Induced spawning and larval rearing of captive yellowfin porgy, Acanthopagrus latus (Houttuyn)

Aquaculture 143 ( 19%) 155- 166

Induced spawning and larval rearing of captive yellowfin porgy, Acanthopagrus Zatus ( Houttuyn) Ming-Yih Leu a,*, Yu-Han Chou b a Husbandry Centre, National Museum of Marine Biology/ Aquarium, Pingrung, 941 Taiwan. ROC b Taihsi Branch, Taiwan Fisheries Research Institute, Y&in, 636 Taiwan, ROC

Accepted 6 February 1996

Abstract Females of yellowfin porgy (Acanfhopagrus Zarus) were induced to spawn by a single injection of 1000 IU kg-’ human chorionic gonadotropin (hCG), 0.5 ml kg-’ Ovaprim (sG~RH-A in combination with domperidone) or a combination of hCG (500 IU kg-‘) with Ovaprim (0.25 ml kg-‘). Ovaprim, at a dosage of 0.5 ml kg-‘, was the most effective. Fish injected with propylene glycol or 500 IU kg-’ body weight of hCG did not spawn at all. Fertilization rates ranged from 72 to 84% and hatching rates were between 60 and 88%. The hatched larvae were reared in 30-45 t cement tanks and fed initially on trochophore oyster larvae (Crussosfrea gigas), followed by rotifers (Bra&onus plicarilis), Artemia nauplii, copepods and finally weaned onto a zein micro-coated diet. Metamorphosis started when larvae reached 9.7 mm TL at 30 days of age, and was complete by Day 38 when larvae were 12.4 mm TL. From Day 20 after hatching, the larger larvae (> 7 mm TL) began to exhibit agonistic behavior. Intestinal swelling was frequently observed in larvae at 22-25 days after hatching (5-8 mm TL). Two types of skeletal malformations, lordosis (lo-21 %) and brachyospondyliosis (l-4%), were frequently observed in the juvenile stage. Initial larval stocking densities were inversely correlated with survival (r = - 0.80, P < 0.01). Optimal initial stocking density was lo-15 larvae 1-l. Larval rearing trials for growth and survival to 50-- 56 days produced juveniles of 20 mm average total length, at a survival rate ranging from 0.7 to 27.5%. Keywords: Acanrhopagrus Zatus; Induced spawning; Agonistic behavior; Intestinal mation

* Corresponding

author.

OO44-8486/%/$15.00 Copyright PII SOO44-8486(96)01272-O

0 1996 Elsevier Science B.V. AI1 rights reserved.

swelling;

Skeletal malfor-

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1. Introduction Yellowfin porgy ( Acanthopagrus lam), a protandrous hermaphrodite (Kinoshita, 1939; Abol-Munafi and Umeda, 19941, is an important sparid fish in fisheries and aquaculture in Taiwan. This species is widely distributed in southern Japan, Taiwan, the East China Sea, the South China Sea, the Indian Ocean, and the east coast of Africa (Masuda et al., 1988). The fish live in coastal shallow waters and are common in brackish water swamps or estuaries. It is considered to be a good candidate for mariculture because of its high economic value and its ability to adapt to variation in salinity and temperature (Kasahara, 1957). The spawning season varies among localities. In Japan (Matsuoka et al., 1975; Abol-Munafi and Umeda, 1994) and Taiwan (Tsay and Yu, 1980) spawning occurs between September and December, and between January and March in Kuwait (Abu-Hakima, 1984). Natural spawning of A. lutus in captivity has not yet been reported. As with many other mariculture species, seed supply is a problem. Some progress has been made in induced breeding. Successful induction of ovulation and fertilization of eggs have been reported by Akazaki and Hashimoto (1978) and Liu and Hu (1980). Tsay and Yu (1981) induced spawning in 3-year-old broodstock from rearing ponds. Embryonic and larval development were described by Akazaki and Tokito (1982). Although hormone induced ovulation is a technique widely used to spawn this fish, a full description of the rearing method has not yet been presented. The major obstacle to successful mariculture of this species in particular is the low survival of its larval stages. Although induced spawning and hatching were achieved, survival of larvae did not exceed 2 days (Tsay and Yu, 1981). This paper reports the results of experiments on induced spawning using different types of hormones and the large-scale rearing of A. Zutus larvae. This would serve as a basis for the establishment of commercially viable hatcheries.

2. Materials and methods 2.1. Broodstock

maintenance

Three separate experiments were carried out at the Taihsi Branch of the Taiwan Fisheries Research Institute, Taiwan, between October and March in 1988-1991. One month before the spawning season, 3 to 5-year-old fish were selected from a broodstock which were held in an 0.1 ha outdoor earthen pond. Males were examined for free milt. The mature females could be distinguished from males by their swollen and soft abdomens. Ovarian biopsy was carried out on females with a 2 mm diameter polyethylene cammla. The females weighed from 449.1 to 1637.2 g and ranged in size from 23.3 to 42.5 cm fork length. The males weighed from 421.8 to 1485.1 g and ranged from 24.5 to 39.6 cm fork length. Brood fish were reared in indoor circular cement tanks of 100 t capacity with salinities of 30-33 ppt and a temperature of 18-25°C. The water quality in the spawning tank was maintained by changing 50% of the tank water daily. Lighting schedule during the preconditioning and spawning period were ambient.

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Facilities and broodstock rearing methods were similar bream (Rhabdosargus sarba) by Leu (1994).

to those described

157

for silver

2.2. Induced spawning In the experiment carried out in 1988, the females were injected intraperitoneally with different doses (500-1000 IU kg-’ body weight) of human chorionic gonadotropin (hCG, China Chemical and Pharmaceutical Co., Taiwan). Control fish were not injected. In the experiment carried out in the 1989, the females were injected intraperitoneally with one of the following preparations: (a) a combination of salmon gonadotropin-releasing hormone analogue [sG~RH-A, (D-Arg6, Pro’, NEt)-LHRH] and domperidone dissolved in propylene glycol as the primary solvent; these two chemicals were obtained in solution form from Syndel Laboratories Ltd. (Vancouver, BC) where they were marketed under the trade name Ovaprim (Henceforth, the name Ovaprim is used interchangeably with the sGnRH-A and domperidone combination); the injection volume was maintained at 0.5 ml kg-’ body weight of the fish (each ~1 of solution contained 0.02 p_g sGnRH-A and 0.01 mg of domperidone); or (b) combinations of Ovaprim (0.25 ml kg-’ body weight) with hCG (500 IU kg-’ body weight). In the experiment carried out in 1990, the females were injected intraperitoneally with either Ovaprim (0.5 ml kg-’ body weight) or with an equal volume of propylene glycol used as a sham control. Injections were not required in all cases for males, because sufficient running ripe individuals were available. Fish were anaesthetized in 200 ppm 2-Phenoxyethanol (Nihon Shiyaku Industries, Ltd., Japan) before handling. After injection, fish were returned to the spawning tank with continuously flowing seawater (200 1 min-I). The spawned eggs were fertilized naturally by the males. Fertilized eggs were collected from the spawning tank using a fine net (100 pm mesh size). Unfertilized eggs which settled to the bottom of the spawning tank were removed by siphoning. The fertilized eggs were then transferred into several indoor cement tanks (30-45 t capacity) for incubation and the larval rearing trials. The eggs were incubated in meshed baskets (350 km) equipped with independent airlift systems which kept the eggs in suspension. Egg number was estimated volumetrically. Fertilization and hatching rates were estimated with 100 eggs from each spawn in a 1000 ml beaker of seawater. Fertilization rate was determined as the percentage of normally developing eggs at 10 h after fertilization. Hatching rate was determined as the percentage of eggs hatched of those fertilized. 2.3. Larval rearing Initial larval stocking densities were 17-37 larvae 1-l in the 1989-1990 experiment and lo-25 larvae 1-l in the 1990-1991 experiment. The feeding scheme used in this study is summarized in Fig. 1. From Day 2 to Day 10 after hatching, the larvae were fed with trochophore oyster larvae (Crussostrea gigas), at a density of 5-10 trochophore larvae ml- ‘. After Day 3, rotifers (Bruchionus plicatilis) cultured with Nunnochloropszs sp., were fed to the larvae. The density of the rotifers was maintained at lo-20 individuals ml- ’ for the first 18 days and at 5-10 individuals ml-’ until 35 days after hatching. From Day 18 to Day 43, the larvae were fed with newly hatched Artemia

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4-Oystert rochophores _Brachionus

plicatilis-

YAArtemia --

salina

nauplii-

-Copepods-

-Artificial

I cl

I

I

I

I

I

10

20

30

40

50

Days

after

hatching

Fig. 1. Feeding scheme for larval rearing of Acunthopagrus

Table 1 Composition

diet-

of zein micro-coated

lam.

diet

Ingredient

g 100 gg’ diet

u-Carrageenan Oyster extract Egg yolk Shrimp extract Squid meal Concentrated fish soluble Egg albumin EPA oil Soybean lecithin Soybean oil Mineral mixture a Vitamin mixture b Papain ’ Total ikin* Proximate analysis (% of diet) Moisture Protein Lipid Ash Nitrogen free extract

2.5 24.5 15.0 5.0 5.0 15.0 10.0 2.5 5.0 5.0 5.00 5.00 0.5 100.0 5.0 9.3 36.4 29.6 9.0 15.7

’ Mineral mixture contained (% of mineral mixture): NaH,P0,.2H,O, 30.305; ferric citrate, 1.435; calcium lactate, 1.964; seaweed powder, 65.746 (as carrier).b According to Halver (19571.’ Nakarai Chemicals Co. Ltd., Japan.* Coating materials.

Untreated hCG 500 IU kg-’ hCG 1000 IU kg-’ hCG 500 IU kg- ’ + Ovaprim 0.25 ml kgOvaprim 0.5 ml kg-’ Ovaprim 0.5 ml kg-’ Sham control

1988

’

100 126 11

34 20 12 b 50

Number of females

4 5 5

3 3 3 4

Age (years.1

928.4- 1420.5 1208.7- 1660.9 1375.6-1637.2

450.9-58 1.2 449.1-538.7 470.5-570.3 977.3-1312.0

(g)

Body weight

lam

59 50 -

56 38

(h)

Latency a

of female Acanthopagrus

a Latency, interval between the time of injection and spawning. b Only three of the twelve fish injected once spawned eggs.

1990

1989

Treatment

Year

Table 2 Results of various hormone treatments for induced spawning

Nov. 20-Dec. Nov. I8-Dec.

6 (17) 7 (20)

94 427 126 747

672 16 154

No. of Eggs collected (no. X 103)

seasons

82.5 84.0

46.8 72. I

(o/o)

Fertilization rate

during the 1988 to 1990 spawning

Dec. 4-Dec. 6 (3) Nov. 2-Nov. 15 (14)

(d)

Spawning period

conducted

88.3 79.6

60.5

(a)

Hatching rate

160

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salina nauplii, the density of Artemia was maintained at l-2 individuals ml-‘. Beginning on Day 20, the larvae were also offered wild collected copepods at a density of about five individuals ml-‘. From Day 30 onwards, a zein micro-coated diet (zein MCD, 400-700 p,rn particle size) containing 36.4% protein was offered to the larvae. The preparation of the zein MCD was described by Leu et al. (1991). The composition of the zein MCD is presented in Table 1. By Day 45, the larvae were fed on the zein MCD only. Incubation and rearing salinity was 30 + 1 ppt until 40 days after hatching and then gradually decreased (lo-20%) per day to 15 ppt by diluting the seawater with freshwater. The water temperature in the rearing tanks during the experimental period was maintained at 22 k 2°C by thermostatically controlled heaters. Water in the rearing tanks was maintained as a static system with very mild aeration (5-10 ml air min-’ > until 9-10 days after hatching. After Day 10, seawater was replaced at 10% per day. At the stage when the fish were fed on Artemia, one third of the rearing water was changed once daily. When the larvae started feeding on the zein MCD, running water at a rate of about 15-20 1 min- ’ was applied to avoid water quality problems. Sediment, unhatched eggs, and dead larvae were siphoned from the tank daily. Salinity, temperature, pH, and live food counts were also monitored daily. The larvae were examined for gut content after feeding using a light microscope. At the end of each rearing trial the number of juveniles was determined by direct count. Correlation between percentage survival and initial larval stocking density was computed.

3. Results The results of the induced spawning trials are summarized in Table 2. In the 1988 spawning season, the untreated females did not spawn. Females injected with 500 IU kg-’ hCG also did not spawn successfully; however, a dosage of 1000 IU kg-’ hCG induced three females to spawn 56 h after injection. A total of 672 X lo3 eggs was collected with a fertilization rate of 46.8%, but none hatched. In 1989, the females injected with hCG (500 IU kg-‘) combined with 0.25 ml kg-’ Ovaprim or 0.5 ml kg- I Ovaprim alone spawned successfully, a total of 16 154 X lo3 and 94427 X lo3 eggs were collected, respectively. Latency periods ranged from 38 to 59 h after the injection. The rates of fertilization and hatching in the fish injected with hCG in combination with 0.25 ml kg-’ Ovaprim were lower (72.1% and 60.5%, respectively) than for fish which received 0.5 ml kg-’ Ovaprim (82.5% and 88.3%, respectively). In 1990, similar to the previous results, the females injected with 0.5 ml kg-’ Ovaprim alone spawned successfully. Spawning was observed 50 h after hormone treatment. A total of 126747 X lo3 eggs was collected with a fertilization rate of 84%. The hatching rate was 79.6%. Spawning was not induced by the sham control treatment. Fertilized eggs were transparent, spherical and pelagic, with a diameter of 0.83 + 0.02 mm, and a central oil globule of 0.22 k 0.01 mm diameter. At a temperature of 21.4-22.8”C, hatching time was 31-28 h after fertilization. Growth of A. latus is shown in Fig. 2. Newly hatched larvae measured 1.98-2.06 mm in total length (TL, average 2.03 mm) with 25 pairs of myotomes. Yolk-sac

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161

30-

25

-

Y=

r= 20

-

15

-

F E .c D : _

lo-

0 2

5

-

Day,

oflcr

hatching

Fig. 2. Mean growth in total length ( *SD, n = 20) of Acanthopagrus 1990-1991 season.

latus during the rearing experiment in

was completed in 2-3 days. The mouth was open by Day 3. At this time the mouth was about 320 km wide. Trochophore oyster larvae first appeared in the guts of the larvae on the 4th day after hatching, at which stage the larvae were about 2.95 mm TL. Feeding on rotifers was first observed 6 days after hatching, when the larvae attained a mean TL of 3.27 mm. The morphological transition from the larval to the juvenile stage occurred during the 30th to 38th day, between 9.75 and 12.41 mm TL. Transition to the demersal life stage was observed at this time. Results of the rearing trials conducted in 1989- 1990 and 1990- 1991 are summarized in Table 3. In 1989-1990, five larval rearing trials were conducted. The juveniles (n = 328 500) reached a mean total length of 20.7 + 3.4 mm after 52 days of rearing. The survival rate ranged from 0.7 to 13.5% with an average of 6.4%. The average initial stocking densities were 25.5 + 8.9 larvae 1-l. In 1990-1991, six rearing trials of larvae were conducted. The (n = 584300) reached a mean total length of 20.3 f 1.5 mm after 50 days of rearing. The survival rate ranged from 5.4 to 27.5% with an average of 14.6%. The average initial stocking densities were 17.6 + 6.6 larvae l- ‘. Initial stocking densities and average survival were significantly and inversely related (P < 0.01, r = - 0.80). Throughout the various rearing periods, several potentially important observations were noted. One of the major problems was the loss of cultured fish caused by disease. resorption

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Table 3 Summary of stocking density, harvest density, survival and growth trials conducted during the 1989- 1990 and 1990- 1991 seasons Trial number

Water volume

Stocked (no.)

Cm31

Stocking density (no. l- ‘)

Age (days)

Acanrbopagrus Survival (o/o)

lams from larval rearing

Harvest density (no. I- ‘1

Total length (mm)

1989-1990 1 2 3 4 5 Mean SEM

30 30 45 45 45 39 8.2

614000 584000 1500000 1657000 778 000 1026600 512212.6

20.5 19.5 33.3 36.8 17.3 25.5 8.9

50 55 56 50 50 52.2 3.0

5.6 13.5 0.7 1.4 10.9 6.4 5.7

1.1 2.6 0.2 0.5 1.9 1.3 1.0

18.5 23.0 25.1 16.6 20.3 20.7 3.4

1990-1991 1 2 3 4 5 6 Mean SEM

30 30 45 45 45 45 40 7.7

750000 750000 792000 792 000 459000 459000 667 000 162207.3

25.0 25.0 17.6 17.6 10.2 10.2 17.6 6.6

50 50 50 50 50 50 50 0

8.7 5.4 14.8 20.1 27.5 11.2 14.6 8.1

2.2 1.4 2.6 3.5 2.8 1.1 2.3 0.9

18.3 20.1 19.0 21.8 22.2 20.5 20.3 1.5

Intestinal swelling was frequently observed in larvae at 22-25 days after hatching (5-8 mm TL), but the cause of this disease is unknown. Overfeeding with Arremia nauplii and copepods often causes mass mortalities of larvae due to indigestion. From about 20 days after hatching, a few of the larger larvae > 7 mm TL began to exhibit agonistic behavior. They chased and sometimes apparently bit eachother’s eyes and tail. Fish were raised up to 50 mm TL, the size at which agonism ceases. Two types of skeletal malformations occurred in the juvenile stage of A. latus. Lordosis, characterized by an abnormal V-shaped curvature of the spine, was found in 10.3% of the fish in 1989-1990 and 21.6% in 1990-9191. On the other hand, brachyospondyliosis, characterized by incomplete growth of centra and arches, was found in 1.3% of the fish in 1989-1990 and 4.8% in 1990-1991.

4. Discussion At the present time, A. Zatus will not spawn in captivity without hormonal intervention, a single injection of Ovaprim (sGnRH-A in combination with domperidone) (0.5 ml kg-‘) alone or a combination of Ovaprim (0.25 ml kg-’ ) with hCG (500 IU kg-’ ) resulted, within 38-39 h, in successful induction of spawning of A. latus. Although hCG is well known to induce spawning in various teleosts, it has been suggested to lose effectiveness in some species because of antibody development in female broodstocks (Marte et al., 1988; Peter et al., 1988). In Taiwan, captive A. Zatus were first induced to

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spawn by injection of hCG combined with a preparation of the pituitary gland from common carp (Cyprinus carpio) in 1980; although fertilization rates and survival were poor (Tsay and Yu, 1981). In this study, female A. lutus injected with 500 IU kg-’ hCG did not spawn successfully. The use of higher dosage (1000 IU kg-’ ) resulted in partial spawning, but none hatched. Furthermore, if fertilization and hatching rates are compared, the administration of 0.5 ml kg- ’ Ovaprim appear to be the most practical method to date for inducing spawning of A. Zufus. The results of the larval rearing experiment showed that the use of oyster trochophore larvae at first feeding, followed by rotifers, Artemia nauplii, copepods and zein MCD, has proved successful. Initial feeding of A. iutus occurred 3 to 4 days after hatching. During this initial feeding period, suitable food should be provided in order to obtain a good growth and survival rate (Abol-Munafi and Umeda, 1993b). Mouth size is a very important factor for feeding in larval rearing of fish; it can be a factor limiting prey size (Shirota, 1970). In intensive larval culture, the rotifer is widely offered as first prey for many species. However, A. lutus larvae indeed have relatively small mouth openings and cannot always be raised with rotifers. The mouth opening of A. lam larvae that had just started feeding was estimated to be about 320 p,rn when the angle between the upper and lower jaws was 90”. Assuming that the size of edible prey was 50-75% of the mouth size as proposed by Shirota (19701, the size of prey edible by A. Zutus larvae was calculated to be 160-240 p,m. Oyster trochophore larvae were first observed in A. lutus larvae fed 4 days after hatching. The size of the trochophores (about 60 p.m> makes them suitable as food for the early larval stages of A. lam (Days 3-5). However, trochophore larva will develop larva-shell in a matter of 16 h at about 23°C (Fujita, 1929) and these might be detrimental to the fish larvae. High larval mortality as a consequence of intestinal swelling in red sea bream (Pagrus major> (Yasunobu et al., 1988) and black porgy (A. schlegeli) (Kusuda et al., 1986; Matsumoto et al., 1988) have also been observed at hatcheries. This parallels our experience with A. lutus in this study. The characteristic symptom of the diseased fish is distinguished by a remarkably swollen intestine, which is usually full of undigested zooplankton. So far, the cause of this disease has not been clarified. Agonistic behavior is a major problem in the juvenile phase and is a common phenomenon in most intensively cultured sparids (Tang et al., 1979; Hussain et al., 198 1; Fukuhara, 1985; Tawada, 1986; Battaglene and Talbot, 1992). It is usually both a cause and an effect of size variation (Hecht and Pienaar, 1993). Moreover, Abol-Munafi and Umeda (1993a) note that the teeth structure is related to the behavior and feeding habits of A. lams. Serrated teeth start to grow in the larvae 6.6-7.0 mm TL 20 days after hatching when agonistic behavior commenced. This behavioral pattern ceased after attaining 50 mm TL when molarifomr teeth were fully developed. Agonism may result in school dispersal, and may well reflect a shift in the costs versus the benefits of schooling as fish mature and become less vulnerable to predation (Ryer and Olla, 1991). However, in terms of the primary goal of larviculture, which is to simultaneously rear robust larvae quickly and efficiently with minimum losses, agonism is a disadvantage that needs to be controlled. A primary prerequisite would be to determine the optimal densities for the species (Hecht and Pienaar, 1993). In red sea bream the rate of agonism is reduced by a reduction in density to less than the 10 larvae 1-l (Foscarini, 1988). For

164

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better survival, the initial stocking density of IO-15 larvae 1-l in the current study appears to be an optimal range. Malformation of the skeleton is a serious problem to many finfish species produced in hatcheries all over the world (Takashima, 1976, 1978; Takashima et al., 1976; Kitajima et al., 1977; Kitajima et al., 1981; Kitajima et al., 1994; Papema, 1978; Tesseyre, 1979; Hayashida et al., 1984; Shimizu and Fujita, 1985; Shimizu, 1987; Chatain, 1994). A high incidence of lordosis and brachyospondylie have also been observed in the juvenile stage of A. lafus. Until now lordosis has been correlated with the absence of a functional swimbladder at the larval stage (Kitajima et al., 1977; Kitajima et al., 1981; Kitajima et al., 1994; Papema, 1978; Iseda et al., 1979; Tesseyre, 1979; Hayashida et al., 1984; Chatain, 1994). A practical countermeasure for lordosis, a tool for cleaning an oily film on the water surface, was devised by Chatain and Ounais-Guschemann (1990). A similar strategy might reduce lordosis in A. lams. However, the causes and remedies of brachyospondylie have scarcely been found. In conclusion, the results of the present study suggest that Ovaprim or a combination of Ovaprim and hCG are more potent agents for successful spawning than hCG alone. Oyster trochophore larvae were a suitable initial diet for A. lams. Many questions, especially pathological factors, raised by this study await further investigations. However, the technique developed in this study should assist with procurement of seed for the establishment of a large-scale hatchery for a culture based fishery.

Acknowledgements The authors are grateful to I-Chou Lin and Chun-Hsien Huang for their assistance with broodstock management and hatchery operations. Thanks are also extended to Dr. Lee-Shing Fang for helpful criticisms of the manuscript.

References Abel-Munafi, A.B. and Umeda, S., 1993a. Studies on the development and differentiation of the digestive system of yellowfm porgy during larval and juvenile stages. Suisanzoshoku, 41(2): 257-264. Abel-MunaIi, A.B. and Umeda. S., 1993b. Effects of temperature, light intensity, salinity and delayed initial feeding on the growth and survival rate of artificially-produced yellowfm porgy Acanthopagrus latus (Houttuyn) larvae. Suisanzoshoku, 41(4): 44.5-453. Abol-Munati, A.B. and Umeda, S., 1994. The gonadal cycle of the yellowfin porgy, Acmthopagrus fatus (Houttuyn) reared in the net cage at Tosa Bay Japan. Suisanzoshoku, 42(l): 135-144. Abu-Hakima, R., 1984. Some aspects of the reproductive biology of Acanthopagrus spp. (family: Sparidae). J. Fish Biol., 25: 515-526. Akazaki, M. and Hashimoto, H., 1978. Studies on the seedling production of yellowfin porgy (Kichinu), Acantbopagrus farm Houttuyn. An anesthetic effect and an ovulation effect by injecting of hormone. Bull. Fat. Agric. Miyazaki Univ., 25: 277-285. Akazaki, M. and Tokito, A., 1982. Studies on the seedling production of yellowfin pogry (Kichinu), Acanthopagrus lutus Houttuyn-II Egg development and metamorphoses of larvae. Suisanzoshoku, 2%4): 218-228. Battaglene, S.C. and Talbot, R.B., 1992. Induced spawning and larval rearing of snapper, Pqrus uratus (Pisces: Sparidae), from Australian waters. N.Z. J. Mar. Freshwater Res., 26: 179-183.

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