Shellfish Breeding and Hatchery Management (2+1)

Procedure 

 

Follow the procedure given below for individual live feeds.

Shellfishes depending on their feeding habits & preference may be fed with live foods such as Cyclops, daphnids, rotifers brine shrimps, earthworms or with moist pellets, dry pellets, flakes and chopped bits of fish, shrimp. beef. oyster crab, liver, spleen, lung, heart and brain.

The following are the general live feeds that are commonly used for the feeding of larvae of shellfishes:

Zooplankton:

Zooplanktonic organisms such as rotifers, copepods & cladocerans like Moina and Daphnia spp.

Rotifers:

The common freshwater rotifer species include Brachionus rubens, B. calciflorus, B. forficula and Keratella tropica. The mass culture of these rotifers could be under taken in plastic through or circular tanks of 250 lit capacity. A mixture of pouttry droppings, groundnut oilcake and triple superphosphate is prepared at 150ppm, 20ppm and do ppm respectively and are added to above tanks containing water. The medium is then inoculated with Brachionus sp. on the third day at the rate of 10-15 animals per ml. The above liquid manure may also be added in alternate days when the density reaches 1 ml organisms/m³. A bolting silk and plankton net of 50 mm mesh size could be used to sieve out the organisms for feeding the fishes. The harvested rotifers should be washed in fresh water before their use in feeding the fish fry. Fiber glass tanks of 1.5×0.6×0.6m capacity have been found to be ideal for the mass rearing of B. plicatilis which is inoculated at one individual per 1 ml of the medium. The growing B. plicatilis under mass culture is feed normally with yeast at 0.04g/l. Green algal concentrate containing Chlorella spp. may also be used to feed these rotifers Harvesting could be done after 20 days when the population of B. plicatilis exceeds 4000nos/ml. The harvestable rotifers which float in the surface are sieved, collected and stored in bins or aluminium packs as vacuum dried for further use.

Copepods:

Cyclopoid and calanoid copepods are also known to be ideal live food organisms. Tanks or fish ponds manured with raw cowdung, groundnut oileake and superphosphate at 330/80/60ppm respectively and are kept under continuous aeration and inoculated with 50 individuals per liter medium would lead to the production of copepods from third day on wards.

Cladocerans:

Cladocerans are otherwise known as water fleas, the size of which vary from 0.5 to 1.5 mm. They are common in seasonal ponds, pools, etc. Especially after the development of phytoplankton blooms on which they normally feed. The production of cladoceransz such as Daphnia organic wastes from cow shed. A liquid manure mixture may be prepared using cow or horse dung, grondnut oil cake and single superphosphate in the ratio 5:5:1. A culture pond of 30 sqm. Area with 1 am depth may be filled withwater. The liquid manure may be dissolved in the pond so as to give a concentration of 220ppm. Aeration may be done to speed up the process of decomposition. Individuals as Moina sp. Or Daphnia carinate may be inoculated at a density of 50 individuals per litre of pond after two days. The cladocerans may go up as high as 5000 organisms/l in six to seven days. The cladocerans may be harvested from the seventh day onwards in alternate days, when their maximum density is reached and the harvest is made by using a plankton net and the concentrate is freeze dried for regular feeding of the fishes as and when required.