Time of response to hormonal treatment but not the type of a spawning agent affects the reproductive effectiveness in domesticated pikeperch, Sander lucioperca

Abstract

Improving reproductive protocols is one crucial step towards aquaculture expansion of pikeperch (Sander lucioperca), which is still characterised by variable and/or low spawning effectiveness. One of the main challenges is to synchronise ovulation at a precisely planned time with a consistently satisfactory reproductive outcome. To this end, the present study examined the effect of different spawning agents (human chorionic gonadotropin [hCG] and salmon gonadotropin-releasing hormone analogue [sGnRHa]) with different doses and application modes (including double injection). The study covered three consecutive spawning seasons, which corresponded to three distinct experiments, where domesticated pikeperch broodstock, commercially grown in a recirculating aquaculture system, was used. In the first year of the study, the effect of different doses of sGnRHa (10, 25 and 50 μg kg -1 ) and hCG (250, 500 and 1000 IU kg -1 ) on the reproductive performance of the domesticated broodstock was evaluated. The results were also compared with literature data for wild fish. During the second and third years, typical indicators of spawning performance (ovulation rate, latency time and egg quality) were followed when a double sGnRHa injection was compared to a single 50 µg kg -1 or 500 IU kg -1 injection of sGnRHa or hCG, respectively; the best results were 2 obtained in the first and second experiments. The results of the present study clearly indicate that various hormonal treatments effectively induced domesticated pikeperch ovulation, although highly variable egg quality was observed throughout the three spawning seasons (maximum hatching rates were 60.6 ± 11.5, 37.7 ± 28.9 and 49.1 ± 24.7% in the first, second and third years of the study, respectively). However, additional analysis of the data from the entire study revealed for the first time that a significant proportion of the lower-quality eggs came from fish that responded 'early' to hormonal treatment (<120 h after injection) regardless of the hormone used. This group represented approximately 40% of the population each year.Further, most of the fish that responded to hormone treatment early exhibited this trait during all three consecutive spawning seasons. This finding indicates that early hormone response is a potential selection trait. The present study showed that controlled domesticated pikeperch broodstock reproduction may involve application of either hCG or sGnRHa, with no clear difference in their effectiveness, although the recommended doses are 500 IU kg -1 and 50 µg kg -1 , respectively.

A novel approach for induced out-of-season spawning of Eurasian perch, Perca fluviatilis

“…Moreover, recent findings of Roche et al (2018) indicate that the application of dopamine antagonists did not have any effect in a closely related species of pikeperch (Sander lucioperca). This result confirms the earlier reports that the application of GnRHa alone is effective in Eurasian perch (Kouril et al, 1997) and pikeperch (Křišt'an et al, 2013;Żarski et al, 2019). However, to date, pure GnRHas were tested only when administered in a single injection in Eurasian perch (Żarski et al, 2015).…”

Domestication modulates the expression of genes involved in neurogenesis in high‐quality eggs of Sander lucioperca

“…Before the collection of samples, the fish were successfully reproduced three times, which made them fully “functional” spawners at the beginning of the experiment, that is, they were capable of successful reproduction every year. The fish were exposed to annual fluctuations of photothermal conditions as described by Fontaine et al (2015), with modifications as described by Żarski et al (2019) aimed at changing the wintering conditions (period with the lowest temperature, mimicking the winter period; fish were exposed to temperatures below 10°C for 4 months). The fish were daily fed a compound feed (50% protein, 11% fat, 10% moisture, 1.55% crude fiber, 1.35% phosphorus, 9.5% ash, and 17.9% nitrogen‐free extract; Le Gouessant, France) throughout the year at a rate of 0.2–1% of the biomass, depending on the temperature and appearance of satiation (Żarski et al, 2019).…”

“…This is the case, for instance, in pikeperch production, which relies mostly on the fish intensively cultured in RAS (Steenfeldt et al, 2015). Despite huge progress in intensification of its aquaculture technology over the last two decades, captive broodstock of pikeperch are still characterized by highly variable and/or lowered spawning performance, reflected mainly in poor egg quality (Schaefer, Overton, & Wuertz, 2016; Żarski et al, 2019). This limits the successful expansion of its commercial production, and is also associated with several concerns regarding the use of fish coming from such a production to support natural recruitment in open water bodies.…”

“…Intrinsic factors related to stress response (Douxfils et al, 2011) and nutritional status (Henrotte et al, 2010) have already been studied. However, in the case of pikeperch the most recent study has shown that there is huge intragroup variability in terms of the quality of eggs (Żarski et al, 2019), suggesting that there are certain individual predispositions for adaptation to the intensive culture conditions. From this perspective, understanding the mechanisms of successful adaptation of particular specimens to captivity is key to elaborate specific husbandry conditions, selective breeding programs, and selection criteria as well as to prepare the potential restocking program for a given population.…”

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

“…Individual organisms are used as the units of replication, yet the number of eggs per individual female is usually counted in the thousands leaving a large space for individual variability. In the case of young and reproductively unexperienced cultured pikeperch breeders, this problem was indeed described (Zakęś et al 2013;Ljubobratović et al 2017b;Żarski et al 2019). Therefore, in order to evaluate the reproductive performance of fish, it is of major importance to evaluate a wide spectrum of parameters.…”