The effect of hormonal preparation (gonadotropins vs. gonadoliberins) on pre-seasonally obtained eggs and larvae quality in pikeperch (Sander lucioperca L.)

Abstract

Although several papers were dealing with intensively reared broodstocks, most of the published artificial reproduction protocols were applied in wild pikeperch breeders. Therefore, we aimed to evaluate the effects of ovulation induction agents, namely human chorionic gonadotropin (hCG) and salmon gonadotropin-releasing hormone analogue (sGnRHa) on the reproductive performance in pre-seasonal artificial propagation of cultured pikeperch. Breeders were harvested from an outdoor in-pond circulation system in mid-September and transferred to indoor facility in late January, conditioned and injected with either 50 μg kg −1 of sGnRHa or 500 IU kg −1 of hCG, with six females in each hormonal group. Stripped eggs from each female were sampled for chemical composition analysis, fertilised with the milt of two males, incubated and obtained larvae were further reared. No significant differences were noticed between the treatments in any of the analysed parameters of embryo survival nor larviculture performance. Rather high differences in intragroup variation were seen between the treatments, expressed in several-fold higher coefficients of variation in embryo survival in experimental and commercial conditions in the hCG group. Eggs obtained from females treated with hCG had a significantly higher lipid content (31.1% ± 2.0%) compared to sGnRHa-treated females (27.4% ± 1.8%). Fatty acid profiles of the eggs revealed differences in total n − 6 and linoleic acid 18:2n − 6 content while n − 3/n − 6 was significantly lower in the hCG group. Gonadoliberins reduced the variability in the spawning outcome. It appears that hormones can modify the eggs' fat content during the pre-season artificial reproduction.

The Effect of Different Surface‐Cleaning Devices on the Success of Swim Bladder Inflation in Zander Larvae

“…Finally, rather high SBI rates in Zander that were obtained by using a sprayer were reported earlier in a larviculture study that evaluated different stocking densities (Szkudlarek and Zakęś 2007). The results of the present study fall within the wide range of recently published data on survival and SBI rate in Zander larvae in our (Ljubobratović et al 2019a, 2019b) and others’ experimental facilities (Colchen et al 2020). The reason for such high variation might be caused by different nutritional, environmental, and/or genetic factors (El Kertaoui et al 2019; Colchen et al 2020).…”

“…Each tank was stocked with 7,000 volumetrically counted, newly hatched larvae (mean initial length 4.5 ± 0.1 mm) for a 16‐d rearing period. The larval‐nursing protocol was performed according to the procedure that was used for earlier studies that were performed at the facility (Ljubobratović et al 2019a, 2019b). The larvae were fed with newly hatched Artemia nauplii every 3–4 h at the rate of 100–300 nauplii·larvae −1 ·d −1 , depending on the size of the larvae.…”