Dr. M.A. HOSSAIN
Chief Scientific Officer
Marine Fisheries and Technology Station
Cox's Bazar-4700, Bangladesh
Aquaculture including sea farming in Asia has a history of thousands of years but the industry is still in its infancy in many Asian countries in general and Bangladesh in particular. The long absence of coastal aquaculture and sea farming development in this part of the world is partly due to the lack of geographically suitable lagoon or broken shoreline, frequent cyclone and tidal bore, insufficient technical and financial inputs to demonstrate its commercial viability. Coastal aquaculture and sea farming on a commercial scale has developed into an important food industry in China, Japan, Taiwan, Philippines and Thailand. It is however, a relatively new commercial venture in Bangladesh. The country produces only one or two species of shrimps through coastal aquaculture. Sea farming except for shrimp is almost non-existent. However, the following species of fin fish, molluscs, and seaweeds have potential for mariculture:
Mugil spp
These finfish are popularly known as Gray mullet, jumping mullet or striped mullet and known as “bata”. There are several species of this group in Bangladesh. They are omnivore in habit, feeds on diatom, blue green algae, green algae, large aquatic plant, detritus, small crustaceans and zooplankton. A mature fish attains 250–400 mm in length. Male matures in first year and female in second year. They breed in offshore and eggs need sea water of high salinity for fertilization. Fry move to mouth of rivers or estuaries following a salinity gradient. These are hardy fish capable to tolerate wide range of salinity. They grow 150–400 mm and 300–1000 g in a year. Maximum recorded size is 900 mm. They are suitable for mixed culture with shrimps since their feeding habits are different from shrimps. They seldom eat shrimps beyond post larval stage.
Liza spp
This group of finfish are available at coastal area in Bangladesh and migrate upstream into freshwater. They are abundant in coastal traditional shrimp farms. They have similar food habit comparable to those of Mugil species. This group do not attain maximum size comparable to those of Mugil species. Food and feeding habit, seed production etc. are similar to those of Mugil sp. These are culturable and suitable for mixed culture with shrimps.
Megalop spp
This group also can tolerate wide range of salinity (0–40%) and migrate to estuaries and rivers and feeds on fish, crustaceans and other animals. Maturing at 250 mm., they breed twice a year in coastal waters, and attains a maximum size of 1000 mm. These fish are incompatible with shrimp but can be cultured with tilapia.
Lates calcarifer
It is carnivorous and feeds on fish, crustaceans, snails and worms. It becomes cannibalistic when food is in short supply. It matures in second year at a size of 400 mm. It breeds only in open sea; eggs being heavy sink to bottom. The fish is capable of tolerating wide variations in salinity, ascends frequently brackish water and tidal rivers, & shows annual growth of 300 mm and 500 g in wild. It can attain a size of more than 3 kg under culture operation within a year. This species has sex reversal characteristics, male after 2–3 active breeding seasons becomes female. Therefore, larger specimens are generally female, suitable for mix culture with tilapia.
Elutheronema tetradactylum
Popularly known as forefinger thread fin, it is one of the most esteemed food fish. Male matures when reaches 225 mm and female at 255 mm. It tolerates wide changes in salinity and exhibits preference for back waters and estuaries. It can well adapt to pond. It enters rivers and brackish waters for spawning and shows annual growth of 190–300 mm. No attempt has so far been made to culture this species in Bangladesh. There is no report of this species available in shrimp farms.
Poultices anguillaris
This catfish is generally found in holes of muddy estuary areas. Looks similar to freshwater catfish, Clarias sp. (Magur) but tail region is gradually tapering to knife shape and has a continuous ocaudal fin. It feeds on fish, crustaceans, crabs, snail and some time on detritus. It attains maximum size of 100 cm. and breeds in salt water.
Polynemus sp
Popularly known as Indian salmon, it is the most desired and tasty marine fishes of south Asia. It is completely marine in habit and seldom comes to estuaries. It is carnivorous and attains maximum size of 1.2 m and 100 kg. No attempt has been made to domesticate this finfish but similar fish (Yellowtail) has been intensively cultured in cages elsewhere.
Epinephelus sp
Popularly known as grouper, it is one of the most expensive fish and cultured in certain countries. It attains maximum size of 1.2 m and over 100 kg. It is carnivorous. Seed production has been achieved in captive condition in south east Asia. Grouper also has sex reversal characteristics, where female turns to male after 2–3 active breeding seasons.
Shrimps
The following species of shrimps are cultured or has potential to be cultured in Bangladesh.
Penaeus monodon
Commonly known as giant tiger shrimp, it attains maximum size of 330 mm and maximum weight of 250 g. However, maximum size in ponds is 120 g. It is omnivorus and detritus feeder. It matures at a size of 330 mm within 15 to 18 months. It can not survive below 15° C. Maturity in ponds has not yet been achieved hence eye stalk ablation is essential. Natural breeding starts in October and lasts upto April, but post larvae are available in Bangladesh coast round the year. Growth attains 150 mm and 30 to 40 g in 100 to 120 days and 225 mm and 80–100 g in one year. It is widely cultured in Bangladesh and elsewhere in south and south east Asia. Production of 20 ton/ha/year is possible per year. Monoculture of this species is common. Seed production in hatchery has been commercially practiced in many countries and can be cultured together with other species of shrimp and plankton feeder finfishes.
Penaeus indicus
It is omnivorous and feeds on diatoms, copepoda, ostracods, amphipods, small crustaceans, molluscan larvae, polychaetes and detritus. This species inhabits upto depth of 90 m, and abundant in shallow waters of less than 30 m depth with sandy bottoms. It is highly euryhaline and can tolerate upto 45 ppt. Breeding occurs during October-November and May-June. Individual shrimp breeds 5 times during life and intervals between two successive spawning is about 2 months. It attains maximum size of 175 mm and weight of 40 g, annual maximum growth of 130 mm for males and 150 for females have been reported. Culture of this species is not common like Penaeus monodon. In coastal traditional farming it comes along with other species.
Penaeus semisulcatus
It is commonly known as green tiger shrimp and often mistaken as Penaeus monodon. It feeds on polychaetes, small crustaceans, parts of fish, diatom, sea weed and detritus. This species prefer higher salinities and can sustain upto a depth of 130 m but abundant in less than 60 m. It prefers mud or sandy mud bottom and it attains a maximum size of 250 mm.
Penaeus merguiensis
This species is omnivorous in feeding habit and takes vegetable matter, copepoda, detritus etc. It inhabits in area upto 35 m but abundant in shallow waters of less than 20 m depth. It prefers sandy mud bottoms and turbid waters. It attains a maximum size of about 200 mm. There is no monoculture in farm, but seeds are trapped along with other in tidal water.
Metapenaeus brevicornis
It is popularly known as yellow shrimp and omnivorous in feeding habit. It is generally available in estuarine areas and can tolerate a wide variation in salinity. It breeds in inshore water and also found in Penaeus monodon farms. It attains a maximum size of 130 mm.
Metapenaeus dobsoni
It is also known as yellow shrimp. Although it is recognized as marine shrimp it is highly adapted to brackish water and omnivorous in feeding habit. It attains Maximum size of upto 130 mm.
Metapenaeus monoceros
It is known as Ginger or Speckled shrimp. It is marine species but found in estuaries also. This shrimp is hardy and can tolerate fluctuations in temperature and salinity. It is omnivorous in feeding habit, it attains maximum size of 100 mm.
All the shrimp mentioned above can be cultured in coastal waters. Seeds of most of the species mentioned above are abundant in nature and unfortunately a great number of these seeds are wasted every year when caught with Penaeus monodon fry. However, hatchery production is also possible for most of the species.
Scylla serrata
It is popularly known as mangrove crab, mud crab or green crab, found in coastal area and a hazard to shrimp farming. Chelipeds is massive and highly priced. It is carnivorous in habit, having maximum carapace length of 150 mm, breadth 215 mm, and maximum weight 2 kg.
Mussels, Perna viridis
It is popularly known as green mussel. This shell fish generally is attached to hard substratum by means of longer, flexible byssus threads, secreted by byssus glands. It is usually found in open coast, harbours, and mouth of estuaries. It is euryhaline, distributed from low water mark to a depth of 3 m and attains maturity in 150 days, breed all round the year with peak during March-October. It feeds on diatom, algae and detritus. It attains a maximum size of 100 mm which it can reach within 15 months.
Perna indica
It is popularly known as brown mussels and attached to rocks, poles, ropes, piers by byssus threads like Perna viridis. It lives in between water level to 6 m depth. Breeding season is from June-August and feeds on phytoplankton and detritus. Maximum length recorded is 118 mm.
Oyster, Crassostrea spp
Three to four species of the genus Crassotrea are available in Bangladesh. This shell-fish is known as back water oyster colonies which is attached to rocky and concrete surface and hard muddy bottom from intertidal zone to a depth of 4 m. It is common in estuaries, back water, ports and harbours. It feeds mainly on diatom, blue green algae, and green algae. Spawning takes place in March to April. It attains maximum length of 110 mm in 17 months.
Pinctada spp
Two or three species of the popularly known pearl oyster are available in Bangladesh water. They are golden yellow in colour, found attached to rocks and dead coral by byssus threads at a depth of 2–10 m. They are filter feeder and breed twice a year i.e. April-May and September-October.
Clam, Meretrix meretrix
It is generally known as Bay clam, hard clam or great clam. It attains maximum size of 75 mm and weight of 40 g and feeds on plankton and detritus. Spawning season extends from September-October.
Meretrix costa
No reports of its availability exist in Bangladesh, but is cultured in India. It is moderately large with thick shell and dull yellowish or brown color and commonly found in all estuaries. Breeding season extends from July - August. It is euryhaline species and grow upto 38 mm and 30 mm in length and breadth with maximum growth of 60 mm in 3 years. It feeds on phytoplankton and detritus.
Ketelysia opima
No reports of its availability exist in Bangladesh. However, it is being cultured in India. Shell is relatively thinner which is smooth and yellowish brown in color and abundantly found in river mouth. It feeds on detritus and planktons. Its maximum size is 41 mm.
Scallop, Anadara sp
Two or three species of this are available in Bangladesh generally known as cockle, blood clam. It is found in muddy and sandy bays, creeks and back waters, and found upto 4 m depth. It attains maximum size of 70 mm and feeds on plankton and detritus.
Sea weeds
Sea weeds are macrophytes, growing mostly on rocks and other plants or substratum in intertidal and subtidal environment. Out of 17 species of sea weed available in Bangladesh water, 2 species have commercial importance which may be cultured in and around Teknaf and St. Martin Islan areas. These species are Hypnea sp. and Sargassum sp.
Very few marine species of finfish, shellfish and seaweeds are commercially cultured at present in our country. More candidate species and hybrid species are needed to diversify commercial culture. Hatchery and grow out techniques of target species are to be developed. This area needs major research efforts.
