brackish water fishes for aquaculture

 Important brackish water fishes

 

             Coastal aquaculture is one of the high potential areas of increasing overall fish and shellfish production of India. With a long coastal line of 8,129 km India Indian water harbor rich brackish water fish biodiversity inclusive of fin fishes, crustaceans, mollusks and sea weeds. Physical resources include a number of brackish water lakes like Chilika, Vembanad and Pulicate lake; esturine system like Hooghly Matlah, Mahanadi, Godavari, Krishna and Kauvery- Coleroon esturine systems on the east coast. The Narmada – Tapti estuarine system on the west coast and an estimated potential area of 1.2 million ha is amenable for coastal aquaculture. The coastal are of the country also has 2.54 million ha of salt affected soil which are unfit or marginally fit for agriculture excluding 0.57 million ha under mangroves. Biological resources include diverse species of crustaceans, fishes, mollusks and aquatic plant. The important species of crustaceans are  P.monodon, P.indicus, P.merguiensis, P.pencillatus,  P.semisulcatus, P.japonicus, P.monoceros and M.dobsonii. Important fin fish species are Lates calcarifer, Mugil cephalus, Liza macrolepis, Chanos chanos, Epinephalus tauvina and E. malbaricus, Lutjanus spp.  Important crab species are Scylla tranquebarica and S.serrata. Important sea weed species are Gelidiella acerosa, Gracilaria edulis, Sargassum spp. and Turbineria species.

 

            A brief description of important brackish and marine water fin fishes are as follows

 

11.1. Elops mechnata:- Body elongate head conical. Maxilla extends behind the eyes and lower jaw is projecting. Dorsal profile is concave. Body is silvery in colour and fins are yellowish with grayish tinge coloration. It is a carnivorous fish feeding mainly on crustacean. It ascends estuaries and rivers attain maximum size of 700mm.

 

11.2. Megalops cyprinoides:- Body is oblong and slightly compressed laterally. Ventral profile is more convex than dorsal. Eye with narrow adipose lids. Vomer, palatines, pterygoides and sphenoid are with villiform teeth. Dorsal fin originates between mid way of snout and caudal base. Caudal fin is deeply forked. Top of head is dark olive, back bluish- green abdomen is silvery with bluish markings. This is euryhaline fish that tolerate 0-40ppt salinity. This fish migrate to estuaries and river, feeds on fish, crustaceans and other animals. Maturity is attained at 250 mm of length and breed twice a year in coastal waters.

11.3. Etroplus suratensis :-Body is oblong and compressed. Cleft of mouth is small. Maxilla extends more than mid way to lower orbit. Lower jaw is slightly longer than upper jaw. Dorsal fin is single with the spinous portion greater in extant than the soft portion. Lateral line is present in upper part of body. Teeth are lobate and are arranged in single row on each jaw. Caudal fin is slightly emarginated. Colour of fish is light green with eight oblique bands arranged vertically. The dorsal, caudal, ventral and anal fins are of dark leaden colour but the pectoral fin is yellowish with a black base. The fish has strong spine on the dorsal and anal fins to defend it from its predators. It attains maturity at 2^nd year of its age when the fish become more than 100 mm in size and can breed in impoundments like pond. During spawning female cleans algae and other growths from a small area on submerged objects and lays eggs which are fertilized by males. Mother guard eggs which remains attached singly to submerged flat surface. Fecundity is 1200-2000 eggs and growth is 120mm attained in first year with 110 g weight. Maximum size recorded is 450mm. It is also a euryhaline fish tolerating 0-40 ppt of salinity. It matures within a year of its life and breed in captive water almost throughout the year. The eggs are attached in some substratum like weed, twigs, bamboo poles stones and husk. The eggs are fertilized by male and further guarded by female. Eggs hatch in seven days. The seed has vertical bands and a spot on caudal peduncle. The fry feeds on zooplankton and insects. The juveniles and adult feed mainly on filamentous algae and food matters of plant origin including Spirogyra.

 

11.4.  Lates calcarifer:- It is also known as “Giant Pearch” and popularly known as “Bhekti”. It is distributed mainly in central and eastern Indian Ocean region. Its existence is common in Australia, Burma, India, Indonesia, Malaysia, Papua, Phillippines, Singapore and Thailand. In India it is available on east and west coast but is more available in West Bengal region.

Body is oblong, moderately compressed; head is depressed and upper profile concave. Mouth is slightly oblique. Canine teeth are absent. Vomer and palate are equipped with villiform teeth. Two dorsal fins are united at the base of dorsal fins. Pectoral is shorter than ventral and rounded, caudal fin is also rounded with a fan shape. The spinuous and soft part of the dorsal fin are separated by a deep notch. The lateral line extends on the tail. In juveniles the colour is olive brown above with silver belly while in adults it is greenish or bluish above and silvery below. It is carnivorous in habit and feed on fish crustaceans, snails and worms. It also shows cannibalistic habit when there is scarcity of food. It matures at second year of its age when it is more than 400 mm in size. It breed only once in a year in open seas. Eggs are heavy that sink to bottom. It is also euryhaline fish species tolerating 0-40 ppt of salinity. It ascends frequently brackish water and tidal rivers. It can grow up to 200 cm and can attain 100 kg weights. Most common sizes are 25-100cm.  Fishes are reported to be caught by seine, gill nets along the coastal areas, lagoons and estuaries. In culture ponds it is known to attain 1.5 to 3.0 kg first year and 5.0 kg in second year.

 

11.5. Elutheronema tetradactylum:-Mouth is large reaching behind the eyes. Teeth are villiform. Preoperculum is serrated. First dorsal fin originates between origin of pectoral and ventral. Origin of second dorsal fin is opposite to that of anal fin. Anal fin margin is deeply concave. Pectoral fin is with four free rays extending to pelvic. Dorsal side colour is silvery green and abdomen is yellowish white. It is less hardy fish predatory in feeding habit mainly feeds on fish, prawn, mysids, amphipods, isopods, stomatopods. Male fish matures when it reaches to 225 mm and female fish reaches to 285 mm. It is tolerant to salinity changes. Enters and survive in back waters and in estuaries. It enters rives and backwater for spawining. In a span of year it attains annual growth of 190-300mm san can attain maximum length of 200cm.

11.6. Mugil cephalus- Mugil cephalus has a robust body and fatty tissue covering most of the eye. Body is oblong and compressed. Head is broader than its height. Lateral lime scales are 38-42. A band of teeth are present on both jaws. There are two dorsal fins. Pectoral fin originates above middle of body depth. Caudal fin is forked. It is blue green on back and silvery on sides and whitish ventrally. There is 6-7 distinct brown bands dawn the flanks and a dark purple blotch at the base of pectoral fin. Although this fish grows to a maximum of 90 cm the common size range from 35-45 cm. It is filter feeder fish mainly feeding on organisms that occupy lower tropic level in food chain. The main food consists of algae, diatoms, crustaceans, decaying organic matter, detritus, and occasionally on zooplankton. It matures at 250-240 mm of length. Male mature in first year and female mature in second year. Breed in offshore. It is euryhaline fish which can tolerate a salinity of 0-75 ppt. They grow fast some species attain weight of 750gm and length of 45 cm by end of first year.  Egyptians and Romans are the pioneers in Mullet culture. It is an important food fish distributed in tropical and subtropical regions of the world including countries Italy, Israel, Egyptian the west and Korea and Japan in the east.  Among 14 valid species of mullet most important species are Mugil cephalus, Liza microlepis, L.subviridis, and L. tade, M. chelo, M. capito, M. saliens, M. oligolepis, M. cephalus, M.dussumieri, M. troschelli and M. corsula, M.tade and M.parsia and M.oligolepis.

 

11.7. Milk fish (Chanos chanos):- Milk fish is fast growing, eurythermal, euryhaline fish mostly feeding on algal growth at bottom of culture pond. It is hardy fish species that survive in even wide fluctuation of dissolve oxygen and it is also less sensitive to disease. Body is elongated, spindle shaped and moderately compressed. Dorsal portion of head is flat, upper jaw over hanging lower jaw and lower jaw also has a tubercle on its tip. Mouth is small, without teeth anterior and transverse. Pectoral fin is pointed with scaly appendages at base. Ventral fins have a long basal scale inserted under middle of dorsal. Anal fin is small with two rows of scale at base. Upper lobe of deeply forked caudal fin is slightly larger than lower lobe. Dorsal side of body is olive green in colour and abdomen in silvery and whites. Dorsal, anal and tail fins have dark margins. Small size fishes enters the back water, estuaries, lagoons and rivers which serve as nursery grounds and spent early part of its life till about one year. For attaining maturity they return back to the sea and spawn annually or biannually in 5^th or 6^th year of its age releasing about 3-7 millions of eggs each time. The seed of this fish is abundant in calm, clear coastal water near estuaries or lagoons where microscopic algal food is available in plenty. It stays here for about one year when and grows to about 50cm weighing to 500-800gm. Generally they feed on lab-lab. The algal mat consisting of a complex animal-plant combination material. The young larvae feed on algae belonging to bacillariophycea, myxophycea and chlorphyceae. Fry and fingerlings feed upon diatoms, algae, lamellibranches, fish eggs etc. It is primarily a phytoplankton feeder. This fish can be induced bred, fecundity ranges between 2.0to 6.0 million. Larvae migrate to coastal water, estuaries and swamps. It is also a euryhaline fish that can tolerate a salinity of 0-40 ppt. It grows to 200-400 mm and gain weight of 800gm in a year. It is especially cultured in South East Asian countries like Indonesia, Philippines and Taiwan for centuries. The ponds facility in which it is cultured is termed as “Tombak”.