Diagrams of R. kanaguvta 106 20. Yield per Recruit as a Function of F of R. kanaguvta; for t = t = 4.0 months 107 21. Yield per Recruit as a Function of F of R. kanaguvta; for t = 4.5 and t = 4.0 months .... 108 vi Figure Page

22. Yield Isopleth Diagrams of R. braahysoma 109 23. Yield per Recruit as a Function of F of R.

braahysoma; for t = tp = 3.0 months . . . 110 24. Yield per Recruit as a Function of F of i?.

braahysoma; for t = 4.0 and t = 3.0 months Ill vii LIST OF TABLES Table Page

1. Morphometric Measurements of Rastvelligev bvachysoma 11 2. Morphometric Measurements of R. kanaguvta 13 3. Frequency Distribution of the Ratios of Head- Length to Body Depth 18 4. Frequency Distribution of the Ratios of Fork- Length to Body Depth !9 5. Frequency Distribution of the Ratios of Intestine Length to Fork Length 20 6. Regressions of Sample No. 1 26 7. Regressions of Sample No. 2 27 8. Regressions of Sample No. 3 28 9. Regressions of Sample No. 4 .' . . . 29 10. Comparisons of Body Proportions Between Males and Females 31 11. Comparisons of Body Proportions Between Class- Modes of 16.0 cm FL and 20.0 cm FL 34 12. Comparisons of Body Proportions Between Class- Modes of 14.0 cm FL and 20.0 cm FL 35 13. Comparisons of Body Proportions Between Class- Modes of 14.0 cm FL and 16.0 cm FL 36 14. Comparisons of Body Proportions Between Samples No. 1 and No. 2 37 vi i i Table Page

15. Comparisons of Body Proportions Between Samples No. 3 and No. 4 . . 38 16. Comparisons of Body Proportions Between Samples No. 1 and No. 3 39 17. Comparisons of Body Proportions Between Samples No. 2 and No. 4 40 18. Comparisons of Body Proportions Between Samples No. 2 and No. 3 . 41 19. Comparisons of Body Proportions Between Samples No. 1 and No. 4 42 20. Covariance Analyses for Pairs of Rastrelliger 43 21. Gill Raker Counts of Rastrelliger 48 22. The Degree of Intergradations of the Total Gill Raker Counts of Rastrelliger 48 23. Productions of Payang Fisheries in the North Coast of Java 54 24. Field Key of Maturity Stages (Males) 58 25. Field Key of Maturity Stages (Females) 59 26. Von Bertalanffy Growth Parameters of Rastrelliger from the Indo-Pacific Region 71 27. Age-Length-Weight Key of R. kanagurta 84 28. Age-Length-Weight Key of R. braahysoma 85 29. The Length-Weight Exponential Values of Rastrelliger of the Java Sea 90 ix Table Page

30. The Length-Weight Exponential Values of Rastrelliger from the Indo-Pacific Region 91

31. Survival Rate of R. kanagurta 95

32. Survival Rate of R. braahysoma 96

33. Mortality Coefficients of R. kanagurta 100

34. Ricker Yield Model of R. kanagurta 115

35. Ricker Yield Model of R. braahysoma . 116

36. Ricker Yield Model of R. braahysoma ... 117 X

ACKNOWLEDGEMENTS

I wish to express my deep appreciation and thanks to my supervisor Dr. Norman J. Wilimovsky who encouraged me to undertake this study, gave advice and criticism. My thanks also goes to Messrs. T.D. lies and Stephen Borden, Dr. D.J. Randall, Dr. J.R. Adams, Messrs. D.E. Wilson, R. Stanley, Ni I-shun and R.S.. Milne for giving useful suggestions. I am very grateful to Messrs. R.B. Wilson, B.J. Anderson and Miss CM. McAskie from the Canadian International Development Agency for contributing in various ways to this study. Finally, I wish to extend my thanks to my superior in the Directorate General of Fisheries, Mr. Moh Unar the Director of the Marine Fisheries Research Institute, and to my colleagues in the Regional Fisheries Services and the Institute for Marine Research in Jakarta for assisting in data collections. i

I. INTRODUCTION

The Kembung -- the genus Rastrelliger -- constitute one of the most important groups of fishes of the artisanal fisheries of Indonesia. On the north coast of Java in 1971, the catch was 10,000 tons, constituting over 10% of the total marine fisheries production of the area. In the five-years development program of the Government of Indonesia (1969/1974), which included investigation of fisheries, this genus with tuna and oil-sardines had priority over other commercial species. During the late fifties an experimental canning project for this genus was unsuccessful due to miscalculation of the stock abundance and mistakes in estimating the economics of the project. Most investigations on Rastrelliger are confined to the neighbouring states of Indonesia. The most important contribution in the Indonesian waters was conducted by de Beaufort (1951) and only few observations have been recorded since. In contrast to the rather extensive fisheries investigations as described above, the identities of the species within the genus are still in doubt. There are many synonyms because local races or indivi• duals have been described under different names. The objectives of this thesis are: (1) to verify the species identities, (2) to study their morphometry, and (3) to estimate the population parameters to aid fisheries management. 2

II. MATERIALS AND METHODS

During the 1972 fishing season (early West Monsoon) samples of Rastrelliger were collected from the two main fishing areas in the Java Sea, i.e., Tanjung Satai in the south west coast of Borneo and Jakarta in the north coast of Java (Figure 1). All the fish were collected from the same fishing gear, the shore seines having stretched mesh size of about 3.0 to 4.5 cm. The samples were temporarily preserved in formalin 10% (+ borax, to retard shrinkage) and transferred to 37% isopropyl alcohol. Measurements were made using dial caliper and a metric scale. Sixteen morphometric, seven meristic and some qualitative characters were examined on a large series of specimens. Proportion were calculated from the numbers of specimens mentioned in the description or appearing on the tables. Meristic characters were determined from radiographs. Clearing and staining were done for bone structure examinations. The measurements and counts used in this study are those defined by Hubbs and Lagler (1964) with some options which are described on page 4. Fisheries data were collected from Regional Fisheries Services, the Marine Fisheries Research Institute and the Institute for Marine Research in Jakarta. Each morphometric character was subjected to regression analysis. Regression lines were compared by covariance analysis. Other characters were treated to basic statistical analyses. 3

Figure 1. Bathymetric chart of the Java Sea. Depth in meters, shaded part represents an area 30 to 60 miles off- shore where sampled Rastrelliger were taken. 4/

All calculations were performed on IBM 1130 and 360/67 Computers, using programs that are available at the U.B.C. Computing Centre.

Anatomical Features, Terms jl. FORK LENGTH (FL): is the distance from the most anterior part of the head (L) to the end of the membranous edge of caudal fin at fork (F).

2. BODY LENGTH (BL): is the distance from the most anterior part of the head (L) to the insertion of the caudal fin's dorsal lobe (B).

3. GILL COVER HEAD LENGTH (LG1): is the distance from the most ante• rior point of the snout (head), i.e., mandibular symphysis L, to the most distant point of the opercular membrane (posterior membranous edge gill cover, G1).

4. MAXILLARY (sheath) LENGTH (UJ): is length of the upper jaw, which is taken from the anterior most point of the premaxillary to the posterior most point of the maxillary.

5. HEAD DEPTH (YJ1): is measured from the midline at the occiput vertically downward to the ventral contour of the head. For the sake of practicality this head depth is measured from the gill cover notch (Y) vertically downward to the ventral contor of the head (J'). 6. DORSO VENTRAL DEPTH (D1V): or anterior dorsal depth, is the distance from the insertion of anterior dorsal (i.e. inter• section anterior margin first dorsal spine, fin held erect, with the contour of the back) to the insertion of anterior ventral fin.

7. DORSO ANAL DEPTH (D2A): is the distance from the insertion first ray of posterior dorsal to the insertion first anal fin ray, it is slightly oblique.

8. GREATEST DEPTH (h): is body depth, i.e., the greatest dorso• ventral dimension, exclusive of the fleshy or scaly structures which pertain to the fin bases.

9. PERPENDICULAR IRIS DIAMETER (Ih): is measured vertically.

10. PERPENDICULAR PUPIL DIAMETER (Eh): is measured vertically.

11. LENGTH OF PECTORAL FIN (Ph): is the distance from the extreme base of uppermost or outermost ray to the farthest tip of the pectoral fin.

12. LENGTH OF PELVIC FIN (Vh): is the distance from the extreme base of the anteriormost ray to the farthest tip of the pelvic fin.

13. INTERORBITAL DISTANCE (00): or interorbital width is the least bony width that is measured where the points are pressed tightly against the bone so as to eliminate so far as practicable the thickness of the flesh overlying the bony rims. 6 14. PECTORAL BREADTH (PP): is the distance measured from the origin of the left pectoral fin to the right pectoral fin, it is a projection.

15. NUMBER OF GILL RAKERS: unless otherwise stated the count is that of the first gill arch. The numbers on the upper limb and lower limb are taken separately; the two figures are separated by a plus sign. A gill raker that straddles the angle of the arch is included in the count of the lower limb. All the rudimentary rakers are included in the count.

16. NUMBER OF RAYS OF THE ANTERIOR DORSAL FIN:, all spines are designated by roman numerals no matter how rudimentary or how flexible they may be. True spines are unpaired (median) structures, without segmentation. Soft rays are designated by Arabic numerals, are usually (not always) branched and flexible, and are bilaterally paired and segmented. 7

III. RESULTS AND DISCUSSION

1. Systematics Studies

Description of the Genus

Rastvelligev Jordan and Starks.

Rastvelligev Jordan and Starks, 1908:607 (ortho-type: Soombev

bvaahysomus Bleeker, 1851).

Description -- Adult small, from 15 to 35 cm. Body fusiform, moderately compressed; body and cheek covered with small scales, those of the breast larger than others. Eyes with well developed adipose eyelid. Mouth moderately large, maxillary reaching to a point nearly vertical below posterior edge of eye. Small teeth in jaws. Vomer and palatines edentulous. Gill rakers long and numerous, featherlike: visible when mouth is opened. Two dorsals, the first spinous. Anal without spines. Five or six finlets behind dorsal and anal. Caudal deeply forked. Pectorals short, pointed with broad base. Pelvics with spines and five rays. Marine, in large schools, inshore. Feeds on both zoo- and phyto-plankton.

Rastvelligev is at present considered to contain two species occurring in abundance throughout the Indo-Pacific Region: in tropical Indian Ocean and western Pacific Ocean. 8

Key to the Species of Rastvelligev Jordan and Starks

1. Greatest body depth in fork length 3.1 - 3.7 (x = 3.4); very finely dendritic cephalic lateral line system; head length slightly lesser than greatest body depth 0.89 - 1.07 (x = 0.98); length of intestine in fork length 2.2 - 3.0 (x = 2.5); digestive tract very convoluted

, R. bvachysoma.

2. Greatest body depth in fork length 3.8 - 4.4 (x = 4.0); not finely dendritic cephalic lateral line system; head length distinctly greater than greatest body depth 1.01 - 1.19 (x = 1.11); length of intestine in fork length 1.3 - 1.4 (x - 1.35); digestive tract less convoluted R. kanaguvta.

Specific Descriptions

1. Rastvelligev bvachysoma (Bleeker) Scombev bvachysomus Bleeker, 1851:356 (description, occurrence). Scombev kanaguvta Bleeker, 1852:34 (nec. Cuvier and Valenciennes, description). Scombev neglectus van Kampen, 1907:7 (description). Rastvelligev bvachysoma Fowler, 1928:132 (morphometric description). Rastvelligev neglectus de Beaufort, 1951:211 (description, figure, occurrence).

Description -- Body compressed, greatest body depth 3.4 (3.1 - 3.7) in FL at origin of the seventh dorsal spine. Head length lesser than or a slightly greater than greatest depth 0.98 (0.89 - 1.07); 9 3.5 (3.3 - 3.7) in FL. Eye about equal to interorbital space. Mouth oblique, maxillary reaching to below hind border of eye. A single series of fine and pointed teeth in the jaws. Palate edentulous. Gill rakers 19 (17-21) on the upper limb of the first gill arch; the longest ones equal or greater than the distance between snout and pupil. First dorsal spine shorter than second. Second dorsal fin concave. Anal fin similar to second dorsal; origin of anal slightly behind that of second dorsal. Pectoral triangular, longer than ventral; about equal or greater than post orbital part of head. Scales ctenoid. Lateral line scales 125 (120-131); slightly curved. Measurements of 117 specimens on Table 1.

Fin formulae: XI(X - XI); D2 12(12 - 13) + 5(5 - 6); A 13 + 5(5 - 6);

P1 18(16 - 18); P2 1.5; vertebrae 31(38 specimens). Colour in life: Bluish-green in the back above lateral lines and silvery in the belly and sides below lateral lines. A row of dark spots along base of first dorsal with dusky in colour. Pectoral, ventral and anal fins yellowish-hyaline with dusky margins. Caudal fin yellowish. Colourations of preserved specimens gradually fades to bluish grey and dull white.

Local common name: Kembung Perempuan. Local habitat: Coastal waters of Indonesian Archipelago. Range: The range extends from Andaman Is. through Indonesian Arch. to Fiji and Solomon Is. Rarely found in South African waters.

2. Rastrelliger kanagurta (Cuvier)

Scomber kanagurta Cuvier, 1817:313 (description). 10

\Scombev loo Lesson, 1829:277 (occurrence).

Scomber chrysozonus Ruppell , 1835:10 (occurrence, figure).

Scomber microlepidotus Ruppell, I bid:37 (description, figure).

Scomber moluccensis Bleeker, 1856:40 (description).

Scomber reani Day, 1870:690 (occurrence).

Scomber lepturus Agassiz, 1874:tab.2 (occurrence).

Eastrelliger brachysomus Jordan and Dickerson, 1908:610 (nec. Bleeker, description, occurrence, figure).

Rastrelliger kanagurta Jordan and Starks, 1917:440 (occurrence).

Rastrelliger ehrysozonus Kishinouye, 1923:406 (classification, synonymy, description, distribution, figure).

Rastrelliger microlepidotus Barnard, 1927:296 (occurrence).

Rastrelliger serventyi Whitley, 1944:268 (occurrence, description).

Description -- Body moderately compressed; greatest depth 4.0 (3.8-4.4) in FL at the origin of the seventh dorsal spine. Head length distinctly greater than greatest depth, 3.6 (3.5 - 3.7) in FL. Eye equal or slightly less than interorbital space. Mouth oblique, maxillary not reaching to a point below hind border of eye or not so far in young specimen. A single series of fine pointed teeth in the jaws. Palate and vomer edentulous. Gill rakers 21 (18 - 23) on the upper limb and 37 (35 - 39) on the lower limb of the first left gill acrh; the longest 11 TABLE 1 Morphometric Measurements of Rastrelliger braahysoma Bleeker (n = 117)

Standard No. Character Mean Error Range

1 Fork Length 15.50 T.39 12.20 - 18.20 2 Total Length 17.40 1.63 13.70 - 20.50 3 Body Length 14.09 1.29 11.10 - 16.50 4 Head Length 4.45 0.43 3.50 - 5.30 5 Maxillary Length 2.46 0.29 1.80 - 3.10 6 Head Depth 3.54 0.37 2.70 - 4.40 7 .Dorsoventral Depth 4.40 0.48 3.30 - 5.60 8 Dorsoanal Depth 4.17 0.42 3.20 - 5.10 9 Greatest Depth 4.53 0.50 3.40 - 5.80 10 Perp. Iris Diam. 0.91 0.09 0.70 - 1.20 11 Perp. Pupil Diam. 0.49 0.05 0.30 - 0.70 12 Pectoral Fin Length 2.19 0.25 1.60 - 2.70 13 Pelvic Fin Length 1.90 0.23 1.40 - 2.90 14 Interorbital Distance 0.94 0.12 0.60 - 1.30 15 Pectoral Breadth 2.10 0.28 1.40 - 2.70 12 equal to distance from pupil to snout. First dorsal spine shorter than second and equal to distance from snout to eye; last spine very small. Anterior rays of second dorsal fin longest, slightly less than fourth spine of first dorsal. The edge of second dorsal and anal fins concave. Origin of anal fin slightly behind that of second dorsal; similar in shape. Pectoral pointed and triangular. Scales ctenoid, lateral line 130 (125 - 140). Measurements of 103 specimens on Table 2.

Fin formulae: D] XI(IX - XI); D2 12(12 - 13) + 5(5 - 6);

A 13 + 5(5 - 6); P] 19(19 - 20); P2 1.5; vertebrae 31 (40 specimens). Colour in life: Bluish with greenish-grey str-ipes above and silvery below lateral lines. Dark spots along the first dorsal base. Pectoral, ventral and anal fins hyaline. Dorsals and caudal dusky along margins. Colour of preserved specimens back bluish grey, dull silvery white.

Local common names: Kembung Lelaki, Kembung, Banyar.

Local habitat: All over Indonesian waters.

Range: The range extends from Durban (South Africa), Persian Gulf, through Central Indo-Pacific area, Ryukyu, Queensland (Australia), Fiji to Hawaii Is.

Nomenclature

The most important study on Rastrelliger in this region was made by de Beaufort (1951). No other work has been done since. In spite of the extensive investigations being done in Thailand and India, the nomenclature of the fish is still in doubt. 13 TABLE 2 Morphometric Measurements of Rastrelliger kanagurta Cuvier (n = 103)

Standard No. Character Mean Error Range

1 Fork Length 17.41 2.08 13.90 - 21.90 2 Total Length 19.39 2.35 15.40 - 24.40 3 Body Length 15.98 1.90 12.60 - 20.00 4 Head Length 4.84 0.57 3.90 - 6.20 5 Maxillary Length 2.48 0.35 1.80 - 3.30 6 Head Depth 3.39 0.43 2.60 - 4.40 7 Dorsoventral Depth 4.27 0.54 3.10 - 5.50 8 Dorsoanal Depth 4.06 0.52 3.10 - 5.20 9 Greatest Depth 4.35 0.58 3.30 - 5.60 10 Perp. Iris Diam. 1.03 0.14 0.80 - 1.50 11 Perp. Pupil Diam. 0.57 0.07 0.40 - 0.80 12 Pectoral Fin Length 2.29 0.33 1,70 - 3.10 13 Pelvic Fin Length 1.93 0.27 1.20 - 2.60 14 Interorbital Distance 1.02 0.16 0.70 - 1.40 15 Pectoral Breadth 2.32 0.38 1.60 - 3.20 14 Its synonymy is rather obscure because local races or individuals have been described under different names.

The taxonomic position of the genus Rastrelliger has been accepted since Jordan and Starks (1908) proposed it for the mackerels having long gill rakers. Starks (1921) raised the subgenus Pneumatophorus as a genus beside the genera Scomber and Rastrelliger. Fraser-Brunner

(1950) and Collette and Gibbs ( 1963) recognized only two genera, i.e.,

Scomber (including Pneumatophorus) and Rastrelliger. There are several interpretations at the species level. De Beaufort (in de Beaufort and Chapman, 1951) lists three species,

Rastrelliger braahysoma Bleeker, R. negleotus van Kampen and R. kanagurta

Cuvier. He noted that R. braahysoma may be a variant of R. negleotus.

Manacop (1956) described only two species R. braahysoma and R. chryso- zonus Ruppell. He further stated that R. negleotus van Kampen is a synonym of R. braahysoma Bleeker, and R. kanagurta Cuvier is a synonym of R. ohrysozonus Ruppell. Jones and Silas ( 1962) recognized two species and considered R. negleotus as a synonym of R. braahysoma and opposed de Beaufort (1951) description. Their incomplete evidence caused some confusion among the workers in Indonesia and adjacent regions who still recognized and used de Beaufort's works. Druzhinin (1968) supports de Beaufort and states that he is not in agreement with Jones and Silas, however, with no strong arguments.

Matsui (1967) proposed a new species, R. faughni sp.n., which formerly was named Scomber australasicus; and recognized two other species,

R. braahysoma and R. kanagurta. His proposal is still widely questioned. 15 The controversy, thus, rests on whether R. braahysoma and R. negleotus are different species. The frequency distribution of the ratios of head length to greatest body depth for Rastrelliger from the north coast of Java and Tg. Satai (Figure 3, Table 3) is distinctly bimodal with a slight over• lap. The degree of intergradation of the two sympatric samples are 5.6% from Jakarta and 2.2% from Tg. Satai area. The frequency distribution of the ratios of greatest body depth to fork length is also bimodal and show no overlap with 0.0% degree of intergradation between these sympatric samples (Figure 2, Table 4). The ratios of the length of intestine to fork length show non-overlapping ranges, of which the degree of intergradation is 0.0% (Table 5). Those characters that belong to two groups that exist sympatrically, with no intergradation between each other, and, there• fore, the two groups should be considered as two valid species. The first group including samples no. 1 and no. 2 is Rastrelliger braahysoma and the second group R. kanagurta, contains samples no. 3 and no. 4. De Beaufort (1951) stated that he recognized R. negleotus van Kampen (1907) with the following arguments "Van Kampen (I.e.) pointed out, that the two common species of Rastrelliger in the Java Sea have been confused by Bleeker and others. The species that Bleeker called loo Cuvier and Valenciennes, is the same as that of French authors, but it is a synonym of kanagurta. The other species is mentioned by Bleeker and others as kanagurta, and had therefore to be renamed. Van Kampen called it negleotus" . With regard to braahysoma de Beaufort 16

Figure £, Graphic comparison of observed ranges and means. Ratio of fork length FL to greatest body depth (h) of Rastrelliger of four samples from two different local• ities. Base line represents range, white bar twice standard deviation, short vertical bar mean. 17

No. If- 1 1 I "-70 LG/h

1 I l N-45

5r- . » 1 • N«o4

H 1 -1 N«72 TL/h

I 1 i N-45

3f ' I i N-34

N-63

6 Q "I I 'i i ^° , f^—1 ,4 , .6 • £

iL. I I 1 K-72 BL/h

2f 1 I I n-4P

3J. I 1 i N-35

' I ' H-67

2 2 8 |' • I '. , V , '1 r-^ , 4f0 , .,2

Figure 3. Ratio of head length (LG), total length (TL), and body length (BL) each to greatest body depth (= height, h) of four samples of Rastrelliger from two localities. Base line represents range, white bar twice standard deviation, short vertical bar mean. TABLE 3 Frequency Distribution of the Ratios of Head Length to Greatest Body Depth of Rastrelliger

Head Lenqth 0.92 Body Depth 0.89 0.95 0.98 1.01 1.04 1.07 1.10 1.13 1.16 1.19 N ' SAMPLE

No. 1 2 1 12 19 . 23 9 6 72 x = 0.996 S.D. = 0.055 2.8 1.4 16.7 26.4 31.9 12.5 8.3 100 No. 2 1 8 7 20 7 2 - 45 x = 0.970 S.D. = 0.038 2.2 17.8 15.6 44.4 15.6 4.4 100 No. 3 1 9 10 8 4 2 34 x = 1.110 S.D. = 0.038 2.9 26.5 29.4 23.5 11.8 5.9 100 No. 4 2 1 16 17 14 7 11 68 x = 1.117 S.D. = 0.034 2.9 1.5 23.5 25.0 20.6 10.3 16.2 100

Intergradation: SYMPATRIC: No. 1 - No. 3 : 5.6% OTHERS: No. 1 - No. 2 : 32.8%

No. 2 -- No. 4 : 2.2% No. 1 — No. 4 : 6.35%

No. 2 — No. 3 : 1,45%

No. 3 — No. 4 : 43.4% TABLE 4 Frequency Distribution of the Ratios of Fork Length to Greatest Body Depth in Rastrelliger

Fork Lenath 3.2 : 3.3 3.4 3.5 3.6 3.7 3.8 3.9 4.0 4.1 4.2 •4.3 4.4 N Body Depth 3.1 SAMPLE

No. 1 1 2 14 20 16 13 7 73 x = 3.46 S.D. = .14 19.2 21.9 17.8 9.6 100 cv = 4.05 1.4 2.7 27.4

No. 2 1 3 12 13 12 4 1 46 x = 3.40 S.D. = .13 2.2 6.5 26.1 28.2 26.1 8.7 2.2 100 cv = 3.68

No. 3 6 9 7 7 4 35 x = 3.98 S.D. = .13 17.2 25.7 20.0 20.0 11.4 100 cv = 3.20

No. 4 9 10 17 19 9 2 2 68 x = 4.03 - S.D. = .15 13.3 14.7 25.0 27.9 13.3 2.9 2.9 100 cv = 3.63 _J Intergradation: SYMPATRIC: No. 1 ~ No. 3 : 0.0% OTHERS: No. 1 — No. 2 : 41.75% No. 2 — No. 3 : 0.0%

No. 2 — No. 4 : 0.0% No. 1— No. 4 : 0.0% No, 3— No. 4 : 42.2% TABLE 5 Ratios of the Length of Intestine to Fork Length of Rastrelliger

SAMPLE Fork- Intestine SAMPLE Fork- Intestine Length Fork Length Length Fork Length

No. 1 17.671 2.48 No. 3 20.434 1.38 17.887 2.51 18.028 1.35 18.238 2.56 19.988 1.37 18.524 2.60 19.694 1.35 18.170 2.55 17.609 1.33 x = 18.098 2.54 19.151 1.36

No. 2 17.535 2.95 No. 4 18.147 1.32 16.351 2.22 19.507 1.38 16.207 2.42 18.693 1.36 17.479 2.61 18.802 1.33 18.747 2.80 15.437 2.31 x = 16.959 2.55 18.787 1,35

Intergradation between SYMPATRIC groups: No. 1 - No. 3 : 0.0% No. 2 - No. 4 : 0.0% o 21 (1951) commented: " It was not 5, as stated by Bleeker, but 6 finlets behind dorsal and anal, and differs from the other Indo-Australian species of Rastvelligev by its great depth " (page 212). In my opinion, Van Kampen's (1907) decision to name the species with great body depth as neglectus cannot be accepted, because Bleeker in 1851 already named it bvachysoma. His view probably was caused by Bleeker's in adequate descriptions since it was described from a single specimen ( 120 mm long and without a caudal fin). Comparison of Bleeker's (1851), Van Kampen's (1907) and de Beaufort's (1951) data with that of the present study are as follows (Figure 3):

R. bvachysoma Bleeker (1851), de Beaufort (1951). - Height 2.79. This is within the range of greatest body depth in

BL of sample no. 1 and no. 2: 2.79 - 3.34 (x1 = 3.14; x2 = 3.10). - Head as long as high. This is within the range of the head length -- greatest body depth ratios of sample no. 1: 0.89 - 1.07 (x = 0.996) and sample no. 2: 0.89 - 1.04 (x = 0.970). - Head 3.15 in length. This is within the range of the ratios of sample no. 1: 2.99 - 3.46 (x = 3.15) and sample no. 2: 3.08 - 3.34 (x = 3.20). - Gill rakers on lower branch 35. This is within the range of sample no. 1: 35-37 (mode = 36) and sample no. 2: 34 - 37 (mode = 35). R. negleotus van Kampen (1907), de Beaufort (1951). - Height 3.1 - 3.4 is within the range of greatest body depth in BL. of samples no. 1 and no. 2. - Head as long as high, is within the range of the head length and greatest body depth ratios of samples no. 1 and no. 2. - Head 3.2 - 3.5 is within the range of head length in BL of samples no. 1 and no. 2. - Head 3.8 - 3.9 in length with caudal. This is within the range of head length in TL of samples no. 1 and no. 2, i.e., 3.74 - 4.08 (x = 3.90) and 3.73 - 4.08 (x = 3.93) respectively. - Gill rakers on lower branch 29 - 34 are within the range of sample no. 2.

These descriptions suggest that R. negleotus van Kampen is a synonym of R. braahysoma Bleeker.

R. kanagurta Cuvier (1817), de Beaufort (1951). - Height 3.4 - 3.8. This is within the range of the greatest body depth in BL of samples no. 3: 3.49 - 3.95 (x = 3.65) and no. 4: 3.46 - 4.17 (x = 3.70). - Height 4.1 - 4.7 in length with caudal. This is within the range of the greatest body depth in TL of sample no. 3: 4.20 - 4.79 (x = 4.43) and sample no. 4: 4.15 - 4.84 (x = 4.49). - Head (somewhat) longer than high, is within the range of the .ratios of head length to greatest body depth of sample no. 3: 1.04 - 1.19 (x = 1.11) and sample no. 4: 1.01 - 1.19 (x = 1.12). 23 - Head 3.2 - 3.3 in length. This is within the range of head length in BL of sample no. 3: 3.16 - 3.36 (x = 3.29) and sample no. 4: 3.14 - 3.50 (x = 3.31). - Head 3.9 - 4.3 in length with caudal. This is within the range of head length in TL of sample no. 3: 3.87 - 4.09 (x = 3.99) and sample no. 4: 3.86 - 4.37 (x = 4.01). - Gill rakers on lower branch 35 - 38, are within the range of sample no. 3: 35 - 39 (mode - 37) and sample no. 4: 35 - 37 (mostly: 37).

The above comparisons suggest that all the descriptions of Cuvier (1817) and de Beaufort ( 1951) are in agreement with the data of samples no. 3 and no. 4, i.e., R. kanaguvta.

Diagnostic Characters

Ratio of Fork Length to Greatest Body Depth

The ratio of values of fork length to greatest body depth ranges from 3.10 to 4.40 (Table 4). The frequency distribution of sympatric samples show two distinct bimodal histograms with no overlap. The values of the degree of intergradation among samples are: Sample no. 1 to no. 2: 41.75% no. 1 to no. 3: 0.0 %( sympatric, Jakarta) no. 1 to no. 4: 0.0 % no. 2 to no. 3: 0.0 % no. 2 to no. 4: 0.0 % (sympatric, Tg. Satai) no. 3 to no. 4: 42.2 % 24 The above data suggest that these characters are useful in distinguishing the two species.

Ratio of Head Length to Greatest Body Depth

The average ratios of head length to greatest body depth ranges from 0.89 to 1.22 (Table 3). The frequency distributions of these ratios for sympatric samples (no . 1 and no. 3; no. 2 and no. 4) shows two distinct bimodal histograms with modes of 0.98, 1.01, and two modes of 1.10. Samples from Tg. Satai area have an intergradation value 5.6% and from Jakarta area 2.2%. The degree of intergradation between areas are: Sample no. 1 to no. 2: 32.8% no. 1 to no. 4: 6.35% no. 3 to no. 2: 1.45% no. 3 to no. 4: 43.4% These characters are key characters that have been used to distinguish species. The present data show slight overlaps, therefore, these characters have disadvantages as key-characters.

Ratio of Other Measurements to Either Head Length or Greatest Body Depth

The ratio of body length BL, fork length FL, and total length TL to head length, shows a considerable overlop with degree of inter• gradation ranging from 13.5 - 34.0% between sympatric samples; while the ratio to greatest body depth the degree of intergradation ranges from 0.0 - 2.1%, thus, generally, the ratios of body part to greatest body depth are useful in distinguishing species. 25 Ratio of the Length of Intestine to Fork Length

The length of intestine in FL (Table 5) between sympatric samples shows no overlap, the degree of intergradation is 0.0%. The first group, i.e., samples no. 1 and no. 2, has ratios 2.2 - 2.95 (x = 2.54); whereas the second group, samples no. 3 and no. 4, has ratios 1.32 - 1.38 (x = 1.35). This ratio is good as key-character for distinguishing species.

2. Morphometric Study

For characters studied, the regression of each character on fork length FL is a rectilinear regression, with correlation coefficient range from 0.71 - 0.99 (Tables 6, 7, 8, & 9).

y = a + bx where: x the independent variable, fork length y the dependent variable, length of any body part

The characters were examined for possible bias caused by sexual dimorphism or strong allometric growth. Analysis of covariance indicated that:

1. longitudinal measurements and pelvic fin length are significantly different (1%) between sexes (Table 10) , 2. perpendicular iris and pupil diameters, pectoral fin length, and pectoral breadth show strong allometric growth (1% level of significance) (Tables 11, 12, 13). 26

TABLE 6 Regressions of Sample No. 1 from Jakarta, N = 72 y = a + bx, where: x is fork length, y is measurements of any body parts, r is correlation coefficient, cv. is coefficient of variation, T is Student's t value.

Character a b S.E. of r c. v. T b % Total length -0.2360 1.1420 0.0292 0.9778 1.37 39.05 Body length 0.0292 0.9076 0.0234 0.9774 1.36 38.71 Head length 0.0187 0.2880 0.0123 0.9416 2.25 23.40 Maxillary ln. -0.5541 0.1959 0.0099 0.9203 3.27 19.68 Head depth -0.2071 0.2427 0.0121 0.9225 2.79 19.98 Dorsovent. d. -1.0954 0.3531 0.0188 0.9132 3.51 18.74 Dorsoana. d. -0.7110 0.3138 0.0185 0.8960 3.65 16.88 Greatest b.d. -1.0948 0.3606 0.0207 0.9008 3.77 17.35 Iris diam. 0.0716 0.0550 0.0065 0.7078 5.82 8.38 Pupil diam. 0.0766 0.0270 0.0032 0.7105 5.30 8.44 Pectoral ln. -0.3756 0.1676 0.0092 0.9078 3.40 18.10 Pelvic length -0.3765 0.1483 0.0165 0.7303 7.04 8.94 Interorbit. d. -0.3006 0.0805 0.0053 0.8742 4.59 15.06 Pect. breadth -1.0682 0.2019 0.0152 0.8452 6.00 13.23 27

TABLE 7 Regressions of Sample No. 2 from Tg. Satai, N = 45 y = a + bx, where: x is fork length, y is measurements of any body parts, r is correlation coefficient, c.v. is coefficient of variation, T is Student's t value.

Character a b S.E.of r c.v. T b %

Total length -0.3889 1.1413 0.0131 0.9972 0.93 86.88 Body length -01.711 0.9199 0.0060 0.9991 0.52 152.83 Head length -0.1638 0.2954 0.0071 0.9875 1.99 41.09 Maxillary In. -0.6566 0.1996 0.0067 0.9766 3.39 29.77 Head depth -0.5317 0.2621 0.0079 0.9807 2.78 32.88 Dorsovent.d. -0.6542 0.3283 0.0102 0.9807 2.84 32.04 Dorsoanal.d. -0.1514 0.2807 0.0106 0.9704 3.11 26.36 Greatest b.d. -0.7970 0.3476 0.0105 0.9810 2.81 33.12 Iris diam. -0.0264 0.0595 0.0029 0.9517 4.00 20.32 Pupil diam. -0.1340 0.0413 0.0025 0.9266 6.23 16.15 Pectoral In. -0.3636 0.1626 0.0053 0.9777 3.04 30.52 Pelvic length -0.2306 0.1350 0.0074 0.9409 4.89 18.21 Interorbit.d. -0.2462 0.0763 0.0050 0.9163 6.70 15.00 Pect. breadth -0.7629 0.1881 0.0081 0.9619 4.68 23.08 28

TABLE 8 Regressions of Sample No. 3 from Jakarta, N = 35

y = a + bx , where : x is fork length, y is measurement of any body part, r is correlation coefficient, cv. is coefficient of variation, T is Student's value.

Character a b S.E.of r cv. T b %

Total length -0.3424 1.1353 0.0302 0.9885 1.23 37.51 Body length -0.2741 0.9318 0.0153 0.9955 0.76 60.59 Head length -0.0060 0.2800 0.0090 0.9831 1.47 30.82 Maxillary In. -0.4448 0.1700 0.0085 0.9610 2.65 19.97 Head depth 0.0842 0.1920 0.0101 0.9567 2.35 18.86 Dorsovent. d 0.3913 0.2229 0.0126 0.9507 2.35 17.60 Dorsoanal d. 0.2400 0.2219 0.0122 0.9533 2.36 18.14 Greatest b.d. 0.1010 0.2460 0.0163 0.9344 2.94 15.07 Iris diam. -0.1854 0.0709 0.0069 0.8713 5.19 10.20 Pupil diam. -0.1016 0.0386 0.0035 0.8832 4.90 10.81 Pectoral ln. -0.3866 0.1555 0.0100 0.9374 3.39 15.46 Pelvic length -0.2247 0.1250 0.0080 0.9382 3.23 15.57 Interorbit.d. -0.0523 0.0606 0.0066 0.8485 5.16 9.21 Pect. breadth -0.9698 0.1916 0.0093 0.9631 3.05 20.54 29

TABLE 9 Regressions of Sample No. 4 from Tg Satai, N = 68 y = a + bx , where: x is fork length, y is measurement of any body part, r is correlation coefficient, c.v. is coefficient of variation, T is Student's t value.

Character a b S.E.of r c.v. T b %

Total length -0.0062 1.1119 0.0124 0.9959 1.21 89.37 Body length 0.1484 0.9090 0.0068 0.9981 0.80 133.03 Head length 0.1895 0.2660 0.0051 0.9881 1.99 52.09 Maxillary In. -0.2823 0.1578 0.0041 0.9778 3.19 37.87 Head depth -0.1805 0.2041 0.0044 0.9845 2.50 45.60 Dorsovent. d. -0.3092 0.2599 0.0065 0.9798 2.92 39.78 Dorsoanal. d. -0.2785 0.2487 0.0057 0.9831 2.65 43.56 Greatest b.d. -0.4484 0.2754 0.0071 0.9786 3.09 38.61 Iris diam. -0.0524 0.0620 0.0030 0.9302 5.52 20.59 Pupil diam. 0.0695 0.0285 0.0018 0.8801 6.27 15.06 Pectoral In. -0.3793 0.1526 0.0044 0.9728 3.71 34.10 Pelvic length -0.2536 0.1253 0.0039 0.9691 3.84 31.91 Interorbit. d. -0.2862 0.0752 0.0033 0.9417 6.12 22.74 Pect. breadth -0.5646 0.1642 0.0063 0.9538 5.25 25.79 30

Sexual Dimorphism

Rastrelliger braahysoma show sexual dimorphism in body length, maxillary length, ventral fin length, and probably caudal fin length (Table 10). The male has a shorter head, shorter maxillary, shorter ventral fin and shorter body; and probably has a longer caudal fin. The purpose of this sexual dimorphisms is not yet been studied in this particular fish. I speculate that this dimorphisms is more for sexual purposes rather than for display; such as longer ventral fin in female is probably for obtaining better balance and diverging the eggs while discharging them. This dimorphism is less likely to appear in fins which are critical for locomotion. The longer body in female can be related to the need for more space in body cavity for eggs, as female gonads are generally much bigger than male gonads. The longer head and maxillary are probably related to the more inten• sive and active feeding in the female than in the male. The above characters should not be used for racial studies.

Allometric Growth

The morphometric data of R. kanagurta suggest that perpendic• ular iris and pupil diameters, pectoral fin length, and pectoral breadth show strong allometric growth (Table 11, 12, 13). These characters cannot be used for racial studies purposes. 31 TABLE 10 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis for the Males and Females Taken from Tg. Satai. Data Show Variance Ratio and its Significance. Fr is the variance ratio to test the significance of the regression difference, Fb to test the regression coefficient difference, Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Total length 3.91** 0.14 5.58* Body length 6.46*** 0.07 1.97 Head length 1.35 7.38** (0.05) Maxillary length 1.36 5.32* 0.51 Head depth 2.11 1.89 0.49 Dorsoventral depth 1.03 0.89 0.36 Dorsoanal depth 1.94 1.52 0.00007 Greatest body depth 1.00 1.90 0.33 Perp. iris diameter 1.16 2.62 0.02 Perp. pupil diameter 1.80 0.87 2.59 Pectoral fin length 2.02 0.17 2.18 Pelvic fin length 14.88*** 0.001 1.63 Interorbital distance 1.24 1.10 0.91 Pectoral breadth 1.05 1.04 0.000003

Significant at 5% level. Significant at 1% level. Significant at 0.1% level.

Note: The above species was named Rastrelliger brachysoma. 32

RASTRELLIGER BRACHYSOMA

Figure. 4 Sexual Dimorphisms.

male

——— female

Figure. 5 Geographical Variations.

— —- from the north coast of Java

from Tg. Satai area 33 Geographic Variations

Comparisons were done on head depth, dorsoventral depth, dorsoanal depth, greatest body depth and interorbital distance since these characters show neither sexual dimorphism nor strong allometric growth in both species. Analysis of covariance on the data indicated that:

1. between sympatric samples (ho. 1 and no. 3; no. 2 and no. 4) these characters show a very highly significance difference (0.01%); 2. the dorsoventral depth, greatest body depth, and interorbital distance have significance intraspecific difference' 5%),

showing geographical variations in-i?. braahysoma (Table 20). The fish from Tg. Satai area possess greater dorsoventral depth, greater body depth, and longer interorbital distance than its counterpart from the north coast of Java. In other words the R. braahysoma from the north coast of Java is more slender than that one from Tg. Satai (Figure 5). 3. R. kanagurta shows geographic variation in its head depth and dorsoventral depth (Table 20). The fish from the north coast of Java possess greater head depth and dorsoventral depth. So thus R. kanagurta from Tg. Satai is slender and has lesser head depth than the one from the north coast of Java (Figure 6). 34 TABLE 11

Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Classmodes of 20.0 cm Fork-Length 17.5 - 22.4 cm) and of 16.0 cm Fork Length (14.5 - 17.4 cm) Taken from Tg. Satai Area Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference.

In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa Maxillary length 1.40 6.12* 0.95 Head depth 1.67 1.51 1.25 Dorsoventral depth 1.15 0.09 2.14 Dorsoanal depth 1.35 0.81 1.05 Greatest body depth 1.18 1.54 0.65 Perp. iris diameter 2.32* 13.97*** (2.54) Perp. pupil diameter 1.29 14.34*** (2.84) Pectoral fin length 1.58 4.03* 0.68 Interorbital distance 1.12 1.91 0.53 Pectoral breadth 3.27** 0.81 0.07

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level.

Note: The above species was named Rastrelliger kanagurta. 35 TABLE 12 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Classmodes of 20.0 cm Fork-Length (17.5 - 22.4 cm) and of 14.0 cm Fork-Length (13.5 - 14.4 cm) Taken from Tg. Satai Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Maxillary length 1.56 0.67 12.20** Head depth 1.40 0.91 4.86* Dorsoventral depth 1.04 0.52 0.58 Dorsoanal depth 2.03 0.06 0.17 Greatest body depth 2.88 0.01 0.12 Perp. iris diameter 2.62 2.27 13.87*** Perp. Pupil diameter 1.07 0.001 21.83*** Pectoral finilength 1.19 1.49 8.17** Interorbital distance 1.37 1.55 3.06 Pectoral breadth 2.29 0.10 0.67

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level.

Note: The above species was named Rastrelliger kanagurta. 36 TABLE 13 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Classmodes of 16.00 cm Fork-Length (14.5 - 17.4 cm) and of 14.00 cm Fork-Length (13.5 - 14.4 cm) Taken from Tg. Satai Data show variance ratio and its significance. Fr is the variance ratio and its significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Maxillary length 0.10 0.11 2.32 Head depth 1.18 2.08 1.04 Dorsoventral depth 1.10 0.09 0.11 Dorsoanal depth 1.49 0.003 0.04 Greatest body depth 2.42 0.02 0.30 Perp. iris diameter 1.12 1.07 0.39 Perp. pupil diameter 1.20 0.65 0.45 Pectoral fin length 1.32 0.89 2.56 Interorbital distance 1.22 2.61 0.003 Pectoral breadth 1.12 0.05 0.01

Significant at 5% level. Significant at 1% level. Significant at 0.1% level.

Note: The above species was named Rastrelliger kanagurta. 37

TABLE 14 Comparison of Body Proportion of Rastrelliger spp. by Covariance Analysis Between Sample No. 1 and Sample No. 2 from Jakarta and Tg. Satai respectively Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.15 1.81 1.26 Dorsoventral depth 1.65* 1.37 3.90 Dorsoanal depth 1.49 2.42 2.36 Greatest body depth 1.92* 0.31 9.90** Interorbital distance 1.82* 0.31 1.15

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 38 TABLE 15 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 3 (Jakarta) and No. 4 (Tg. Satai) Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference.

In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.05 1.20 6.51* Dorsoventral depth 1.28 5.89* 1.54 Dorsoanal depth 1.05 3.80 2.23 Greatest body depth 1.07 2.80 0.39 Interorbital distance 1.19 3.03 0.84

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 39 TABLE 16 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 1 (Jakarta) and No. 3 (Jakarta) Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.44 9.41** (>D Dorsoventral depth 2.21* 28.92*** (>D Dorsoanal depth 2.31** 14.83*** (>D Greatest body depth 1.62 17.26*** (>D Interorbital distance 1.54 5.26* 25.41***

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 40 TABLE 17 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 2 (Tg. Satai) No. 4 (Tg. Satai) Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.31 43.43*** (>D Dorsoventral depth 1.04 31.96*** (>1) Dorsoanal depth 1.46 7.80** (>1) Greatest body depth 1.09 31.39*** (>1) Interorbital distance 1.009 0.03 19.82***

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 41

TABLE 18

Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 2 (Tg. Satai) and No. 3 ( Jakarta) Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.25 27.65*** ( 1) Dorsoventral depth 1.34 38.75*** ( 1) Dorsoanal depth 1.54 11.73*** Greatest body depth 1.18 28.36*** Interorbital distance 1.18 2.93 W\ 9.87**

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 42

TABLE 19 Comparison of Body Proportions of Rastrelliger spp. by Covariance Analysis Between Samples No. 1 (Jakarta) and No. 4 (Tg. Satai) Data show variance ratio and its significance. Fr is the variance ratio to test the significance of the regression difference. Fb to test the regression coefficient difference. Fa to test the adjusted mean difference. In the case where the regression coefficient difference is significant, the test of the adjusted mean becomes inappropriate.

Character Fr Fb Fa

Head depth 1.52 9.84** ( 1) Dorsoventral depth 1.72* 25.61*** ( 1) Dorsoanal depth 2.18** 13.79*** ( 1) Greatest body depth 1.75* 17.65*** ( 1) Interorbital distance 1.84* 0.56 54.49***

* Significant at 5% level. ** Significant at 1% level. *** Significant at 0.1% level. 43

SAMPLE NUMBER CHARACTER No.l

Head depth

Dorsoventral depth -

No.2 Dorsoanal depth

Greatest body depth * **

Interorbital distance * No. 2

Head depth ** ***

Dorsoventral depth

No. 3 Dorsoanal depth

Greatest body depth •if*-*

interorbital distance * **# ** No. 3

Head depth **-•)<• *

Dorsoventral depth **

No.4 Dorsoanal depth

Greatest body depth * *#*

Interorbital distance *** ##*

Fr Fb Fa Fr Fb Fa Fr Fb Fa

Table 20.Covariance analyses for pairs of Rastrelliger. Fr, Fb and Fa are the variance ratios used to test the significance of difference in regression line, regression coefficient and adjusted mean respectively.

* : Significant at 5 7* level. ** : " 1 io " *** : 11 0.1 fo " RASTRELLIGER KANAGURTA

Geographical Variations.

• from Tg. Satai area

- from the north coast of Java 45 3. Meristic Characters

Number of Vertebrae

Total numbers of vertebrae appeared to be constant as all specimens examined had 31 vertebrae. 26 specimens of 7 - 9 cm FL possessed 31 vertebrae. There is no difference in vertebrae number between R. braahysoma and R. kanagurta.

First Haemal Spine

The first haemal spine appeared constant on the tenth vertebrae in Rastrelliger.

Sample no. 1, i.e., R. braahysoma from the north coast of Java have a mean of the first haemal spine location of 9.9 (0.3 S.D.) with coefficient of variation 3.1%. Sample no. 2, no. 3, and no. 4 appeared constant on the tenth vertebrae.

First Dorsal Spine

The first dorsal fin spine counts appeared variable between 10.6 (0.5 S.D.) to 11.0 (0.0 S.D.). Analysis of variance indicated highly significant differences (1%) between R. kanagurta from the north coast of Java and the one from Tg. Satai area. The fish from the former area has eleven spines on its first dorsal fin, whereas the one from the latter area is variable, 46 either possessing eleven or ten spines (x = 10.6, S.D. = 0.5, n = 20).

Dorsal Fin Rays and Finlets

The second dorsal fin rays plus finlets counts appear to be less variable. The coefficient of variation ranged from 0.0 to 2.9%. There is no significant difference between species. The fin-rays vary from 12 to 13 and the dorsal finlets from 5 to 6.

Anal Fin Rays and Finlets

The counts of anal fin rays and anal finlets appeared constant, i.e., 18. The fin-rays are 13 and the anal finlets vary between 5 and 6.

First Occurrence of Haemal Brace

The first haemal brace occurred as a structure on vertebrae as described by Roedel (1952) (Figure 7). He suggested that this character is good for distinguishing race in Pneumatophorus. The first occurrence of haemal brace in Rastrelliger appeared on either the thirteenth or the fourteenth vertebrae. The coefficient of variation range from 2.2 to 3.6. The means range from 13.7 (0.5 S.D.; n = 20) to 13.9 (0.3 S.D.; n = 20). Figure 7. First Occurence of Haemal Brace on Vertebrae (after Roedel, 1952).

1. Partially Formed Brace 2. Haemal Brace 48 TABLE 21 Gill Raker Counts of Rastrelliger

Part of Gill Coefficient of Species Name Arch Mean S.D. Variations N

R. braahysoma Upper 19.0 1.0 5.47 14 Lower 35.8 0.9 2.46 25 Total 55.0 1.0 1.82 15

R. kanagurta Upper 20.6 1.3 6.27 28 Lower 36.6 1.0 2.73 30 Total 57.2 1.9 3.27 28

TABLE 22 The Degree of Intergradation of the Total Gill Raker Counts of the First Left Gill Arch of Rastrelliger

Gill Raker Count 54 55 56 57 58 59 n

Species

R. braahysoma 40 26.7 26.7 6.6 - - 100

R. kanagurta 14.3 7.1 10.7 21.4 25 21.4 99.9

Intergradation = 19%. 49

Analysis of variance indicated that there is no significant difference between and within species. Therefore, this character cannot be used in racial studies of Rastrelliger spp.

Gill Raker

The gill raker counts on the first left gill arch show consider• able variations. The coefficient of variation of the gill raker counts on the lower limb in R. kanagurta was 2.7, and the mean was 36.6 (S.D. = 1.0); in R. braahysoma was 2.5 and 35.8 (S.D. = 0.9) respectively. Those values of the upper limb were 6.3 and 20.6 (S.D. = 1.3); and 5.5, 19.0 (S.D. = 1.0). The total gill raker counts on the first left gill arch show overlap between species; the degree of intergradation was 19% (Tables 21, 22).

4. Qualitative Characters

Colouration

No distinct differences exist in body colouration among samples. The dark spots or stray spots below the first dorsal and on the tip and outer margin of the first dorsal fin show a slight difference in the degree of darkness between fi. braahysoma and R. kanagurta. The former species possesses darker colour on its tip and outer margin of the first dorsal fin, whereas the second one has clearer longitudinal bands above the lateral lines. 50 Cephalic Lateral Line Canal

There is an apparent difference in the appearance of the cephalic lateral line system between the two species.

R. braahysoma possesses a very finely dendritic canal system; whereas R. kanagurta has a less finely dendritic one (Figure 8). This character is useful in distinguishing species, and can be used as a key characters.

Digestive Tract

The digestive tract in R. braahysoma is much more convolut• ed than that of R. kanagurta. This different appearance is related to the longer intestine in the first species. The shape of the stomach differs only in the presence of a small flappy tip at the bottom of the stomach of R. kanagurta (Figure 9).

5. Population Study

Rastrelliger Fisheries

Rastrelliger is fished in practically all coastal areas of Indonesia; and is caught maily by payang-net. The payang net is an encircling surface seine with a bag, and have the upper lines . shorter than the lower ones. The fishermen usually use a lure that is called rumpon to attract the fish and concentrate them. The payang-net is 51 dragged passing underneath or alongside the rumpon and is hauled up to the vessel. The operation takes place during the day. Thousands of such rumpons lie scattered over the Java Sea. Several fishing gears such as shore seine, gill net, and traps are utilized along the coastal areas. In the late part of 1971, the purse seine was introduced in the Bay of Jakarta. It has operated economically since 1972 in the coastal areas of the north coast of Java. The fish caught consist of two species, R. brachysoma or Kembung Perempuan which is caught mainly in the coastal zones; and R. kanaguvta or Kembung Lelaki of the offshore areas. The major part of landings comes from the Sunda Shelf area, in particular the north coast of Java, the south and the south west coasts of Borneo (Kalimantan) and the east coast of Sumatra. The production in the north coast of Java is estimated as exceeding 10,000 tons per year, of which the greater part of the landing consists of R. kanaguvta (Table 23). In the eastern part of Indonesia the fishing activities are not yet developed.

Population Parameters

The present study of Rastrelliger population dynamics in Indonesian waters begins with analysis of variables or parameters of its populations. Detailed analyses of variables affecting yield have been attempted in the Gulf of Thailand and Indian waters. 52

Figure 8. Cephalic Lateral Line System of Rastrelliger.

R» brachysoma II. R. kanagurta

Abbreviations: CL, cephalic lateralis;' F, frontal; 10, interorbital; LL, linea lateralis; POC, postocular commi- sure; SO, supraorbital; ST,supratemporal. 53

Figure 9. Dimension of measurement of the digestive tract of Rastrelliger.

1. stomach; 2. pyloric; 3. intestine.

I. ths stomach of R. brachysoma

II. the stomach of R. kanagurta 54 TABLE 23 Production of Payang Fisheries in the North Coast of Java of R. kanagurta

1969 1970 1971 Month (tons) (tons) (tons)

I 210 275 535 II 203 358 521 III 408 528 863 IV 849 1,093 1,156 V 547 645 1,003 VI 499 528 934 VII 431 562 739 VIII 438 424 588 IX 551 593 869 X 725 735 1,011 XI 802 774 1,033 XII 509 584 906

Total 6,172 7,099 10,158

Sources: (1) The Sea Fisheries Service of Jakarta-Raya in Jakarta, (2) " of the Province of West Java in Bandung, (3) " of the Province of Middle Java in Semarang, (4) " of the Province of East Java in Surabaya. 55 The information available does not meet the data requirement of modern management models. Moreover, some difficulties such as un• detectable growth rings on scales and other skeletal structures, varia• bility in growth rates, indefinite spawning periods and the paucity of catch statistics lead to at best, approximate estimations of parameters. However, the results reported here compare favourably with the results obtained by various investigators from the adjacent regions.

Sexual Conditions

Maturity

The importance of age at sexual maturity for management purposes is obvious. Nikolskii (1969) states that because of differ• ences in growth rates, young hatched at the same time will reach maturity at different ages. Sexual maturity may be governed by attainment of a certain size rather than age. The size at maturity is therefore an important parameter in management, especially for tropical species, wherein exploitation should allow an adequate number of spawners, i.e., larger than or equal to the size at sexual maturity, to assure a continued supply of young fish.

The data suggest that Rastvelligev kanaguvta in the Java Sea attains its sexual maturity at 19.0 (18.0 - 20.5) cm TL or at about 7 months of age (Figure 29 i_n Appendices, Table 27). Chidambaram and Venkataraman (1946) found the minimum size at sexual maturity of R. kanaguvta in Indian waters to be 20 cm. 56 In the same waters Pradhan (1956) suggested 22.4 cm TL at maturity. Pathansali (1966) reported that R. kanagurta caught at Pangkor Is., Malaysia, attained sexual maturity at 17.5 - 19.8 cm. The size at ma• turity of the same fish in waters of the Philippine was recorded as 21.0 - 21.9 cm (Philippines Fisheries Handbook, 1952). Tiews (1958) gives 18.0 cm for this fish in the same region. No records are avail• able from the other regions of the Indo-Pacific area. R. braahysoma attains its sexual maturity at 17.3 (17.0 - 17.5) cm TL or about 7.5 months old (Figure 11, Table 28). The only other comparable data for this species were obtained in Manila Bay, The Philippines, where the size at maturity was 15.0 - 16.9 cm (Philippines Fisheries Handbook, 1952); Tiews (1958) gives 16.5 cm. Beverton (1963) studied the age at maturity of clupeids and engraulids and stated that fish with high K value (von Bertalanffy growth parameter) mature at an earlier age than fish with low K. The data suggest that Rastrelliger follow this pattern. R. kanagurta with a higher K value (= 0.23) mature at a younger age (= 7 months) than R. braahysoma with a lower K value (= 0.19) that mature at 7.5 months old (Table 26, 27, 28; Figure 11, 29 i_n Appendices).

Gonads

Several indicators of the maturity stages are available either for the field or laboratory. These keys have been described by Indian workers and were developed from The Key to the Stages of Sexual Maturi- 57 ty of the Herring by the International Council for the Exploration of the Sea (Pradhan and Palekar, 1956). In this study the field keys were employed (Table 24, 25). No fecundity study has been carried out. Devanesan and John (1940) estimated an average of 94,000 eggs per female R. kanaguvta in Indian waters. Boonprakob (1966) estimated 86,000 eggs per female for advanced group eggs and 479,000 eggs per female for total ova of the same species caught in the Gulf of Thailand. For R. bvachysoma he estimated 100,000 - 166,000 eggs per female for advanced group and 200,000 - 500,000 eggs per female for total ova. Furthermore, he writes that R. kanaguvta released 20,000 eggs per batch and R. bva• chysoma between approximately 20,000 and 30,000 eggs per batch.

Spawning

The mature gonads of R. kanaguvta are found mostly in January and May (Figure 10), but there is evidence that stage IV (mature) gonads are found in September. The data suggest that in the Java Sea there are two spawning seasons, the first during the West Monsoon probably from October to February and the second during the East Monsoon from June to September. Pathansali (1961) assumed that the spawning season of R. kanaguvta on the west coast of Malaysia is from October to April. Jones and Rosa (1962) stated that the spawning season of this fish in Indian waters appears to be from March to September. 58 TABLE 24 Field Key of Maturity Stages of Rastrelliger (Males)

Extent of Testes in Body Cavity General Appearance of Testes Stage and State

Less than 1/2 length Very small translucent or I of cavity whitish strand visible Immature Slightly more than Distinct ovoid or elongate II 1/2 length of cavity flat body visible; mostly Maturi ng translucent; whitish About 2/3 or over Opaque; white and flat; some• III length of cavity times creamy Maturing Much over 2/3 to full Opaque; white; soft; sperm IV length of cavity extrusable Mature Much reduced in size, Bloodshot and flabby, partly V about 1/3 of cavity translucent Spent

Note: For Fresh Material. 59

TABLE 25

Field Key of Maturity Stages of Rastrelliger (Females)

Extent of Ovary in Body Cavity General Appearance of Ovary Stage and State

About 1/3 length of Translucent; redish to pink• I cavity ish in colour; ova invisible Immature About 1/2 length of Translucent; pinkish in II cavity colour; ova invisible Maturing About 2/3 length of Pinkish yellow colour; III cavi ty granular, opaque in Maturing appearance

Over 2/3 to full Orange to pink in colour; IV length of cavity superficial blood vessels Mature conspicuous; translucent eggs visible; ripe eggs are extrusable

Shrunken to about Remnant of disintegrating V 1/2 length of opaque and ripe ova visible; Spent cavity; walls loose may be dark red or translucent

Note: For Fresh Material. 60 R. bvachysoma from Tg. Satai appears to have a long spawning season that lasts from May to October. This conclusion is based upon the maturity stages data (Figure 11) and the disappearance of this fish for several months during which time they migrate from the area to spawn. In the Gulf of Thailand, Boonprakob (1966) reported that the spawning season of R. braohysoma is from January to August. Druzhi- nin (1968) states that in Burma waters the same species has a spawning season that lasts from September to May. Jones and Rosa (1962) state that Rastrelliger spawn in succession over a prolonged period and only a small portion of ova mature each time giving a "speckled" appearance stage. Pathansali (1966) states that there is considerable difference in the maturity stages of R. kanagurta ovaries within fish of the same school and in the same size range. This resulted in peculiar modes of egg ripen• ing and spawning. As the spawning of any one batch of ova is not simultaneous in all fish, a number of broods are produced during each reproductive season. Boonprakob (1966) suggested that a spawner of R. braohysoma after releasing the first batch of eggs probably releases subsequent batches of eggs at short intervals of time. Evidence of repeated spawning is not unusual in the family Scombridae. Fry (1936) identified repeated spawning in Scomber japonicus which he says may spawn two or more times a season. The spawning season is from April to August and occurs off the California Coast. 61

Nov.71 Jun.7? 40-

20

Dec.71 Jul.72 40-

20

0- Jan.72 Aug.72 4G-

2G

C- Feb.72 Ser>.72 UC

2G

C-

4C

2C

C May.72 4C

2C

i nniy/T 1 IffllTY

Figure 10. Sexual Maturity Stages Com-oosition of R. kanagurta from the north coast of Java, 62

Sexual Maturity Stage

17 18 19 20 21 TL (cm)

Figure n Length end Sexual Maturity Stage Compositions of R. brachysoma from Tg. Satai, on March 1°72. 63 If the number of batches can be determined, the time taken by each batch to develop could be determined which in turn would allow one to measure the length of the breeding season. Without knowledge of a definite breeding season it is difficult to determine annual re• cruitment and to relate recruits to the broods of young in one year. Repeated spawning within a year creates sub-year classes, possessing different growth rates, which causes overlaps in the length frequency distribution making the different age groups difficult to identify. Fry (1936) states that Scomber scombrus spawns in water deeper than 70 meters, with a temperature range of 16.7 to 20.6° C. He found pelagic eggs of s. japonicus floating at or near the sur• face in the open sea. Bigelow and Welch (1925) found eggs in water temperature ranging from 4 to 17.8° C with salinity from 31.9 to 33.0 °/oo. The surface ( < 10 m) temperature in the Java Sea and adjacent areas in January, February, and March ranges from 27.5 - 29.0° C, and the salinity ranges from 32.0 - 33.0 °/oo. In April, May, and June the temperature is approximately 29.0°C and the salinity approaches 33.5 °/oo (in the eastern part of Java Sea it is 34.25 °/oo). These conditions continue throughout July, August, and September, except in the eastern part of the Java Sea where sali• nity is slightly higher. In October, November, and December the temperature' and salinity decrease to 27.5° (the western edge of the Java Sea: 27.5 - 29.0°) and 32.5 °/oo (the eastern part of the Java Sea ranges from 33.5 - 34.5 °/oo) (Barkley, 1968). 64

The salinity in the coastal areas is generally lower than that of the offshore due to the inflow of rivers. This condition might prevent egg development as they need water of high density for the osmotic requirements of the eggs.

If Rastrelliger spawns in the same depth as Scomber they must migrate to deeper waters from the Java Sea area (where the depth does not exceed 50 m). These areas could be the South China Sea, the Indian Ocean or the eastern part of the Java Sea adjacent to the Flores Sea. I suspect that the West Monsoon population spawns in the South China Sea or the Indian Ocean, and the East Monsoon population in the Flores Sea.

Egg and larval studies in the above areas and in the Java

Sea might help elucidate the spawning behaviour of Rastrelliger.

Sex Ratio

The males and females of R. kanagurta in the commercial catches exist in approximately equal proportions with a ratio of 1.0

to 1.1. The unpublished data of the Institute for Marine Research

in Jakarta show that in the West Monsoon (1971/1972) the ratio is 1.0

to 1.2 and in the East Monsoon (1972) it is about equal. In Indian

waters, Jones and Rosa (1962) observed a ratio of 1.0 to 1.0.

In R. braahysoma the ratio is 1.3 to 1.0 (1972); whereas Druzhinin (1968) recorded a ratio of 1.0 to 1.7 between males and fe•

males in Mergui Arch., Burma. 65

! Longevity

The data suggest that R. kanaguvta in the Java Sea can attain 24.0 cm TL or 3 years of age (Table 26, 27). In unpublished data of the Marine Fisheries Research Insti- ' tute in Jakarta, Kadir (1966) recorded a specimen of 26.5 cm caught in the south west of Borneo. The largest specimen caught in Indian waters was 27.0 cm (Jones and Rosa, 1962). De Beaufort (1951) record• ed a length of 37.0 cm.

R. bvachysoma can reach 23.0 cm TL or 3 years of age (Table 26, 28). In the Gulf of Thailand it is recorded as 21.0 cm and de Beaufort (1951) recorded 21.9 cm.

Environmental Tolerance

Although there is no definitive study concerning the hardi•

ness of these fish, some information.is available from various

investigations..

Pradhan (1956) writes that R. kanaguvta can withstand low salinity of 2.04 °/oo but without stating the duration. Jones and

Rosa (1962) write that the fish are known to enter estuarine water of

Kali River, India, and ascend along the tidal current to a distance of

more than 2 km during the month of April and May when the range of sali•

nity is 29.7 - 34.6 °/oo. Moreover, they stated that the genus Ras•

tvelligev is distributed in the Tropical Indo-West Pacific Faunistic Region only; it does not extend eastward to the East Pacific Barrier.

Oceanographically the former region possesses a high surface tempera 66 ture which does not fall below 17°C in any season and at the 200 m isobath the temperature is 15°C. Pradhan and Gangadhara (1962) state that R. kanagurta appears to be more succeptible to changes in temperature than salinity. The tolerance to these factors depends upon the size of the fish in that larger fish are more resistance to a higher temperature and salinity.

Competitor and Predator

The scads (Decapterus spp.) and the oil-sardines (Sardinella . spp.) seem to be the most important competitors for food. . The fishes, like Rastrelliger, are plankton feeders. The tuna and tuna-like fishes (Katsuwonus spp. and Euthyn• nus spp.), sharks and porpoises are Rastrelliger predators.

Parasites

Unidentified nematodes were recovered from the body cavity of R. kanagurta but none from R. braahysoma. Several Indian investigators recorded trematode, cestode, and copepode parasites in R. kanagurta (Silas, 1962).

Growth

Growth is manifested as an increase in the size of an organism. The best measurement is weight. However, since accurate weighing is not easily done at sea, growth can be determine from length data; therefore, the length-weight relationship is necessary. The methods used in growth studies are generally involved: 67

J tracing the seasonal or annual increase in mean or modal length of successive age groups in the population;

- the back calculation method of Petersen (1891), i.e., by taking measurement of skeletal structures, usually scales (Lea, 1910) or otoliths (Hickling, 1933);

- by tagging, i.e., by measuring the increase in length of tagged fish between capture and recaptures.

The first method gives the average growth characteristics of a population and the last two methods give growth data for indivi-. dual fish, or the last one can also be used to provide data to supple• ment the other methods.

George and Bannerji (1964) used the first method to study the age and growth of Rastrelliger kanagurta in India and Hongskul (1972) combined the first and the third methods to study the population dynamics of R. braohysoma in the Gulf of Thailand. In this study the modal progression method as described by George and Bannerji (1964) was employed. The main difficulty in deter• mining length frequency distributions was caused by the prolonged and fractional spawning season.

Another important consideration involves determining the age of first appearance. To obtain an accurate estimation, larval and juvenile studies must be conducted. Larval collections have been done in India, but did not involve growth and age studies.

Growth Model 68 The well known Von Bertalanffy's (1934) model was employed. The method of fitting has been described by Beverton and Holt (1957), Ricker (1958), and others. In this study a computer program developed by Allen and mo• dified by Wilimovsky (1972) was used (Figure 12, 13). The length at any time t is given by:

K(t lt = L (1 - e" " V)

where: lt the length at time t L the asymptotic length that is the value of 1 assum• ing age increases indefinitely K the coefficient of growth rate at which a fish approaches its maximum length t the hypothetical time at which the length of a fish would have been zero.

Von Bertalanffy growth parameters obtained in the Indo-Paci- fic Regions show considerable variability (Table 26). The inconsis• tency among the estimations from various investigators may partly derive from the variability of samples, average modes employed, and probably the overlapping lengths in the late ages, as growth signifi• cantly decreases creating poly-age groups. The last reason may have resulted in an over estimate of the growth rate. Hongskul (1972) states that those parameters obtained from tagging data and modal progression method analysis are nearly the same. ITTING OF VON EERTALANFFY GROWTH EQUATION KEM3LNG PEREMPUAN (RASTRELLIGER BRAGHYSOM/

20.0 ,

0.0 0.9 1.8 2.8 3.7 4.6 5.5 6.4 7.3 8.3 9.2 10.1 11.0 (month)

Figure 12 Growth Curve of R. braohysoma. Abscissa-age in months; ordinate-!ength in cm. (IBM 1130, CALCOMP 565) FITTING OF VON BERTALANFFY GROWTH EQUATION KEMBUNG LELAKI (RASTRELLIGER KANAGURTA)

22.4 +

Figure 13 Growth Curve of R. kanagurta. Abscissa-age in months; ordinate-length in cm. (IBM 1130; CALCOMP 565) 71

TABLE 26 Von Bertalanffy Growth Parameters of Rastrelliger from Various Authors and Localities in the Indo-Pacific Region

Species Author-Year-Locality K L *o oo (month) (cm) R. kanagurta George and Banerji (1964) - Cochin 0.43 21.77 - Calicut 0.26 23.26 - Karwar 0.36 22.40 Pooled 0.30 22.84

R. kanagurta Sudjastani (1973) - Java Sea 0.23 0.92 23.89 (0.02) (.13 SE) (.52 SE) (SE)

R. negleotus (braahysoma) Hongskul (1972) - the Gulf of Thailand 0.28 -0.03 20.91

R. braahysoma Sudjastani (1973) - Java Sea 0.19 0.10 22.92 (0.02) (.18 SE) (.76 SE) (SE) 72 The estimated parameters of the Von Bertalanffy model of from the Java Sea are:

R. kanagurta R. braahysoma

K 0.2316 (0.0176 S.E.) 0.1885 (0.0187 S.E.) 0.9182 (0.1294 S.E.) 0.0993 (0.1817 S.E.) month *0 L 23.8886 (0.5186 S.E.) 22.9170 (0.7638 S.E.) cm

The Point of Inflection on the Growth Curve

Theoretically a stabilized fish population has its maximum yield influenced by the nature of growth and depends on the rates of natural and fishing mortality (Tester, 1952). As it is known that a fish has maximum change in weight at the inflection point, then, it is necessary to know the position of the inflection point on the growth curve. Tester describes three types of growth curves, the growth curve with the inflection point in the early of life, about mid-life, and late in life. Rational management and exploitation of a fish species requires knowledge of the inflection point position in the growth curve primarily in its relations to the age at sexual maturity. Ssentongo (1971) generated a formulae that derived from the Von Bertalanffy's growth equation to determine the age at the inflect• ion point. It is: 73

t. n = 1/K In b + t i.p. o where: t. is the age at the inflection point. I • [J • b is the length-weight exponent

The inflection point of Rastrelliger kanagurta is at the 5.9 months (17.8 cm TL), whereas for R. braahysoma it is at 5.7 months (15.1 cm TL). Both species have inflection points early in life, meaning they attain their maximum growth increments before they reach the age at sexual maturity (7.0 and 7.5 months of age for R. kanagurta and R. braahysoma respectively). Thus, the exploitation of the

Rastrelliger should be beyond the inflection point to allow sufficient spawners (certain age classes). The natural mortality coefficient of the fish is high, about 0.4, so that kind of exploitation could mean a loss of biomass. However, the results of the Ricker Yield Model suggest that at the present conditions where the age at first capture

(t£) is 3.0 months for R. braahysoma and 4.0 months for R. kanagurta, the exploitation will hot endanger the populations since the stocks exhibit strong 7.0 - 8.0 months age classes (Tables 34, 35 and 36).

Behaviour

Hardenberg (1938) states that Rastrelliger are pelagic and migrate. Their migration in the Java Sea follows the migration pattern of the scad (Deoapterus spp.) one of their competitors for food, but is generally later by one or two weeks. He describes that at the end of 74 the West Monsoon a stock of oceanic Rastrelliger is present. At the beginning of the East Monsoon the water of the Java Sea begin to flow in a westerly direction and the Rastrelliger moves off in a westerly direction and disappears. After some weeks a new stock enters the Java Sea through its eastern entrance. At the end of the East Monsoon the reverse happens and two new stocks enter the Java Sea, one from the north west out of the South China Sea and one from the south west out of the Indian Ocean. An attempt was made to prove this hypothesis. As was described in the previous section, there is geographical variation in R. kanagurta in head depth and dorsoventral depth. I suspect that these differences suggest that the two samples might come from two different populations. Secondly, there are two spawning seasons in this area, i.e., from October to February (in the West Monsoon) and from June to September (in the East Monsoon). Moreover, the catch per unit of effort and total effort relationship (Figure 14) suggests that there are two different populations involved in one calendar year. The first population was present in the months of January, February, March, and reappeared in September, October, November and December; while the second population was present in April, May, June, and July. These evidences support the hypothesis of Hardenberg (1938). In addition to these migrations, Rastrelliger appears to exhibit local movement. Pradhan (1956) writes that in Karwar, India, during a north-easterly wind, R. kanagurta schools enter inshore waters. Jones and Rosa (1962) state that schools of this fish usually move 75

CPUE |- 2001

i 1 \ i 1 1 1 5 10 15 20 25 TOTAL (X 1000) EFFORT

Figure. 14. Relation^between Total Effort (Total Catch/Catch per unit of effort) and Catch Per Unit of Effort of R. kanagurta from the north coast of Java, in 1971 (arable-numbers represented months).-

West Monsoon East Monsoon 76 with the current of water at high tide. When there is a strong easterly wind the schools come close to the shore through deeper layers of water.

The migration of R. braahysoma was observed in Tg. Satai area. This fish always disappears during the months of May to October. It seems they migrate to somewhere nearby this area to spawn, since their gonads in April are mostly mature. The local movement has also been observed in the Gulf of Thailand area (Hongskul, 1972). The reason for this phenomenon is not yet clear, but Harden- berg (1955) states that this fish tends to follow the highest densities of plankton.

Age

The ability to determine the age of fish is an important tool in fisheries biology and management. The evaluation of age allows one to understand the age composition of a fish population and to determine the role of particular age classes in the fluctuations. The existing principle of age determination is based on the recognition of seasonal changes in the form and composition of skeletal structures or other hard parts which have been named growth marks or growth checks. Those marks are a result of fluctuations in the growth of the. fish. The ease and accuracy in applying the principle depends upon its existence and regularity. Research on this problem started almost 77 a hundred years ago. Reibisch (1899) was among the early investigators to use otoliths, Heincke (1904) used bones and Dahl (1909) has described the method of age determination in detail. It is known that the growth rate of fish is not uniform, even when the.entire life cycle takes place in an almost steady state environmental condition such as that found in tropical waters. There is also the so-called seasonal variation in growth rate. This variation will be expressed in the hard parts of the fish such that periods of rapid growth will be indicated by wide zones and slow growth by narrow zones. Generally, in the temperate zone, where in winter the growth rate is at its minimum, the fluctuating periodicity is annual; whereas in tropical waters it is completely different. As early as Hoffbauer's (1898) work on carp scales, the use of scales for age determination has depended upon the appearance of recognizeable yearly growth rings called annuli. Annuli have a differ• ent appearance in different species. In many species false annuli or accessory marks have been observed and sometimes they are difficult to distinguish from true annuli. Van Oosten (1957) states that these false annuli can be attributed to growth cessation caused by disease, parasitism, injury, starvation, or a temporary drop or rise in tempera• ture or some other similar unfavourable environmental changes. However, the causative factors in the formation of these growth checks have not yet been determined.

As has been stated before, scales and otoliths will be used for age determination. On the scale the fast growing zones are represented by wider sclerites or circulii and the slow growing zones 78 by narrow sclerites arranged close together in the form of bands or rings. The literature which deals with temperate fish species describes that these rhythms of growth are seasonal and that there is a close relation between periodic structure of the fish hard parts and the growth of the fish. In several instances those hard parts show the secondary rings or false annuli described above in addition to the normal annual rings. Some doubts have been raised as to the qualify• ing characters of an annual and a secondary ring. This leads to the some uncertain assumptions in the quality of the causative factors that are responsible for the formation of the growth checks of a fish in tropical waters.

The classic theory that growth rate is greater during the period of higher temperature is well known. Cutler (1918) states that temperature was a controlling factor of sclerite width in the scale of

Pleuroneotes. A higher temperature produce wider sclerites correspond• ing to the summer zone and lower temperatures produced narrow sclerites or the winter zone.

Dannevig's (1925) experiments gave the contrary results, that is, that the sclerite width was greater at lower temperature and lower feeding. Dannevig (1925), and Graham (1929) state that there is a marked correlation between sclerite width and growth rate caused by an inherent rhythmical response.

The narrow zones on the scales and otoliths of cod (Dannevig,

1933) and the transparent zones in the otoliths of hake (Hickling, 1933) have been observed to be found during the last part of the summer and autumn in the majority of the specimens; whereas in several other 79 fishes these growth checks are laid down during the period of lowest temperature. This contradiction in the relation of temperatures to the formation of the annual growth checks throws doubt on the possible influence of temperature in the phenomenon of periodicity of the structure of the hard parts of fish (Menon, 1950). Gray and Setna (1931) found that Salmo irideus [S. gaivdnerii) which had been fed continuously throughout the year did not show any well defined summer and winter zones Brown (1946) observed that in specimens kept under controlled temperature, food, light, flow of water, and amount of living space, composition and aeration of water, the annual periodicity is markedly visible on the scales. Fage and Veillet (1938) suggest that the maturation of gonads was generally followed by a decrease in the growth rate. Menon (1950) speculates that an inherent physiological rhythm is a more probable causative factor in the formation of the growth checks. Chidambaram et al. (1952) state that there is a decrease in the rate of feeding and the amount of food consumed during the maturation of gonads. Food is an important factor in the growth of a fish and maturation of gonads is a momentous physiological event in the growth history of the animal. The simultaneous occurrence of reduced feeding and gonad maturation may play an effective part in the periodic formation of the growth checks." Schneider (1910) suggests that the decrease of feeding at the spawning time, associated with the drain on the reserves to supply material to the gonads, is a heavy excess of output over input of materials (in/ Hickling, 1933). 80 The growth checks similar to those found in temperate fishes have been reported in the tropical fishes by Hornell and Naidu (1924), Devanesan (1943), Nair (1949) and others. However, the validity and interpretation of these checks remains uncertain. A detailed study of the life history of the oil-sardine (Sardinella longioeps) by Hornell and Naidu (1924) gives interesting details on the question of the age and growth rate of the fish. They studied the growth rate by size analysis and computed the age by Petersen's method in addition to scale reading. Their works lead several Indian scientists to determine age and growth of Rastrelliger kanagurta.

Seshappa (1958) states that R. kanagurta greater than or equal to 23 cm TL exhibit clear rings on the scales. He believes that these are spawning marks, and thus could be useful in age studies. Since this fish reaches sexual maturity at 20 cm TL (Chidambaram et al., 1946) or at 22.4 cm TL (Pradhan, 1956) there is no reason why the rings only exist at size 23 cm or above if the causal factor is spawning. More studies must be conducted to decide whether those rings are useful for age determination of this fish. In general, the absolute age determina• tion of tropical species has not yet proven to be successful. A review of the literature suggests that not enough work has been done on the physiological factors responsible for the formation of growth rings. At present, very little is known of the basic chemistry and histology of this phenomenon. As has been stated above it is not yet possible to determine the absolute age of tropical species, i.e., Rastrelliger, using the 81 growth checks. In spite of the inaccuracy, the statistical method demonstrated by Petersen (1891) and others remains the best technique to obtain the relative or the statistical age of this fish. This method has been observed to be satisfactory for fisheries work involv• ing lower age classes provided there are relatively large samples.

In this study the statistical age of Rastrelliger was deter• mined by the modal progression method as described by George and Bannerji (1964). By following, for several seasons, the modal progression of the average length from the time of first appearance in the fishery, von Bertalanffy growth parameters can be estimated and the age-length key can be generated. Rastrelliger kanagurta exhibit the following characteristics:

1. the length frequency distribution data indicates that a mode of 14.5 cm appeared in June and mode of 14.0 cm appeared in November (Figure 16); 2. the maturity stages data show that the largest percentage of sexually mature individuals was found in January and May (Figure 10) ; these data suggest that the 14.5 cm mode which appeared in June and the 14.0 cm mode which appeared in November must represent the broods that hatched in about February and June respectively. Therefore, the R. kanagurta of 14.0 - 14.5 cm length are about 5 months old. 82 R. braahysoma:

1. the length frequency distribution data of November exhibit modes of 10, 11, 12, and 16 cm (Figure 15); 2. the maturity stages data of March and April indicate mostly sexually mature where 100% of individuals were found in mature gonad conditions (Figure 11); 3. this fish always disappears in May and reappears at the end of October and is never caught during this interval (in Tg. Satai) These evidences suggest that the polymodal population was a result of a prolonged spawning season that lasts from May to September. Therefore, the smallest mode must come from the latest hatched brood, viz., the 10 cm R. braahysoma has to be 3 months old. The Von Bertalanffy growth parameters from both species have been described in the previous section. By employing those parameters and using the age-length formulae derived from the Von Bertalanffy equation as:

t = 1/K ( -In (1 - lt/L)) + tQ the age length key can be generated (Tables 27 and 28). The results for R. kanagurta indicate that the calculated lengths have higher value than the observed modes in younger groups but are approximately equal in oTder age groups. In R. braahysoma, however, a very slight difference exists. 83 Age and Size Composition

E. kanagurta of 10 months age class (21 cm TL) were dominant in the 1972 catch (Table 39 j_n Appendices). The fish older than 18 months (23 cm TL) were rarely represented. The range of the samples was from 4-24 months of age (12.5 - 23.5 cm TL); generally the commercial catch is from 6 to 12 months old (17.0 - 22.5 cm TL). George and Bannerji (1964) states that the commerical fisheries for this fish in India depend mainly on fish ranging in size from 18 - 22 cm TL, i.e., the fish which are in the 0-year completing its first year of life through the fishery. Manacop (1955) states that R. kanagurta caught in the Philippine has an average length of about 25 cm. Druzhinin (1968) recorded the fish caught in Burma waters con• sists mainly of 19.1 - 21.0 cm FL (or 21.2 - 23.3 cm TL, converted; whereas Druzhinin and Myint (1968) recorded a range of 15.6 - 22.5 cm FL (or 17.3 - 25.0 cm TL, converted) in their samples in the same area, Mergui Arch., Burma.

In this study E. braahysoma of the 9 months age class (18.5 cm TL) were dominant in 1971/1972 catch; fish older than 18.0 months of age (22 cm TL) were rarely caught (Table 38 j_n Appendices). The range of the samples was from 4"- 21 months of age ( 10.0 - 22.5 cm TL ); but generally the fish in the commercial catch range from 7 to 12 months old (17.0 - 20.0 cm TL). Hongskul (1972) observed a range of 10.0 - 23.0 cm TL in the Gulf of Thailand fishery; however, the fish caught were generally within the 14.0 - 22.0 cm TL range. Manacop (1955) recorded an average 84 TABLE 27

Age-Length-Weight Key of B. kanagurta from the Java Sea

Age Computed Length Observed Mode Computed Weight (Month) (cm) (cm) (g)

1 4.93 - .99 2 8.85 - 6.39 3 11.96 - 16.71 4 14.43 - 30.43 5 16.38 14.5 45.60 6 17.93 16.8 60.87 7 19.16 18.2 75.23 8 20.14 19.3 88.22 9 20.91 20.8 99.45 10 21.53 21.2 109.17 11 22.02 21.6 117.30 12 22.41 22.0 124.07 18 23.52 - 144.77 24 23.79 - 150.15 36 23.88 - 151.97 85 TABLE 28 Age-Length-Weight Key of R. braohysoma from Tg. Satai

Age Computed Length Observed Mode Computed Weight (Month) (cm) (cm) (9)

1 3.93 _ 1.33 2 7.19 - 7.56 3 9.89 10.0 18.94 4 12.13 12.0 34.09 5 13.98 13.5 51.31 6 15.52 15.7 69.97 7 16.79 16.3 86.95 8 17.84 17.9 103.55 9 18.71 18.5 118.76 10 19.44 19.5 132.60 11 20.03 20.0 144.53 12 20.53 - 155.16 18 22.15 - 193.10 24 22.67 - - 36 22.89 - - Figure 15. Length-Frequency Distribution of R. braohysoma from Tg. Satai in the 1971/1972 fishing season. 87

H 1 1 1- H 1 1 l- 0ct.71 May.72 2a. a. 40 Nov\71 Jun.72 20-

o- /\ \

•40..Dec,7 1 Jul.72 20- • a. 40-- Jan.72 Aug.72 20-

Q. 40- Sep.72 20 Feb.72 a. 40- Mar. & Apr.72 Oct.72 20- 0 —i 1 1—-—i \ i—i It 16 18 20 $2 tk cm 14 16 18 202224 TL(

Figure 16 Length-Frequency Distribution of R, kanpgurtn from the north copst of JPVB in the 1971-1Q72 fishing sepson. 88 of about 18.0 cm TL in the Philippines waters and Druzhinin (1968) recorded a dominant group of 18.1 to 21.0 cm FL (20.3 - 23.6 cm TL, converted) in Burma waters. In the same location Druzhinin and Myint (1968) recorded a range of 16.6 - 22.0 cm FL (18.6 - 24.7 cm TL, con• verted) in their samples.

The above data suggest that the Rastrelliger fisheries in the Indo-Pacific Regions all involve the same size range of fish and it can thus be concluded that these fisheries depend on a single year class, i.e., one year olds.

Age and Size at First Capture

The age and size at first capture of R. kanagurta was 4 months of age (12.5 cm TL) and for R. braohysoma it was 3 months old (10.0 cm TL) (Figure 15, 16). ' Jones and Rosa (1962) state that the smallest dominant group was 12.0 cm TL for R. kanagurta in India; while Hongskul (1972) uses age at first capture 4 months as a parameter in his study of R. braohysoma population dynamics in the Gulf of Thailand. No other record of this parameter is available in the Indo-Pacific Regions.

Age and Size at Maturity

The importance of this parameter is related to the need for adequate spawning stock to assure a continued supply of young. The discussion has been conducted on pages 59 and 71. 89 Maximum Age and Size

In this study the maximum length of R. kanagurta was 23.89

cm TL (0.52 cm S.E.) and for R. braohysoma it was 22.92 cm TL (0.76 cm S.E.). Both being over 3 years of age (Table 26, 27, 28). Comparison within the Indo-Pacific Regions were described in the previous section.

The Length-Weight Relationship

In fishes the length and weight relationship can be adequately represented by:

W = a Lb where b is an exponent with a value between 2 and 4.

If b = 3.0 it indicates isometric growth, while b values other than 3.0 are indicative of allometric growth.

The length-weight relationship of R. kanagurta was determined separately for males and females, sexually mature, immature and undiffer• entiated. The total length TL of samples ranged from 10.0 to 22.5 cm. The b values obtained are listed in Tables 29 and 30. Comparisons within the Indo-Pacific Regions, i.e., Indian waters and the Gulf of Thailand show that the b values of this fish from the Java Sea area are lower. It is well known that this coefficient differs between species and also often differ between population within species. The differences TABLE 29 The Length-Weight Exponential (b) Value of R. kanagurta from the Java Sea Identification B Variance a Variance ANC0VA (the Signifi• (In) (In) cance of F Value) Male 3.134 0.0068 -12.15 0.1930 F(c.v.) = - F(b) = - Female 3.013 0.0072 -11.49 0.0332 F(a) =*

Sex Unidentified 3.175 0.0013 -12.38 0.0332 F(c.v.) = - F(b) = - Sex Immature F(a) = - (mixed) 3.189 0.0062 -12.44 0.1776

Sex Unidentified 3.175 0.0013 -12.38 0.0332 F(c.v.) = - F(b) = * Sex Mature (mixed) 3.010 0.0037 -11.48 0.1063 F(a) = **

Female, Maturity Stage < III 2.933 0.0073 -11.08 0.2084 F(c.v.) = - F(b) = - Female, Maturity F(a) = ** Stage > III 3.078 0.0687 -11.82 0.0199

All Mixed of R. kanagurta 3.193 0.0004 -12.46 0.0106 All Mixed of R. braahysoma 2.880 0.1266 -10.29 0.3325 Note: *is 5% level of significance. ** is 1% level of significance. ^ o TABLE 30 The Length-Weight Exponential (b) Values from Various Author in the Indo Pacific Region of the Rastreliger

Identification Author (Year) b Variance a Variance R. kanagurta: Rao, K.V.N., (1962) Waltair, India Male 3.2628 - .004983 - Female 3.2785 .004874

R. kanagurta: Pradhan, L.B., (1956) 3.1737 - .005978 Karwar, India

R. kanagurta: Vanichkul, P. and V. Hongskul (1963), Gulf of Thailand Male 3.7633 - -6.7081 - (log) Female 3.0375 -5.0244 (log)

R. neglectus Vanichkul, P. and V. Hongskul (1963), Gulf of Thailand Male 3.1463 - -5.2417 - (log) Female 3.1235 -5.1819 (log)

| R. braohysoma Jones and Silas (1962) 3.5779 - -6.0421 - Andaman Is., India R. kanagurta Jones and Silas (1962) Andaman Is., India 3.3087 - 5.5390 - (log)

vo 92 may be due to sex, maturity and season. Vaznetsov (1953) states that during development fish pass through several stanzas, each of which may have its own b value. Tesch (1968) states that within any stanza the b value will often be nearly constant throughout the year or throughout a series of different environments, whereas the a_ value will vary seasonally, and between habitats. The analysis of covariance indicates that b differs signi• ficantly (5%), in R. kanagurta, between sexually-unidentified and sex• ually-identified (mixed) specimens (Table 29). There is no difference of b values due to sex or sexual maturity stages. The coefficient a_, by contrast, show significant differences due to the above evidences (Table 29). These two conditions suggest that the fish exhibits at least two stanzas during its life; the first is while it is young and sexually undifferentiated. The second stanza begins as soon as its sex can be identified which is probably a few months before it reaches maturity. In many species several stanzas are completed during embryonic and larval life, and all subsequent growth comprises a single stanza (Tesch, 1968). Hecht (1916) states that in fish the body form is laid down very early in life and is maintained within narrow limits throughout the period of growth, and thus has uniform but indeterminate growth. Ssentongo (1971) says that this kind of growth applies only to external surfaces for Kellicot (1908) shows that in a dog fish the brain and viscera differ in their growth rates in much the same way as in higher vertebrates. To obey Hecht1s law Ssentongo states that the b 93 value should be within a 2.5 - 3.5 limit, otherwise the b value cannot apply over a wide range of length without causing profound changes in body form. Furthermore, he suspects that these values came from biased samples.

Recrui tment

Recruitment is generally defined as the number of fish of a single year group entering the exploitable phase of a stock, or, as the number of fish of a single year group arriving on a fishing grounds. It is important in fisheries management as an index of abundance that is used for prediction, and has been discussed in detail by Ricker (1954 , 1958), Beverton and Holt (1957), Gushing (1973), and others.' 1 Recruitment in Rastrelliger has not yet been studied. Whether it occurs early or late in life is determined by the relative proximity of the nursery grounds to the fishing grounds. This relationship is not

yet understood. However, to determine the age at recruitment (tr) the most direct information available is that obtained from landing samples. The estimated t will not be higher than the true value, since rejection of the smallest fish will not occur. This is caused by the nature of the market and fisheries systems in the area, where neither mesh size nor legal fish size regulations exist, and all sizes of fish are marketable. The data suggest that the t for R. braahysoma was 3.0 months of age (10.0 cm TL) and for R. kanagurta was 4.0 months of age (12.5 cm TL) (Figure 15, 16). 94

The change in recruitment seems to exert more influence than

does fishing pressure on stock fluctuations of Rastrelliger as this fishery depends on a single 0-year class.

The stock recruitment relationship which is necessary to

relate the abundance of pre-recruit phase to age class strength is not yet established. Therefore, the increase in fishing intensity

should be conducted cautiously.

Survival Rates

The method of a single catch curve analysis as described by

Robson and Chapman (1961) was employed (Figures 17 and 18; Table 31

and 32). This method has been shown by Bayliff (1966) to be better

in estimating this parameter than other methods.

The survival rates of R. kanagurta for three different fishing seasons were calculated in monthly periods.

In West Monsoon 1971 the survival rate was 0.3348 (variance =

0.0010); in the East Monsoon 1972 was 0.7154 (variance = 0.0020), and

in the West Monsoon 1972 was 0.3540 (variance = 0.0020). A marked difference between the survival rates in the West and East Monsoon suggests that they are two different populations, which again supports

Hardenberg's hypothesis (1938).

Assuming that the fishing and natural mortalities are constant, then there was an increase in the recruitment of 5.47% in the 1972

West Monsoon's population.

The survival rate of R. braahysoma from Tg. Satai in 1972 fishing season was 0.4411 (variance = 0.0002).

Hongskul (1972 reported that the average of the instantaneous 95 TABLE 31 Estimation of Survival Rates of R. kanagurta in the Java Sea by the Method of Robson and Chapman (1961)

1. November 1971

Age-Month Frequency Coded Calculation Age

7 . - - T = 10+2(7)+3(2) = 30 n = 41+10+7+2 = 60 8 m = 2

T 30 9 - 5 18 s = n-m+ T - 60-2+3 0 = 0 34 10 41 0 11 10 I variance = s^"s^ = 0.0026 n(l-s3) 12 7 II 18+ 2 III

2. December 1971

Age-Month Frequency Coded Calculation Age

7 - T = 14+2(5)+3(2) = 30 n = 51+14+5+2 = 72 8 18 m = 2

9 - „ _ 30 _ n ~n 36 72-2+30 10 51 0 11 14 I variance = •30^",3^2= 0.0021 72(1-.30^) 12 5 II 18+ 2 III 96

TABLE 32 Estimation of Survival Rate of R. braohysoma in Tg. Satai Area (1972)

Age Coded (Month) Frequency Age Calculation

9 450 0 T = 786

10 327 I n = 998

11 206 II m = 2

12 13 III s = 0.44

18+ 2 IV variance = 0.0002

0.8185 0.5589 I 1 1 1 1 1 1 1 1 1 1 1 1 1 K 5 6 7 8 9 10 11 12 H 16 18 AGE

Figure 17. Catch curves for R. kanagurta of the north coast of Java, A. West Monsoon 1971; B. East- Monsoon 1972: C. West Monsoon 1972. Abscissa- age ln months; ordinate- logarithm of the %- frequency. 98 ln %f

3f

2+

It

01

-14-

k 5 67 8 9 10 11 12 14 16 18 AGE

Figure. 18. Catch curve for R. brachysoma of Tg. Satai in 1971-1972 fishing season. Abscissa- age in months; ordinate- logarithm of the % - frequency. 99 total mortality (Z) during 1962-1968 of R. braohysoma in the Gulf of Thailand varied between 0.7028 - 1.3470, with an average value of 1.0124 along the western coast and the inner Gulf). Assuming the natural mortality rates of this species is equal then the lower instantaneous mortality (Z = 0.8185) in the Tg. Satai area is probably due to a much lower fishing pressure as compared with the Gulf of Thailand.

Mortalities

There are a number of approaches that can be taken to estimate mortality of exploited fish populations.. Tagging of fish and subsequent recaptures is the best field technique that can be employed in the calculation of mortalities and other population parameters. Monitoring of the catch and fishing effort is another useful technique since catch per unit of effort is approximately proportionate to stock abundance. Total mortality can also be inferred from the age compositions of the catch. This approach was employed in this study by utilizing the method described by Robson and Chapman (1961). The separation of total mortality into its components, nature and fishing mortalities, is difficult if fishing represents only a small fraction of the total mortality (Cushing, 1968). Assuming that natural mortality of R. kanagurta is constant throughout the year, Gull and's (1969) method can be used to estimate these parameters (Table 33). He states that if the amount of fishing 100

TABLE 33 Estimates of Mortalities of R. kanagurta by the Method of Gulland (1969)

November 1971 December 1971

s = 0.34 = 0.30 i = 1.0789 (or Z) = 1.2040 f = 5,853 (total effort) = 6,923

Gulland's equation Z = q f + M

1.0789 = q x 5,853 + M 1.2040 = q x 6,923 + M then: q = 0 00012 M = 0 37 (natural mortality) fishing mortality = 0.70 fishing mortality = 0.83 101 changes this will result in a change in total mortality. He shows that plotting estimated total mortality Z against fishing effort (f) values yields a straight line with a slope q(= the coefficient of catchability), and an intercept M on the y-axis.

The estimated survival rate of R. kanagurta in November 1971 was 0.34 (rounded value; variance = 0.0026) gives an instantaneous total mortality Z of 1.08. In December 1971 it was 0.30 (rounded value; variance = 0.0021) with a corresponding Z of 1.20. The total effort f (= total catch divided by catch per unit of effort) were 5,853 and 6,923 unit efforts for November 1971 and December 1971 respectively (Table 41 in Appendices). By employing Gull and's method described above, those data of

R. kanagurta give an estimate of q = 0.00012, F = 0.70 in November 1971 and F = 0.83 in December 1971, and an instantaneous natural mortality M of 0.37.

The natural mortality and growth ratio (M/K) of R. kanagurta of the Java Sea then was 1.6. Bannerji (1970) suggests that this ratio for R. kanagurta population in the eastern coast of India ranged from 1.5 to 2.5 (with various values of K and an estimated value of M = 0.65). The M/K value of this fish from the Java Sea compared favourably with the M/K values obtained by Bannerji in Indian waters.

Hongskul (1972) estimates the M/K ratio for R. braohysoma in the Gulf of Thailand to be 2.0. If the R. braohysoma population from Tg. Satai has the same M/K value as in the Gulf of Thailand, the natural mortality M and fishing mortality F values will be 0.38 and 0.44 respectively (K was 0.19; and Z was 0.82). 102 These estimated parameters will be used later in population dynamics studies.

Dynamics of Populations

The results obtained as mentioned in the previous sections indicate the characteristics of the Rastrelliger populations in the Java Sea. They possess high values of growth and natural mortality rates. The stock recruitment relationship cannot be determined in this study, thus only the yield per recruit model has been used. The model is based on the assumption that catch obtained from a year class throughout its fishable life span is proportional to its initial numbers when recruited.

Beverton and Holt Yield Model

Beverton and Holt (1957) have derived a yield model that is very useful for evaluating the potential yield of a fishery. Their equation is:

3 ;-nK(tc-t0) Y/R = FW e-^W Z (1-e ,-(F+M+nK)(tx-tc) n=0 F+M+nK

The basic assumption is that growth is isometric.

Y yield in weight, R number of recruits entering the fishery at age t

W oo maximum weight of an individual fish, hypothetical age of zero length, ortpis age at time of recruitment,

or tp, is age at first capture, age of exit from the fishery, 103 K the Von Bertalanffy growth parameter, U is 1,-3, 3, and -1 for n = 0, 1,2, and 3 respectively.

It is well accepted that the growth of many fish is not isometric. For such growth the calculation of yield can be conducted by using the Incomplete Beta Function that was described by Jones (1957) and the equation was expressed by Wilimovsky and Wicklund (1963) as:

2 Y = F/K R W e ^"^) { [x, P, Q]-[Xr P, Q] } where: Z instantaneous total mortality,

X e~K(tc-t0)

Xi e-K(t-t0)

P Z/K Q 1 + b; bis the length-weight exponent.

Wilimovsky and Wicklund (1963) prepared a table for this function. Employing the Beverton and Holt (1957) model, the yields were calculated and isopleth diagrams were constructed (Figures 19, 20, 21, 22 and 24).

R. kanagurta:

tno = 0.92 months,

tr = 4.0 months, t = 4.0 months, t = 18.7 months, K = 0.2316

Wm = 152.0 grams 104 R. braohysoma:

tQ = 0.10 months

t r = 3.0 months t = 3.0 months t = 21.3 months K = 0.1887 = 213.0 grams.

The model was simulated with various parameter values, the fishing mortality F ranged from 0.1 to 1.5 with 0.1 increments; the natural mortality M ranged from 0.1 to 1.0 with 0.1 increments; and t from 4.0 months for R. kanagurta and 3.0 months for R. braohysoma to 12.0 months with one month increments. Detailed discussion on the concept of yield models have been given by Beverton and Holt (1957), Ricker (1958), Schaefer and Beverton (1963), Gulland (1969), and others. In an exploited fish population the fish are recruited to the fishery at age t but are not caught until the age at first capture, t . In Rastrelliger fisheries in the Java Sea, where there is no fishing regulation such as legal mesh or fish size, the t is equal to t . This condition of the fishery is named a "knife-edge" fishery.

Observation on yield of R. kanagurta as revealed by the isopleth diagrams are given below (Figures 19, 20 and 21). The greatest yield of R. kanagurta can be obtained if the size of first capture is 15.5 cm TL with a fishing mortality of 1.4 105 (the natural mortality was 0.4). The yield in weight per recruit in this condition is 22.4 g; and at present where the fishing mortality is 0.8, the yield in weight per recruit is 21.5 g. The age at first capture at present is 4.0 months (with F = 0.8) and the yield per recruit is 21.3 g. The fishing intensity can be increased without affecting the fishery until the maximum yield per recruit is reached at a fishing mortality of 1.3. This means that at maximum fishing pressure, the increase of 62.5% fishing mortality will cause the yield per recruit to increase by 1.6%. A greater increase of fishing mortality or fishing pressure of 75% that gives a yield per recruit increase of 4.2% can be achieved if the fishery started to catch the fish at 15.5 cm TL (or 4.5 months of age). An estimated natural mortality of 0.38 and fishing mortality of 0.44 (see the previous section) were employed in constructing the isopleth diagram of R.. braahysoma of Tg. Satai (Figures 22, 23 and 24). Under the present condition where the fishing mortality is 0.44, the natural mortality is 0.38 and the size at first capture is 10.0 cm TL, the yield in weight per recruit is 18.0 g. The highest yield per recruit of 20.8 g can be obtained if the length of first capture is 12.0 cm TL and the fishing mortality is 1.5. The fishing pressure can be doubled without harming the stock since R. braahysoma has an asymptotic yield per recruit to fishing mortality relationship diagram for natural mortality greater than 0.4. Under this condition the yield per recruit will gain an increase of only 15.6%. 106

I 1 1 1 1 1 1 > 1 1— 1 1 1 1 )—— .1 .2 .3 .4 .5 .6 .7 .8 .91.0 .1 .2 .3 .4 .5 F

Figure 19. Yield isopleth diagram of R. kanagurta. Yield in weight per

recruit (Yw/R) was at an intervals of 2 grams; natural mortal•

ity (M) was 0.4, tc = 4.0 months. The fishing mortality F = 0.8 was in 1971. 1 1 1 1 1 1 1 1 —| 1-

-1 *2 «3 '«5 .6 .7 .8 .9 1.0' .1 .2 .3 .4 .5 F

Figure 20. Yield per recruit as a function of fishing mortality of R. kana• gurta. The natural mortality M range from 0.05 to 1.0; t = t = 4.0 months. The fishing mortality F = 0.8 was in 1971. c r Figure 21. Yield per recruit as a function of fishing mortality of R. kana• gurta; the natural mortality (M) range from 0.05-1.0: t=45 and t = 4.0 months. c 109

I 1 1 1 1 1 1 : i 1 1 1 1 1 1 1 -I 1 .2 .3 .4 .5 .6 .7 .8 .9 1.0 .1 .2 .3 .4 .5 F Figure 22. Yield isopleth diagram of E. bvachysoma. Yield in weight per

recruit (Yw/R) at an interval of 1.0 gram. The natural mortal ity (M) = 0.4 and the age at first capture t = 3.0 months. Figure 23. Yield per recruit as a function of fishing mortality (F) of R„. braahysoma from Tg. Satai; with t = 3.0 and t = 3.0 months, the natural mortality (M) ranged from 0.1 to 1.0: Figure 24. Yield per recruit as a function of fishing mortality of R. braahysoma. The natural mortality M range from 0.1 to 1.0; t = 4.0 and t = 3.0 months. 112

As has been stated above, the highest yield per recruit increase can be obtained by increasing the size at first capture from 10.0 cm to 12.0 cm TL. However, since the estimation of parameters

were drawn from the H. braahysoma situation in the Gulf of Thailand

(Hongskul, 1972), these predictions need verification with original data from these areas.

The Incomplete Beta Function gives unbiased yield estimates

for fish with allometric growth. It was described by Jones (1957) and

an equation was generated by Wilimovsky and Wick!und (1963) from the Beverton and Holt Yield equation. The differences in yield absolute values obtained are caused partly by log transformations and probably the rounded figure of the instantaneous total mortality Z. However, the absolute yield value is not of primary importance in this study but it responded to the changes of parameters.

Ricker Yield Model

Ricker (1958) gives a yield model which is based on an empirical growth relationship. It permits simulation of growth and mortal• ities when they cannot be expressed in a single function of time. This model is probably the best yield model available that can be applied to tropical species which possess a short life span, seasonal growth, and variable fishing intensity over a fishing season. This 113 has been demonstrated by Bayliff (1966) for anchovieta, Cetengvaulis mysticetus, in the Gulf of Panama. The equation is:

+ 9 1 ( PT*W1 e T " T)

i

T=TR R where: Y£ equilibrium yield under given conditions, g instantaneous rate of growth, i instantaneous rate of total mortality, p instantaneous rate of fishing mortality, q instantaneous rate of natural mortality, T time interval (months), T^ the first period under consideration, T the last period under consideration, W weight of an individual fish during that period.

The assumption of the model are:

1. growth and mortality rate are independent of population size; 2. catchability is constant throughout fishing season; 3. the population is stable.

A computer program by Wilimovsky (1972) was used. The results appear on Tables 24, 35 and 36. 114

The total equilibrium yield of R. kanagurta for an instantan• eous fishing mortality of 0.8 and natural mortality of 0.42 was 1.35 g per gram recruit. The fishing mortality 0.0 for age classes 11, 12, 13, and 14 months old is related to unavailability of these groups as they were leaving the fishing ground in the East Monsoon (for West Monsoon population) and were being replaced by another new stock that enter the fishing ground. This situation likely serves as a "natural" closed fishing season for the fishery, which will strengthen the incoming stock on the fishing ground. The same situation occurs with R. braahysoma in Tg. Satai area where the fish are unavailable during the months of May to October. The total equilibrium yield for a fishing mortality of 0.48 and a natural mortality of 0.34 was 1.96 g per gram recruit. If the fishing is doubled, the yield will increase to 2.98 g per gram recruit with a decrease in the mode length of the biomass from 21.3 cm TL to 20.9 cm TL. The increase in fishing pressure tends to decrease the mean size (length) of the biomass. YTFl r> VQDFL = AR 1 Tr-iVFT I C r.SA.'i

AGE MEAN MEAN G 0 P G-P-Q WEIGHT STOCK MEAN YIELD LENGTH WEIGHT CHANGE BICMASS

4,00 144. C. 1C00. 93. V 0. 40 0.0 3 0.C60 C.29S 1.347 1173. >— 5.00 164. 0. 1347. 0.23 0.03 0.030 C.174 1.190 1475. lis. i 6.C0 179. 0. 1604, 0.21 0.03 0.030 0.103 1.114 1696. 135 . 7.CO 192. 0. 1737. 0.15 0.02 0.0 = 0 0.042 1.04 3 1S26. .146. 6.00 2C1 . 0. ISo:.. 0. 11 0.C3 o.oeo 0.2 09 1.009 1374.' " 149. 9.00 209 . 0. 16S2. 0. 09 0.03 -0.016 0.953 1567 . 149. 10.00 21 = . 0. o.oeo 1852. 0.07 0.02 0.000 0.041 1.0-2 1B91. 0. , 11.CC 22C. 1921. c. 0.05 0.03 coco 0.C26 ' 1.026 1936. 0. 12.00 224. 0. 19S2. 0. C4 0.02 O.CCO 0.012 1.012 1994. 0. 13.00 227. c. 2C07. 0. 04 0.03 0.000 0.010 1.010 2017." 0. 14.00. 2 30. 0. 2023. 0.0 2 0.0 3 0.030 -C.032 0.920 1947. 155 . 15.CC 232. c. 1S67. 0.01 ~0"f03~ -0.C96 0.903 1732. 14 2. 16.00 233 . 0. ~67b so ~ 1696. ! 0. Oi 0.02 -0.093 0 . 9 1C 1620. 129. i 17.00 234. 0. o.cso 1544. 1 0.01 0.03 0.020 -0.096 0.903 1473. 117. 13.00 233 • 0. 1402. r—-—i 1 TOTAL YIELD = 1245. i TOTAL 1.56 0.42 0.50 0.343

TABLE 34 Instantaneous rates of growth (q). natural mortality "(a) and fishina mortality (p) for R. kanagurta of the Java Sea. The fishing and natural mortality is divided evenly through the year, except during the months which where it migrates Trom the Java Sea and, therefore, unavailable to the fishermen, g - p - q is equal to g - i. Instantaneous rates of growth (g) distributed according to their observed seasonal "Incidence. The computdliun uT equilibrium yield, in successive, ribhiny

seasons, from 1 ,000 weight-units at age 4.0 months. : YIrL!) ? A 3 I Tr> rTTT "FAN r •on"!.

AGE MEAN ME A.N G 0 P C-K-Q A'E I oHT STOCK MEA.^I YIELD LENGTH WEIoHT CnAMGE 61C r'.AS S

3.00 99. 0. 1000. r• 0.53 0.02 0.040 0.525 1.690 1343 . 5 3. 4.00 121. 0. 1690. 0.39 0.02 0.040 0.332 1.394 2023. 30. 5.30 139. - 0. 2 3 5 6. 0.31 0.02 0. 040 0.257 1.293 2702 . ICS . • ". Z C 0. 30<-9. 0. 22 0.02 0.040 0 . .6 3 1.13 3 3323 . 133. 7.0 0 16S. 0. 3607. 0.17 0.02 0 4 C 'L 0 0.112 1.119 3823. 152 . S .00 17S. 0. 4039. 0.13 0.02 0.040 0.077 l.OSC 4201. 163 . 9.00 1 S 7. c. 4 3 6 3. C. il 0.02 0 • 0 9 C 1.094 4569 . C. +i vn • w.-\ vr\ 1 94 . c. c.coo 4775. COS 0.02 . C.06 6 1.06c 493= . 0. 11 .CC 2 00. 0. coco 5101. 0.07 0.02 0.000 0.C51 1.052 5234. 0. 12.00 2C5 . o.. 5363. 0.05 .0.02 n 1.C37 54 6 9 . 0.

TOTAL 2. 36 0. 34 C.4S 1.540 • TOTAL YIELD = 1962 .

TABLE 35. Instantaneous rates'of growth (g), natural mortality (q) and fishing mortality (p) for R. brachysoma from Tg. Satai area. As in TABLE 34, except that the computation of equilibrium yield from 1 ,000 weight-units al aye 3.0 inuriLlis. : ; — ———. sir*-* Yf-i n r

, AGE MEAN MEAN G 0 p G-P-Q WEIGHT STOCK, 1 MEAN YIELO LENGTH WEIGHT CHANGE BIC.v.ASS • 3 .CO 99. 0. 1000. 0.58 0.02 0. C30 0.4i-5 1.624 1512. 104. t 4. CO 121. 0. 1624. 0.39 0.02 0. C 8 0 0.292 1.339 1399. 1 T i • 5. CC 139. 0. 2175. 1 0.31 0.02 0.C3O 0.217 1.242 2439. 195. 1 6. CO 155. 0. 2704. iI 0. 22 0.02 0.030 0.12S 1.136 2 5 59. 23i. i 7.00 168. 0. 3074. i 0. 17 0.02 0. 030 0.072 1.075 3190. 25 5 . S .00 173. C. 3307. 0. 13 0.02 0. 0 3 0 0.027 1.037 3269 . 269 . 9.CO 137. 0. 3432. 0.11 C.C2 0. GOO 0.090 1.C94 3 594. °» • 10.00 • 194. 0. 3756. 0.0 3 0.02 0. CCO 0.066 1.06 3 33S4. 0. 11. C C 2 CC . o. • 4 012. 0.07 CO 2 O.OOO 0.051 1.C52 4il7. 0. 1 2 .CO 2C5 . 0. 4222. 0.05 0.02 0. OCC 0. C 2 6 1.037 4302. 0 • 13.CO' • 209. 0. 4331. 0.04 __C_02_ _0.COO 0.029 1.029 4446 . 0. 14.00 213. 0. 4511. 0. 04 0.02 o.oac -0.059 0.942 433C. 350. 15.00 216 . 0. 42^9. 0.02 0.02 C C 3 0 _ ^ ~- ~i i 0.929 4099 . 327. 1 6 • G C 218. 0. . — w . U / Z 3943 . _C 0. C2 0.02 _C80 __^0 JLC7 3 0.92 3 303. 20^- . 17.CO 220. 0. 2665. 0.02 0.02 0 . C 5 0 -0.07 2 0 • v 2 S 3537. 232 . 15.00 222 . 0. 3406. 0.01 . C.C-2 0. 030 -0.037 0.916 261. 19.00 223. 0. . 3122. 0.01 0.02 . 0.030 -0.03 7 0.916 2 992. 239. 20. CO 224. 0. 2 6 6 2 .

! : : TOTAL 2. 36 0. 34 0.96 1.060 ' TOTAL YIELD = 29S3.

TABLE 36. Instantaneous rate nf growth (g), natural mnrtality (q) anH fichjng mortality (p) of R. braohysoma from Tg. Satai area, as in TABLE 35, except tha the fishing mortality (p) was doubled. ~ ; ": 118

IV. GENERAL DISCUSSION

>* The genus Rastvelligev has been accepted since the time Jordan proposed it (Jordan and Starks, 1908). There are two species within the genus that have caused controversy, namely Rastvelligev bvachysoma Bleeker (1851) and R. neglectus van Kampen (1907). Some recognize them as two valid species and others think that R. neglectus is a synonym of the former species. This problem probably exists because past systema• tic studies of marine fishes involved too few specimens and were less analytical than the systematic studies of fresh water fishes (Hubbs, 1943). Natural populations are almost always distinguishable by differences in their morphology. The general method used to identify populations at any rank is by determining the differences of their morphological characters. These characters can be divided into two kinds, qualitative and quantitative characters. Any of the latter can be expressed either as a count (meristic character) or as a measurement (morphometric character). Two closely related species usually differ in several characters. Sometimes the differences between them are not pronounced, thus the characters employed should be those that exhibit the greatest divergence. The degree of differentiation is difficult to determine, especially from small samples, but, as Hubbs (1943) stated, it is the truest measure one can obtain of the stage of speciation. In search for distinctive characters, one seeks those which reflect inheritable genetic differences regardless of sex, size, and environment. 119 Determining whether two characters do or do not intergrade is a main problem is systematics. The degree of intergradation as described by Ginsburg (1938) and Royce (1957) was employed. As has been stated in the previous sections each morphometric character was subjected to regression analysis. Regression technique was chosen because of its value in morphometric study in that the size or growth of one character is related in a particular way to the size or growth of another character. Analysis of covariance was used to compare regression lines; this provides answers as whether two or more samples differ more than would be expected from chance. The factors such as the distinctness or the size of the gap, the evolutionary role or the nature of the adaptation zone and the degree of difference must be weighed before any decision on the systematic status is to be made. The greater the difference or the gap between two clusters of species, the greater the justification for recognizing both clusters as separate taxa. The difference is measured not only in terms of phenetic distance but in terms of biological significance. The existence of a gap implies reproductive isolation and this difference may be used for taxonomic recognition of the species. The difference in the utilization of the environment is responsible for the size of gap between taxa. The data obtained during this study suggest that in the Java Sea there are only two species of Rastvelligev, R. bvachysoma and R. kanaguvta; other species are reduced to synonyms. Rastvelligev is distributed abundantly in the Indonesian waters. This genus is caught in the Java Sea and contributes signif- 120 icantly to marine fisheries production. The problem of whether or not this Rastrelliger is composed of a number of populations has not yet been analysed. Hardenberg's hypothesis (Hardenberg, 1938) based on Decapterus migration patterns describes the Rastrelliger stocks in the area and is the only population study to have been attempted. In order to approach the above problem and to verify the hypothesis, morphometric studies have been conducted. Four samples from two different fishing grounds were compared. The results of the comparisons of R. braahysoma sub-samples from Tg. Satai area suggest that longitudinal measurements and pelvic fin length are significantly different (1%) between sexes (Table 10). These characters were deleted from further morphometric analyses. To avoid possible bias due to allometric growth, comparisons among R. kanagurta sub-samples from the north coast of Java were done by length-groups. The results are that the perpendicular iris diameter and the perpendicular pupil diameter, pectoral fin length, and pectoral breadth are significantly different (1%) among the groups (Tables 11, 12., 13). These characters exhibit strong allometric growth and thus, should be deleted for further analyses. The characters that do not exhibit either sexual dimorphism or strong allometric growth are compared among samples and the results are shown on Table 20. The data suggest that R. braahysoma exhibits geographical variation in the dorsoventral depth, greatest body depth, and interorbital distance, R. kanagurta in the head length and the 121 dorso ventral depth. Therefore, from the standpoint of morphometry there are two different populations of Rastrelliger spp. in the Java Sea area which supports the Hardenberg hypothesis for R. kanagurta stocks. The meristic characters examined do not exhibit inter- or intraspecific differences. The qualitative character in distinguishing species is the appearance of the cephalic lateral line canal system. The landings of Rastrelliger mostly come from the Sunda Shelf area. In this study, as has been stated before, two species of Rastrelliger are recognized, R. braahysoma or Kembung Perempuan and R. kanagurta or Kembung Lelaki. Kembung Lelaki is caught mostly by payang-net in the offshore regions, while Kembung Perempuan is caught in the coastal areas by several kinds of fishing gears such as gill- nets, shore-seines, and traps.

The data in this study suggest that the Rastrelliger fisheries depend mainly on the 0-year class which is completing its first year of life in the fisheries. The fish are immature or just mature. The success of this kind of fishery will depend on the strength of the incoming 0-year class which is dependent on the seasonal survival rate of the young, and the conditions of the environment that influence migration of the fish to the fishing grounds. The change in recruit• ment seems to have a stronger influence than fishing pressure on the fluctuation of the stock. The study of stock-recruitment relationships are a necessity and must be undertaken to relate the abundance of the 122 pre-recruit phase to age class strength for fishing success prediction. The data suggest that the Kembung fisheries in the Java Sea have not yet reached maximum exploitation which suggests the possibility of increasing production by increasing fishing intensity. Since the parent-recruit relationship is not yet established the increase should be undertaken cautiously to avoid causing a decline in recruitment sufficient enough to hurt the fisheries. However, the "natural" closed fishing seasons in the Java Sea are likely to keep the fisheries in good condition. 123

V. CONCLUSIONS

Analyses of morphometric data suggest that there are two species in the genus Rastrelliger, Rastrelliger braahysoma and R. kanagurta. R. negleotus is considered to be a synonym of R. braah• ysoma. Both species exhibit intraspecific geographical variations in the dorsoventral depth, the greatest body depth and the interorbital distance in the former species; and in the dorsoventral depth and the head depth in the latter ones. Analysis of catch curves indicates a variation in the instan• taneous total mortality coefficient; fori?, kanagurta it is 1.08 in November 1971 and 1.20 in December 1971. It also indicates variation in the survival rates of the West and East Monsoon Rastrelliger kanagurta populations, that is of 0.34 and 0.72 respectively. The survival rates of the West Monsoon population in 1971 and 1972 are nearly the same. The estimated natural mortality M was 0.40.

R. braahysoma had a survival rate of 0.82 in the 1971/1972 fishing season, with an estimated natural mortality M of 0.40. The fishing mortality F of R. kanagurta in the north coast of Java area was 0.83 (December 1971) and it was 0.44 for R. braahysoma in Tg. Satai area (1971/1972 fishing season). In order to determine the potential yield of the fish populations, the yield per recruit models of Beverton and Holt (1957) and of Ricker (1958) were employed. The data suggest that yield can be increased by 124 increasing the fishing pressure more than 60% for R. kanagurta and can be doubled for R. braahysoma of Tg. Satai area. The greatest yield for both species can be achieved by extending the age or size of the first capture to 4.5 months of age (15.5 cm TL) and 4.0 months of age (12.0 cm TL) respectively. The fluctuations of the catch during past years was probably caused by failure or success of recruitment rather than by the increase in fishing pressure. The fish populations do not appear to be in a state of over- exploitation, therefore, the fishing activities should be increased to gain more food and to increase employment. However, since the parent- . recruit relationship is not yet known, the increase should be undertaken cautiously. 125

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Vanichkul, P. and V. Hongskul. 1966. Length-weight relationships of chub-mackerel {Rastrelliger spp.) in the Gulf of Thailand. Proo. Indo-Pacif. Fish. Coun., 11(2): 20-23. 135 van Kampen, P.N. 1907. Uber Zwei Scomber - Are tn des indischen Archipels. Bull. Dept. Agric. Indes. Neerl., 8(Zool. 2): 1-8.

Van Oosten, John. 1957. The skin and scales. Jto M.E. Brown et al., The Physiology of Fishes New York, Academic Press, 1957. von Bertalanffy, L. 1934. Untersuchungen uber die Gesetzlichkeit des Wachstums, Arch. Entw. Mech. Org. Berlin, 131: 613-652.

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Wilimovsky, N.J. and E.C. Wicklund. 1963. Tables of the incomplete Beta function for the calculation of fish population yield, Vancouver, Univ., British Columbia, Institute of Fisheries, 291 pp.

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Whitley, G.P. 1944. New Sharks and fishes from Western Australia. Australian Zoologist, 10: 252-73. 136a

c

APPENDI CES Body measurements of Rastrelliger.

CO 137

5 10 15 20 25 TOTAL (X 1000) EFFORT Figure 14 a. Relation between Total Effort and Catch Per Unit of Effort; and between Total Effort and Total Catch of R. kanagurta

from the north coast of Java in 1971. This is the simpli• fication of Fi%ure 14; fitted by eyes. Catch I (X 10tons!

140

40

30

28

26

24

22

20

18

16

14

12

10

8

6

4

2

0 •i 1 1 » 1 —I** 1 \ 1 1 r 2 3 4 5 6 7 8 9 10 11 12 1971

28. Monthly productions of the north coast of Jev in 1971. A. R. kpnpgurta; B. Decautprus snn.t C, Euthynnus snn. 141

%

40 ••

30 ..

20 +

10 1

1 o • ' 1 1 1 1— I J I I I 1=3=

17.0 >5 18.0 >5 19.0 5 20.0 >5 21.0 <5 22.0 >s 23.0 TL (cm) Figure 29.Frequency distribution of mature R. kanagurta from the Java Sea (1972) . 142

Tw/R

1.0 tc

R. kanagurta.

R. brachysomp.

Figure 30. Yield per recruit es a function of t0 with fishing mortality F ranged from .1 to 1.5. 143 TABLE 37 Rastrelliger braahysoma Productions of Tg. Satai Area

Month 1968 (ton) 1969 (ton) 1970 (ton)

I 357 360 600 II 398 373 712 III 303 511 584 IV 143 136 281 V 55 64 120 VI 7.5 9 56 VII - _ VIII - • - _ IX - - _

X •• - - _ XI 70.6 120 85 XII 287 592 239

Total 1,621.1 2,165 2,678

Source: The Sea Fisheries Service of the Province of West Kalimantan (Borneo) in Pontianak. 144

TABLE 38 Age Distribution of R. braahysoma in Tg. Satai Area in 1971/1972 Fishing Season

Age (Month) Frequency % In %

4 12 .75 .2914 5 27 1.7 .5195 6 190 11.8 2.4707 7 263 16.4 2.7958 8 116 7.2 1.9773 9 450 28.0 3.3329 10 327 20.4 3.0136 11 206 12.8 2.5515 12 13 .81 .2114 13+ 2 .13 2.0832 145

TABLE 39

Age Distribution in the Catch of R. kanagurta in the Java Sea

Age West Monsoon East Monsoon West Monsoon (Month) 1971 (f) 1971 (f) 1972 (f)

4 - 4 -

5 - 16 -

6 - 32 1

7 24 33 5

8 22 27 8

9 70 23 24

10 no 22 52

11 30 21 14

12 15 16 7

13+ 6 9 4 146

TABLE 40 Average Effort of a Payang-Boat in 1971 in the North Coast of Java n = 8 boats; power = 20 H.P.; crew = 16

Month Fishing Day Fishing Trip

I 22 4 II 10 2 III 22 4 IV 14 3 V 17 3 VI 14 3 VII 13 3 VIII 12 2 IX 16 4 X 18 4 XI 13 2 XII 16 4

Total 187 38

Average 15.6 3.2 147

TABLE 41

i?. kanaguvta Statistics in 1971 in the North Coast of Java

Month Total Catch Catch/Boat/Day Effort =Tota l Catch (kg) (CPUE) C/B/D

I 535,004 19.2 27,865 II 520,879 26.6 19,582 III 863,163 65.4 13,198 IV 1,156,411 51.9 22,282 V 1,002,515 78.2 12,820 VI 934,393 125.2 7,463 VII 739,127 148.3 4,984 VIII 587,734 25.6 22,958 IX 869,431 38.8 23,626 X 1,010,473 62.6 16,142 XI 1,032,547 176.4 5,853 XII 905,458 130.8 6,923