Artificial propagation of European perch (Perca fluviatilis L.) by means of a GnRH analogue

摘要

Mature females were administered intramuscularly a single dose of a mammalian GnRH analogue ([D-Ala~6]GnRHProNHEt) and/or an extract of dehydrated carp pituitary dissolved in physiological solution (0.9 g.l~(-1) NaCl). Males were not treated at all. In the first experiment, carp pituitary (at doses of 0.75, 1.5, 3 and 6 mg.kg~(-1)) was administered to 4 groups (n = 5) of females placed in submerged cages (without males and without replicates). The first control group was injected with physiological saline and the second control group with GnRH analogue (100 #mu#g.kg~(-1)). Mean temperature was 16.1 +- 1.1 dreg C. Ovulation did not occur either in females treated with pituitary or in those treated with physiological saline. Females treated with GnRH did ovulate and they were artificially stripped out. The number of stripped eggs was 40.7 +- 18.4 10~3 eggs per I female. Relative working fecundity in this group was 128.6 +- 53.7 10~3 eggs.kg~(-1). The second experiment was performed with artificial propagation of females placed in cages without males, after hormonally induced ovulation by means of a single 100 #mu#g.kg~(-1) dose of GnRH analogue. Twenty five females (80%) out of 35 fish injected were artificially stripped out. Relative working fecundity was 102.1 +- 49.5 10~3 eggs.kg~(-1). Relative weight of stripped eggs was 18.7 +- 3.7%. The third experiment was performed with two groups of 7 females each, treated with 100 #mu#g.kg~(-1) GnRHa and placed in cages (without replicates) in order to compare the effect of presence/absence of males on ovulation and performance of spawning. Among the females stocked with males at a 1: 1 ratio, 57% of females spawned successfully. In the absence of males, 100% females ovulated and spawned successfully. The relative working fecundity was 64.7 +- 14.5 and 52.2 +- 26.5 10~3 eggs.kg~(-1), respectively. No significant differences (P < 0.05) were found in fecundity indices between the groups of spawned females. The estimated fertilisation rate ranged within 60-95%. No desticking of eggs was performed, eggs were hatched in aerated cages placed in a flow-through trough. The management of methods of controlled reproduction in perch will contribute to the production of stockfish for open waters, as well as for ponds with market production of this species.