INS/81/008/Technical paper No.9   March 1989 INDUCED SPAWNING AND LARVAL REARING OF SEABASS (LATES CALCARIFER BLOCH) IN CAPTIVITY CONTENTS

S. Chantarasri, Hanung Santosa, Hardoto
and
Sumbodo Kresno Yuwono

Project Document Identification

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C O N T E N T S

1. INTRODUCTION

2. ACKNOWLEDGEMENT

3. MATERIALS AND METHODS

3.1 Broodstock
3.2 Induced gonadal maturation
3.3 Rearing of larvae
3.4 Tank management
3.5 Grading
3.6 Stocking density

4. RESULTS

5. DISCUSSION

6. LITERATURES CITED

LIST OF TABLES

Table 1 Types of hormones, dosages and time intervals used for induced spawning of Lates calcarifer, from 22 October - 25 December 1988

Table 2 Hatching and survival rate of seabass egg and larvae from 23 October - 25 December 1988

Table 3 Stocking rate of seabass larvae at different ages

Table 4 Survival rate of seabass larvae of the third batch

Table 5 Amount and cost of Artemia used for the production 1,000,000 seabass larvae per crop (30 days old)

Table 6 Cost of trash fish used for the production 1,000,000 seabass larvae per crop

Table 7 Amount and cost of hormones used for the production 1,000,000 seabass larvae per crop

LIST OF FIGURE

Figure 1 Feeding scheme on larval rearing of seabass

INDUCED SPAWNING AND LARVAL REARING OF SEABASS
(LATES CALCARIFER BLOCH) IN CAPTIVITY

S. Chantarasri, Hanung Santosa, Hardoto
and
Sumbodo Kresno Yuwono

Abstract

Seabass (Lates calcarifer) were successful induced to spawn in captivity by hormonal induction. The hormones used for the trials were HCG + Synthetic hormones (Puberogen). The dosages used were 250 IU HCG + 50 RU of Puberogen per kg of fish for first injection and 500 IU HCG + 100 RU of Puberogen per kg of fish for the second injection at an interval of 24 hrs. The fish responded well to the hormones and dosage given. The fish spawned naturally in a 8-ton fibreglass tank within 10 hrs after the second injection.

The larvae were reared in a 1.7 tons fiberglass circular tank at an initial stocking density of 60–100 larvae per litre. Feed used were Tetraselmis chuii + Brachionus + Artemia nauplii + subadult Artemia + minced fish. The third batch produced 600 000 of 30-day fry. The average survival rate from yolkfish to 30 days old fry was about 45 percent.

The results suggested that inducing the fish to spawn during off spawning season by hormones manipulation might result in high percentage of unfertilized eggs and abnormal fry. As other marine fish, the seabass fry required a diet containing high level of highly unsaturated fatty acid (HUFA) to obtain fast growth and high survival rate.

1. INTRODUCTION

Seabass, Lates calcarifer (Bloch) has been commercial cultivated species with high potential in freshwater ponds, brackishwater ponds and marine netcages in Indonesia, Malaysia, Taiwan, Singapore, Hongkong and Thailand. The seabass is relatively highly-priced and widely accepted species and becomes an attractive commodity for both large and small-scale fish culture enterprises.

Seeds used for culture in Indonesia at present are normally obtained from the wild. The availability of fry from natural water however, fluctuated widely from time to time, making its supply erratic and inconsistant. To ensure adequate and regular supply of seed for culture, and to reduce negative impact on wild stock juveniles, the National Seafarming Development Centre was established to play a role of marine finfish seed production and distribution Centre in Lampung. As requested by the Government of Republic of Indonesia, the United Nations Development Programme and the Food and Agriculture Organization of the United Nations has provided the technical assisstant through the FAO/UNDP Seafarming Development Project INS/81/008.

The breakthrough in induced spawning of seabass in captivity through hormones manipulation came on April 8, 1987. Since then the Seafarming Development Centre has carried on the programme to improve the hatchery techniques and to intensity its production, and to obtain data for packages of technology. The report is a part of the work carried out at the Seafarming Development from September-December 1988 in refinement of technology and as a part of transfer of technology programme to Indonesia.

2. ACKNOWLEDGEMENTS

The authors are grateful to Dr. Banchong Tiensongrusmee the Chief Technical Advisor of the FAO/UNDP Seafarming Development Project INS/81/008 for his supervision, guidance and his constructive criticism throughout the work both in hatchery operation and in preparation of the report. Appreciation is also extended to Mr. Kisto Mintardjo, the Project Co-Team Leader for his cooperation and support. The success of seabass seeds production was perfectly met with the sustained hard work and enthusiastic cooperation of colleaques of the hatchery unit of the National Seafarming Development Centre particularly, Mr Hardoto and Mr. Saharoon deserve special thanks. The authors are also grateful to Dr. Albert G.J Tacon, feed advisor, for his valued suggestion in feed and larval diet nutrition.

3. MATERIALS AND METHODS

3.1 Broodstock

Broodfish used in this trials were the broodfish that have been developed for hatchery uses since 1986. The fish were kept in floating cages (3.0×3.0×2.0m) anchored at the Seafarming Development Centre, Lampung Bay. The cages were made of polyethylene netting attached to GI pipe and bamboo frames kept afloat by plastic drums. Broodfish were fed daily with fresh trash fish at the rate of 1 per cent of body weight.

3.2 Induced gonadal maturation

Broodfish weighing about 2–5 kg were selected for the induced gonadal maturation. Only males and females with milt and egg stage V were used (Tiensongrusmee, et al 1989). Milts were observed at the genital opening of the mature male by applying slight pressure on the abdomen. The assessment of maturity of the female fish was made from eggs sampled by catheterization from the midportion of the ovary. Only females bearing uniform, spherical and non-adhesive eggs with a diameter of 0.5mm or more were selected for the trials. Hormones used were HCG and synthetic hormone (Puberogen) at dosages and time intervals as shown in Table 1.

Ethylene glycol at dose 1:10 000 was applied for general handling of broodfish. The fish spawned in 8-ton rectangular fiber glass tank. Fertilized egg were collected by using a fine net of 120 micron mesh size seiring out form the tank. Other foreign materials and detritius included in the collection were removed by screening. Unfertilized eggs settled on the bottom of the hatching tanks were removed by siphoning. The eggs were hatched out in 15 hrs at the water temperature of 27 degree celsius and the salinity ranging between 29–30ppt. The average size of fertilized eggs were about 0.75mm in diameter with 0.20 mm in the diameter of oil globule.

3.3 Rearing of larvae

The larvae were reared in indoor tanks at a stocking rate of 60–100 larvae per liter. The newly hatched larvae were measured at average 1.47mm. After one day old, the Tetraselmis chuii of density around 20,000–50,000 cells/ml was given to the larvae both as food and also for improving the water quality. On Days 2–4, rotifer size of 60–150 micron at the rate 3–5 pcs/ml was given. From Day 5 to Day 16, the mature rotifer was given at the rate 5–10 pcs/ml. During the first 16 days period, the larvae were in indoor tanks. All larval tanks were covered with cement tile. Covering the tank is not only good in maintain the water constant at 27–28 degree celsius, but also prevents blooming of diamtom due to the light stimulation.

Artemia was given when the larvae reached the age between 9–10 days old. The density of Artemia nauplii given was 3–5 pcs/ml. The Artemia was given until Day 25. For the third batch, pre-adult Artemia fed with Tetraselmis or Chaetoceros sp enriched with cod liver oil was given to the larvae at Days 21–30 at the density of 0.5–1 pcs/ml.

Minced fresh sardine or yellow stripped Caranx after scale and skin removed was given to the larvae at Days 25–30. Weaning for seabass fry to mince fish was started on Day 21. It took about 3 days for seabass fry to accept the minced fish as the wild stock.

3.4 Tank management

The rearing tanks were cleaned and dried before using. The amount of water replacement in the rearing tanks per day depends on food given at different ages. During the period of rotifer feeding, approximately 10–20 per cent of the water were changed. The volume of water change was increased to 50–60 per cent during the period that Artemia nauplii and sub-adult Artemia were given. The water exchage was increased to 100 percent when the trash fish was given. Feeding scheme of seabass larvae and fry age from Days 0–30 is given in Figure 1.

3.5 Grading

Stocking the same size of larvae and fry will reduce the rate of canibalism. Thus the survival rate will be increased and the growth rate of the fish could also be faster and more uniform in size. Grading was done by using the plastic mosquito nets of various mesh sizes to separate the fry into different size group as required with mortality less than one per cent.

3.6 Stocking density

During the first week, the larvae was stocked at a density of 60 000–100 000 larvae/cu.m of water. The stocking density was reduced to 35,000 to 40,000 larvae/cu.m in the second week, 15,000–20,000 larvae/cu.m in the third week and 6,000–10,000 fry/cu.m in the fourth week (Table 3).

4. RESULTS

From 22.10.88 to 25,12,88 three batches of broodfish were treated with the dosages of 250 IU HCG + 50 RU Puberogen per kg of fish for the first injection and 500 IU HCG + 100 RU of Puberogen of 250 per kg of fish for the final injection at interval of 24 hrs.

The first batch started the injection on 22 October 1988. Six broodfish ranging between 1.5–2.5kg were selected from 12 broodfish. About 2 millions fertilized eggs were obtained from 3 females. About 400,000 fry were hatched out. The hatching rate was 75%. The survival rate was good during the first 15 days. The larvae looked healthy with big abdomen. The mortality started at Day 18. Eventhough the fry looked healthy but the majority of the fry did not have a dorsal fin. Only 3 percent of the normal fry survived through Day 30. It was observed that the fry of this batch was sensitive to handling and frighten easily when disturbed. This is probably an early symtom of deficiency of highly unsaturated fatty acid (HUFA) shown in the larvae. The second batch was operated on 25 November 1988. Six broodfish sized 1.5–2.5kg were used at male and female ratio of 1:1. About 1.5 million fertilized eggs were obtained. The hatching rate was about 70%. Unfortunately all of the larvae were abnormal. The larvae had a small oil globule, not enable to float, tending to settle on the tank bottom and drown. All died after the second day.

The third batch was started on 25 December 1988. Three females size 4kg and 3 males size 3–3.5kg were used. About 3.5 million fertilized eggs were obtained. About 1.35 million larvae were hatched out. The hatching rate was 70 per cent. The larvae of this batch was normal and healthy. About 600 000 of 30days old fry were obtained. The larvae was fed with Argentemia Brand (Grade I Gold label). The period from hatching to metamorphosis was 24–26 days. The survival rate from Days 0–30 was about 46 percent.

Eight fibreglass circular tanks (1.7 ton each) and nine fibreglass both circular and rectangular tanks (8 ton each) were used for larval rearing. The tanks were covered with cemment tiles in order to maintain water temperature at the range of 27–28 degree celsius. The salinity of seawater for the larvae from 1–15days old. 16–23days old and 24–30days old were the range of 29–30ppt, 25–26 ppt and 28–31 ppt respectively (Table 4). PH of water was between 7.3–7.9.

Cost of feed, hormones and chemicals for the production of 1 million of the 30days old fry are summarized below.

About 15kg of Artemia was required. The price of Artemia is Rp140.800/kg (Table 5). The cost of Artemia per fry is about Rp. 8.5 million. Twenty one kg of Trash fish were needed for larvae from Days 21–30 and 2 kg/day for broodstock. The trash fish price was around Rp1000/kg (Table 6). Cost of hormones and Chemicals was around Rp.200,000. (Table 7). Costs and returns analysis of the production will be given in separated report.

5. DISCUSSION

The results suggested that for the successful induced spawning through hormones manipulation, the broodfish should have a minimum size at least 3 kg. The broodstock after treated with hormones spawned nutrally in the 8-ton rectangular tank after the second dosage of hormones was applied.

The high mortality and abnormal of fish larvae observed in the first and second batch might be due to following factors.

i. Off season spawning

The spawning season of seabass in Lampung area starts from January to June. The first batch was induced in October and the second one in November. Eventhrough the fish responsed well to the hormones and dosages given, but it was likely to have a negative effect on quality of eggs and milts causing abnormal off-springs as results shown in the first and second batch. However, it requires further studies for confirmation.

ii. Poor conditions of broodfish

The broodfish used in the trials were from the stock that have been heavy used in 1987 and the broodfish did not received proper diet as it should be due to shortage of budget of the national counterpart and quality of the trash fish given was poor. To remedy the problem. After the second trial in November, the feed and feeding of brood stock were under closed supervision of the FAO/UNDP hatchery advisor. Only good quality of the fresh trash fish was given at one percent of body weight daily prior to spawning (Halver, 1985 referred to King 1984). The 100 mg of vitamin E was given to each fish one week as supplementary feed by inserting in trash fish body cavity. This is to increase tocopherol level that required in development of ova.

The keys of the success of the third batch probably are not only contributing to the improving of broodstock nutrition, but also due to the improving in the nutrition diet given to the larvae during Days 3–30. Rotifer size about 60–150 u enriched with COD liver oil and Artemia nauplii and Artemia pre-adult enriched with Tetraselmis were used to improve the larval nutrition diet.

The result suggested that W3 HUFA is an essential for larvae and fry of Lates calcarifer nutrition. The result agreed well with the findings of Franicevic et al, (1986) who reported that larvae and fry of seabass Dicentrachus required diet containing high level of 20:5W3 and 22:6W3 and also of Lisac et al, (1986) who worked on seabeam Sparus auration.

The big difference in the survival rate of the turbot larvae fed with San Fransiscan Artemia nauplii (35%) and Brazilian Artemia nauplii as reported by Bromley and Sybes (1985) also confirmed the diet nutrition of different brands of Artemia used in the trials. The fry of the first two batches were fed with Artemia Bio-marine brand whereas the third batch was fed with Argentemia. The latter claims that the nauplii contained high level of HUFA than the former one. The experiment on diet nutrition of different brands of Artemia are being carried out to elaborate the finding.

Able to maintain the water temperature in the rearing tank constant at 27–28 degree celsius during 24 hrs period by covering the larval tanks is also another factor that contributed to the high survival rate of the larvae of the third batch.

The last factor contributed to the success of the third batch is the hard working of the hatchery staff throughout the rearing cycle. The experience in larvae rearing of the staff of the hatchery unit gained through On-the-job training from the Project since April 1987 is significant.

6. LITERATURES CITED

Bromley P.J. and P.A. Sykes, 1985 Weaning diets for Turbot (Scopthalmus maximus L). Sole (Solea solea). Nutrition and feeding in fish. Academic Press. N.Y. 489 pp.

Franicevic, V., D. Lisac, I. Buble, Ph. Leger and P. Sorgeloos 1987 Internal study on Artemia VLII. The effect on the nutrition quality of Artemia on the growth and survival of seabass (Dicentrachus labrax L) larvae in a commercial hathery, In: Proceedings of the conference or production in Marine hatcheries. Roving Zadar (Yugoslavia) 10–28 February 1989. 10 pp.

Halver, John E., 1985 Recent advances in vitamin nutrition and metabolism in fish. Nutrition and feeding in fish. Academic Press. N.Y. 489 pp.

Lisac, D., V. Franicevic, Z. Vejorlka, J. Buble, Ph. Leger and P. Sorgeloos. 1986 Internal study tour on Artemia VLIII. The effect on growth and survival of seabream (Sparus aurata) larvae. Paper presented at the Conference Ichthyopthologies in Aquaculture, October 21–24, 1986. Inter University Centre, Dubrovrik. 10 pp.

Tiensongrusmee, B., S. Chantarasri, Sumbodo Kresno Yuwono and Hanung Santosa. 1989 Propagation of seabass, Lates calcarifer in captivity. The Seafarming Development Project INS/81/008/Manual 15, 56pp.

Table 1. Types of hormones, dosages and time intervals used for induced spawning of Lates calcarifer, from 22 October - 25 December 1988

¹ First dosage of hormone injected
² Second dosage of hormone injected

Table 2. Hatching and survival rate of seabass egg and larvae from 23 October - 25 December 1988

¹ Notes: Figures in parentheses are survival rate of30days old seabass larvae from the yolk fishin percentage.

Table 3. Stocking rate of seabass larvae at different ages

Table 4. Survival rate of seabass larvae of the third batch

Table 5. Amount and cost of Artemia used for the production 1,000,000 seabass larvae per crop (30 days old)

1 Pre-adult of Artemia is prepared and applied
2 Argentemia cost Rp. 140,800/kg.

Table 6. Cost of trash fish used for the production 1,000,000 seabass larvae per crop (30 days old)

1 Trash fish cost Rp.1000/kg.

Table 7. Amount and cost of hormones used for the production 1,000,000 seabass larvae per crop

Figure 1. Feeding scheme on larval rearing of seabass