Lobster Farming

Hatchery technology

The greatest hurdle in commercial culture of spiny lobster is lack of a proven hatchery technology for commercial seed production. Prolonged larval phase (> 300 days for cold water and  semi-tropical species) and consequently, problems in food and water management are the major constraints for successful development of hatchery technology for many tropical species. Inspite of recent advances in larval culture, commercial seed production technology is a distant reality.

First success in larval culture of spiny lobster was achieved by Prof. Jiro Kittaka of Japan in 1986-87 and the Japanese successfully completed the larval phase of Jasus lalandii. Larvae were cultured in a medium of the microalgae Nannochloropsis sp. and fed on mussel (Mytilus edulis). Later four more species were reared to settlement. Countries like Australia, New Zealand and South Africa also succeeded in rearing the phyllosoma larvae to the postlarva (puerulus). However, all the species took more than 300 days to complete the larval phase and therefore the economical viability of hatchery for lobsters in doubtful.

Broodstock and  breeding

Egg bearing females from the wild   or  from captive  broodstock are the two sources from which healthy larvae can be obtained for larval rearing.  Egg bearing lobsters with eggs in different stages of development are available throughout the year. Peak breeding of P. homarus homarus in India is from December-March along the southwest and east coast of India and for P. polyphagus the period is from September-October.         Handling, transportation and maintenance in captivity until hatching have to be done carefully to avoid any stress to the egg bearing female. Exposure of egg bearing lobsters outside water shall be minimized as these eggs are prematurely shed by the mother.

P. homarus homarus  has been  reared to maturity in captivity  and the females are capable of breeding repetitively through out the year).  Healthy larvae can be obtained from repetitive spawning.

Culture of spiny lobster larvae by Japanese

Egg bearing lobsters procured from holding tank owners are unsuitable as poor water conditions lead to microbial infection and premature egg shedding. Egg bearing lobster is to be procured directly from gillnet fishermen and transported to the hatchery without stress. The lobster is to be transferred carefully to the hatchery tank containing microfiltered and sterilised seawater (1000-1500 l). Newly deposited eggs are orange in colour.  The eggs change in colour during embryonic development and become dark brown just before hatching. Incubation period is normally 20-
30 days for newly deposited eggs depending on water temperature.   The egg mass may attract filamentous bacteria,
fungus and protozoans and therefore breeders from both wild and from brodstock holding tanks are to be transferred to the hatching tank   after  exposing to 50 ppm  fprmalin for 30 minutes.

Larval culture protocol (Japanese culture system)

‘U’ shaped polycarbonate or glass tanks  were used by the Japanese investigators.  The tank designed by Massachusetts Institute of Technology and used for rearing American lobster larvae was modified and used. Series of tanks are connected to a reservoir containing microalga. The upwelling movement of water keep the larvae and food in suspension. Excess water entering into the tank is drained out through a central pipe. The mesh around the drainage prevents escape of larvae and feed. A disadvantage is gradual fouling of mesh which blocks the waste removal. Microalgae has to be renewed periodically. Damage to larvae due to entangling on the mesh screen has to be prevented by adjusting the flow rate. The central pipes are periodically removed and cleaned and replaced.  Later clear water systems  with recirculation were used.

Food and feeding

Phyllosoma larvae are carnivorous. Food is captured by the third pereiopod initially; soft food (Artemia, Sagitta, Ctenophore medusae etc) alone can be fed. Most suitable food for early stage larvae is freshly hatched Artemia nauplii. For later stages, preference is for larger food items.  Mussel gonad, Sagitta sp., cultured Artemia juveniles, Ctenophore medusae   and newly hatched fish larvae are the potential food items were used for different stages. Suggested food for larval rearing of Jasus sp. are: upto fifth stage, Sagitta, fish larvae for middle stages and cultured fish fry of 4.5-7.5 mm for final stages. However, complete larval culture  was successfully carried out on feeding with mussel. Artemia enriched with PUFA or microalgae, showed high food value. Marine bivalves contain essential amino acids and fattyacids and have high food value. Mussel gonads should be kept in suspension to facilitate feeding by the larva.

Water quality

In clear water, larvae were infected with stalked protozoans (Vorticella, Zoothamnium). Treatment with formalin (30 ppm, 24 hr) and streptomycin at 10 ppm is effective but not recommended as repeat treatments are injurious. Water temperature is maintained at 20-25°C for different species; salinity varied between 33.5 to 35.5 ppt and   pH 50 ranges from  8.0-8.6. The median lethal limit (LD) of ammonia-N for a 72 h period was 8 mg/l for 13-15th  instars of P.japonicus. COD is an index of dissolved organic matter. The upper limit of COD was set at1.2 mg/l. The median lethal limit  of heavy metals, copper and zinc was determined at 0.3 mg/l and 6 mg/l, respectively for P. japonicus. In green water microflora was significantly lower.  Pseudomonas  prominent in green water.  Vibrio and Aeromonas more in clear water. Japanese prefer ‘instars’ to arbitrary ‘stage’ to sequence development of larvae. For rearing Jasus sp. mussel is the most successful food for complete development.