Introduction
Pikeperch (Sander lucioperca) is a fast-growing freshwater predator with high-quality flesh and strong market demand (Policar et al., 2019). Its intensive larviculture nevertheless remains the main production bottleneck. Survival during the larval stages commonly falls below 20% under standard protocols, a loss attributed largely to inadequate rearing protocols and poor early nutrition (Yanes-Roca et al., 2020b). These problems are compounded by the biology of percid larvae, which hatch at a small size with a limited mouth gape that constrains the ingestion of live prey such as Artemia (Kestemont et al., 1996). The type and duration of the first live feed therefore strongly influence survival, growth and digestive-system development (Imentai et al., 2020, 2022), and enriching rotifers and Artemia has been shown to improve early growth and survival in pikeperch (Yanes-Roca et al., 2020a). Biofloc technology offers a complementary and sustainable route to improving larval feeding. It generates microbial aggregates that are rich in protein and fatty acids and contain bioactive, energy-rich compounds such as polyhydroxybutyrate, giving them a high nutritional value for cultured species (De Schryver et al., 2008; Khanjani et al., 2022). We therefore evaluated biofloc-enriched rotifers and Artemia against a standard live-feed control, hypothesising that it improves feed intake, growth and survival and fosters a more diverse and stable larval gut microbiota.
Materials and Methods
Pikeperch larvae were reared in a recirculating aquaculture system in four replicate tanks per treatment (525 larvae per 3.5 L tank; 150 larvae L-1). Two treatments were compared. A control-fed standard live feed (rotifers and Artemia) and a Biofloc-enriched treatment fed the same live feed enriched in a separate system. The RAS system has temperature (16.6 ± 0.2 °C), dissolved oxygen (9.2 ± 0.1 mg L-1) and salinity (5.5 ± 0.4 ppt). Larvae were sampled for total length (TL), eye diameter (ED), gut-fill score (0–4, expressed as % of maximum) and swim-bladder inflation. Fatty acid composition, oxidative-stress biomarkers and gut-microbiota (16S rRNA) analyses are ongoing. Data are presented as mean ± SD. Significant difference is presented as p < 0.05.
Results and Discussion
At 20 DPH, the two treatments differed markedly in larval size. Mean total length was greater in the biofloc-enriched group (11.28 ± 0.56 mm) than in the control (10.79 ± 0.40 mm; p = 0.003). Eye diameter followed the same trend, being larger in the biofloc-enriched larvae (0.82 ± 0.06 mm) than in controls (0.78 ± 0.05 mm; p = 0.010). This difference was not evident during early development however the treatments remained comparable in size until approximately 10 DPH, then diverged around 14 DPH, and the gap increased progressively thereafter until termination. In contrast, the remaining endpoints did not differ between treatments. Gut fill remained high in both groups, with no appreciable difference between the biofloc-enriched (91.3 ± 14.7%) and control larvae (88.8 ± 19.0%), indicating active feeding in both treatments. Swim-bladder inflation was equivalent, reaching 80% in each group. Survival was higher in the biofloc-enriched treatment (43.6 ± 13.1%) than in the control (29.9 ± 4.4%).
Biofloc concentrates microbial protein, lipids and bioactive compounds that enrich the nutritional profile of live prey, and in this trial those nutrients reached the larvae one trophic step up through gut-loaded rotifers and Artemia rather than by direct grazing (De Schryver et al., 2008; Khanjani et al., 2022). The larval performance improved by 20 DPH without any compromise to feed intake or swim-bladder inflation. Total length and eye diameter were both significantly higher under enrichment. The control TL of 10.79 mm matches the value reported for untreated pikeperch at 21 DPH by Yanes-Roca et al. (2020b). Gut fill exceeded 88% in both groups. Swim-bladder inflation reached 80% in each treatment, indicating that enrichment did not interfere with the surface air-gulping window that governs inflation success in pikeperch (Fazekas et al., 2021). The growth advantage was absent at first feeding and emerged only from around 14 DPH, in line with a cumulative effect of first-feed quality on pikeperch performance and digestive development (Imentai et al., 2020). Comparable benefits of biofloc as a live-feed supplement have been documented in other freshwater species like in Betta splendens, partial replacement of Artemia with ex-situ biofloc maintained growth and survival relative to Artemia alone (Stringhetta et al., 2024). These preliminary results identify biofloc-enriched live feed as a practical and sustainable route to improving early growth in pikeperch and reducing reliance on conventional enrichment products.
Acknowledgment
This research was funded by the Grant Agency of the University of South Bohemia (GAJU 111/2026/T).
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