LAUSR

The objective of this study was to determine differences in relevant parameters of the basic chemical composition of flesh (descriptors: dry matter - DM, crude proteins - CP, net proteins - NP and net muscle proteins - NMP, fat - F, ash - A) of communal stock of diploid (2 n) and triploid (3n) tench (Tinca tinca L.) of the same origin, in relation to sex (F: female vs. M: male) and age (T 3 : 36 months, after overwintering vs. T 3+ : 42 months, after one summer in the pond). Altogether 137 siblings of tench were studied. The basic chemical composition of flesh of 2n and 3n tench of T 3 age was found to be nearly the same. The only significant difference ( P < 0.05) was found in DM content in diploids (5.7% higher DM content in females). Marked changes in the basic chemical composition were related to the increasing age of tench: after one summer in the pond (from T 3 to T 3+ ) the DM content increased significantly in all groups of tench (by 5.4% in 2n females, P < 0.05; by 6.5% in 2n males, 9.9% in 3n females and by 7.4% in 3n males, all at P < 0.01). The content of nitrogenous substances was found to increase significantly (P < 0.01) in flesh of 2n males: CP by 3.2%, NP by 4.2% and NMP by 3.3% and in flesh of 3 n males: CP by 7.0%, NP by 6.6% and NMP by 7.3%. Muscles of 3n females contained 107.3% higher fat content ( P < 0.05). The proportion of ash decreased in 2 n and 3n by 2.5% and 1.7%, respectively (P < 0.05). The flesh quality of T 3+ tench after one summer in the pond was higher if compared with that of T 3 tench after overwintering. Related to the ploidy level, more favourable chemical composition of flesh and more favourable flesh quality were found for triploids of T 3+ age.