Egg incubation time and hatching success in tench Tinca tinca (L.) related to the procedure of egg stickiness elimination

Abstract

Summary The experiment showed different results after a short (2 min) enzyme alcalase Merck EC 3.4.21.14 (5.0 ml L−1 concentration) treatment of tench eggs in contrast to the traditional methods of eliminating egg stickiness involving milk solution (50 g L−1) treatment for 70 min followed by the addition of a talc suspension (33 g L−1) for 10 min or treatment by fine clay suspension (20 g L−1) for 60 min or talc suspension (33 g L−1) for 80 min. The alcalase enzyme treatment resulted in decreased egg stickiness compared with the conventional milk/clay/talc treatments, indicated by lower duration of egg incubation and higher hatching rates (anova for hatching rate, P < 0.0084). The highest hatching rate (93.2%) was achieved using the enzyme; the lowest (31.3%) was using a talc suspension (control hatching rate was 86.2%). Duration of egg incubation at degree-days (D°) after enzyme treatment (58.6 D°) was about 4–5 h shorter than the classical method using milk solution and talc suspension (63–65 D°). Prolongation in the latter classical method may also be explained by a hardening of the egg envelopes.