Introduction
Aquaculture is a key contributor to global food security . However, it faces numerous challenges that threaten its sustainability and its ability to meet the growing demand for animal protein (Ruben et al., 2025). The common carp is one of the most important freshwater species both in Europe and globally (FAO, 2024). Meeting the nutritional requirements of broodstock is a key factor in ensuring a healthy breeding population, successful reproduction, and ultimately, healthy offspring (Fernández-Palacios et al., 2011). Alternative feed additives, such as microalgae (Ansari et al., 2021), may improve gamete quality and contribute to more consistent reproductive outcomes. However, data on reproductive parameters of broodstock fed algae-supplemented diets remain limited . The aim of our study was to investigate the effects of 3% microalgae feed supplement on sperm quality and quantity in common carp.
Materials and methods
The experiments were conducted at a Hungarian fish farm (Szegedfish Ltd). To carry out the sperm quality and quantity analyses, two groups were established. The control group was fed a conventional diet, while the experimental broodstock received feed enriched with 3% microalgae (Chlorella spp., Scenedesmus spp., Coelastrella spp., Acutodesmus spp.) 1 month prior to the spawning season. Sampling was performed at three consecutive date ( N = 6 individuals per sampling and group) during the spawning season . Average body weight and length were recorded prior to stripping. During sampling, the following parameters were measured and calculated: total volume of milt (TVM), volume of milt per kg of body weight (VOM), spermatozoa per millilitre (SPZ), total sperm production (TSP), total sperm production per kilogram of body weight (TNS), osmolality and pH of the seminal plasma, as well as sperm motility and kinetic parameters (Cejko et al., 2011). S ugar and ion content: glucose (GLU), fructose (FRU), calcium (Ca), potassium (K), sodium (Na), and magnesium (Mg), and sperm fatty acid profile: total fatty acids (TFA), saturated fatty acids (SFA), unsaturated fatty acids (UFA), polyunsaturated fatty acids (PUFA), omega-3 fatty acids (OM3), and omega-6 fatty acids (OM6) were also assessed.
Results
Results were evaluated using two-way ANOVA. First, control and algae groups were compared at the same temperature. Second, values at different water temperatures (18,5 °C ; 20,5 °C ; 21,8 °C ) were compared within each group.
Traditional Sperm Parameters
At 20.5 °C, VOM and TNS were significantly higher in the algae group. OSM differed significantly across all sampling times. At 21.8 °C, pH was lower in the control group.
In the control group, SPZ increased with temperature, OSM peaked at 20.5 °C, and pH was highest at 18.5 °C. BCF was highest at 18.5 °C. In the algae group, SPZ, TSP, and TNS peaked at 20.5 °C, while pH was highest at 18.5 °C.
Sugar and Ion Content
At 20.5 °C, K and Mg were higher in the control group; at 21.8 °C, K was higher in the algae group. I n the control group Ca, K, Na, and Mg concentrations peaked at 20.5 °C. In the algae group, K concentration was significantly lower at 18.5 °C, while Na peaked at 20.5 °C. Mg concentration also differed significantly between 18.5 °C and 20.5 °C.
Fatty Acid Content
Fatty acid composition showed the largest differences. At 20.5 °C, TFA was higher in the control group; at 21.8 °C, it was higher in the algae group. Fatty acid composition showed the largest differences. At 20.5 °C, TFA was higher in the control group; at 21.8 °C, it was higher in the algae group. In the control group, all fatty acid parameters (except OM6) peaked at 20.5 °C. In the algae group, most values were significantly higher at 20.5 °C than at 18.5 °C. No significant differences were observed in this group between the lowest and highest temperature.
Discussion and conclusion
A 3% algae supplementation significantly improved sperm quality parameters compared to the control. Physiological values (sugar, ion, fatty acids) were influenced by both treatment and temperature, with highest values generally at 20.5 °C . The algae group showed increasing quantitative values with rising temperature.
Our findings suggest that pre-spawning algae supplementation improves sperm quality in common carp under optimal temperature. Future research should include closed-system, multi-group experiments, extending to fertilization trials.
Acknowledgements
The experiments were funded by the EKÖP-24-V/MATE-6 University Research Fellowship Programme and co-financed by the project 2022-1.2.6-TÉT-IPARI-TR-2022-00002 within the framework of the National Research, Development and Innovation Fund announced by the Ministry of Culture and Innovation . This work was financed by the Research Excellence Programme and the Flagship Research Groups Programme of the Hungarian University of Agriculture and Life Sciences.
References
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