Method of evaluation of wild common tench, Tinca tinca (L.), female suitability for artificial reproduction during the spawning season

The aim of this study was to evaluate the suitability of females for artificial reproduction of common tench based on an analysis of the size and percentage share of oocytes sampled <em>in vivo</em>. The females were collected from natural waters (lakes) during the spawning season, After catching, the selected fish were transported to the hatchery, where the fish were kept under controlled conditions and oocytes were collected from all females. It was found that sampled oocytes were different in size and developmental stages. Oocytes were classified into 3 groups: small, medium and large. The diameter intervals for each group were 0.18-0.22 mm, 0.48-0.57 mm and 0.95-1.01 mm, respectively. Analysis of the percentage of the largest oocytes showed that their numbers decreased in time from over 40% on Day 1 to slightly over 10% on Day 10. A positive correlation was found between the percentage of the largest oocytes in the cathetered egg sample and the weight of the stripped eggs during artificial reproduction. The percentage of the largest oocytes (diameter 0.95-1.01 mm) might be used as an indicator of the possibility of reproducing wild tench. No statistical differences were observed in latency time and embryo survival of females showing different quantities of the largest oocytes