The requirement of nutrients varies throughout the life

cycle of an individual. At early stages, the requirement of

nutrients is comparatively high which declines with age.

Also the requirements depend upon the feeding habits

that change accordingly to the morphology of digestive

system. Considerable effort has been made in Australia,

Thailand, Philippines and more recently Israel, in defining

the nutritional requirements of seabass in order to improve

production (Boonyaratpalin and Williams, 2001). Feeds

and feeding are the critical factors that determine the

economic viability of commercial aquaculture of the

species concerned and this topic assumes much more

significance in a carnivore species like seabass. Based on

the nutritional requirements we know that this fish

requires a high protein high energy diet. Further, being a

predatory carnivore in nature, weaning them to formulated

feed is the critical factor which influences the success of

grow out culture of seabass. Understanding the nutritional

requirements of the candidate species is the first and

essential pre- requisite for the development of cost

effective, efficient and eco friendly feeds

Ahamed Ali, S

Ambasankar, K

Syama Dayal, J

CMFRI Digital Repository

National Training on 'Cage Culture of Seabass' held at CMFRI, Kochi66Central Marine Fisheries Research InstituteFeeds and feeding of seabass in hatchery,nursery and grow out systemusing formulated feedsAmbasankar, K., Ahamad Ali, S. and Syamadayal, J.Central Institute of Brackishwater AquacultureNo. 75, Santhome High Road, R.A. Puram, Chennai-600 028, Tamil Naduambasankar@ciba.res.inThe requirement of nutrients varies throughout the lifecycle of an individual. At early stages, the requirement ofnutrients is comparatively high which declines with age.Also the requirements depend upon the feeding habitsthat change accordingly to the morphology of digestivesystem. Considerable effort has been made in Australia,Thailand, Philippines and more recently Israel, in definingthe nutritional requirements of seabass in order to improveproduction (Boonyaratpalin and Williams, 2001). Feedsand feeding are the critical factors that determine theeconomic viability of commercial aquaculture of thespecies concerned and this topic assumes much moresignificance in a carnivore species like seabass. Based onthe nutritional requirements we know that this fishrequires a high protein high energy diet. Further, being apredatory carnivore in nature, weaning them to formulatedfeed is the critical factor which influences the success ofgrow out culture of seabass. Understanding the nutritionalrequirements of the candidate species is the first andessential pre- requisite for the development of costeffective, efficient and eco friendly feeds.Feeding of larvae in hatchery and nurseryLarvae of finfish and shellfish are generally fed with livefood organisms (phytoplankton or zooplankton or both)in the initial phase. Investigations revealed that thedeveloping larvae do not have the full complement ofdigestive system developed. The larvae of seabass are noexception to this.  Studies conducted at CIBA on themetabolic changes and nutrient turn-over in developingseabass larvae revealed that the growing larvae requirethe essential amino acids leucine and lysine at higherlevels in the larval diets (Syama Dayal et al., 2003).  Beingcarnivorous, seabass larvae are fed with zooplankton suchas rotifers for the first two weeks post hatch (PH) andthen switched over to brine shrimp (Artemia) nauplii.  Thesize of the rotifers plays an important role in the successfulrearing of the larvae. Super small size rotifers are preferredfor feeding seabass larvae. Since, Artemia is an expensivelive-food, its replacement by prepared diets has assumedsignificance in the hatchery and nursery rearing of fishlarvae.  In this context, formulated micro particulate andmicroencapsulated diets have been successfully used forfeeding the growing fish larvae.Compounded micro diets for seabass larvaePhysical aspectsSizeDiet must be prepared as microparticles, whose size mustbe adapted to the size of the larval mouth. As an example,size of the microparticulated diets used for seabass larval67From 14 - 23 December 2009National Fisheries Development Boardexperiments was 50 to 125 µm at first feeding, then 125-200 µm from Day 14 to Day 25, then 200-400 µm toDay 40 (Cahu and Zambonino Infante, 1994). The size ofcommercial microparticles used in hatchery for seabassor sea bream weaning, used from Day 40, is generally400 to 600 µm. Accurate size of the microparticles isessential and must be well calibrated to minimize waste.Particularly, small microparticles (less than 50 µmdiameter) cannot be easily detected by larvae, whereaslarge ones are difficult to ingest and may even promote ablockage of the digestive valve (Walford et al., 1991). Thecomposition of microparticles must be homogenous;hence, ingredients must be incorporated as very fine meal.The size of the meal particles must be much smaller thanthe size of the final dietary microparticle. Diet, such asfish meal, must be ground and sieved before beingincluded in microparticles. Concerted efforts made byCIBA scientist lead to the development of micro diets forseabass larvae and the different micro diets used for larvalrearing are given below.matrix such as agar, carrageenan or calcium alginate or bya protein such as casein or zein. Microencapsulated dietsare prepared with a cross-linking agent. Microencapsulationproduces regular shape and water stable microparticles, butthe microcapsules can be difficult to digest. The ability oflarvae to break microcapsules depends on the thickness ofthe capsule coating.Buyoancy of the dietDietary microparticles must be distributed in large excess.Indeed, early stage larvae have a limited movement andmicroparticles must be caught during their fall in the watercolumn. Good results can be obtained with low densitymicrocapsules (400-600 g/L), sinking at about 25 cm/haverage.Visual and chemical stimuli of the dietLight intensity, color of microparticles and tank are essentialfor ingestion. Some pigments, such as asthaxanthin, havebeen incorporated in microparticles, more for improving theManufacturing techniquesNutrient leaching is one of the problems in developingsuitable diets for fish larvae. Particles must be water-stable,palatable and digestible. Diets used for late weaning (afterDay 40) in the hatchery can be crumbled, prepared bygrinding and sieving pellets, but diets of smaller size mustbe prepared in microbound, microcoated, ormicroencapsulated form. In microbound diets, thepowdered ingredients are microbound with a water stablevisibility of the particle by larvae than for their nutritionalvalue. Free amino acids, such alanine, glycine and arginineand the compound betaine, have been identified as efficientchemical stimulator for microdiet in gilthead sea breamlarvae (Kolkovski et al., 1997).Thus, larval feed development largely depends on:? Selection of nutrient specific to the species? Nutritional balance of formulationMD-200 MD-300 MD-400Micro diets developed at CIBA for seabass larvaeNational Training on 'Cage Culture of Seabass' held at CMFRI, Kochi68Central Marine Fisheries Research Institute? Retention of nutritional components? Homogeneity of particles? Particle size and distribution? Density of particles? Water solubility? Storage stability? Packing requirementsApart from providing a balanced diet, the other problemrelated to larval rearing is the weaning of larvae. Some ofthe larvae tend to grow faster naturally than the other inthe stock, which have to be segregated time to time forhigher survival ability and production. These fast growingones are not necessarily due to nutritionally imbalancedfeed but could be due to number of other factors that thehatchery operator usually faces.Practical feeding of micro diets in sea bass larvalrearingWeaningThe age at which weaning is carried out varies considerablydepending on the larval size and rearing method employed.The use of micro diets in larvae is essentially preceded byweaning them to formulated diets. The weaning of larvaecan be carried out in following ways:1. By having a intermediate feeding phase using frozenor freeze dried zooplankton2. Using simultaneous distribution of live prey and driedfeed. It can be started at an early stage.3. Co-feeding but shortening the live prey co feeding toone or two days. This results in better sizehomogeneity4. Starving the larvae and then introducing the microdiets. This method can only be practiced in larvaewhich are in good healthMicro diets distributionThe major bottleneck associated with micro diets feedingare over feeding of larvae and pollution of theenvironment. The food particles must be made availablein large number around the larvae. Small particles floatinitially and then fall to the bottom. The larvae are notinterested in diet that are floating or lying at the bottomof the tank but fed on those particles that pass by theirvicinity. Feeding frequencies and feeding period has to beextended as the larvae are very sensitive to starvation.However, they can not ingest their daily ration in two tothree meals as the resting time in the digestive tract oflarvae are very short compared to juveniles. These featuresof larvae necessitate continuous and excess feeding. Thus,it is essential to use feeders in larval rearing of seabassusing micro diets.Feeds and feeding of seabass in grow-out cultureIn some of the East Asian countries and also in India,seabass is cultured in grow-out ponds using low valuefish (trash fish) and tilapias in fresh condition. Since,procurement and storage of these feed-fish is not onlylaborious but also quite expensive. Hence, formulatedfeeds are essential for the propagation of large-scalefarming of seabass.Asian seabass is cultured in Australia and Thailand usingformulated feeds (Boonyaratpalin, 1991).  As in the caseof other carnivorous species, feed formulations for seabassutilize marine fish resources (for meeting proteinrequirement) and fish oils along with plant protein sources.The animal ingredients are kept above 60% of theformulation to get protein levels in the range of 45-52%.Experiments conducted at Muttukadu field laboratory ofCIBA had shown that feeds with substantial fishmealcomponent (30-40%) only have good acceptability forseabass. Higher the proportions of fishmeal better theacceptability. The texture and size of the feed affectsacceptability of the feed. If the flavour and texture of the69From 14 - 23 December 2009National Fisheries Development Boardfeed are not to the liking of the fish, it spits out the feedsoon after ingesting. The use of animal protein sourcessuch as fishmeal is inevitable in order to keep higherprotein levels in the feed. However, plant ingredients suchsoybean meal and other oil seed residues may be utilizedin the feed formulations. Marine fish oils should beincluded in the feed formulations as a source ofpolyunsaturated fatty acids (PUFA). Studies conductedat CIBA revealed that the amino acid, glutamic acid, is auseful feed attractant for seabass.Seabass feeds on moving prey; hence the physical designof the feed plays a very important role. The fish readilyaccepts soft semi-moist feeds with appropriate size toswallow vis-à-vis the size of the fish. The lower lip of thefish is curved slightly upward, which pose disadvantagewhile biting the feed. Floating and slow sinking pelletfeeds are more suited for feeding seabass. Such feeds aregenerally processed in extruders.fed into an extruder by proper arrangement of water/steam injection facility. The extruder operates at highpressure (14 98 kg/cm2) and steam (Pressure 5   7 kg/cm2)injection.   Depending upon the characteristics of the feedmixture and moisture content, the pressure developsbefore the material passes through the die. Because ofthis the temperature rises and the material is forcedthrough the die and the pressure suddenly drops. Thetemperature of the material rises to 110   130oC for ashort spell of time and cooks the food, gelatinizing thestarch present in the feed mixture. This imparts goodbinding and water stability to the resultant pellets.However, the pellets expand as they come out of the diedue to sudden drop of pressure and air gaps develop insidethe pellet, which makes them float or sink very slowly.This is an excellent process for producing floating pelletsfor finfish culture. By adjusting the pressure in the barreland moisture in the feed, it is possible to prepare sinkingpellets by extruder. The new generation extruders aremade with twin screw barrel arrangement, which are moreversatile for feed manufacture. The size of the pelletdiameter ranges from 0.5 mm to 8.0 mm.The characteristics of extruder pellets are? Reduction in pellet disintegration and loss in water.? Increases starch digestibility due to good cooking? Can be worked with higher moisture and oil (fish oil)levels in the feed.? Extruder pellets float or sink slowly.? Making charges for extruder pellets are higher due tohigh cost of extrudersAt CIBA, formulated feeds developed as floating andsinking pellets were successfully tested in grow-out pondsand the fish growth was found to be 500 g in six months.The fish should be fed at the rate of 10% of their bodyweight to start with. After four to six weeks the feedingrate may be reduced to 8%. As the fish grow in size thefeeding rate should be gradually reduced to 5%, 3% andSinking feeds for seabassFloating feeds for seabassExtruder technologyThe basic components in an extruder are a barrel fittedwith a die plate and a screw shaft conveyer, which isconnected to a high-speed motor. The feed mixture isNational Training on 'Cage Culture of Seabass' held at CMFRI, Kochi70Central Marine Fisheries Research Institutefinally 2%. The total biomass in the pond should beperiodically estimated by suitable means (by castenetting) for adjusting the feed. The entire quantity of feedin a day should not be given at one time but divided andfed 3-4 times a day.ReferencesBoonyaratpalin, M. 1997. Nutrient requirements of marine foodfish cultured in Southeast Asia. Aquaculture 151, 283-313.Boonyaratpalin, M., Williams, K.C. 2001. Asian sea bass, Latescalcarifer. In: Nutrient Requirements and Feeding of Finfishfor Aquaculture (C.D. Webster and C.E. Lim Eds.). CABIPublishing, Wallingford, UK. pp 40-50.Cahu, C.L. and Zambonino Infante, J.L. 1994. Early weaning ofsea bass (Dicentrarchus labrax) larvae with a compound diet:effect on digestive enzymes. Comp. Biochem. Physiol., 109A:213-222.Kolkovski, S., Koven, W. and Tandler, A. 1997. The mode of actionof Artemia in enhancing utilization of microdiet by giltheadseabream Sparus aurata larvae. Aquaculture, 155: 193-205.SyamDayal, J. Ali, S.A., Thirunavukkarasu, A.R., Kailasam, M.and Subburaj. R.2003. Nutrient and amino acid profiles ofegg and larvae of Asian seabass,Lates calcarifer (Bloch). FishPhysiol. Biochem. 29: 141–147Walford, J., Lim, T.M. and Lam, T.J. 1991. Replacing live foodswith microencapsulated diets in the rearing of sea bass(Lates calcarifer) larvae: do they ingest and digest protein-membrane microcapsules? Aquaculture, 92: 225-235.

Feeds and feeding of seabass in hatchery, nursery and grow out system using formulated feeds

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Feeds and feeding of seabass in hatchery, nursery and grow out system using formulated feeds

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