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After artificial reproduction of tench, larvae must be maintained indoors, and studies on rearing conditions are needed, focussing on the reduction of labour and costs. Three experiments on larvae (5th day post-hatch) were conducted for 25 days using Artemia nauplii as the sole food in order to determine basic feeding and density conditions during the first rearing period. Tench were maintained in 25 l fibreglass tanks, supplied with an artesian water flow throughout of 0.2 l min À1 . Water temperature was 22.5 ± 18C, and the photoperiod was natural. Larvae fed on a restricted amount of nauplii reached high survival rates, even with the minimum of 50 nauplii larva À1 day À1 . This amount of food may be sufficient at least for the first 25 days of exogenous feeding if fast growth is not the priority, and high densities can be maintained with good survival rates (over 90% up to 160 larvae l À1 and 77% with 320 larvae l À1 ). When food was supplied in excess once a day, high survival rates were achieved (91-97%), without differences among the densities tested. Animals at a density of 100 l À1 reached the highest length (15.57 mm) and individual weight (46.8 mg). This growth is greater than those reported in studies feeding several times a day. It could be deduced that, while live food remains available for tench, it is not necessary to feed so frequently. Considering the relationship among the initial number of animals, final survival and growth and ration supplied, the new data reported here are useful to establish suitable stocking densities under both culture and experimental conditions.

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Although it is generally accepted that sexual maturity of tench (Tinca tinca L.) is not reached before 2-3 years of age, a successful experiment on artificial reproduction in 1-year-old tench is described. It was possible to obtain semen and eggs from 48% of males and 27.7% females kept in a small concrete tank at a final density of 3 kg m )3 and fed on a commercial dry diet. Two hormonal treatments were applied: the first with 1354 degree-days and the second with 2353 degree-days. In each experiment, the positive response in males and females was around 80%. Total egg production exceeded 11% of body weight, fertilization rate was above 90% and hatching rates around 50%. These results differ little from those reported for older breeders.