tailieunhanh - Manual on the Production and Use of Live Food for Aquaculture

Sử dụng thức ăn tươi sống trong Nuôi trồng thủy sản (The success of any farming operation for fish and shellfish depends upon the availability of a ready supply of larvae or ‘seed’ for on-growing to market size. However, for many fish and shellfish species (. carps, marine finfish, crustaceans, bivalves etc.) this has only been possible in recent years through the development and use of a succession of live food organisms as feed for the developing larvae. The aim of the present manual was therefore to review and summarise the latest developments concerning the production and use of the | To have a better control over the quality of the trochophores, one can divide the broodstock animals after the spawning shock over individual containers. After spawning is completed the females should be taken out so as to let the eggs settle on the bottom. Clumps of eggs must be separated to obtain good fertilization and this is achieved by pouring the content of the dishes or beakers through a 60 µm mesh screen and collecting the individual eggs on a 15 µm mesh sieve. The eggs are then washed with clear seawater, screened on their quality (eggs must hydrate within 10 min. in seawater and must have a uniformly dense, granular appearance), and pooled. Sperm from various males is pooled to ensure a good genetic mix in offspring. Fertilization is carried out by gently mixing 2 ml of a dense sperm suspension to 1 l of egg suspension, after which the suspension is allowed to stand for several hours. Within this period the fertilized eggs start to divide. However, densities of developing embryos should not exceed 80,