2. Cold shock at +CO 0,2 (experiment 2, fig. 1).
a) Embryonic eyed-stage. - Generally, the activation rate computed at D25
decreased with the shock duration and differed considerably in terms of the parameter
t.
b) Viable fry. - Shock durations of 6 to 15 hrs induced an appreciable increase
in the hatching rate as compared to the results obtained in the control batch. The t
values varied widely again.
The proportion of hatched fry to the number of live
embryos at 2 D5 reached 25 p. 100 in the best case (T = 10 hrs ; t = 1 min). The
20 fingerlings analyzed at 3 months proved to be diploid.
3. Cold shock at - 0.4 °C (experiment 3, table 3). - The use of a lower temperature
did not disturb the activation rate ; good hatching rates were obtained, especially
for t = 0.1 and 10 min. All the metaphases were diploid (20 fingerlings).
A small
number of twisted fingerlings (about 5 p. 100) was recorded at hatching time.