"This paper not to be cited without prior reference to the authors"

, International Council for theExploration of,the Sea

C.H. 1975/E: .12Fisheries ImprovementCoomittee

Mariculture potential of siganids: the choice of species========================================================

•Introduction

by

H. v. Westernhagen and H. RosenthaI

Diologische Anstalt Helgoland

2 Hamburg 50 (Zentrale)

Germany

Although the possible suitability of siganids fortropical aquaculturc

has aiready been mentioned by Ablan and Rosario (1961) it was only

recently that thiswidely distributed tropical fish group has attracted

. the attention of several aquaculturists throughout the world. An·,'

integration of efforts onthe investigation into the aquo.culture potential

of siganids was firstc'alled' for bya working group on the occasi~n of thc

Siganid Mariculture Imple~entation Conference at the Hawaii Institute of

• Harine :Biol~gy in 1972 (Anonymous, 1972). Since this time several reporto

on the food requirements of Sig~nido.e (:Ben-Tuvia ~~; 1973~ Tsuda and, .

Dryan, 1973; Westernhagen, 19730., b, 1974) and controlled o.rtificial

fertilization (Fujito. o.nd Ueno, '1954; Popper et al., 1973; Soh~nd Lam,. --1973; Westernhagen and RosenthaI, 1975) appeared in the literature, and

larvae to juvenile rearing on n~tural diet was first'reporte~ by May et~ .

(1974) for Siganus canaliculatus.

From these and other r~ports it appears that the species which stimulated

the most interest and yielded the most promising results for successful

rearing and breeding in the past was Siganüs oramin (Schneider) frequently

also called ~ canaliculatus (Park). The prescnt study tries to evaluate

thc possible importance of members of the family Siganidae for aquaculture

purposes.

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. .~ ... '"," t ••.•...•..... "'\.,

2

.. ~.'''.';.. ",

Material and methodi~

, I,

l

This studY'·is partially based on da~a obtained from siganids reared from

juveniles to adu.l'is in a closed sea water system for 320 days' and: fed

artifi~ial diet. Live juveniles were ~hipped from Manila (The Philippines)

to Hamburg in autumn 1974 (details available in Westernhagen'and RosenthaI,, . ,

1975). The other specimens used were collected in J~ne 1975 onCebu Island,

The Philippine~, and,pre~erved in a 4% sea water':' formaldehydemixture,. '''- .. . '.... . .

airshipped to Hamburg, Germany, where, they were immediately weighed and

measured.

Since there is no consistency and agreement,as tothe nomenclature of

siganids, in this report we shall use the names employed by Herre and

Montalban (192'8) in' their workon the Philippine siganids. In order to •

facilitate species identification for thereader the names of the species

that are being dealt with as weIl as some explanatory remarks are, given

below..~ " ,

Names of species

Siganus oramin (Bloch and Schneider). This species is frequentl~ called

,~ canaliculatus (Park) (Fowler,1928;, M~r~hall, ,1964; Lam,' 1974,' Tsuda• • I '. I

et al., 1974, May et al., 1974). In The.Philippines itis the most abundant-- --: .' ."

.rabbitfish species where it grows up to ~20 mm in length. It is olive green, .

in colour withcharacteristic emaIl white spots on the eides. A co~on fis~

also"on ;the' Ceylonese (Munro, 1955) and,Indian coast (Day, 1958) where it". . - . .; . '.

grows to around 250 mm, as weIl as in the tropical Indo Pacific (Smith,

1965; He~re and Montalban, 192~).

Siganus ~oncatenata '(Cuvier and Valenciennes). Thi~ spec'iesis also called. , '

~guttatus (Bloch) (Munro, 1958; Lam,. 1974). This bandsome ~ish is very

c~mmon' in the Phil~ppines. It i8 reported t6,grow'more'than 500 mm in

length. Cuvier and Valenciennes (1835) described itas occurring in the

, Molucca~' and JaVa,'and Fowl~r (1'928) and Day (1958) found it iri 'the' 'Malay'. .. " .. . .

,Archipelago, the Andaman Islands and the East Indies.

Sißanu~ striolata(GÜnther). This 'species·is usually,calied.§.:. spinus

(L1nne); 'and i~ very commo'n i~' Th'e Philippines. It hasbeen des~r'ibed by

Fowler (1928), Munro (1955), Marshall (1964), and Tsuda ~~(1974) as a

rather small (max. 220 mm) but common species in India, Ceylon"the East

Indies, and east Australia.

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Siganus virgata (Cuvier and Valencionnes). iThio unmiotakeable species io

fairly co~on'in The Philippines but appears to be confined to the southeast

Asian region. Cuvier and Valenciennes (1835) reported it from Java; Day

(1958) from South India and Munro found it'in wost New Guinea. It doee not

grow very large; Herre and Montalban (1928) roported only 190 mm.

Siganus hexagonata (Bleoker). This species is also called ~ chrysospilos

(Bleeker) by,Munro (1958). It belongs to the larger ones,of the rabbitfish

family and attains a longth of ovar 300 n:.m, (Herre and I1ontalban, 1928).

Siganus fuscescens (lfouttuyn). This specieo io obviously idontical to

~ rivulatus (Forskal) when comparing tho description of both forms. This

.. has already been suspected by Cuvier and Valenciennes (1835) when under

the descriptionof Amphacanthus fuscescens ,they wrote: " ••• rapporte du Japon

un amphacanthe encore tres senblable par les fornes et les proportions a ce

siganus d'Egypte" which was ~ rivulatus. The same deductions have boon made

by B~n-Tuvia (1964). The species is common on the east coast of A~stralia

(M~rshall~ 1964), and Fowler (1928) reportod it'separated as rivulatus and

fuscescens from the East Indies"Japan andAustralia. According tci Smith

(1965) it is distributed throughout the tropical Indo-Pacific. Rocontly it" '

has,invaded the Heditorraneanthroughthe Suez Canal as roportod by Ban-Tuvia

(1964, 1966). It is said to be a fairly largo species attaining a maximum

length of about 350 mm and ,even 400 ~ (Ben-Tuvia ~~, 1913) then

weighing closo to 500 g.

Results

On the basis of their body proportions ~he 6 spocies can bo devided into

two groups~ Group 1 eOr.!prising the more slender species with S. oramin,

.2.:...striolata and ~ fuseescens" and Group 2 eontains'~ eoncat~nata,

~ hexagonata and ~ virgata, spccioothat gonerally exhibit deeper bodiee

than members of Group 1.

~ striolata appears to be the smallest speeies dealt with in this study

(Fig. 1). The maximum size of the specimens examined was only around 16 er.!

total length eorresponding to about 10 g wet weight. The bulk of, tho fishcs

oampled was mueh smaller; about 80 ~~ of the fish measured 8 to 14cm and

weighed·10 to 45 g, rcspeetively. Out of 251 fishos meacured only 8 were

heavier than 50 g. lh. oramin (Fig. 2b), ~ virgata (Fig•. 1) and lh. fuseescens

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(Fig. 3) were of moderate size with naxim~ total ler.gths betwecn 200 nm to

240 mm and corresponding weights of 160 to 230 g. Acain thc majority of the

fishes measured ü to 14 cm in total length.

The largest species of this study were ~ hexagonata (Fig. 3) and

s. concatenata (Fig. 4b) with maximum lengths of 360 to 380 mm and

eorresponding weights of 750 to'1100 g. Due to their fairly rare oeeurrenee

in Cebu (The Philippines) sampIe size of ~ fuseeseens, ~ virgata, and

§.:. hexagonata were small allowing only limited interpretation of their

length/weight ratios.

Data shown in Fig. 20. and 4a are derived from speeimens reared in a elosed

sea water system on eonmereial feeds. There was only little differenee in ..

the length/weight relationship of fishes reared in eaptivity (Fig. 2 and 4)

and wild eatehes.

~ oramin reared in eaptivity on artifieial diet grew to 0. greater weight

than did wild eatehes of 0. given length.(total length 16 em: reared fish =

65 g; wild fish = 50 g).

~ eoncatenata showed a similar differenee between wild eatehes and pellet

reared speeimens (total length 16 en : reared,fish = 95 g; wild fish = 80 g).

Figure 5 shows growth rates of ~ eoneatenata and ~ oramin fed commercial

feeds over 0. period of more than 300 days. While growth of s. oramin

appears to level off at 16 em total length, there is still ero1l1th increment

to be expected in ~ concatenata of this length. These results were obtainelt

with commercial rabbit feeds not specially dcvoloped for tho dietary

requirements of siganido.

Differenceo in length/weight ratio of all species under study are shown in

Pig. 6, demonstrating the large size and weight of ~ eoncatenata and

.§.:. hexagonata.

Diseussion

Haximum length and weight

From the above it beeomes evident that not all if an~r of tho siganids havc

0. real potential as fioh to be introdueed into a~uaculturo. Duc to its sm~ll

:r.18.ximun size, t:cntiollcd also b2r FO',ller (1928), Harre and rJnntal1Jan (1 )?9),

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Hunro (1955) and Harshull (1964), h strioluta is by no Douns u suituble

speeies for aquaeulture purposes. With un indieated ~aximUD length of

240 mm the largest individuals would ultinutely weieh only 150 g (tuken

from Pig. 1A, ~ oraoin whieh has a similar length/weight ratio). Most

individuals though would be expeeted to weigh less, sincethey are already

mature at uround 120 on (Westernhagen, 1973) and growth slows down. Another

drawback for the eulture of ~ striolatais thc fact that aceording to

loeal fishermun this species frequently tastes sli~ltly bitter•

. Although h oramin, ~ virgata, und h fuseeseens grow to a greater size

than the forner species, and the biegest speeinens of ~ oramin and

h fuseeseens reaehed around 240 Dm, approxinutely 230 g (h virgata remains

tt smaller), the bulk of the specinens neasured and observed by UD was

eonsiderably smaller. Similar to ~ striolata, ~ oramin reaehes maturity

at 110 to 140 mo (I1anacop, 1937; Westernhagen, 1973; Lam, 1974; Westernhagen

and Rosenthal, 1975), whieh as ean be seen fron Pie. 5s1ows down growth

considerably. Maximum attainablc length of S. oramin probubly lies between

250 mo (Day, 1958; t1arsehull, 1964) und 350 00 (Munro, 1955). The largest

speeinen found by ua during this study wus 240 mm long, whieh is in good

agreement'with datu given by Herre and Montalban (1928) for The Philippines.

•

As for h fuseeseens no exaet dato. ure uvailuble onits size ut maturity.

Popper ~~ (1973) deseribe h rivulutus speeimens of 120 to 170 g to be

already ~ature. After Pig. 4 this \lould be around 220 mm totul length,

Den-Tuvia et~ (1973) found that ~ rivulatus grow up to 150 g (210 mm)

at the end of its first year then probubl;;" being already nature. This

species doea not grow nueh lurger than S. oranin as ean bo seen from. ,- -. .

literature reeords. Herre und Hontalban (1920) indicuted u maximum length

of 290~ and Smith (1965) gi~es 350 mm as maximum length of ~ rivulatus.

Den-Tuvi~ ll!!:l:.. (1973) mentioned that the speeies: "••• ~ay reueh an

approximate size of 400 Drl ••• " but no exuct duta were uvailable to them.

As ean be seen frOI:l Pig. 3 the length/weight relutionship of this epeeieo is

very mueh the same as in ~ oramin.

~ virgata us one of the medium sized siganids, does probably not grow much;

larger thnn 250 mm, as dedueted from reports of Philippine fishermen. The. .. :" ",

biggest speeimen examinedby IIerre and Nontalban (1928) was 190 mm long and

during.this study a 210 mmspeeimen was the lurgest individual eneountered.

'Due to its deep body it grows heavier than ~ oramin or ~ fuseeseens of the

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same length (Fig. 6), reaching about 170 G at 200 mm •

.§.:. concatenata and .§.:. hexagonata ,,,ere the largc~t spccies found in this

study, attainingmore than 350 mm and weigh~ng b~tween 750 and 1100 g.

From Fig. 5 it can be dcrived that .§.:. concatenatais likcly to grow larger

than .§.:. oramin. There was still growth increment over the rearing periotl 01'

300 days in ~ concatenata. The fishes did not show signa of maturity, some

reaching 280 mm. Due to theirdeep bodies, .§.:. concatenata and .§.:. hexagonata,

at a given length, are heavier than members 01' Group 1. Eoth species at

200 mm weigh around 140 g while .§.:..oramin and ~ fuscescens 01' the same

length weiGh only 100 g.

•Feasibility of farming and its profitability

Prom the above it appears that ~ concatenata and .§.:. hexagonata have

certain potentials fo:r being introduced into fjsh farming. Yet data

obtained in the course of rearing experiments with S. concatenata indicate

that' there are still SODe obstacles to be cleared mmy before any of the

siganids could be successfully introduced into Do.riculture proGrammes. Thc

major impediment to this endeavour is certainl:l the slO\1 growth of these

fishes as shown in Fig. 5,for lo.borator;,r reo.red specimens.As for .§.:. oramin,

growth 01' ~ concateno.to. is relativelJr slow. After 200 experimental days the

fishes reached 0. total length of 130 Dm, which amounts to a weight of about

50 g. These data are in good agreement ,dth gro,,,th rates. reported by LlI.vin"end

Alco.la (1973) 1'01' ~ oramin from Tho Philippines, thus wo can assume that.

growth rates in our sea water systom compare favourably with growth obtained

in 0. natural environment. Growth of ~ rivulatus, as reported by Den-Tuvia

et äL,.(1973), appears to be equall;y slow. The authors reported that

~ rivulatus in the Mediterranean grows to about 150 g at the end of ito

first yeo.r. The same groVlth "ms displayed by ~ ooncatenata reared in our

sea water'systeD (Fig. 4 and 5).

If we compare growth rates recorded for siganide with those knownfor milk­

fish Chanos chanos (Forskal) under'culture, prospects for future larGe scale

cultu.re of eiganids do not look vor;!, promieing (Tablc 1), although pricce

forsr:J.all S. oraminappeared to bo fairl;,;, high. Yet this i8 due to thc fact

that priccs are GOmellhat ovorcstiLmtod becausc omall 1'is11oo are sold eingl;,/

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on the market (Table 2). As already mentioned one major disadvantage 01'

oiganids io their slow growth. Hilkfish reared in The Philippines from fr.J

may reach marketable size (300 g) after 90 dayo (Blaneo, 1912) although it

usually takes four months (Villadolid and Villaluz, 1950; Villaluz, 1953).

After. 90 days siganido would measure only 10 to 80 mm weighing ~O g.

Similar results ware obtaincd by Tsuda et~ (1914) rearing ~ oramin

(canalieulatus) in Guam. The data given by Don-Tuviu et~ (1973) ar,e 01'

the sane order of magnitude. ~ rivulatus (fuoeeseeno) roared in sea eugoß

over aperiod 01' 84 da~'o only sho\Ted an inereaoe in weight from 7.3 to

28.5 g.

Even the higher priees 01' oiganids eompared to thosepaid formilkfish on

Philippine markets (Table1) would not compenoate for thc slower growth

unless this ean be remedied, by the eholee 01' rJore adequate eheap

artifieial feeds.

Polyeulture 01' milkfioh and, siganids does not appear tobe a means 01'

cnhaneing produetion 01' fishponds over the introduetion 01' rabbitfioheo,

sinee siganids have 'thc samediot als milki'ish (Herre and Hendoza, 1929;

Esguerra, 1951; Touda and Bryan, ,1973; Westernhagon, 1913a, b, 1974), even

showing the same prei'eronees i'or acarophytes fluch afl Graeilaria eoni'ervoides

(Abagon~~ 1951; Domantay, 1959). Thus siganids in milkfish ponds are

usually eonsidered unwanted eompetitors (Rabanal ~~ 1951) redueing

profit, even though thoyeanbe readily sold on the markste at considerable

~ prieeo when they are still omall (Table 2).

The vast areas still available for aquaculturo development in The Philippin~s

ean not poosibl:'I,converted excluoivoly into milkfish PClnds. For one reason

theJT da ·not meet the' ,particular reC].uiremonts nessesrmry for raising milkfiDh.

Yet siganids eould possibly be rearod in ponda whieh are not suitable i'or

milkfish eulture (Ablan and Rosario, 1961). Experiments conducted by

Ben-Tuvia ~~ (1913) also showed thei'easibility oi' eulturing aiganids in

sea eages which would reduce operational costs substantially.

The advantage siganids have over milkfish io thc possibili t Jr 01' prcpagating

the former in captivity (May et ale 1915; Westernhagen and Rosenthal 1915).

This l.ould secure unlimited seed provision, a Icajor impedoucnt in the further

expanoion ofmilkfish cuiture (Delnondo, 1912).

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The gist of the discussion indicatesthat intentions to utilize members of

this family for cultivation in warm water effluents of temperate regions

will not materialize.

Summary

1. l~mes of several species of siganids are discussed and compared with

names employed by different authors.

2. Six species of siganids Siganus oramin, ~ concatenata, ~ striolata,

~ virgata, ~ hexagonata and ~ fuscescens were collected in The Philippines

and their .length/weight ratio determined. 4t

3. Live ~ oramin and ~ concatenata were airshipped from The Philippines

to Hacburg and reared on commercial feeds for more than 300 days in a closed

seawater system and their length/weight ratio determined.

4. Length/weight ratio of wild and laboratory-reared specimens were

different. Reared ~ oramin and ~ concatenata being heavier than wild

catches of the same length.

5. Maximum lengths and weights of siganids and their feasibility as

aquaculture objects are discussed. ~ concatenata and ~ hexagonataare

the only species that grow sufficiently to be worth considering them for 4taquaculture endeavours.

6. Growth rates of siganids and milkfish (Chanos chanos) are ~ompared and

i t is concluded that unless same means to induce gro\olth in siganids is found,

members of this family would not be suitable for extensive aquaculture

purposes.

We are indebted to G. Fürstenberg and J.Klinckmann for expert technical

assistance and H. Dlake for advice on the preparatiol1 of the manuscript.

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Ref'erenees

Abagon, N.A., Bunag, D.U. und Vera, A.N. de (1951) "Gulaman dacat"

as supplemer.tary feod for baneos. Bull. Fish. Soc. Philipp., 2, 41-49.

Ablan, G.L. a~d Hosario, \l.H. (1961) Teuthid fiah for marine eulture in

the Phi1ippines. Fish. Gaz. ~li1ipp., 5, 23-24.

AnonJ~ous (1972) Plans for a siganid fish farming program. }linutes of the

Siganid Narieulture Implomantation Confercnee, Hawaii Institute of

Harine Bio1og'.{, Univ. Hm'raii, Honolulu, 1-22.

Ben-Tuvia, A. (1964) Two siganid fishes of Red Sea origin in the eastorn

Hediterranean. Bull. Israel Soa Pish. Hes. Station, 37, 3-9.

Ben Tuvia, A. (1966) l1ed Sea fiohen rcccllil~J found in thc lIedi terranc::1.11

Sea. Copeia, 1966~ '254-275.

Ben-Tuvia,A., Kiasi1, G."'. and POJ:Jlor, lJ. (1975) Experimcnts in rearillC'

rabbitfish (Siganus rivulatun) Li Oel'. ioJ'uter. AquQeultu:t'o, 1, 359-364.

B1aneo, G.S. (1972) status and prol)lüns of eOD.otal anuaeulture in thc

Philippines.In:I'illa;)r, fr.V.H. (Ed.) Coastal anuaculture in thc

Indo-Pacific region. Food und J~ß'rjctllturc Organination cf thc United

Nations, Fishing HelTS (Books) I,ol,don, 60-67.

Cuvier, H.B. and Valenciennos, lI.A. (1835) IIistoire naturelle des poi8sons.

Levrault, Paris, 10, 1-482.

Day, F. (~95a) The fishes oflndia. Willian Dawson, London, 1, 1-778.

Delmendo, M.li. (1972) The status of fis~ seed produetion in Thc Philippines.

In: Pillay, Ir. V.H. (Ed.) Coastal aquaeulture in the Indo-Pacific reGion.

Food and' Agrieulture Organisati.on of the Uni ted Hatious, Pishinß. ile",s

(nooks) London, 208-212.

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Domantay, J.S. (1959) The possibility of agarophytes propagation with the

oulture of milkfish Chanos ohanos (Forskal) in braokish water fishponds.

Fish. Gaz. Philipp., 3, 22-29.

Esguerra, R.S. (1951) Enumeration of algae in Philippine bangos fishponds and

in the digestive traot of fish with notes on oonditions favourable for

their growth. Philipp. J. Soi., 1, 171-192.

Fowler, H.W. (1928) The fishes of Ooeania. Mem. Bernioe Bishop Mus.,

10, 1-540.

Fujita, S. and Ueno, }1.(1954) On the development of the egg and prelarval

stages of Siganus fusoesoens (liouttuyn) by artifioial insemination. 4tJap. J. Iohthyol., 3, 129-132.

Herre, A.W.C.T. and Mendoza, J. (1929) Bangos oulture in the Philippine

Islands. Phil. J. Soi., 38, 451-509.

Herre, A.W.C.T. andMontalban, H.R. (1928)The Philippine siganids.

Philipp. J. Soi., 35, 151-185.

Larn, T.J. (1974) Siganids: Their biology and narioulture potential.

Aquaoulture, 3, 325-354.

I.ilvina, °E.H. and Aloala, A.C. (1973) Eoologioal studies on Philippinc •

siganid fishes in southern Hegros, Philippines. Paper presented on the

oooasion of the moeting of the Federation of Institutes of Marine

Soienoes in 1973 at the University of San Carlos, Cebu City, Philippines.

Harshall~,T.C. (1964) Fishea of the Great Barrier Reef and ooastal waters

of Queensland. Angus and Roberson, Sydney, 566 pp.

May, R.C., Popper, D. and 11cVey, J.P. (1974) Rearing and larval development

of Siganus oanalioulatus (Park) (Pisoes: Siganidae). Hioronesia, 1'0,

285-298.

Hunrc, I. S.ll. (1955) Thc marine and fresh water fishes cf Ceylon.

Halstead Press, S~/dney, 351 pp.

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Munro, I.S.R. (1958) The fishes of the New Guinea region. Papua New

Guinea Agric. J., 10, 97-369.

Popper, D., Gordin, H. and Kissil, G.W. (1973) Fertilization anel hatching

01' rabbitfish Siganus rivulatus. Aquaculture, 2, 37-44.

llabanal, H.R., Montalban, li.ll. and Villaluz, D.K. (1951) The preparation

and manageL1ent 01' bangos fishpond nurser:r in the Philippines.

Philipp. J. Fish., 1, 3-34.

Smith, J. 1.13. (1965) The sea· fish08 of southern Africu. Contral Heus Agenc;{,

Cape Town, 580 pp.

Soh, C.1.and 1arn, T.J. (1973) Inducod breeding and eurly development of

the rabbitfish, Siganus oramin (SclmoLder). Proc. Symp. BioI. Hes. Hat.

Dev., 1973, 49-56.

Tsuda, ll.r.i'. and Ilryan, P.G. (1973) J'()od ·p.:··eferGilCC of juvcllile S1ga11u.'8

rostratus and s.. spinus in Gun". \;oP/.' i<, i :.i'[ 5, GO,t-GOi).

Ts:uda, R. Il1., :nr~/un, P.G., ::'itzgor:.H1, if.,!~ rd. '.'-'oblaD, H••T. (197,~)

Juvenile- adult rcaring of ~:~ (i'; ucu~:: ~ico.:c.. idQ.e) in Guan.

Seventh 'Ilecllll.1.cnl ::cot.:L[~ 01, : ,,;, ,er (Ci, ",ul~l1'Olofa, 'l'anea, j·ul.\' 1~j-1 Sl,

1'97/" 1-4 (mimeo).

Villadolid, D. V. and Vi.Llaluz, ]J. L. (19:50) A Ilrelild.i.llar.y Dtud:,; on banGos

cul tivatian and i ts relation Ln i\ 1[,'<10 culture ir. the IJhiIippines.

Dept. Ar;ric. jfat. lios. l)op. J.:;\lJI" jO (frOl.l lillnluz, D.K., '195;;).

V111cluz, D.K., (1953) l'i~h farmin(.;' :i1l tilO l)hilippinos. JJooktmn lnc.,

Ilanila, 336 pp.

Hesterl;.hagen, H. von (1973a.) The natural 1'ood of thc rabbHfishco

Siß'anus oramill and S. striolat[l.• lIar. ])101., 22, 367-370.

\1esternhcf,'en, H. von (1973b) A preUrJinary stud:r on the food preferencos

of Sirranus concatenata (Cuvier o.nd ValcllcLonnes). PhiLpp. 3ci., 10, (;'1-73~

""0'1-,~-

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Westernhagen, H. von (1974) Food preferences in cultured rabbitfishes

(Siganidae). Aquaculture, 3, 109-117.

Westernhagen, H. von, and RosenthaI, H. (1975) Hearing and spawning

siganids (Pisces: Teleostei) in a closed seawater systen.

Helgoländer wisse Meeresunters., 27, 1-18.

•

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Table 1

Some marketing characteristicsof Siganus spp. and milkfish.

7 Fesos = 1 $ US.

Palatibility

Possibili t;rto farm

Growth untilmarketable

Weight atmarketablesize

Price/kile

Fry productienin captivity

Feod'

Sellability efsmall fish

excellent

+

12 months

150 g

7-10 Pesos

+

algae

geed

Nilkfish

good

+

3 months

300 g

2-4 Pesos

algae-

fair

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Table 2

Prices of siganids and milkfish on CebuIsland (The Philippines);'

Prices for milkfish strongly depend on weather conditions.

Bad weather - high prices. 1 Pesos = 1 $ USo

Species Length Weight Price/fish Price/kilo------- _i~~2_ _~~2__ __t~~!~2 __ __iE~!~2 __

oramin 5 5· 0.05 10.01-11 1-20 0.1 14.3.-5.0

11-14 20-35 0.2 10.0-5.114-16 35-50 0.3-0.5 11.4-8.0 e

concatenata 5 5 0.05 10.015 80 0.50 6.220 150 1.00 6.125 300 1.80 6.028 450 3.00 6.138 1100 1.00 6·4

hexagonata 5 5 0.05 10.020 . 150 1.00 6.132 550 3.50 6.431 830 . 4·50 5.4

virgata 11.5 . 100 0.50 5.0

Chanos chanos 330 1.0-1.5 3.0-4.5

-15- .

...A- ,

•

700

'50

50

o

~ ~lflJl1hJ

y" 0017 .3034r, 0995n,24

8 12 16 20 0Totallength lern}

?_~t!.!9lo.!~

y, 0013 .3069r, 0996n' 251

8 12 16

Fig. 1 Length/weight relationship of Siganus striolata and

~ virgata from Cebu (The Phillppines).

",1)

5 ~r~lTlln A

'1"0008. 3262

n0982n: 1')4

..

'?"Q!amin 8

,/=00"7x 2928

r ,.OQ84

n= 37'j

/

'\,..' ." .

'2 '6 20 0 4Totallengthkml

'2 '6

Fig. 2 Length/weight relationship of Siganus oramin. A - laboratory

reared specimens; B,- wild catches from Cebu (The Philippines).

•

J.A....

f

.s !YrtCpscP.~~

y=oooa. 3155

r -1000n.7

50

200

2. hexog2.!lQ.!2.

y=0015 x 3020

r =0.999n= 22

800

200

1000

1502 600:c 2-.Il'

"...'"~~

400 100

8 12 16 20 24 28 32 36 40Totollength lem)

28242012 16Totall.ngth feml

Ol-t--.-.-=r=:::..,-.-.---.-.-.----.-.-.----.---,o

OI+-.-.,....~=r--r......,....--_._,....,r_T.....,.........,....--_r_-r-T'"""""'1---.

o 4

Fig. 3 Length/weight relationship ofSiganus fuscescens and

~ hexagonata from Cebu (The Philippines).

100

300~O

2no1100

~~!:I.s:~~ A ~ concatenata 8y. 0012 • 3 250 y.0017x 3046

r·09A9 r·0996n, 10]

900 n.]2

,',Cj

700

'"h. 100..,,: 500

3632252014820Totollength km)

15178o+---.-""'F'1:.:r---r--r---r--r----.---r--.--­

o

Fig. 4 Length/weight relationship of SiRanus concatenata. A - labora-

tory reared specimene; B - wild catches from Cebu (The Philippinee).

.\.~

•

•

20·

y • 2 aai x 0 295

r·09aOn .11L

15

0-!-~--r"--T1-r-rTl-r-rTl-r-rTl-r-rTl-r--'2-r50--'T1-r-.:"!30=-OTlrT-r:3!50:r-o 50 100 150 200Experimental days

20

y • 0 042 • L 293 x

r·0956n. '41

15

E~.cc;. 10c!!'n~

o+-r-T-,-,.-r-r-r.,.-;rr---rTl-r-rTl-r.--IT-r..-IT-r..-rr-r-TI-r.-ri:!I-::--o ~ m ~ ~ ~ m ~

Experimental days

._---- -_._------

Fig. 5 Growth of pellet fed 'Siganus oramin and ~ ooncatenata rearedin a closed seawater system.

•

..

1200

1000

800

7,.

j 600

~

400

200

• S. concatenata• S hexagonata.. S.oramln

• S.virgata• Sstriolala

. //(I'

~~~

36322816 20 24Total length lem)

1284O~--r---r---r-'~~~--r-.,----.----r----,r-r-~,-.---,---,---,--.­

o

Fig. 6 Length/weieht relationship of Siganus concatenata, ~ hexagonata,

~ oramin, ~ striolata and ~ virgata from Cebu (The Philippines).

(