Effetto delle condizioni di allevamento sulla crescita e la morfologia della tinca

The aim of this work has been to evaluate the effect of stocking density on tench (Tinca tinca) when reared in a water circulation plant. 1200 fishes, about ten-month-old, have been stocked in 4 tanks (200 L) at 2 density: 1.1 kg/m3 (N=200) and 2.2 kg/m3 (N=400) and fed with an extruded feed for salmonids (CP 49%, EE 23%; 2% bw). The total weight of fish per tank was periodically measured, while samples of 10% of tench were taken at 16 months of age and subjected to the same body measurements previously obtained at 4 months of age. Then the same body indices were computed Growth doubled density in all tanks in 6 months, without differences. On the contrary, morphology resulted affected. In fact, on the basis of the differences between body indices, the maximum height changed its position towards tail in fish stocked at the higher density. The same measurements were taken again at 22 months of age on fish maintained at the lower density. Growth resulted generally poor, although mortality remained low. Stocking density, together with rearing conditions and behaviour of tench appeared to affect both growing performances and morphology.