The Effect of Brachionus calyciflorus (Rotifera) on Larviculture and Fatty Acid Composition of Pikeperch (Sander lucioperca (L.)) Cultured under Pseudo-Green Water Conditions

Abstract

A new cultivation system with the chlorophyte Monoraphidium contortum combined with a self-sustaining culture of the freshwater rotifer Brachionus calyciflorus was applied for Sander lucioperca (L.) larviculture. Survival, morphometrics, as well as fatty acid composition of pikeperch larvae were analyzed after a ten-day feeding period. By using the pseudo-green water technique with improved aeration and water movement at the surface, survival rates reached up to 94%, with a total larval length of 8.1 ± 0.3 mm and a specific length growth rate of up to 4.1% day−1 for S. lucioperca. The biochemical composition of B. calyciflorus and especially its contents in C18 PUFAs and suitable n-3/n-6 ratios met the nutritional requirements of pikeperch larvae. The high abundance of highly unsaturated fatty acids (HUFAs) in the diet appeared to be less important in the first feeding due to a possible retention of essential fatty acids, which originate from the yolk sac reserves, at adequate levels. Exponential growth of microalgae and zooplankton under the applied conditions was most effective when stocking M. contortum five days and B. calyciflorus three days before adding the fish larvae. Appropriate timing and sufficient live feed density allowed a successful integration of B. calyciflorus into pikeperch larviculture. We hypothesize that feeding pikeperch larvae with a self-sustaining Brachionus-culture under pseudo-green water conditions with minor disruptions during larviculture will improve survival and growth. This system is a first step towards pikeperch larviculture inside recirculated aquaculture systems (RAS) under continuous feed supply with live feed within the same aquaculture unit.

Pikeperch larviculture (Sander lucioperca [L., 1758]) with Brachionus plicatilis (Mueller, 1786) (Rotifera) and Apocyclops panamensis (Marsh, 1913) (Copepoda)

“…In E2, the decrease was 85.4% for B280 + A120, 60.0% for B340 + A60, 60.3% for B400, 57.7% for B420 + A180, 62.5% for B510 + A90, and 68.1% for B600. However, our total FA data in both experiments were higher at dph 11 compared with the concentrations found at dph 6 in Bischoff et al (2018), when the pikeperch larvae had consumed all the yolk sac reserves and started starving. Consequently, the larvae must have fed on B .…”

“…The larvae were smaller (4.06 mm) at 3 dph in E2 than at 1 dph in E1. Consequently, the total length at dph 11 was also lower than in E1 and, in both experiments, lower compared with earlier studies (Bischoff et al, 2022; Imentai et al 2019a; Imentai et al, 2020; Yanes‐Roca et al, 2018, 2020). This is a result of the initial status of the larvae, which was not identical, showing the importance of the different larval quality at hatch (Policar et al, 2019).…”

“…The total body length as well as yolk sac and oil droplet sizes were measured under a stereo light microscope (SZX10 Olympus, Hamburg, Germany) connected to a UC30 digital camera (Olympus, Hamburg, Germany) and the software package cellSens Dimension 1.6 (Olympus Soft Imaging Solutions, Hamburg, Germany). Yolk sac volume and oil droplet volume were calculated according to Bischoff et al (2018). Finally, we calculated the specific growth rate (SGR) [%/day] as follows: where L t and L o represent the average length of the larvae at time t and time t = 0.…”

“…Under consideration of recent improvements in pikeperch larviculture as done in Szczepkowski et al (2011), Ljubobratović et al (2015), Yanes‐Roca et al (2018), Bischoff et al (2022) or Imentai et al (2022), successful rearing practices involve live feed that covers the nutritional requirements. The most widespread practice so far is the use of Artemia sp.…”

“…The most widespread practice so far is the use of Artemia sp. as the first exogenous feed (summarized in Policar et al, 2019; Steenfeldt, 2015), but its exclusive use is still debated (Bischoff et al, 2018). Alternative diets such as the marine rotifer Brachionus plicatilis (Müller, 1786) are commonly used as the first live feed source for species like gilthead seabream, Sparus aurata (Pantazis et al, 2014; Rodríguez et al, 1997) or greater amberjack, Seriola dumerili (Hamasaki et al, 2009), mainly because of their small size, high culture densities, and fast reproduction (Hagiwara & Marcial, 2019; Lubzens et al, 1989).…”