Coastal Aquaculture and Mariculture

Unit 8- Deep sea fisheries

8.2.1.Conservation of endangered marine animals of India
Whale Shark (Rhincodon typus)
It is the largest of all fishes. It is a pelagic species that occurs in continental shelf and offshore waters in both tropical and warm temperate waters of all oceans. It may grow up to 18 m in length, but fish of 4 m to 12 m in length are more commonly seen. Frequent entangling of this giant cartilaginous fish in trawl nets has been reported in India particularly in the east coast. This is included undermSchedule -I part II A of the Wildlife (Protection) Act, 1972. The ban should be continued to help resuscitation of the stock. This species also has been included in the IUCN Red List (2000) as vulnerable and listed as 'species under threat'.
Sharks and Rays
In India, a total of 110 species of elasmobranchs which include 66 species of sharks, 4 species of saw fishes, 8 species of guitar fishes and 32 species of rays have been reported. Sharks are slow growing, viviparous, with long gestation period and limited fecundity. The size at first maturity is also high. Many species of sharks and rays use the bays and estuaries as nurseries which are susceptible to overexploitation.
The stock assessment studies on elasmobranchs indicated that there is overexploitation of some species while some of the species are underexploited. Hence, a ban was imposed under the Wild Life Protection Act, 1972, on the capture of three species of sharks namely, Glyphius gangeticus, G. glyphius and Carcharhinus hemiodon, two species of rays such as Himantura fluviatilis and Urogymnus asperrimus, three species of saw fishes such as Pristis microdon, P. zijsron and Anoxypristis cuspidatus and one species of guitar fish, Rhynchobatus djeddensis. All these species have also been brought under IUCN Red List (2000) either as vulnerable or endangered. To replenish the stocks, management measures like restriction of trawling during peak spawning period of elasmobranchs can be enforced for sustaining the juvenile population. Operation of gilInets or other entangling nets for the capture of juvenile elasmobranchs in the bays and estuaries which serve as nursery grounds need to be prohibited.
Seahorses
Seahorse belongs to the family Syngnathidae which also includes pipefishes. This family consists of about 215 species. 33 species of seahorses have been recorded throughout the world. In India 6 species of seahorses were recorded and they are Hippocampus trimaculatus, H. kuda, H. fuscus, H. spinosissimus, H. kelloggi and H. histrix. The species, H. histrix was recorded for the first time in India by Fisheries College and Research Institute, Thoothukudi in 2003. Seahorses are used in traditional medicines especially in Chinese medicines. India was one among the 20 nations exporting seahorses. Their medicinal value and international demand resulted in overexploitation of wild population. Life history strategies of seahorses make populations susceptible to over-exploitation. The strategies include male's brooding behaviour, low fecundity, decreasing reproductive potential, lengthy parental care, monogamous, sparse distribution, low mobility and small home ranges. In addition to these, destruction of habitats like coral reef, mangroves, seagrass beds and estuaries, increase in demand and catching accidentally as by-catch in fishing nets particularly in trawl nets are threats faced by seahorses.
Recently, all the syngnathids that include seahorses and pipefishes were included in Schedule I of the Wildlife Protection Act, 1972. However, clandestine catching and exporting are still taking place in some places. Sea ranching of seahorses should be done periodically to improve the stock. CMFRI has succeeded in production of young seahorse in captivity and planned to range seahorses in the sea. Fisheries College and Research Institute, Thoothukudi sea ranched young ones of seahorses in hulf of manager during 2003 -05.
Brindle Bass Giant Grouper (Epinephelus lanceolatus)
This species occurs in tropical waters throughout the Indo-Pacific but is also recorded occasionally in temperate waters. It grows to at least 2.7 m in length and over 400 kg. It is one of the largest bonyfish and is the largest on coral reefs. Since large area of reef is required to support such a large predator, their populations are always relatively low even in areas that are not regularly disturbed by people. This species is found to be vanished from the reefs due to overfishing. Sporadic occurrence of this species is reported along both the coasts. Fisheries College and Research Institute, Thoothukudi reported a specimen of this species of about 30 years old measuring 210 kg and 202 cm caught by trawl net at Gulf of Mannar in 2003. Hence, in order to protect this endangered species from further extinction, it has been brought under the schedule I -Part I A of the Wildlife Protection Act, 1972.
Molluscs
There is no organized fishery for commercially important molluscs except very few. As far as gastropods are concerned, organized fishery is only on sacred chank along the main coast, Trochus and Turbo in Andaman Islands and Cypraea in Lakshaweep (CMFRI, 2003). Among the gastropods, one of the overexploited species is sacred chank, Turbinella pyrum. This species is now in the vulnerable stage. Hence, conservative measures are to be enforced. Government should enact laws to prevent the fishing of undersized chanks. There must be a fixed season declared for chank fishing over the chank grounds. The fishing for chanks should be banned for 3 months (Jan -Mar) every year in order to conserve the egg capsules and baby chanks. In addition to chanks, other gastropod shells were also over exploited for food as well as to support the shell craft industry.
Bivalves are perhaps the least managed resources along the Indian coast. Till 1961, pearl oysters were fished for golden coloured pearls. Pearl oyster beds along the Gulf of Mannar coast were destroyed by indiscriminate trawling and pollution caused by industrial effluents. Indiscriminate exploitation of seed clams is prevalent in Kerala and Andhra Pradesh. Destruction of seed mussel has been observed as the fishermen discard the seed mussel after they are fished from the natural bed (Mohan Joseph and Jayaprakash, 2003). Similary, population of the only shelled cephalopod, Nautilus pompilus has also become very rare.
Hence, 19 species of gastropods belonging to the genera, Cassis, Charonia, Conus, cypracasis, Tudicla, Cypraea. Fasciolaria, Harpulina, Lambis, Strombus, Trochu and Turbo, 3 species of bivalves such as Hippopus hippopus, Tridacna maxima and Tridacna squamosa and 1 species of cephalopod, Nautilus pompilus have been included in the Schedule I of the Wildlife Protection Act, 1972. In addition, searanching should be done periodically to improve the stock of the vulnerable and endangered molluscs, for which hatchery technology should be developed if not available. The existing chank beds, pearloyster beds and clam beds should be totally banned from trawling activities.