Increasing demand for protein, especially animal-based proteins and the large amounts of protein feed inputs required for production, has largely driven the research on spirulina as an animal feed. This short communication summarizes the results from two larger research projects investigating spirulina as an animal feed. Overall, spirulina appears to be a prospective protein source in poultry and pork production, as well as aquaculture. However, spirulina as a feed can have implications for system productivity and end product quality, depending on animal production system. Neither swine productivity nor product quality was negatively affected with spirulina as a feed, which is likely due to the low amounts of protein required in swine finishing diets. Spirulina as a feed does negatively affect poultry and fish productivity as well as alter product quality, primarily raw meat color. Therefore, future research focused on sustainability analysis and product processing and acceptance should investigate the trade-offs of incorporating spirulina into poultry and fish diets.

Microalgae are increasingly being studied to replace fishmeal in aquafeed production. Low level Spirulina supplementation to various fish species has been widely investigated, demonstrating enhanced growth and better product quality. In order to evaluate the effects of a full fishmeal replacement with Spirulina (Arthrospira platensis) on growth and product quality in African catfish (Clarias gariepinus), two isoenergetic diets were formulated and fed for ten weeks to 120 fish with an average initial weight of 50 ± 3 g. Full supplementation of Spirulina resulted in reduced growth (p < 0.001) whereas feed conversion ratio was on par (p > 0.05). Furthermore, Spirulina-fed fish showed a more intense yellow coloration in skin, and raw and cooked fillet (p < 0.001). The analysis of fatty acids revealed higher proportions of C16:0 (p < 0.001) and C18:2n6 (p < 0.05) in fish fed the Spirulina-diet while C24:0 (p < 0.01) and C20:5n3 (p < 0.001) were found to be higher in the control group. Even though no statistically significant differences in the overall SFA, MUFA and PUFA were detected, a slight increase of the n6/n3 ratio was observed in the Spirulina-fed fish. Without further optimization of the feed ration, a complete fishmeal replacement with Spirulina can lead to economic losses. It remains to be studied whether the observed changes in product quality affect consumer acceptance.

An increasing number of fishmeal supplements are becoming the focus of aquaculture research, with a special emphasis on microalgae/cyanobacteria such as spirulina being considered as sustainable alternatives. New feed ingredients can have a far-reaching impact on the intestinal microbiome and therefore play an important role in the development and the health of fish. However, the influence of these alternatives on the microbiome is largely unknown. We undertook a 10 weeks feeding experiment on 120 African catfish with an initial body weight of 50.1 ± 2.95 g. To understand the effect of the spirulina supplementation, two isoenergetic experimental diets were formulated, containing either fishmeal or spirulina as a protein source. The 16S rRNA sequencing was used to analyze the intestinal bacteria microbiota. Results show that the observed richness indicated no significant statistical difference, but Chao1, ACE, Shannon, and Simpson indices indicate a possible increase in bacterial richness for the spirulina diet. The most abundant bacteria in both experimental groups were Fusobacteriia with the only taxa from the genus Cetobacterium. The bacterium from genus Romboutsia was more likely to be found in the microbiome of fish fed the fishmeal diet. In spirulina-fed fish, the genera Plesiomonas and Bacteroides were the most dominant microbes observed. Even though some genera were more abundant in the spirulina group, the overall microbial community structure was not affected by diets.

The European grayling is a salmonid species experiencing a sharp population decline, and conservation measures have been initiated through artificial propagation. As the species is not commonly cultivated in aquaculture, there is little information on their optimal reproduction conditions. Therefore, this study has combined a two‐pronged approach of examining the temperature of the natural spawning area during the spawning season, while also experimentally testing four different incubation temperatures under standardized aquaculture conditions. Nine egg clutches from pond‐reared females were fertilized with a sperm mix from 10 wild grayling. Eggs were divided into four treatment groups and incubated at 6, 8, 10 and 12°C. Hatched larvae were then collected and examined for body weight, yolk‐sac weight and length. Both the temperature of the natural habitat and the physiological parameters of the larvae indicate that 6 and 8°C are the optimal hatching temperatures for grayling reproduction. The hatching rate was highest at 8 and 6°C, at 80.35 ± 6.30% and 76.87 ± 8.01%, respectively, although it gradually decreased with increasing temperature. The impact of warmer water temperatures hindered survival rates, resulting in a significant decrease in hatching rates at 10°C (68.46 ± 13.85%) and 12°C (45.54 ± 27.14%).

Identifying alternative protein sources is essential for the sustainable development of aquaculture. Duckweed ( Lemnaceae ) represents a promising alternative feed ingredient for aquaculture, yet research into its applications as a dietary component is scarce. In this study, 240 mirror carp ( Cyprinus carpio var. specularis ) with an average weight of 73.4 g, were fed diets containing either 0% (DW0), 10% (DW10), 15% (DW15), or 20% (DW20) duckweed over a 14‐week period. Overall, duckweed inclusion in carp diets significantly influenced performance, fillet composition, colour, and sensory attributes. The fish accepted the diets across all treatments. Yet, growth performance was lower in groups receiving duckweed‐inclusive diets ( p < 0.05) while less differences were found between the inclusion rates. No alterations in meat quality were observed. Fillets from duckweed‐fed carp exhibited higher crude protein and ash content, but reduced fat and moisture levels. Skin and fillet colour shifted towards more green and yellow hues in accordance with the increasing dietary duckweed levels. Fatty acid analysis revealed increased proportions of omega‐3 and omega‐6 fatty acids in fish fillets with inclusion of duckweed, while levels of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) were comparable across feeding types. Sensory evaluations indicated stronger fishy notes in duckweed‐fed carp along with increased sweet odour and a trend towards a buttery taste. This study demonstrates the applicability of duckweed in common carp aquafeeds and its prospects for performance, composition, meat quality, pigmentation and sensory perception, thereby laying the groundwork for further investigations into consumer acceptance, digestibility, and its use in other fish species.