Introduction
The development of industrial pike- perch rearing technology has been limited by the lack of larval artificial diets that can fully meet the nutritional requirements of fish in the early stages of ontogeny. Previous attempts to grow pike-perch on a mono-diet of artificial feed from the start of exogenous feeding have failed. Total larval mortality occurred during the first 2-3 weeks of feeding. To solve this problem, we studied the proximate composition of the natural diet of pike-perch larvae, which consisted mainly of zooplanktonic organisms. We assumed that it should reflect the nutritional requirements of early larvae (Lyutikov et al., 2025).
The obtained results of the proximate compositional analysis of zooplankton allowed us to select the most suitable feed component for the development of artificial starter feed for pike- perch larvae, which was a microbiosynthetic protein - Bacterial Single-Cell Protein (BSCP) based on methane-oxidising bacteria Methylococcus capsulatus . BSCP contains similar protein and nucleic acid levels, amino acid composition and molecular weight distribution of peptides as zooplanktonic organisms. The aim of this study was to evaluate the efficacy of BSCP in both intact and hydrolysed forms as part of the initial diet of pike-perch larvae.
Materials and Methods
The studies were conducted at the “Forvat” LLC fish farm (60°36’14.91"N 30°23’53.54"E). The larvae were obtained from natural spawning of 4-year-old pike-perch, reared from yearlings under industrial conditions in cages on artificial diets only. After becoming horizontal, the larvae were placed in production square tanks (in 3 replicates) with an area of 4 m2 and a water level of 0.25 m. The stocking density of the larvae was 25 individuals L-1 . The larvae were fed hourly from 8 a.m. to 10 p.m. The photoperiod, lighting and water temperature were natural throughout the experiment; the water temperature increased steadily from 16 to 21°C during the experiment. BSCP ("GIPROBIOSINTEZ" LLC, Russia) and its hydrolysates were added to the diet at the stage of mixing of the diet components , which was then extruded. The extrudate was dried, crushed and dispersed into 0.1 to 0.3 mm fractions. A mixture of fish oil and phospholi pids was added to the diet, dried and packed in vacuum bags, which were stored at -18 °C until use.
Results
After 23 days of rearing, the body weight , SGR and surviving of pike-perch larvae were highest in the group of fish fed diets containing BSCP L (low degree of hydrolysis). The number of non-feeding larvae in this group was less than 1% (Table). Using BSCP H in diets (high degree of hydrolysis) resulted in a decrease in body weight, growth rate, and surviving of pike-perch larvae (Table) . The proportion of non-feeding larvae in this group was 57%. The larvae fed with diets containing native BSCP showed intermediate values of estimated characteristics (Table).
It is clear that BSCP L has a positive effect on the growth, survival and feeding of pike- perch larvae, due to an increase in the amount of low-molecular-weight peptides (compared to intact BSCP) available for absorption by larvae whose digestive system is immature. On the other hand, BSCP H leads to a sharp increase in the proportion of peptides and amino acids, which has a negative effect on the fish rearing.
Conclusion
Obviously, the main direction of industrial farming technology of larvae and juvenile pike-perch will be the development of complete artificial diets capable of satisfying the nutritional needs of fish . For this, the BSCP and its hydrolysates are suitable sources with the necessary amount of peptides and free amino acids, which is especially important during the period of rapid growth of pike-perch.
Lyutikov A, Korolev A, Trifonov A, Zubareva A, Nedoluzhko A. The Diversity and Biochemical Composition of Zooplankton as a Potential Indicator of Dietary Requirements for Pikeperch Larvae ( Sander lucioperca). Hydrobiology. 2025; 4(2):13. https://doi.org/10.3390/hydrobiology4020013