Development of New Technology in Tilapia Culture Systems

 

Hambal Hj. Hanafi and Chuah Hean Peng

Freshwater Fisheries Research Centre (FFRC),

Batu Berendam,

75350 Melaka,

Malaysia

e-mail: pppat@streamyx.com

 

 

Abstract

 

Malaysian farmers, in 2000, produced 16,383 mt of the Red Hybrid Tilapia in cages, tanks, pens and ponds. Growth rates of about 5 gm/day were consistently obtained for fish of an initial weight of 50 gm to a harvest size of 800 -1200 gm. Feed cost remains the major constraint to the development of the industry. Waste management is fast becoming an environmental issue. A green-water tank culture system with efficient waste management and water-saving features is arguably the best solution with respect to the biology of Tilapias and to fulfil the requirements of HACCP besides achieving a comparatively low eco-footprint status. Fry production was done in concrete tanks. Nursery in fibreglass tanks gave good survival with acceptable growth rates. Final grow-out was done in 25-mt tanks and cages to an average harvest size of 800 gm. The use of vacuum swing adsorption oxygen generators, hanging mats, improved cage construction materials, automation for real-time trending of system parameters, automatic feeders, and well-designed filtration systems offers various options to develop and modernize culture systems for Tilapia enabling the farmer to “manufacture to order”. The installation of an emergency aeration system can reduce the risk of mortality caused by dissolved oxygen deficiency. Health monitoring can prevent or reduce disease problems.  Harvesting and grading is done using newly designed equipment to reduce the need for manual labour. The initial capital investment remains economically unattractive for the basic installation of such a culture system in view of the low market value of Tilapia and relatively exorbitant costs of necessary equipment and commercial formulated feed. A farm-made experimental moist formulated diet can cut down feed cost by more than 50% while enhancing the efficiency of feed utilization to obtain a better feed conversion ratio.

  

Introduction

 

Assessment of existing culture systems in Malaysia

 

The phrase, "from tree-dwellings to towns" aptly describes the development of Tilapia culture systems in Malaysia; from extensive to semi-intensive/intensive culture and subsequently to super-intensive operations. In 2000, a total of 16,383 mt of Red Tilapia was produced in Malaysia.

 

The classification of systems and the requirements by each particular "intensity" of culture may be broadly tabulated as follows (Table 1). An alternative approach was adopted by Little (1998) who categorized Tilapia production systems with respect to their roles: ‘smallholder’, ‘commercial’ and ‘industrial’.

 

Table 1: Classification of culture systems based on production capacity (modified after Tacon, 1997)

 

Requirements

Production (mt/ha/yr)

0-1  1-15 15-20 20-100 100-1000
Extensive

Semi-intensive

   
   

Intensive

   
Fertilization - x x - -
Suppl. feeding - - x - -
Complete diet - - x x x
Aeration - - x x x
Recirculation - - - x x
Raceway/Cage - - - - x

 

 

In Malaysia, the dominant pond culture practice is semi-intensive in nature. Most extensive and to a smaller extent, semi-intensive culture systems attempt to optimize the use of primary production which is enhanced by fertilization in a process referred to as "controlled eutrophication" (Tacon et al., 1994). The various niches existing in such an environment may be utilized by various compatible species in appropriate stocking ratios. Normally, species of lower trophic levels are cultured. Environmental impacts of this type of culture systems are minimal because a lot of nutrient recycling occurs during culture. The main disadvantage of this system is the production of an assortment of fish species of highly variable grades and sizes requiring a significant amount of labour for the process of sorting. Such products may be suitable for village consumption but in terms of quantity they cannot cater for the larger commercial demand. The more ambitious farmers engage in semi-intensive monoculture using complete formulated commercial pelleted feeds and depend less on the pond’s natural productivity. If Tilapia is the species cultured, some farmers are able to obtain a food conversion ratio (FCR) of 1.3, deemed reasonably good. Aeration devices such as paddle-wheels, Aire-O2, and more recently, long-armed paddle wheels may be used when culture intensities approach the higher end of semi-intensive systems or in the event of a sudden deterioration of dissolved oxygen levels.

 

Cage culture has become an excellent means to produce Tilapia with little or no off-flavour. Basic cage installation is also relatively cheap and management is made easy. Most cage culture operations are being cariied out in lakes, reservoirs and other impoundments. Some farmers conduct cage culture in ex-mining pools where the water is normally oligotrophic. Presently, stocking rates of 10-30 fish per cubic metre of water is practised. Schmittou (1993) was able to stock 500 individuals/m3 in his innovative LVHD (Low Volume High Density) cages. Cage culture production ranges from 0.1 to 0.2 mt per cubic metre. A farm having 120 cages in a three-acre ex-mining pool in Simpang Pertang, Negeri Sembilan, has consistently produced about 20 mt of the Red Hybrid Tilapia per month (pers. comm.) with an overall FCR of about 1.3. On the research front, the last decade has seen the advent and rise of cage systems for monoculture. Traditional cages made of bare wooden frames buoyed by empty plastic or fiberglass-coated metal drums with nylon nets have evolved into rigid Netlon cages to elaborate giant cages using intricately engineered patterns of galvanized iron pipes equipped with harvesting hatches placed at strategic locations on the cages (Berita Perikanan, 1998). Perhaps the most utilitarian of all is the self-tilting ‘Wawasan 2020’ cages of Lake Kenyir, Terengganu, designed by Pathmasothy (1994). The size of the cages took into consideration the specifications of locally available materials, good water flow through the cage, and durability. For the purposes of cleaning, sampling, grading and harvesting, the cage may be tilted simply by releasing a fastening pin to allow air-filled drums to push it up above the water. Each unit of the system is made up of four 3 x 3 x 1 m cages. A farmer with a minimum of three to four units would be able to earn a good steady monthly income. Stocking density was 500 Red Tilapia per cage. After a culture period of five to six months, fish attained an average weight of 600 gm. The food conversion ratio was 1.3 using 28-30% Charoen Pokphand (CP) formulated pellets.

 

Cage culture is also carried out in rivers and irrigation canals. In the Terengganu River, 24 cages of 16 x 20 x 8 feet dimension, and three rectangular earthen ponds of 60 x 200 feet dimension, were used to produce Red Tilapia besides a few other freshwater species. After a culture period of 7 to 8 months, the Red Tilapia attained a size of 600–1000 gm (Cawangan Komunikasi, 2002). In the Linggi River, 318 cages produced on average, 10 mt of Red Tilapia (Mohd.-Samsi, 2001). In the Pedu-Muda irrigation scheme, 400 cages in canals are capable of producing 280 mt of Red Tilapia annually with 40% of the fish being more than 500 gm (MADA, 2002).

 

‘Hybrid systems’ are practiced where aquaculture takes over from other agricultural activities. Sometimes topographical features become constraints to the construction of well-planned culture systems.  Existing resources and facilities are adapted to optimize usage and production. Impoundments for water storage may be utilized for cage culture while ponds are constructed on whatever limited land space for fry production or for part of the grow-out cycle. An aquaculture operator in Simpang Pertang used 55 cement and earthen ponds to produce on a monthly basis, 300,000 Red Tilapia fry and 40,000 African catfish (Clarias gariepinus) fry (Unit Akuakultur, 2002). Another farmer in Rawang used cages and concrete tanks of an assortment of designs and sizes for fry production, hormonal treatment for sex-reversal, nursery and at least three stages of grow-out for Tilapia production (pers. comm.).

 

  

Development of an improved production system

 

Considering the requirements of Tilapia

 

The objective of aquaculture is to produce as much marketable fish as possible from a given volume of water in the shortest time and at the cheapest cost (New, 1987). In addition to this, aquaculture should also be carried out with minimal impact on the environment. In essence then, any development should seek to increase productivity from a given space, decrease the culture period, increase the efficiency of feed intake, and adequately address the problem aquaculture effluent has on the environment.

 

For Tilapia culture, one should also take into account its biology and intrinsic characteristics, and shortcomings such low market value, high feed cost, and mortality owing to handling (routine grading and harvest). Tilapias are low in the food chain, being herbivorous and omnivorous, having the ability to utilize a wide variety of locally available ingredients, making it economically feasible to farm. After an initial planktivorous stage, Tilapia fry begin to adopt an omnivorous habit, consuming mainly phytoplankton and detritus. If given formulated pelleted feeds, Tilapia seem to prefer smaller pellets than other species of comparable size. Owing to the absence of a true stomach, Tilapia feed constantly unlike some predatory fish such as the Marbled Goby (Oxyeleotirs marmoratus) and the Striped Snakehead (Channa striatus) which normally consume a big meal and then go off to rest for a long period of time. Gastric secretions in the Tilapia are at their maximum efficiency only in the late morning (Jauncey, 1984) resulting in food consumed in the early part of the morning being insufficiently digested. The implication of all these is that one should always feed Tilapia later in the day and at a frequency of four times a day. Little additional advantage is gained by feeding more than four times daily (Kubaryk, 1980). It has been shown that Tilapia may be farmed on an industrial scale in intensive cage or tank culture systems fed low-cost nutrient inputs devoid of fishmeal (El-Sayed and Tacon, 1996)! This further makes it feasible to farm the Tilapia since in formulating diets, the fish nutritionist should attempt to spare the protein which is always an expensive ingredient.

 

Tilapia production is set to become the number one aquatic crop. Salmon and shrimp are relatively expensive items owing to their culture technologies, higher feed costs and greater disease susceptibilities. Carps, the current leading aquaculture crop, have too many interstitial bones in the fillets which the unaccustomed consumer finds daunting or even disastrous. Carps often possess off-flavours. Tilapias are very versatile and can be produced in diverse manners: ranching in large lakes, cage culture, pond culture both static and flow-through systems, pens or enclosures in irrigation canals, tanks and raceways, in both monoculture and polyculture, and more recently, in aquaponics systems. Tilapia are hardy withstanding adverse water quality and low dissolved oxygen levels. However, this does not imply that they should be cultured under such conditions since poor water quality often retards feeding and growth and hence productivity. Tilapia are resistant to diseases, and when problems arise, they are readily treated. It is of little wonder that Tilapia production has been embraced by many for its ecologically sustainable characteristics and should be remembered when developing production systems (Fitzsimmons, 2000).

 

 

A system to farm Tilapia

 

The proposed culture operation further developed by the Freshwater Fisheries Research Center (FFRC) covers all aspects from broodstock maintenance and breeding to final harvest (Hambal, 2000).

 

 

Broodstock maintenance and selection

 

As practiced in the FFRC, Tilapia breeders are maintained in greenwater 2-mt rectangular fibreglass tanks and provided with ample aeration. Waste is siphoned from small netlon cages which have been placed in the tanks to create static zones and into which solid wastes are swept by the movements of fish and the powerful action of their caudal tail. Collection receptacles such as bottles also proved to be effective in preventing solid wastes from being meshed up and thereby causing deterioration of water quality. Potential breeders are selected based on fast growth at the fingerling stage and then again before being used as breeders per se. This type of selection is based on the observations in a study where each member of a cohort was grown individually in an aquarium. Individuals that grew faster in the early stages continued to have the same size advantage later on in the adult stage (Chuah, 1986). Depending on size and stage, 40 to 400 individuals are stocked in the broodstock tanks. Territorial males are examined for desired morphological characteristics such as small head, deep body, healthy scales, operculum thickness, and colour. Phenodeviants are discarded though they often grow just as well as normal fish. Females that have already bred are preferred over virgin females, some of which rarely breed at all if selected to go into breeding tanks. The breeding ratio for broodstock maintenance must always be one male to one female to minimize the probability of inbreeding. Effective population number and inbreeding effects are dealt with in Tave (1986) and Kincaid (1983).

 

 

Fry production in tanks

 

Fry production is best done in concrete tanks. Abalos (1998) managed to produce 29,000 fry per month for five months using 500 Nile Tilapia (Oreochromis niloticus) females bred with 100 Blue Tilapia (Oreochromis aureus) males in 154m2 of spawning and fry-rearing area. This gave an average of 58 fry/female/month (range was 37-74 fry/female/month) or 188 fry/m2/month. Suhairi et al. (2002) used a  3.6 x 2.7 x 0.5 m (0.3 m water depth) concrete tank set-up with partitions for male territories and housing 7 males and 25 females of 250 gm weight to produce 47,655 Red Hybrid Tilapia fry (26-52 mm total length) in a 76-day trial. This gave an average of 760 fry/female/month or 1961 fry/m2/month. In this type of system, breeders are selected based on characteristics such as growth rate, body conformation and colour. They are then being monitored constantly for performance. Fry are collected as soon as they emerged from their mother’s mouth using fine netting material to minimize injuries. It is best to collect them when they are still schooling. The productivity of this system can still be improved by skillfully replacing non-breeding males and females with good breeders. Individual fish may be tagged with a passive integrated transponder (PIT) in order to evaluate its performance. As such, the system has yet to achieve its full potential. Bhujel et al. (2000) found that 25% of females did not spawn in a 35-day breeding selection period. Others spawned once or twice. Breeding the females that spawned twice during the selection period significantly increased the production of fry over a subsequent breeding period of three months in hapas, averaging 3780 fry/m2/month. One-time spawners gave an average of 3180 fry/m2/month while non-spawners produced 2130 fry/m2/month. Table 2 summarizes the fry production capacity and estimated cost for these three “variations on a theme”. However, fry production in tanks offers substantial advantages over conventional production in ponds. Space requirements are reduced compared to production in ponds. Management is made simple: minimal servicing in terms of waste removal, ease in feeding, cleaning, health monitoring, prophylaxis, disease detection and treatment, and efficient feed usage. Quality fry can be produced with great efficiency.

 

 

Table 2: Fry production capacity and estimated costs

 

Author

Production capacity (fry/ m2/mth)

Estimated cost (US$)

Abalos (1998)

Suhairi et al. (2002)

Bhujel et al. (2000)

                       188

                     1961

                     3780

         0.01-0.03

         0.005-0.01

         0.01-0.02

 

 

Fingerling production in tanks

 

Fry collected are nursed in fibreglass tanks covered with Netlon® netting to prevent predation by mainly Kingfishers (Halcyon spp.). Fry collected from the above system are suitable for sex reversal by hormonal treatment. After one month’s culture, fry are graded and restocked for further nursing until they attain a weight of 50 gm. It is better to rear fry in green water where they can feed on plankton according to their natural feeding habit at this stage of their life cycle. The presence of benthic organisms and zooplankton will also augment their diet as they develop into juveniles.They are then graded and stocked into 25-mt tanks or cages for final grow-out.

 

Bailey et al. (2000) conducted intensive production of Tilapia fingerlings in a recirculating system. The initial weight was 4.3 gm. Stocking densities in 2-m3 rearing tanks were 200 and 450 fish/m3. Final weights were 69.3 gm and 55.1 gm respectively after 12 weeks giving growth rates of 0.78 and 0.60 gm/day respectively. Survival rates were 92.1 and 91.9 % respectively. The FCR's were 1.22 and 1.25 respectively. This implies a production cost of RM 0.12- 0.16 (US$0.03-0.04) per fingerling.

 

 

Grow-out to market size in cages and tanks

 

In a cage culture experiment in the Durian Tunggal Reservoir, Malacca, with a stocking density of 32 Tilapia/m3, the growth rate for 108 to 313 gm was 4.8 gm/day (Ahmad-Ashhar, 2002). In another trial, the growth of an unselected local Red Tilapia strain was compared with that of Genetically Male Tilapia (GMT) acquired from the AIT (Asian Institute of Technology), Thailand. The results are as in Table 3. After 89 days, the mean weight of Red Tilapia was 786 gm while the GMT attained a mean weight of 432 gm. The growth rates were 6.57 gm/day and 2.64 gm/day for the Red Tilapia and the GMT respectively (Ahmad-Ashhar et al., 2003). With further improvement on the cage design to optimize the excellent water quality in the impoundment, the growth rate can be improved. Handling is the main problem because of the deployment of unskilled labour and logistics, namely, transportation of fingerlings to the cages from production centres and the distance of cages from the shore. Biofouling by bryozoans was also a problem. Cages were hauled to shore and washed using high-pressure water jets to dislodge the bryozoans.

 

Culture in tanks offers the main advantage of being able to realize the concept of “manufacturing to order”. Every part of the culture can be controlled to exact specifications such as levels of dissolved oxygen, pH, temperature, ammonia, nitrate and nitrite. There are minimal health problems and where and when they do occur, they are arrested at the earliest stages because of routine health inspection by the Fish Health Section at the FFRC.   The  same cannot be said of culture in cages where the aquaculturist needs to contend with factors beyond his control. It is almost impossible to treat diseases without contaminating the surrounding waters with antibiotics and chemicals.

 Table 3: Cage culture of Red Tilapia and Genetically Male Tilapia in the Durian Tunggal Reservoir, Malacca (Ahmad-Ashhar et al., 2003)

 

Local Red Tilapia

Genetically Male Tilapia

Culture period (days)

Initial weight (gm)

Final weight (gm)

S.D.

Range (min.-max.) (gm)

Growth rate/gm/day

                  89

                201

                786

                192

             500-1210

               6.57

                   89

                 198

                 432

                 167

              120-870

                2.63

In a static rain-water 25-mt circular tank provided with basic aeration, a trail to gauge the performance of two initial sizes of the Red Hybrid Tilapia, the Mossambique Tilapia (Oreochromis mossambicus) and the Zilli Tilapia (Tilapia zillii) showed that for fish fed 28% crude protein commercial formulated pellets, growth rates were 4 gm/day from 61 to 659 gm and 6.4 gm/day from 459 to 1459 gm (Chuah and Mohd.-Saki, 2000). The survival rate was 100% for all four groups. The results are as in Table 4. An additional few hundred Red Tilapia fry were obtained at the end of the trial.

 

Table 4: Growth rates and fillet weights of four different Tilapia groups (Chuah and Mohd.-Saki, 2000)

 

Group

Initial weight

Final weight

% fillet

Growth rate

Red Tilapia 1

Red Tilapia 2

Mossambique

Zilli

   61 gm

 459 gm

 166 gm

 153 gm

   659 gm

 1459 gm

   444 gm

   383 gm

   37%

   41%

   41%

   37%

   4.0 gm/day

   6.4 gm/day

   1.8 gm/day

   1.5 gm/day

 

 

Health management issues

 

The adage “Prevention is better than cure” is still very applicable to Tilapia culture. Prevention means the dual tasks of quarantine and sanitation. It is critical that fish are quarantined and treated before they are introduced into tanks or cages for culture. Fish should be observed and examined for disease pathogens and signs of sickness. Salt is normally used to dislodge external parasites. A dosage of 3% salt solution is used as a bath treatment. Fish are placed in the salt solution until they roll over, that is, to the extent that they can withstand the salt solution. Tilapia fry can be transferred straight into water with salinities of up to 30 ppt and survive for a very long time without harmful consequences. They are then transferred into clean fresh water for recovery. This treatment is normally sufficient to rid the fish of most external parasites.

 

There is a lot to be desired in terms of proper sanitation: sterilization of equipment, workers’ education, break-cycle, dealing with biofilms, and proper disposal of dead or diseased fish. Routine health checks and prophylactic treatment must be conducted to ensure that fish are healthy. Libey (1998) made a comprehensive list of major points of isolation to prevent the introduction of pathogens into culture systems. Simple precautionary measures involving water, air, feed, fingerlings, equipment and humans can greatly reduce the risk of disease introduction and promote good husbandry practices. Smith (1998) recommended providing pathogen-free water with the use of filtration, UV and ozone treatment. He suggested that a manual of standard operating procedures should be established for biosecurity measures and disease monitoring.

 

The use of vaccines is becoming a possibility although the immune response in fish is less predictable because they are cold-blooded and therefore may have to be vaccinated more frequently (Klinger and Francis-Floyd, 1998). However, vaccine development is very expensive and there are only a few diseases of Tilapia which cause sufficient financial loss to warrant the development of vaccines.

 

In order to reduce the occurrence of antibiotic resistance (AR), the Food and Drug Authority (FDA) of the United States, restricts the use of antibiotics for food fish to terramycin and Romet®-30. Most antibiotics are reserved for human use. Many bacterial strains that infect fish are already resistant to these two antibiotics (Crosby, 1998). Local feed-millers or specialized fish clinics should look into the production of medicated feeds such as in the US since oral administration is preferred to bath techniques. In the US, some 40% of antibiotic prescriptions are wrong: either they are not needed or the wrong antibiotic was given or the dosage was incorrect (Bachmann, 2003). Ideally, any antibiotic treatment should be administered by trained fish health personnel after a bacterial culture and antibiotic sensitivity test.

 

 

Water quality management

 

The main parameters to monitor are dissolved oxygen, pH, temperature, ammonia, nitrite, and alkalinity. Water quality management may be automated using probes and a computer to obtain a real-time sequence of important parameters. Alarms or auto-correction may be activated to alleviate any water quality problem (Lee, 1998). When used together with back-up equipment such as an emergency generator and aeration devices, automation will greatly cut down the risk of catastrophic mass mortality in case of power system failures. Carbon dioxide strippers are now available to improve living conditions in tank systems. Protein-skimmers can effectively remove a substantial proportion of the dissolved solids. Well-designed filtration systems are important for the reduction of ammonia and nitrogenous substances. A new development in tank systems is the realization that solid wastes should be removed intact and not meshed up through the filtration system. Correct water flows and specially created static zones can trap solid wastes for removal before their contents are leached into the water.

 

 

Proper effluent management

 

A typical Tilapia aquaculture farm with a FCR of 1.5 would produce about 0.5 mt of waste per mt of fish harvested. Maugle and Fagan (1998) noted that complete feeds with low environmental impacts for Tilapia reared in tanks should be extruded feeds, including crumbles, rather than pelleted ones because they have greater digestibility and better water quality characteristics. Nutrient compositions of typical feeds are given for four size categories of Tilapia. The impacts that effluents may have on the environment are as shown in Table 5. Nitrogenous wastes and phosphorus increments from cage culture are shown in Table 6. New culture systems need to accord emphasis on this aspect. Gone are the days when a farmer can simply abuse the environment through irresponsible feed and effluent dumping. A code of good aquaculture practice (GAP) is being implemented in Malaysia. This will encourage the development of responsible aquaculturists who are committed to the long-term viability of their livelihood.

 

Table 5: Characteristics of effluents from intensive aquaculture, and some of the potential environmental impacts (Phillips, 1995)

 

 

Effluent characteristics

 

 

Origin

 

Potential environmental impact

 

Dissolved nutrients

(particularly N and P)

and organic material

 

 

Particulate material

 

 

 

Chemotherapeutants

 

 

 

Fish excretion, dissolution from feed particles, recycling from pond bottom sediments

 

Uneaten feed, fish faeces, organic debris (from pond bottom) and plankton

 

Disease treatments, predator control

 

Eutrophication problems in water receiving effluent; degradation of water quality in common water bodies

 

Increased organic loads in surface waters, reduced dissolved oxygen, siltation

 

Possible toxic effects on non-target organisms; health risks to farm workers and consumers

 

Table 6: The nitrogen and phosphorus waste from intensive cage culture of rainbow trout in Scotland and Sweden (quoted in Phillips, 1995) – units are in kg/mt of salmonid fish production (and % of total input)

 

 

Inputs with feeds

        (kg/mt)

Output with fish harvest (kg/mt)

Waste nutrients

        (kg/mt)

Scottish rainbow trout cage farm.

Nitrogen

Phosphorus

 

Swedish rainbow trout cage farm.

Nitrogen

Phosphorus

 

 

131 (100%)

  32 (100%)

 

 

 

116 (100%)

  22 (100%)

 

 

 27 (21%)

   5 (16%)

 

 

 

30 (26%)

  4 (18%)

 

 

104 (79%)

  27 (84%)

 

 

 

  86 (74%)

  18 (82%)

 

Wastes and nutrient-rich effluent from aquaculture may be channeled for agricultural use. This is done in Israel where water is scarce. New water is initially used for aquaculture. Aquaculture effluents are used to irrigate and fertilize crops. Some studies are done to use worms such as the West-African nightcrawler, Eudrilus eugeniae, and the brandling worm, Eisenia foetida for composting sewage sludge and manure (Mason et al. 1992). In the FFRC, the original design of the research complex of 192 ponds made use of a Melaleuca swamp forest as a wetland to soak up aquaculture wastes before the water went back into public waters. Nowadays, constructed wetlands are being developed to treat effluent before it is discharged into public waters.  In the Kent Seafarms, San Diego, constructed wetlands were capable of removal of 200 to 400 mg NH3/m2/day, or more (Massinggill et al. 1998).

 

Tank culture is the ideal system for the collection and treatment of aquaculture effluent. Cage culture systems depend on the ecosystem to absorb additional organic and nutrient load. Shelton et al. (1998) evaluated composted fish wastes from processing and mortalities, and are confident of composting procedures for fish manure and filter sludge. In the future when water problems become more severe, tank culture may be the best solution.

 

Handling and harvesting: mechanization

Grading of fish is highly desirable to cull stunted fish and reassign fish to culture facilities according to size. Mechanization in the likes of fish pumps, Archimedes screw pumps and fish graders can greatly improve the efficiency of Tilapia culture. The FFRC has so far fabricated two such devices. Further refinements are needed to increase their effectiveness.

 

Predation

Tank culture also affords protection from predators such as birds, Monitor Lizards (Varanus salvator) and otters (Lutra vulgaris). In the FFRC, observations indicated that each Great Egret (Egretta alba) can consume as many as six three-inch Tilapias in an hour.

 

Nutrition: “custom-made” formulated feeds for Tilapia

 

The FFRC has come up with an extruded formulated feed that is specially tailored toward the nutrition requirements and feeding habit of the Tilapia. Trials showed that the FCR was about 1.3. Observations in a large display aquarium showed that the feed was well-liked by Tilapia (Pathmasothy, unpublished). Floating commercial pellets because of their inherent hardness have to be regurgitated over and over again before they are eaten. This implies some degree of nutrient leaching. Freshly prepared extruded pellets also have nutrients and vitamins intact compared to commercial pellets which are bought in great bulk and then stored before being fed to fish. If farm operators are not dogmatic about proper storage procedures, there may be great losses caused by protein deamination, lipid rancidification, vitamin deterioration and toxin development where humidity, thermal gradients, rodents and insects are present (Fox, 2000). It has been estimated that the feed prepared by the FFRC can reduce production costs by up to 50%. The Department of Fisheries is putting this feed to test this year by transferring this feed technology to farmers in Negeri Sembilan and Kelantan.

 

 

Novel products

 

Aquamats

 

Some promising products have emerged recently. Aquamat is a carpet-like material that is hung in the water column by a sealed PVC rod and anchored to the bottom by means of two simple hooks. The basic principle behind its use is that the mat becomes a substrate for the growth of periphyton which is grazed by fish. Its bacterial flora also aids in the breakdown of nitrogenous wastes. In a cage culture operation in Timah-Tasoh Dam, Perlis, aquamats were grazed to the extent that they were reduced in size. In the FFRC, trials in fibreglass tanks showed some degree of disintegration but tanks with Aquamats rarely experienced mortality and Tilapia were healthy. The Aquamats also functioned as hides for Tilapia that were harassed thereby reducing stress.

 

Ozonizers

 

Ozonizers produces powerful and unstable bonding of three oxygen atoms that react readily with carbon compounds. As ozone (O3) breaks down to O2 a great deal of energy is released, breaking apart other chemical compounds and destroying bacteria, fungi, viruses, and large organic molecules. Ozone has advantages over chlorine because it does not form chloramines which is toxic to fish. In high concentrations, ozone is dangerous to all living tissues. Therefore, ozone should never be added directly into culture tanks. Water to be treated is passed through a contact chamber. In the event of a leak in the ozone system, there should be a leak detector installed to trigger off an automatic shut-off. Virtually all aquariums in the US, as well as many European and Japanese facilities, make use of ozone for water purification (Baltimore Aquarium, 2003).

 

Vacuum Swing Adsorption Oxygen Generator

 

Vacuum swing adsorption oxygen generators have been in used in other disciplines of science for purposes such as chemical processing and energy conversion processes. Li-X zeolite (Si/Al=1.0) is currently the best sorbent for air separation by adsorption processes (Yang and Hutson, 2000). Using a cleverly designed valve, a VSA oxygen generator is capable of producing 93-99% pure oxygen (Air Products, 2003). With the VSA, a continuous supply of oxygen is available to aerate culture tanks or cages permitting the aquaculturist to use higher stocking rates. The VSA is a very robust machine and may be used in adverse weather conditions. In the FFRC, oxygen from the VSA was used to pack fish for transport.

 

Nutraceuticals

 

Nutraceuticals is a hybrid of nutrition and pharmaceuticals. Equine probiotics have been used for some years now to successfully treat digestive problems by encouraging the formation of healthy intestinal bacterial flora in the gut. In a preliminary trial conducted in the FFRC, bacterial concoctions mixed in the feed have been shown to improve Tilapia growth by 20%. Fish treated with nutraceuticals continued to have that advantage over untreated fish after the termination of treatment. It is probable that nutraceuticals improve intestinal bacterial flora of Tilapia and also help to improve the general well-being of the fish through better digestion and the prevention of the colonization of harmful pathogens in the digestive system.

 

Immunostimulants can also be added to Tilapia feeds to improve resistance against diseases (Barker, 1998). Peptidoglycans are being used to increase the non-specific immune system of Tilapia. Peptidoglycan is a semi-rigid, tightknit molecular complex in the cell wall of bacteria. Peptidoglycan functions to give a bacterium its shape and prevent osmotic lysis. Consequently, antibodies developed by the fish are effective against bacterial infections.

 

Automatic feeders

 

In a sun-rich country like Malaysia, solar energy should be harnessed for powering automatic feeders. The FFRC has used Kemers (Kemers Maskin ab, Sweden) solar-powered automatic feeders in its cage culture trials in Tasik Kenyir, Terengganu. Automatic feeders can help farmers to obtain better feed efficiency besides being labour-saving and power-saving. Cage-culture operators often face the problem of feeding hundreds of cages, each round of “hasty” feeding could take up to an hour. Therefore, if requested to feed fish four times a day, it becomes a mammoth task. Solar-powered automatic feeders promise to be a solution to such a problem freeing workers for other chores.

 

 

Discussion

 

The most economical operation was achieved by an operator using an impoundment in Bakri, Johore, to ranch Tilapia and a few other species of freshwater fish using cheap poultry by-products. He could still make profits selling Tilapia at slightly over RM1.00 (US$0.25) per kilogram. The main set-backs were improper aquaculture practices such as the use of chicken offal as feed, and harvesting the fish efficiently at the end of the culture period since the water was rather deep (more than 7 meter in depth). Also, the use of the impoundment was subject to proper approval by the local water authority (pers. comm.). Ranching has weaknesses such as poaching, proportion of harvest meeting the required market size, harvesting inefficiency, harvesting equipment and handling problems. If ranching is conducted in a reservoir for domestic water supply, there will always be concerns concerning eutrophication or even minor unfavourable water quality changes. Here economics is good but sustainability and quality are compromised.

 

Cage culture is an excellent alternative for the growout stage, with its advantages of added control over the culture process, harvesting ease, management, production of fish with no off-flavours, and good returns. With the availability of large areas of potential cage culture sites in Malaysia, this system of Tilapia culture is on the rise. Shallow reservoirs like the Timah-Tasoh Reservoir in northen Peninsular Malaysia offer the added luxury of natural food like algae especially beneficial to Tilapia. Ahmad-Ashhar et al. (1992) found that most of the fishes in the reservoir consumed a high proportion of insects, an average of 37% of the gut content. It is possible that Tilapia could adapt itself to consume a certain amount of insect matter thereby increasing the profitability of its culture in such an environment.

 

Cage culture problems are mainly those with severe weather changes and the introduction of disease organisms by new consignments of fish that have not been ‘properly’ quarantined. The cause of mortality may also be due to ingestion of toxins from pelleted feeds that have not been stored in the proper way. In an informal survey, it was noticed that practically none of the Tilapia farmers knew how to manage pelleted feeds.! Cage culture operations also face the logistic problems since they are normally sited in remote areas. Workers are hard to find because most people prefer to work in a more social environment. By far, the greatest concern for cage culture systems is long-term sustainability. If very intensive culture is practiced, the amount of effluent contaminating surrounding waters could significantly alter the whole environment. In Lake Kenyir, Terengganu, the cladoceran, Bosminopsis dietersi, was found in greater concentrations around cage culture set-ups (Chuah, 1993). It is very likely that the eco-footprint of cage culture may be too great for it to be appealing ecologically speaking.

 

Tank culture is the ideal system for Tilapia grow-out. Conventional recirculating systems do not take advantage of the natural ability of Tilapia to harvest algae from the water as food. A study conducted in Israel using stable carbon isotopes ratios in fish flesh and various natural and commercial nutrient sources revealed that 50-70% of Tilapia growth was attributed to natural nutrient sources even though the fish consumed high quality pelleted feed (Castaldo, 1995). This implies that greenwater tank culture as advocated by Martin (2003) should be developed for Tilapia. The productivity of Martin’s system was reportedly 22.4 times that of pond culture. Also the amount of water needed for the system is merely 4.4% that required by pond aquaculture. Nutrient recycling in the greenwater system converts waste nutrients into plankton and bacteria that are cropped by Tilapia thus lowering feed conversion ratios and feed costs. Also, concentrated solid wastes may be used as agricultural purposes and Moina production which can then be used to feed Tilapia fry, ornamental fishes and fry of other fishes. The recycling and removal of waste with minimal water usage mean that there is little ecological impact from such an operation. With the present avaibility of VSA oxygen generators, oxygen requirements of an intensive culture can be adequately met without the cumbersome logistics and potential dangers of having heavy high pressure oxygen cylinders around. Automated real-time water quality monitoring can greatly reduce the risk of system failures. The social advantage is that Tilapia cultures need not be done in remote areas since tank culture systems require less space and water. However, presently the cost of equipment renders it an enormous economic risk. Perhaps, the concept that the greenwater tank system can deliver goods “manufactured to order” can entice potential investors to develop a viable set-up in Malaysia. Davlin (1995) commented that this is aquaculture at its highest and best use. By quality we include freshness, taste, texture, colouration, and purity, the assurance that the food produced for human consumption is pure, unadulterated by toxins, heavy metals, radioactive isotopes, Escherichia coli, paralytic shellfish poisoning or PSP, hepatitis viruses, ciguatera, saxitoxin and brevetoxin. The more the aquaculturist controls the environment for his culture the more he can assure his customers that his products are free from contaminants.

 

Culture technology for Tilapia is highly versatile: from open water ranching in large impoundments to highly stocked tank systems. Table 7 gives a comparison of fish production from five types of intensive culture systems. Parker (1976) concluded that the more artificial the system was, the greater the energy costs would be for fish production. More natural systems have a higher energy cost for harvesting. Land, water and energy are necessary for all fish production units but their proportions vary with system design. Pond culture is the most economical in energy cost but the most costly in terms of land. Cages may be the cheapest in land costs but energy and water requirements increase as production increases. In terms of water used, flow-through raceways are the most costly while closed cycle systems are the most economical. Closed cycle systems also have the greatest energy demands but lowest land and water costs. They are also have the greatest risk of disease infection though they allow for the best disease control. In ponds, many pathogens may be present yet cause no harm owing to low stocking densities and a lack of stress in the fish. Selection and development of an appropriate culture systems should be made after a thorough evaluation on a case-by-case basis. Besides the characteristics of each particular system, factors to be considered expertise of management, backup system requirements, availability of commercial feeds, availability of labour, marketing strategies, and above all, return on investment (Parker, 1976). The subtleties of designing tank culture systems to increase profitability are dealt with by Summerfelt et al. (1998) involving factors such as culture tank size, carrying capacity, stock management, and waste manangement.

 

 

Table 7: Comparison of fish production in terms of fish weight gained with respect to area, volume, water used and flow rate, from five types of intensive culture systems (Parker, 1976)

 

System

Fish/area

  (mt/ha)

Fish/volume

     (kg/m3)

Fish/water used

        (kg/m3)

Fish/flow rate

(kg/l per min)

Pond

Cage-static water

Raceway

Cage-flowing water

Closed-cycle

2.24

2.24

42.56

4064.48

1399.55

0.16

222.4

7.6

4.32

211.2

0.0128

0.0128

0.00051

0.00051

14.9

8867

8867

7.3

7.3

1.2

 

 

Other than the growout the established but traditional techniques of broodstock maintenance, breeding and nursing of Tilapia fry in ponds will have to be replaced with a more reliable technology. The tank system introduced by previous researchers and highly commended by FFRC for these  activities should be able to overcome the setbacks in those systems and meet the stringent quality fry market demand.

 

The Tilapia ex-farm price is expected to increase as  more people appreciate its proper place as a top quality fresh fish in healthy local cuisine. In certain regions of Malaysia such as Penang Island, consumers highly prize freshness which is something that freshwater aquaculture can offer consistently. Value-added products such as fillet, fish fingers, and the like are quality-compromised products as far as Tilapia is concerned though Johnson (1998) extolled the virtues of value-adding quite convincingly and even gave good guidance on creative marketing strategies. Tilapia producers have to resort to these because, for the time being, the fresh fish market cannot absorb large quantities of fresh healthy Tilapias and marketing agents have yet  to acquire the requisite skills to manage live fish. One should always remember that in Asia, the gourmets go for freshness and regard stored food as inferior in true taste and nutritional quality. As a famous chef in China when interviewed on his preference for fish, remarked that anyone can cook a marine fish because it already has its own peculiar taste, but freshwater fish pose a challenge to the true skills of the chef to create his own special taste into the fish. Maybe it is about time that some people stop questioning whether Tilapias are good enough to be eaten; instead they should ask themselves whether they are skillful enough to cook it. However, it cannot be denied that value-added products have an immense role of creating new market opportunities and catering for the needs of today’s “time-deficient” modernists who prefer to use the microwave oven more than conventional kitchen utensils. Ideally, Tilapia culture researchers and farmers must quickly develop an economically viable greenwater tank culture system that can give consumers the assurance that Tilapia are “manufactured to order” without polluting the freshwater in the country.

 

 

Conclusion

 

There’s a need to continuously inject new culture systems and technology into the Malaysian aquaculture industry so as to meet the targeted production of 120,000 mt of Tilapia in the year 2010. The industry also needs to be perpetually competitive in order to survive and ever energetic to penetrate new markets. The systems forwarded should also adopt and practice the good aquaculture practices and produce quality products to meet the  standards set for the global markets. The new protocol/system which has been successfully practiced at FFRC has taken these into consideration and has a good potential to be developed further in particular to meet the economic returns expected in any viable venture.

 

  

Acknowledgements

 

It is an honour and privilege to be invited by WorldFish Centre for the presentation of this paper. We would also like to thank the Director General of the Department of Fisheries, Malaysia, Dato’ Hashim bin Ahmad for the permission to present this paper, the encouragement of the Director for Research, Fisheries Research Institute, and the assistance of the research staffs of the FFRC in particular Mr. Suhairi Alimon and Mr. Ahmad Ashhar for the preparation of this paper.

 

 

 

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