Seed Production And Culture Of Lobsters

Lobster farming is currently reliant on a natural supply of wild plueruli. Two to three million plueruli are caught each year between October and March, of which around 70 per cent are P. ornatus and 25 per cent P. homarus.  The only other developed fishery for spiny lobster plueruli is in southeast Lombok, Indonesia, where around 5 lakhs plueruli are captured each year.  In this fishery, 90 per cent of the plueruli caught are P. homarus and the rest are primarily P. ornatus.Clawed lobsters comprise a family (Nephropidae, sometimes also Homaridae) of large marine crustaceans.
They have long bodies with muscular tails, and live in crevices or burrows on the sea floor. Three of their five pairs of legs have claws, including the first pair, which are usually much larger than the others. Highly prized as seafood, lobsters are economically important, and are often one of the most profitable commodities in coastal areas they populate.  Clawed lobsters are not closely related to spiny lobsters or slipper lobsters, which have no claws (chelae), or to squat lobsters. The closest living relatives of clawed lobsters are the reef lobsters and the three families of freshwater crayfish.

TAXONOMIC CLASSIFICATION

Kingdom           :    Animalia
   Phylum             :    Arthropoda
    Class                :    Malacostraca
Order                :    Decapoda
  Family               :    Scyllaridae

DISTRIBUTION

Lobsters can be found all over the world. They can be found throughout the Atlantic  and Pacific 

ocean at depth any where from 1m – 480m. They are usually found around depth of 40 – 50m. Large concentration can be found along the eastern US coasts and the water surrounding Europe. 

BIOLOGY

Spiny or rock lobsters have a sub cylindrical body with long cylindrical antenna with whip like flagellum. The carapace is covered with numerous spines and tubercles. The slipper or sand lobsters with a dorso-ventrally flattened body and short antenna without whip like flagellum. 

BREEDING

 Egg bearing females for the hatchery operation can be obtained from the wild or from captive brood stock. The brood stock can be built up either by growing juveniles to sexual maturity or bringing  sexually mature adult lobsters and induce them to breed under controlled conditions. Juveniles of the spiny lobster P homarus were reared to sexual maturity and successfully bred in captivity.  Food plays a major role in inducing maturation and for spiny lobsters, highest breeding activity was observed on feeding with mussel meat. For successful mating a female to male ratio 2: 1 was found to be sufficient.

SEED AVAILABILITY

Among the shallow water species occurring along the Indian coast, Panulirus homarus, P. ornatus, P. polyphagus and Thenus orientalis are the most promising species. These species can be easily distinguished by the colour and morphological features.The hatchery production of T. orientalis has already been accomplished. Artisanal gears such as trammel nets, gill nets and traps are also used for fishing in inshore areas.

Hatchery production of lobsters

 Hatchery production of lobster larvae (Phyllosoma) is technically challenging because of the protracted duration of larval development and the large number of moults involved and the delicate nature of the larvae.  Japanese research and development of hatchery technology is the most long-standing at over 100 years, but in recent times the most significant developments have come from Australia and New Zealand. Small numbers of plueruli have been produced in research hatcheries and several groups (government and private) are now commercialising their technology. 

NURSERY

 The captured plueruli are very delicate and mortality can be very high (>50 percent).

  The bulk of plueruli are transported in small  boxes.  The nursery phase typically involves stocking the plueruli at 50-100/m2 into submerged cages, consisting of mesh surrounding a steel frame.

 Each cage is placed on the sea floor at 2-5 m depth and a feeding tube from the surface to the cage provides the means to feed the baby lobsters. Finely chopped trash fish, crustaceans and molluscs are used as food. The nursery phase lasts for 3-6 months, during which the lobsters grow to 10-30 g. Floating nursery cages are 3 m x 3 m x 2 m deep, consisting of fine mesh, suspended from a floating bamboo frame.

The cages are furnished with seaweed (Gracillaria sp.); this provides shelter for the small lobsters. They are fed with chopped fish flesh and on-grown for 1-3 months until Farmed lobsters are traditionally fed a mixture of fish, crustaceans and molluscs which come from the fish markets nearby. This so-called ‘trash fish’ can be highly nutritious if fresh and handled appropriately. Food conversion ratios are often poor and considerable pollution occurs in the vicinity of the cages

The fecundity of P homarus ranges from 50,000 to 5 lakhs depending upon the size of the lobster.

 Though the fecundity of captive lobsters was estimated to be 20% lower than those of the wild, egg quality was comparable to that of wild lobsters and hatching gave viable larvae.The fecundity, yolk, carotenoid content, hatch percent of eggs and larval and considerable pollution occurs in the vicinity of the cages. Manufactured pellet diets are available, although there has been little uptake to date.

Larval rearing 

 The incubation period in tropical lobsters range from 20 to 25 days depending upon the water temperature. Newly deposited eggs on the abdominal pleopods change colour from deep orange to deep brown before hatching. Microbial infestation is relatively lesser in captive breeders. The breeder has to be transferred to the hatching tanks containing sterilized seawater as soon as the egg bearing lobster is cited in the brood stock tank. Moderate aeration is to be provided. Hatching takes place during night and the larvae are highly photo tactic. Healthy larvae actively swim on the surface of water and can be collected and transferred to larval rearing tank after estimating total larval numbers. 

Fig. Life stages of lobster

Transportation

Lobster seeds are first transported to farms, which on average takes up to 12 hours. Transport from the lobster farms to trading centers  occurs in open, aerated seawater tanks on trucks and normally takes anywhere from 7 to 20 hours.The live lobsters are then exported overseas once they are packaged in polystyrene boxes which are up to 20mm in thickness, together with plastic bags containing water and ice to help keep the lobsters cool. Small holes are also provided in the boxes for ventilation.

Growth Rate

Under sub-optimal rearing conditions, the Indian spiny lobsters, Panulirus homarus and P. polyphagus were grown from pluerulii to 80g size in 12-16 months and then to 30g in another 12 months.

 In the tiger lobster, P. ornatus, 380g size was obtained in 20 months.  Fattening of juveniles of 100 g and above to required commercial size is more promising than rearing pluerullii to marketable size.Three to seven fold growth enhancement was achieved in four species of Indian spiny lobsters by eye-stalk abalation. The tiger lobster has been grown from 100- 1500g in eight months by this technique. The ethics of enhancing growth by removal of eye-stalk and the consumer acceptance of eye less lobster are the points to be considered before applying this technique. Researchers find out the same result can be achieved by inactivating the eye-stalk hormones by laser or other modern techniques, rather than by eye-stalk abalation.

Cultivation in cages

After the lobster seed is sold to farmers, they are normally placed into sea cages and grown to adult size for harvest at about 1 kg. This takes about 18– 24 months. Three methods of cage culture exist. The first farming method, is a floating cage,  The second farming method is wooden fixed cages, made from 2.5m length by 10 cm width wood with salt resistance, placed about 2 m apart so to create a square shape and normally have an area of 20-40 m2 up to 100-200 m2 with varying cage size.

 The third cage farming method is the submerged cage method, made from iron mesh with meshing of 15–16 mm, with an overall size of the cage ranging from 1 - 16 m2 and with a height of 1 - 1.5 m.

Fig. stages in cage culture

 Feeding

After settling, young, lobster are quite aggressive competing for habitat and food. When cultured in Vietnam, lobsters are normally fed “trash” fish, such as lizard fish and pony fish, that are caught as a by-product of fishing activities. They  are also fed mollusk such as sea snails, oysters, and cockles etc.  These raw foods are given to the lobsters in the cages after being chopped into small pieces.

Factors influencing growth of lobsters

Water quality parameters in larval culture system of   spiny lobsters:- Temperature - 20.0 -21.5 o C Salinity (ppt)- 33.5-35.5 and PH- 8.0- 8.6.

Salinity, dissolved oxygen (DO), pH, temperature and nitrogenous metabolic wastes, especially, ammonia, are the major water quality parameters regulating lobster growth. Stocking density, provision of shelter, handling stress and intensity of light also influence growth in captivity. Quality of feed plays a major role in obtaining optimum growth and body colouration.

SCOPE FOR CULTURE / FATTENING OF INDIAN SPINY    LOBSTERS SEED

All commercially important species of shallow water spiny lobsters in India have been bred in captivity, but their whole larval cycle is yet to be completed. Scientists at the Central Marine Fishers Research Institute (CMFRI) were successful in rearing lobster larvae to more than half way stage and efforts are on to complete the larval rearing process.