La produzione di novellame di specie ittiche marine in Italia

In the last five years, the productive capacity of the Italian marine fish hatcheries has increased more than thrice, rising from 3.4 million fingerlings in 1986-'87 to 11 million in 1990-'91. The 18 hatcheries that are currently operative can be classified into three main types, named traditional, transitional and advanced, according to their technological level evaluated on the basis of: 1) reproduction control; 2) water quality control; 3) larval rearing technique; 4) fry quality and 5) research for technological improvement. The first type is characterized by the absence of broodfish stocking, occasional water quality control, high percentage of abnormal larvae (around 60) and low productive capacity. In transitional hatcheries, a small broodstock is maintained and larvae are reared up to 50 days in closed or partially closed circuit systems with control over the most important water parameters. Nutritionally enriched rotifers and Artemia are often used for larval feeding and the incidence of developmental abnormalities is on the average about 35. In almost all advanced hatcheries, operations are carried out in closed or semi-closed circuit systems designed according to modern engineering and biotechnological criteria. Gametes are provided by a permanent selected broodstock which is subjected to ecophysiological conditioning. Devices to avoid gas hypersaturation of the water and to remove oily films from its surface are usually present. Annual production per hatchery reaches 2 million fingerlings with 90 inflated swim bladder and no more than 5 deformities. Larval survival rate is generally higher than 10. Laboratory work to reduce theratologies and diseases and to improve fish quality through mass selection, chromosome manipulation and sex control is implemented in some cases.