CENTRAL INSTITUTE OF FISHERIES EDUCATION

VERSOVA

MUMBAI

AN ASSIGNEMENT ON

CAGE CULTURE OF SEA BASS AND POMFRET

COURSE: AQC- 506

SUBMITTED TO

Dr.PARAMITA

Scientist (AQC)

Submitted by Reg.No

IRSHAD AHMAD AQC-MA20-3

CAGE CULTURE OF SEABASS (LATES CALCARIFER)

Lates calcalifer (Bloch) is commonly called the seabass or giant sea perch. It has been cultured in Southeast Asia for more than ten years, in marine, brackish, and fresh waters. The cage culture of seabass in coastal waters is the most popular in Thailand, Hongkong, Taiwan, Malaysia, Singapore and Indonesia. The method is simple and highly profitable compared to pond culture. Thus, the cage culture of seabass has expanded very rapidly in the last five years in Thailand. However, the major constraints to rapid expansion, are the disease outbreaks during culture period and insufficuent supply of trash fish.

Despite some imperfections, the basic techniques of seabass cage culture have been developed and now considered economically viable.

1. Selecting a Suitable Site for Cage Culture

Criteria for selecting a suitable site for cage culture of seabass are the following:

1. Water salinity (which should range from 10–31 ppt).2. Tide and water depth. Water depth should be more than 2–3 meters.

This is due to the usual size of culture cage which is 5 m × 5 m and 2 m deep. The tidal fluctuuation should allow the water depth to be at least 2 meters at the low water of spring tide.

3. Current and waves. Area should be protected from strong winds, waves and current. An ideal area would be in protected bays, sheltered coves and inland sea.

4. Water quality. The site should be relatively free from domestic, industrial and agricultural wastes and other environmental hazards.

5. Water circulation. The site should have enough water circulation to improve on poor water quality that could occur at some period in the culture due to the decomposition of waste material which often accummulate at the bottom under the net cage.

The water quality parameters which are considered of minimum range for cage culture of seabass are shown in

Table 1. The suitable water quality for cage culture of seabass.Parameters Ranges

pH 7.5–8.3Dissolved Oxygen 4.0 – 8.0 mg/L.Water salinity 10 – 31 ppt.Water temperature 26 – 32 °cAmmonia — nitrogen less than 0.02 mg/L.Hydrogen sulfide None

2. Nursery.

Seabass fry and fingerlings should be reared in concrete tanks up to the size 2.5 cms or 1 inch. After that, they can be transferred for rearing in nylon net cages until they attain 25 cm or 10 inches in about 2 to 3 months of culture period. The most convenient cage design is a rectangular cage made of synthetic netting attached to wooden, GI pipe or bamboo frames. It is either a) kept afloat by styrofoam, plastic carbuoy or b) stationary by fastening to a wooden or bamboo pole at each corner. The size of cage varies from 0.9 × 2.0 m and a depth of 0.9 m to 1.0 × 2.0 meters and a depth of 1.0 meter (Figure 1). The mesh size of the nylon net is 1.0 mm. However, after a month of nursing, they can be transferred to cages with nylon net with mesh size of 0.5 cm. This would allow water to pass through the cages more freely. The stocking density is approximately 1,000 fingerlings per cage. Grading of fingerlings has to be done at least once a week during the nursery period. Stocking is done separately for each size group. This would minimize the losses from cannibalism. Fingerlings of 2.5–5.0 cms should be fed with ground trash fish at 8–10 percent of body weight daily or about 4 to 5 times a day. After that, they can be fed with finely chopped trash fish.

Table 2. Suitable mesh size of nylon net for various lengths of cultured fish.MESH SIZE LENGTH OF FISH0.1 cm 2.0 cm0.5 cm 2.0 – 10.0 cm2.0 cm 10.0 – 30.0 cm4.0 cm More than 30.0 cm

Figure 1. Nylon net cage for nursing seabass fingerlings.

The net cage should be checked daily to ensure that it is not damaged by crabs or clogged with fouling organisms. The cage should be cleaned every other day by soft brushing in order to allow water circulation in the cage.

The survival rate for the nursery period would be 50 to 80 percent. This would depend on feeding, aquatic environmental conditions, and the expertise of the fish farmers.

3. Rearing Marketable Fish

Fish are reared from juvenile to marketable size for another 5 to 20 months. The marketable size requirements of the seabass are between 700–900 g and 2,000–3,000 g. However, the size between 700–900 g is demanded by the local market and consumers in neighboring countries.

There are two types of cages used in seabass culture in Thailand:

a. Floating Cages

The net cages are hung on GI pipe, wooden or bamboo frames. The cage is kept afloat by styrofoam drum, plastic carbuoy or bamboo. The most convenient dimension for a cage is that of a rectangle and a volume of 50 cubic meters (5.5 m × 6 m × 2 m). The cage unit is stabilized with concrete weights at each bottom corner (Figure 2). The cage unit has to be anchored to the bottom. The cages might be rocked a little by strong wind and current. Floating cages can be set on coastal waters where tidal fluctuation is wide.

Figure 2. Floating cage.

b. Stationary Cages

This type is fastened to wooden poles installed at its four corners (Figure 3). Stationary cages are usually set in shallow bays where the tidal fluctuation is narrow.

The mesh size of nylon net would depend on the size of fish as shown in Table 2. Firstly, finglerlings should be transferred to a nylon net (mesh size of 2.0 cm) for about 2 months of culture period. Them they are moved to a cage net of 4.0 cm mesh size until harvest.

Figure 3. Stationary cage.

Stocking density for marketable fish culture varies from 12 sq. meters to 300 sq. meters (Table 3), depending on water quality and the environmental conditions of the culture site. Floating cages can be stocked with more than stationary cages. This is because floating cages are usually set in sites with better aquatic environmental condition such as deeper water, narrower fluctuation of water salinity, more rapid circulation and further away from sources of pollution.

Table 3. Growth of seabass at different stocking densities in cages (after Sakares, 1986).

Culture period(days)

Stocking density100/m3 150/m3 200/m3 250/m3 300/m3

  30 (1m) 119.7 g 115.6 g 116.7 g 117.7 g 117.8 g  60 (2m) 222.7 g 218.4 g 208.6 g 212.4 g 208.1 g  90 (3m) 309.0 g 306.4 g 294.4 g 293.1 g 285.1 g120 (4m) 380.0 g 361.2 g 368.0 g 353.0 g 345.7 g150 (5m) 448.0 g 420.5 g 418.0 g 410.9 g 379.4 g180 (6m) 523.4 g 495.8 g 463.3 g 449.9 g 436.5 g210 (7m) 573.3 g 569.9 g 551.4 g 527.9 g 505.4 g

Trash fish is the main feed for seabass culture. Trash fish should be fresh and clean. The trash fish should be chopped and fed twice a day, in the morning and afternoon. The size must be suitable for the size of the mouth of the fish. The farmers should give the feed slowly and watch the fish. Feeding should be stopped when the fish no longer come up to the surface; it shows that the amount of feed is enough for them.

Food conversion rate of seabass culture in Thailand decreases with stocking density. They range from 3.0 to 10., 0. It also depends on the quality and quantity of trash fish. Normally, seabass can grow at an average of 1 kg/yr.

Survival rates for marketable fish culture would be about 80–95 percent in normal culture conditions.

The cages should be checked bimonthly or monthly to ensure that they are not damaged by fouling organisms, crabs or flotsam. The cages should be cleaned or changed every month. Therefore, fish farmers should have spare nylon net cages. Changing cages also allows the farmer to check on the number and health of the fish.

Silver pomfret (Pampus argenteus) as a new candidate species for aquaculture

Research on developing the culture technology for the silver pomfret Pampus argenteus Euphrasen was initiated for the first time during 1998 by the Mariculture and Fisheries Department (MFD) of Kuwait Institute for Scientifi c Research (KISR) and succeeded in larval rearing of this species

with the eggs collected from the wild (Almatar et al., 2000). Since then several investigations have been carried out at MFD, Kuwait, relevant to hatchery larval rearing (Al-Abdul-Elah 2001), feed requirement and growth under tank culture conditions (Cruz et al., 2000; Almatar and James 2007), breeding under domesticated culture conditions (James and Almatar 2007) and health management (Azad et al., 2007) of this species. In more recent years, during 2005, East China Sea Fisheries Research Institute and Shanghai Fisheries University in China have initiated research on the culture of silver pomfret and has succeeded in the larval rearing of this species based on the eggs collected from the wild (personalcommunication, Huang Xu-xiong, Shanghai Fisheries University, China). Other countries in Asia are also showing interest in developing the culture technology for this species because of its depleting wild stock, market demand and high price.

Hatchery and larval rearingThe hatchery performance of silver pomfret shows that it is possible to produce about 3.5 g size fingerlings for grow-out stocking within 50 days after hatching from the egg. Another advantage is that the larvae readily accept inert feed after a brief exposure to Artemia nauplii. This makes it easy to wean them to formulated feeds, enabling reduction in usage of costly live feed such as Artemia nauplii during the larval rearing period. Furthermore, unlike other carnivorous marine fish species, there is no cannibalism during the larval rearing period, making this species easier to handle. Research efforts have improved the survival rate of larvae from less than 1% during 1998 and 1999 to about 4% as of 2000 due to the improvements made in the administration of live feed in the hatchery. It is anticipated that further research will continue to improve larval survival and facilitate commercial ventures.

Growth performanceTo understand the optimum growth of silver pomfret, species specific formulated feed is required but it has not yet been developed. However, investigations carried out at MFD, Kuwait with an objective of screening the commercially available formulated feeds for this species have observed the suitability of salmon feed for the grow-out culture of silver pomfret. Research carried out at MFD during 2004 enhanced the growth rate of this species by using feed additives along with salmon feed and achieved growth rates of up to 1.5 g/fi sh/day. Recent investigations carried out on the growth performance of silver pomfret under tank culture conditions, using tank capacities varying from 4m3 to 125m3, show that the growth is fast in the initial period before winter under Kuwait’s climatic conditions. Under ambient seawater culture conditions the average body weight increased from 3.7g to 81.9g within three months of culture. The growth

rate is signifi cantly higher during summer and early winter when the ambient seawater temperature is above 26°C. In general, the growth rate of fi sh in relation to the tank culture water temperature shows a linear relation in which the fi sh growth rate increases with temperature up to 30°C. After 14 months of grow-out the combined male and female size rangedfrom 74-315 g (mean size 182.7±50.5 g). Wide size variation occurred in the population due to the smaller size of males compared to that of females. Furthermore, the males dominate in the population constituting 60-70% during the culture trials. The grow-out studies under tank cultureconditions show that it is possible to obtain marketable size fi sh of over 250 g size after 20 months (1.8 years) culture period. This growth rate is considerably higher than the estimated Silver pomfret fingerlings produced in the hatchery. Age of 2.86 years requirement for the wild stocks of silver pomfret to reach about 300 g size (males and females combined) under Kuwait’s climatic conditions. The results obtained till now are very encouraging to identify silver pomfret as a potential new candidate species for aquaculture.

Broodstock development and spawning.

The present cultured brood-stocks of silver pomfret at MFD/KISR originated from the wild eggs collected during 2004. Spawning of cultured silver pomfret under captive culture conditions was a challenging issue and remained elusive over the years untill 2006. Overcoming some of the technical constraints the MFD/KISR made a breakthrough for the fi rst time during 2006 in achieving natural spawning of two-year old cultured brood stocks kept in 125 m3 capacity tanks. Although matured males were present in the population, the eggs were not fertilized during 2006. However, during 2007 fertilized eggs were obtained through natural spawning in the brood-stock holding facility as well as through hormone induction. This has enabled us to produce hatchery reared progeny of this species for the fi rst time and showed the possibility of breeding the fish for commercial applications. Furthermore, breeding the fi sh under culture conditions will enable commercial hatchery production and farming of this species to meet market demand. Aquaculture of silver pomfret will alleviate the pressure on capture fishery and thereby allow for the recovery of its rapidly depleting wild stocks.

ProspectsThe temperature dependent growth of silver pomfret shows the possibility to achieve increased growth under tropical climatic conditions (26-30°C) thereby shortening the grow-out culture period. This will be a considerable economic advantage for commercial farming since this species is widely distributed in the tropical waters and fetches a very high market price.

Further research requirements augment for refi nements toenhance the egg quality and spawning of domesticated broodstock, hatchery larval survival and grow-out production assessments using earthen ponds and sea cages.

REFERENCES

Kungvankij, P. et. al. 1986. Biology and culture of seabass (Lates calcarifer), NACA Training Manual Series No. 3, NACA/RLCP. Bangkok, 70 p.

Sakaras, W. 1986. Optimum stocking density of seabass (Lates calcarifer) culture in cages. ACIAR Proceedings No. 20. 172–175pp. Canberra Printing Co. Melbourne.

Tookwinas, S. et. al. 1987. Cage culture of brackishwater fish in Satul Province. Technical Paper, Brackishwater Fisheries Division, Dept. of Fisheries. 30p.

Tookwinas, S. 1985. Consideration aspects for coastal aquaculture survey. Thai Fisheries Gazette. 38(4): 243–249.

Al-Abdul-Elah K.M., Almatar S., Abu-Rezq T. and C.M. James. 2001. Development of hatchery technology for the silver pomfret Pampus argenteus (Euphrasen): effect of microalgal species on larval survival. Aquaculture Research, 32: 849-860.Almatar S.M., Al-Abdul-Elah K. and T. Abu-Rezq. 2000. Larval developmental stages of laboratory- reared silver pomfret Pampus argenteus. Ichthyological Research, 47: 137-141.Almatar S.M. and C.M. James. 2007. Performance of different types of commercial feeds on growth of juvenile silver pomfret, Pampus argenteus, under tank culture conditions. Journal of the World Aquaculture Society, 38: 550-556.Azad I.S., Al-Marzouk A., James C.M., Almatar S. and H. Al-Gharabally. 2007. Scuticociliatosisassociated mortalities and histopathology of natural infection in cultured silver pomfret (Pampus argenteus Euphrasen) in Kuwait. Aquaculture, 262: 202-210.Cruz E.M., Almatar S., Abdul-Elah K. and A. Al-Yaquout. 2000. Preliminary studies on the performance and feeding behaviour of silver pomfret (Pampus argenteus Euphrasen)fingerlings fed with commercial feed and reared in fi berglass tanks. Asian Fisheries Science, 13: 191-199.James C.M. and S. Almatar. 2007. A breakthrough in the spawning of domesticated silver pomfret. Aquaculture Asia-Pacifi c, 3 (1): 26-28.