Penaeus MonodonHatchery Management

Introduction

• Giant Tiger Prawn (P. monodon, also known as "black tiger shrimp") occurs in the wild in the Indian Ocean and in the Pacific Ocean from Japan to Australia. The largest of all the cultivated shrimp, it can grow to a length of 36 cm and is farmed in Asia. Because of its susceptibility to whitespot disease and the difficulty of breeding it in captivity, it is gradually being replaced by L. vannamei since 2001.

P. Monodon Taxonomy

Kingdom : Animalia Phylum: Arthropoda Subphylum: Crustacea Class: Malacostracea Order: Decapoda Suborder: Dendrobranchiata Family: Penaeidae Genus: Penaeus Species: P. Monodon

Biological Features

• The shell is smooth, polished and glabrous.• The rostrum extends beyond the tip of the

anntennular peduncle, is sigmoidal in shape and possesses 6-8 dorsal and 2 ventral teeth, most 7 and 3 respectively.

• The carapace is carinated with the adrostal carina almost reaching the posterioi margin of the carapace.

• The gastro orbital carina occupies the posterior one-third to one half distance between the post-orbital margin of the carapace and the hepatic spine.

• The hepatic carina is prominent and almost horizontal.

• The antennular flagellum is subequal to or slightly longer than the peduncle.

• Europods are present on the first four pereopods but absent in the fifth.

• The abdomen is carinated dorsally from the anterior one-third of the fourth, to the posterior end of the sixth somites.

• The telson has a median groove but w/o dorso-lateral spines.

Life Cycle

• The eggs are demersal and tend to sink while larvae are Planktonic.

• Prawn larva thrives mainly offshore and undergoes three main stages: nauplius, protozoea, and mysis.

• At the postlarval and juvenile stages, the prawn migrates toward the estuary.

• As it grows, it starts moving to the shallow coastal waters. The adult prawn inhabits the open sea.

• Sexes are separate and can be easily distinguished through the external genitalia located at the ventral side. The thelycum in females and petasma in males.

• During mating, the male deposits the spermatophore inside the thelycum of the female.

• Mating can only occur between newly molted females and hard-shelled males.

• Spawning tanks place throughout the year. The eggs are fertilized in the water after the female simultaneously extrudes the eggs and the spermatophore.

• The number of eggs released by a single spawner varies from 248,00 to 811,000.

Eggs

• The eggs are small, spherical, and vary from 0.25 to 0.27 mm in diameter.

• The developing nauplius almost fills up the entire space inside the egg.

• At 28-30°C, the eggs hatch 12-17 h after spawning.

Nauplius Stage

• Stage after eggs have hatched.• The prawn nauplius is very tiny, measuring

from 0.30 to 0.58 mm in total length.• It swims intermittenly upward using its

appendages in a “bat-like” manner.• It is attracted to light and in aerated tanks, it

will concentrate in the most lighted areas if aeration is stopped.

• The nauplius molts through each of six sub stages for a total of about 1.5-2 days.

• The substrates differ from each other mainly on the furcal spine formula. The latter indicates the number of spines at each side of the furca.

Protozoea Stage

• Its body is more elongated and measures from 0.96 to 3.30 mm in total length.

• It consists of the carapace, thorax and abdomen.

• It can also be distinguished by its movements, it swims vertically and diagonally forward towards the water surface.

• The protozoea undergoes three sub-stages. The paired eyes of protozoea I can be obscured as two dark spots in the upper portion of the carapace.

• These eyes become stalked at protozoea II.• At protozoea III, the dorsal medain spine at

the sixth abdominal segment first appears.

Mysis Stage

• Shrimp-like with the head pointing downward.• Its body measures from 3.28 to 4.87 mm in

total length.• The telson and uropods are developed.• The mysis swims in quick darts accomplished

by bending the abdomen backwards.• For mysis sub-stages, the most prominent

change is the development of pleopods.

• The pleopods appear as buds at Mysis I, which protrude at Mysis II and finally become segmented at Mysis III.

Postlarval Stage

• The post larval resembles an adult prawn.• At postlarva I the rostrum is straight and

exceeds the tip of the eye.• It usually has one dorsal rostral oine w/o any

ventral spine.• Plumose hairs are present on the swimming

legs.

Reproduction

• P. Monodon is heterosexual.• The female attains a relatively larger size than

the male.• The sexually mature prawn can be

distinguished by the presence of the external genital oragans: joined petasma, a pair of appendix masculina on the exopods of the second pleopods, and a genital opening on the coxa of the fifth of pereopod for the female.

• In females, the thelycum is situated between the fourth and fifth pereopod w/ the genital opening on the coxa of the third pereopod.

Male Genital Organ

• The internal reproductive organ of the male consists of paired testes, vasa deferentia, and terminal ampoules located in the cardiac region dorsal to the hepatopancreas.

• The testis is translucent and composed of six lobes, each connected in the inner margins leading to the vas deferens.

• The vas deferens consists of four porions, namely: the short narrow proximas vas deferens, and the muscular portion referred to as terminal ampoule.

• The terminal ampoule contains the terminal spermatophore and opens at the base of the coxopod of the fifth pereopods.

• The spermatozoa are minute globular bodies composed of the head of about 3 microns in diameter and a short spike.

• The petasma is a pair of endopods of the first pleopods formed by the interlocking hook-like structures.

• The appendix masculina is oval and is located on the endopod of the second pleopod.

Female Genital Organ

• Consists of paired ovaries and oviducts.• Ovaries are bilaterally symmetrical, partly

fused and extend almost the entire length of the mature female.

• It is composed of the anterior lobe located close to the esophagus and the cardiac region of the stomach; the lateral lobes located dorsal to the hepatopancreas; and the abdominal lobe w/c lies

Hatchery Facilities

Larval and Postlarval Tanks

• Rubberized canvas, marine plywood, fiberglass, or concrete.

• These can either be circular, oval or rectangular, depending on the operator’s preference or financial capability.

• The capacity of each tank may be from 1-20 t but 10-12 t tanks are more economical and practical

• Depth should only be about 1m because tanks w/c are too deep are difficult to manage.

Algal tanks

• Minute plants (phytoplankton) are needed as food for the early life stages of prawn.

• Algal tanks must be shallow (ideally 0.5 m deep) to allow sufficient light prevention.

Spawning Tanks

• It is advantageous to have smaller tanks w/ volumes ranging from 0.25 to 1 t where egg washing is done

Artemia Hatching Tanks

• Artemia or brine shrimp is a protein-rich live food organism given to prawn larvae starting at the Mysis stage.

• Artemia is available in cyst form w/c has to be hydrated and incubated in tanks for at least 18-24 h.

Reservoir

• Storage tank is necessary for chlorination and holding of filtered and treated water for daily use.

• This must have a total capacity of at least 50% total larval tank volume.

Aeration System

• Aeration is necessary in hatchery operations to keep food particles and algal cells in suspension and to maintain sufficient dissolved oxygen levels.

• Continuous aeration is essential during operations. A standby generator will be very useful during power interruptions.

Preparation of Spawning, Larval, and Nursery Tanks

• To prevent disease outbreak, the hatchery should be totally dried after several production runs.

• Tanks and facilities in the hatchery must also be cleaned well prior to a hatchery run.

• New tanks need to be filled w/ fresh or seawater for at least a week to avoid mortalities due to toxic effects of chemicals used during construction of the tanks.

Selection and Stocking of Spawners

• Nauplii to be reared to the fry stage can come from

a) broodstock – wild or pond-reared immature females induced to mature by unilateral eyestalk ablation.

b) Wild spawners – female prawns caught from the sea w/ developed ovaries.

• The number of spawners needed for a hatchery runs is dependent of the nauplii requirement.

• For every million nauplii about 4-5 wild spawners or 7-8 m female broodstock are needed.

• Spawner procured as nauplii source must be carefully selected to obtain high fertilization and hatching rates of eggs.

• Stage of maturity should not be used as the basis for selection.

• Spawners must also be disease free. To ensure development of the eggs, females should be mated to ensure release of sperm cells necessary for fertilization.

Stocking of Nauplii

• During stocking and throughout the culture period, prawn must not be exposed to abrupt changes in environmental conditions.

• The prawn must be given time to gradually adapt to new conditions to avoid stress and mortalities.

Feeding

• Nauplii subsits on the yolk stored in their bodies.

• Larvae start to feed at the first protozoeal sub stage ( diatoms like Skeletonema or Chaetoceros)

• Larvae at the second protozoeal sub stage may be fed Tetraselmis.

• At the Mysis Stage, some fish protein must be present in the diet.

• Newly hatched artemia nauplii and microparticulate diets, most commonly used protein source w/c contain about 45-50% protein.

• When they reach the postlarval stage, egg custard, trash fish, mussel meat or ground dried acetes (small shrimp or alamang) can be given to supplement the Artemia nauplii diet.

Water Management and Treatment

• The quality of the rearing water in larval tanks deteriorates after sometime due to the accumulation of feces, and decomposition of uneaten food and dead larvae.

• The resulting water temp. and salinity after water change must not differ by more than 1°C or 2ppt.

• In high density cultures by more (100 nauplii/liter) water change is done daily starting at the second protozoeal substage.

• About 30% of the water volume is changed at the protozoeal stage and 50% at the Mysis stage.

• At lower density (50-80 nauplii) water change is done only after all the prawn in the tank have metamorphosed to the post larval stage.

• The latter water mngt. Scheme and lower stocking densities result to better survival rates because of lesser stress due to water change.

• Water for rearing is treated w/ 5-10 ppm hypochlorite.

• Treated water can be neutralized by strong aeration until all chlorine residues are evaporated or by addition of sodium thiosulfate.

• Hypochlorite kills are retards the growth of possible harmful microorganisms. However, it is also toxic to larvae or postlarvae so water must be neutralized.

• Water should also be treated w/ 5-10 ppm EDTA (ethylene diamine tetracetic acid) to chelate heavy metals.

• High survival rates could also be obtained when water is allowed to stand about 3 days after neutralization before this used for culture.

Harvest, Transfer, Packing, and Transport

• Proper procedures must be observed for harvest, packing, and transport to ensure high survival of prawn fry.

• The number of fry loaded per bag will depend or the size and age of fry, travel time, distance, and means of transportation.

• During extended transport periods, water temperature must be reduced to decrease molting and metabolic rates and the incidence of cannibalism among prawn fry.

• However, there is no need to lower water temperature in transport bags when transporting at night or during cool weather.

Seawater Quality and Quantity

• Seawater w/ minimum seasonal fluctuation in quality is most desirable.

• It should not be affected by inland discharges containing agricultural runoff or industrial wastes.

• Turbidity should be as low as possible.• Adequate volume of seawater should be

available when needed.

• The best method to determine the suitability of seawater for larval rearing is to conduct preliminary larval rearing experiments using pails or small tanks on the site.

• The production of post larvae w/ reasonable survival rate from eggs in a series of at least three runs would indicate the likelihood of success.

Source of Spawners

• Whether the spawners to be used in the hatchery are matured by means of eyestalk ablation in tanks, cages or pens, or caught from the wild, it is most desirable for a hatchery site to be near the source of spawners for a constant supply. Although there are existing techniques of transporting spawners over long distances, the quality of eggs may be greatly affected by the transport stress.

Road Accessibility

• The hatchery should be accessible by road for convenience in transporting supplies and other necessities for the hatchery operation.

• This can also minimize transport problems in the distribution of the post larvae to be reared in ponds far from the hatchery.

Availability of Electric Power

• Electric Power is necessary for the life system in the hatchery.

Fresh Water Source

• The need for fresh water is minimal but an adequate supply is essential for miscellaneous activities and personal needs of hatchery staff.

Availability of Technical Staff

• The technical expertise necessary for hatchery management at this stage is still rare.

Harvesting

• Harvesting is done by first draining out three-fourths of the volume of water in the tank. A strainer is used to prevent the fry from being drained out. The drain valve is then opened slowly and the contents discharged into a 150-L harvesting box. The upper one-fourth portion of the walls of the harvesting box is fitted with plastic screen to allow the water to overflow while retaining the fry inside.

Questions?