Largemouth bass (Micropterus salmoides Lacepede): reproduction management and larval rearing in Italy.

This work reports the results of preliminary experiences of controlled reproduction and larval and juveniles rearing of largemouth bass carried out during year 2001. The trial was repeated in 2002. Broodfish were submitted to sexing based on observation of secondary sexual characters: ripe females were selected on the basis of distended and soft abdomen and a red, swollen and protruding urogenital opening; ripe males were fluent when stripped. For every year, 20 couples were stocked in 1-500 m2 natural pond, 1 m deep. Before the filling, the earthen basin were fertilized with manure (2 t/ha) and 20 nests were placed at 80 cm depth, 4-6 m spaced. Broodstocks, weighing 500-800 g, were released and the behaviour was observed in order to verify if eggs had been laid. 18-23 days after hatching, larvae were collected and transferred in 1.5 m3 black coloured cylindrical fibreglass indoor tanks at a stocking rate of 30-50 larvae/l. The newly hatched Artemia (4 nauplii/ml) were used to feed the larvae for 15 days. Successively, copepods and cladocerans, collected from a pond used for this purpose, were administered and an extruded feed was progressively added till the weaning was reached. Feed was supplied by means of an automatic feeder operating in one 12-hour cycle. During the larval and juvenile rearing, grading fish was carried out at different times. At the end of this phase, fingerlings were harvested and mean weight and survival rate were calculated. At the end of July, fish were transferred in ponds were they stayed until harvesting that occurred at the end of October.