The nutrient composition of yellow mealworm (YM) Tenebrio molitor varies based on the stages of the life cycle, the rearing conditions, and the feeding substrate. This study monitored the growth of yellow mealworm larvae at 8, 10, and 12 weeks of age, separating samples into large-sized and small-sized insects. During the experiment, we measured the nutrient composition: dry matter (DM), crude protein (CP), crude fat (CF), crude fibre, chitin, crude ash, and nitrogen free extract (NFE) of YM at different age groups and sizes. We measured the nutrient composition of the pre-moult, moult, cuticle, and pupae as well. The results show that there is no significant difference between the compositions of the different age groups, but larger-sized individuals had a higher DM and crude fibre and lower chitin and NFE than the smaller sizes. The pre-moult and moult stages showed no significant difference in nutrient composition. Although the cuticle had a high DM (97.5%), that did not cause any significant difference between the DM of the moult and pre-moult, because it is only a negligible part of the total wet weight. With the increased DM, the crude protein content and the chitin content, fibre, ash content, and NFE increased, while the fat content decreased. The DM, CF, and chitin contents of pupae are significantly lower than those of the pre-moult and moult stages. Our results show that it is the size and not the age that has a positive effect on the nutrient composition of YM.

Sustainability is becoming increasingly important in the world we live in, because of the rapid global population growth and climate change (drought, extreme temperature fluctuations). People in developing countries need more sustainable protein sources instead of the traditional, less sustainable meat, fish, egg, and dairy products. Alternative sources (plant-based, such as grains (wheat, rice sorghum), seeds (chia, hemp), nuts (almond, walnut), pulses (beans, lentil, pea, lupins), and leaves (duckweed), as well as mycoproteins, microalgae, and insects) can compensate for the increased demand for animal protein. In this context, our attention has been specifically focused on duckweed—which is the third most important aquatic plant after the microalgae Chlorella and Spirulina—to explore its potential for use in a variety of areas, particularly in the food industry. Duckweed has special properties: It is one of the fastest-growing plants in the world (in freshwater), multiplying its mass in two days, so it can cover a water surface quickly even in filtered sunlight (doubling its biomass in 96 hours). During this time, it converts a lot of carbon dioxide into oxygen. It is sustainable, environmentally friendly (without any pesticides), and fast growing; can be grown in indoor vertical farms and aquaculture, so it does not require land; is easy to harvest; and has a good specific protein yield. Duckweed belongs to the family Araceae, subfamily Lemnoideae, and has five genera (Lemna, Spirodela, Wolffia, Wolffiella, Landolita) containing a total of approximately 36–38 recognised species. Duckweed is gaining attention in nutrition and food sciences due to its potential as a sustainable source of protein, vitamins, minerals, and other bioactive compounds. However, there are several gaps in research specifically focused on nutrition and the bioaccessibility of its components. While some studies have analysed the variability in the nutritional composition of different duckweed species, there is a need for comprehensive research on the variability in nutrient contents across species, growth conditions, harvesting times, and geographic locations. There has been limited research on the digestibility, bioaccessibility (the proportion of nutrients that are released from the food matrix during digestion), and bioavailability (the proportion that is absorbed and utilised by the body) of nutrients in duckweed. Furthermore, more studies are needed to understand how food processing (milling, fermentation, cooking, etc.), preparation methods, and digestive physiology affect the nutritional value and bioavailability of the essential bioactive components in duckweed and in food matrices supplemented with duckweed. This could help to optimise the use of duckweed in human diets (e.g., hamburgers or pastas supplemented with duckweed) or animal feed. More research is needed on how to effectively incorporate duckweed into diverse cuisines and dietary patterns. Studies focusing on recipe development, consumer acceptance, palatability, and odour are critical. Addressing these gaps could provide valuable insights into the nutritional potential of duckweed and support its promotion as a sustainable food source, thereby contributing to food security and improved nutrition. In summary, this article covers the general knowledge of duckweed, its important nutritional values, factors that may affect their biological value, and risk factors for the human diet, while looking for technological solutions (covering traditional and novel technologies) that can be used to increase the release of the useful, health-promoting components of duckweed and, thus, their bioavailability. This article, identifying gaps in recent research, could serve as a helpful basis for related research in the future. Duckweed species with good properties could be selected by these research studies and then included in the human diet after they have been tested for food safety.

The harvesting of plant biomass is usually implemented as an effective tool for plant management and removing the nutrients absorbed in plant tissues. Here, the influence of harvesting different biomasses (50%, 33%, 25%, and 0% (no harvest)) of watercress (Nasturtium officinale) was investigated in integrated recirculating aquaponic systems (IRASs) for rearing common carp (Cyprinus carpio). Twelve independent IRASs were designed (4 × 3); each system consisted of a fish rearing tank, a waste collection tank, and a hydroponic bed. Water quality parameters and the growth of both fish and plants were measured in all the systems, and then the nutrient removal capacities of the hydroponic beds were calculated. The results revealed that increasing the biweekly harvested biomass of the plants decreased the growth of the watercress, while it did not affect the growth of the common carp. Increasing the harvested biomass of the plants also decreased the nitrate nitrogen and orthophosphate removal efficiencies of the aquaponic systems, while it did not affect the ammonia and nitrite nitrogen removal efficiencies. Therefore, a biweekly harvesting of less than 25% of the biomass of the growing watercress is recommended for efficient nutrient removal and the sustainable growth of both watercress and the common carp in aquaponic systems.

This study aimed to estimate the efficacy of two pike-perch juvenile production technologies: exclusive Recirculating Aquaculture System (RAS) culture (the RAS group) and pond larviculture with a transfer to the RAS at the 42nd day post-hatch (DPH). Both direct weaning on dry feed (the Pond-D group) and 10-day gradual weaning using bloodworms (the Pond-B group) after transfer to the RAS were evaluated in pond-nursed fry. Their survival and morphometric indices were monitored after the RAS habituation period (first 10 days), after the 18-day post-habituation period and after an additional 30 days of on-grow. Our results indicate a negative allometric growth of the pond-nursed fish during the nursing period, which was slower (p < 0.0001) in comparison to the RAS-nursed fry (16.3 ± 0.4 vs. 17.8 ± 0.7%/day). After transfer, these fish grew faster than the RAS-nursed fry (7.7 ± 0.1, 4.9 ± 0.5 and 6.1 ± 0.6 during habituation, 8.5 ± 0.6, 9.3 ± 0.5 and 6.7 ± 0.1%/day during post-habituation period, in the Pond-B, Pond-D and RAS groups, respectively). However, four weeks afterwards, the RAS-nursed fry were again superior in terms of growth (4.0 ± 0.1, 3.6 ± 0.2 and 4.6 ± 0.2%/day, for the Pond-B, Pond-D and RAS groups, respectively), and this was accompanied by a significantly lower feed conversion ratio in this group. Although the survival of the RAS-nursed fry during the nursing period was lower in comparison to the pond-reared fry (11.3 vs. 67.3%), the RAS seems to provide a long-term growth advantage.

Hungary is one of the largest common carp-production countries in Europe and now, there is a large number of local breeds and strains in the country. For proper maintenance of the animal genetic resources, information on their genetic diversity and structure is essential. At present, few data are available on the genetic purity and variability of the Hungarian common carp. In this study, we genetically analyzed 13 strains in Hungary and, in addition, the Amur wild carp, using 12 microsatellite markers. A total of 117 unique alleles were detected in 630 individuals. Low levels of genetic differentiation (F_st and Cavalli–Sforza and Edwards distance) were estimated among strains. The AMOVA showed the low but significant level of genetic differentiation among strains (3.79%). Bayesian clustering analysis using STRUCTURE classified the strains into 14 different clusters. The assignment test showed that 93.64% of the individuals could be assigned correctly into their original strain. Overall, our findings can be contributed to complementing scientific knowledge for conservation and management of threatened strains of common carp.

This study examines the sustainability and economic viability of intensive common carp (Cyprinus carpio) production in recirculating aquaculture systems (RASs) in Hungary. Using a deterministic model, the research identifies production costs, profitability, and the critical factors influencing economic efficiency. It also evaluates the impact of key variables, such as the feed purchase price, the market-sized common carp sales price, the specific gross yield, the electricity price, and electricity consumption, on economic performance by using a sensitivity analysis. Primary data were collected from an experimental trial conducted under controlled conditions in Hungary, dividing the production process into three phases: pre-rearing, post-rearing, and market-sized fish production. The unit production cost of market-sized common carp in 2024 was 5.47 EUR/kg, with energy (47.01%) and feed (24.18%) as the main cost drivers. While the sales price covered variable costs, it failed to offset fixed costs, resulting in a loss of 0.41 EUR/kg. The results reveal that while RAS technology offers high productivity and efficient resource utilization, its economic viability is challenged by high initial investment and operational costs. Nevertheless, the study identifies optimization opportunities in feed management, water usage, and electricity efficiency to enhance sustainability and profitability. These findings emphasize the importance of integrating economic, environmental, and technological considerations to advance intensive aquaculture practices.