Southeast Asian Fisheries Development Center Aquaculture Department
SEAFDEC/AQD Institutional Repository http://repository.seafdec.org.ph
Journals/Magazines Aqua Farm News
1992
Can they be bred in captivity?
Aquaculture Department, Southeast Asian Fisheries Development Center
Southeast Asian Fisheries Development Center, Aquaculture Department (1992). Can they be bred in captivity? Aqua Farm News, 10(6), 7-9.
http://hdl.handle.net/10862/2611
Downloaded from http://repository.seafdec.org.ph, SEAFDEC/AQD's Institutional Repository
Can they be bred in captivity?
LUTJANUS JOHNI
The J o h n ’s snappe r (Lutjanu s jo h n i), also know n as golden snapper, is a popula r food fish in S ingapore. It m ay be d istinguish ed from o th e r lutjanids by its golden color, and a distinct dark spot on each scale, form ing d a rk streaks along the body. T he fish is found in coastal areas in the N orth A ndam an Sea and the South C hina S ea and m ay be caught in large schools w ith traw l. At present, the J o h n ’s snappe r is the third m ost im portant fa rm fish next to grouper and sea bass in S ingapore. The seed supply fo r farm ing com es fro m the w ild and is lim ited and irregular. B reeding experim ents have been conducted on the John's sna p p e r in S ingapore.
The broodstock are held in floating cages 5 x 5 x 3 m d eep at a d e nsity of 6-7 kg /m 2, or a total of 30-50 fish p e r cage. M ales and fem ales are kept to g e th e r in the sam e cage. The broodstock are fed on ce daily, in the m orning, w ith trash fish at 2.5% of body w eight.
In general, fe m ales attain m aturity at the age of 3 -4 years (3.5-4.5 kg), w hile m ales m ature at 2.5-3 years (2.3-3.0 kg). G onadal develop m e nt is m onitored m onthly to detect onset of spaw ning. O varian develop m e nt is determ ined by sam pling fro m 2-3 fem ales w ith a polyethylene cannula (2.5 m m in dia) and exam ining oocytes u n d e r a m icroscope. The m aturity of m ales is based on the m ilting co ndi
tion. M ilting m ales are available alm ost through- o u t the year, w hereas, ripe fem ales with oocytes at yolk globule stage can only be obtained during January to August. This period is considered the spaw ning season of John's snappe r in S ingapore.
Tw o spaw ning m ethods have been d e veloped so fa r fo r J o h n ’s snapper. Both m eth
ods use the horm one hum an chorionic g o n a dotropin o r hC G at 1 0 0 -5 0 0 IU/kg fo r the first in
jection and 250-500 IU/kg fo r the second injec
tion (24 h later). The artificial spaw ning m ethod em ploys m anual stripping of eggs and milt follow ed by artificial fertilization. This m ethod w as first used on J o h n ’s sna p p e r in the late 1970s, and has since been im proved and re
fined to give relatively co nsistent results. The
sp o ntan eous s p a w n in g m e th o d c o n s is ts of spontan eous o vu la tio n and natural fe rtiliza tio n in either 10-m 3 circ u la r fib e rg la s s o r 4 0-m 3 re c
ta n g u la r concrete tank. T he m e th o d w a s developed fo r John's s n a p p e r in th e e a rly and m id-1980s.
Artificial spaw ning usually produces 0.58- 0.81 m illion eggs per fem ale (average, 0.69 m il
lion eggs). A sig n ifica n t portion of the eggs is either prem ature o r o ve r-rip e , indicating non- sim ultaneou s m aturation.
In spontan eous spaw ning , th e fe c u n d ity and spaw ning pattern of J o h n ’s s n a p p e r d iffe r w ith th e type of spa w n in g tank. In th e 10-m 3 tank, the eggs are disch a rg e d all at one tim e, on average 0.92 m illion p e r fe m a le . In th e 40- m 3 tank, spaw ning is spread o v e r 4 days, at average fecundity of 2.83 m illion. T he m ean percentage of b uoyan t eggs o b ta in e d from spontan eous spaw ning in 4 0 -m 3 ta n k is 67% , higher than in 10-m 3 ta n k and fro m artificial spaw ning (44-48% ). A p paren tly, sp o n ta n e o u s spaw ning is a b e tte r m ethod fo r Jo h n 's s n a p per in term s of fe c u n d ity and egg quality.
D evelopm ent of the eggs at 27.5-28°C and 29 ppt is detailed in the fig u re on p. 8.
Source: L.C. Lim, L. Cheong, H.B. Lee, and H.H. Heng. 1985. Induced breeding studies of the John's snapper, Lutjanus johni (Bloch), in Singapore.
Singapore J. Pri. Ind. 13(2): 70-83.
Aqua Farm News X (6) November - December 1992 7
The fertilized egg (A) o f John’s snapper is trans
parent, spherical, and non-adhesive. The surface of the egg shell is smooth and non-segmented. The yolk is also non-segmented. Fertilized egg is usually buoy
ant and a single oil globule is present, whereas sunken eggs usually have multiple oil globules. The perivite
line space is narrow. The egg diameter ranges from 0.77-0.85 mm with mean 0.80 mm. The diameter of oil globule is about 20% o f the egg diameter, with a range o f 0.15-0.17 mm and mean 0.16 mm.
The embryonic development is similar to many other pelagic eggs. At 27.5-28.0PC and 29 ppt, the one-cell stage (B) appears within 10 min after fertiliza
tion while the first cleavage (C) occurs within 20 min after fertilization. Subsequent cleavages (D-G) occur at every 10-15 min. Cleavage continues until the multiple-celled (H) stage is reached at 1 h 25 min. The
blastula stage (I) occurs at 2 h 5 min. The early gastrula (J) stage is reached at 4 h 25 min. The neural groove appears at the late gastrula stage (K-L) a t 7 h 10 min. The neurula stage (M) is reached a t 8h 20 min.
At 9 h 25 min, the early embryo (N) is formed. The first movement of the embryo (O-R) occurs at 14 h 40 min.
The movement becomes more vigorous towards hatch
ing. First hatching (S) occurs at 17 h after fertilization.
The larva breaks egg membrane, and the head emerges first. A ll the larvae would have emerged by 17 h 30 min.
The hatching time o f John's snapper is highly temperature dependent, being 14.5-15.0 h at 29.0- 29.5°C and 17.0-17.5 h at 27.5-28.0°C. The hatching rate varies with the method of spawning: 30-55% in artificial spawning, 50-75% in spontaneous spawning in 10-m 3 tanks, and 70-85% in spontaneous spawning in 40-m3 tanks.
8 Aqua Farm News X (6) November - December 1992
LUTJANUS ARGENTIMACULATUS
The red snapper, Lutjanu s arg e n tim a cu latus, w as spaw ned at the AQ D T igbauan Main S tation for the first tim e on 20 A ugust 1992 by Dr. A rnil C. Em ata, study leader fo r snapper broodstock developm ent.
The spaw ners (fem ale of body w eight 4.25 kg and m ale of 3.6 kg) w ere held in a circular concrete tank (4-m dia. by 1.5-m deep) and injected w ith 1500 IU hum an chorionic g o
nadotropin p e r kg of body w eight. T he fish spaw ned b etw een 5:00 to 5:30 PM, 27 hours after injection. A total of 1.3 m illion eggs w ere collected by seining and by m eans of an air-lift egg co llector installed in the tank. Fertilized eggs w ere spherical (0.7-0.8 m m dia.), buoy
ant, transparent, and w ith a single oil globule 0.08-0.18 m m in diam eter. F ertilization rate w as 95% . H atching o ccurred 16 hours fo llo w ing spaw ning. A total of 305 000 larvae w ere
produced (hatching rate, 23% ). Larvae w e re reared to 25 days using A Q D ’s fish hatchery techno-logy.
P relim inary w ork on go n a d a l d e v e lo p ment indicates that w ild -ca u g h t red sna p p e r held in concrete ta nks and flo a tin g net cages are sexually m ature from early M ay to late O ctober. M ales and fe m ales used fo r induced spaw ning can rem ature in three w e e ks. M ature fem ales w eigh m ore than 3.5 kg and can spawn 1.3 million eggs. Further research should now focus on d e velop ing reliable te c h n iq u e s fo r spaw ning and larval rearing.
T his first recorded spaw ning of s n a p p e r in the P hilippines holds prom ise fo r the a q u a c
ulture industry. Snapper fry are not abun d a n t in the w ild, and they m ay have to com e fro m the hatchery. S nappe rs have en o rm o u s potentia l as cultured species and have e xce lle n t m arket value locally. Infofish In te rn a tio n a l indicates that the m arket fo r snappe rs is g ro w in g in H ong Kong, S ingapore, and Japan.
Dr. Arnil C. Emata (left), study leader for snapper broodstock de
velopment at SEAFDEC/AQD, said that the Philippines now joins Sin
gapore, Malaysia, and Thailand in having successfully matured and spawned snappers in captivity.
Available soon!
The Proceedings of the Aquaculture Workshop for SEAFDEC/AQD Training Alumni will be available in early 1993. The workshop was held 8-11 September 1992 at Tigbauan, Iloilo, Philippines. The vol
ume includes the experiences of the training alumni (from three SEAFDEC Member Countries - Malaysia, Thailand, and the Philip
pines) in shrimp and marine fish seed production, grow-out culture, fish disease problems, and fish nutrition. SEAFDEC/AQD research, training, and information activities are also covered.
Aqua Farm News X (6) November - December 1992 9
