Effects of hCG and salmon gonadoliberine analogue on spermiation in the Eurasian perch (Perca fluviatilis)

Abstract

This study analysed (i) the effect of human chorionic gonadotropin (hCG) and salmon gonadoliberine analogue (sGnRHa) on the effectiveness of induction of spermiation and (ii) the effect of latency time following the application of those spawning agents on the quantity and quality of the sperm of Eurasian perch, Perca fluviatilis, obtained during out-of-season spawning. For this study, pond-reared fish were used which had been acclimated to the controlled conditions. Three groups were distinguished which were treated with either saline (0.9% NaCl; control group), hCG (500 IU kg−1) or sGnRHa (100 μg kg−1). The fish were kept in a recirculating system at 12 °C throughout the study, during which sperm was collected every two days between the 2nd and 10th day following hormonal treatment. During the study, quantitative (e.g. sperm volume, total sperm production) and qualitative (measured with a computer-assisted sperm analysis system – i.e. CASA) parameters were monitored. The results of the study indicate that the hormonal treatment had a highly beneficial effect on the spermiation rate (100% in experimental groups from day 6 following injection) as well as quantity, which increased 50% in experimental groups (over 2200 × 109 of spermatozoa per kg of body weight) by day 4 following injection. For the sperm quality, both spawning agents tested had a rather positive effect, although sperm motility rate (MOT) was seen to be significantly reduced on day 10 following the application of hCG (MOT = 72.8% ± 8.1), which was not observed after the application of sGnRHa (minimum mean MOT 81.7% ± 6.1). The results clearly indicate that hormonal treatment had a positive effect on spermiation in Eurasian perch, most apparent from day 6 following injection, regardless of the hormonal agent used. Though application of sGnRHa allowed a high volume of high quality sperm to be stripped for two days longer (up to day 10 post-injection) compared to the application of hCG.