Recirculating aquaculture technology, which includes aquaponics, has been under development for the past 40 years from a combination of technologies derived from the wastewater treatment and aquaculture sectors. Until recently, recirculating aquaculture systems (RAS) farms have been relatively small compared with other types of modern aquaculture production. The last two decades have seen a significant increase in the development of this technology, with increased market acceptance and scale. This chapter provides a brief overview of the history, water quality control processes, new developments and ongoing challenges of RAS.

Agrivoltaics and aquavoltaics combine renewable energy production with agriculture and aquaculture. Agrivoltaics involves placing solar panels on farmland, while aquavoltaics integrates photovoltaic systems with water bodies and aquaculture. This paper examines the benefits and challenges of agrivoltaics and aquavoltaics, focusing on their potential for Croatian agriculture and freshwater aquaculture. Benefits include dual land use, which allows farmers to produce clean energy while maintaining agricultural practices. They diversify renewable energy sources and reduce dependence on fossil fuels and greenhouse gas emissions. Solar panels in agrivoltaics provide shade, protect crops, reduce water needs, and increase yields. Challenges include high initial costs and limited accessibility, especially for small farmers. Integration with existing systems requires careful planning, considering irrigation, soil moisture, and crop or fish production. Maintenance and cleaning present additional challenges due to dust, debris, and algae. Policy and regulatory frameworks must support implementation, including incentives, grid integration, land use regulations, and conservation. The location, resources, and crops grown in Croatia present an opportunity for agrivoltaics and aquavoltaics, considering cultivation methods, species, and regulatory requirements.

A ten-week feeding trial was carried out to investigate the effects of replacing fishmeal (FM) with soybean meal (SBM) and brewer’s yeast (BY) on growth performance, blood parameters, oxidative stress and micromorphology of liver and intestines in brown bullhead (Ameiurus nebulosus L.). Fish were fed nine feeds in which FM was replaced with 25%, 50%, 75% and 100% SBM (K1, K2, K3 and K4) and 17% + 8%, 42% + 8%, 67% + 8% and 92% + 8% of SBM/BY combination (K5, K6, K7, K8). Growth indices showed greater outcomes for the K2 group in comparison to all other groups. A decrease in plasma cholesterol and triglycerides concentrations was found after FM replacement. Activity of SOD was higher in groups K4, K7 and K8. The early inflammatory indications with abnormal vacuolization of lamina propria and basal epithelium were present in diets K4 and K8. Hepatocytes were irregular in shape with signs of inflammatory reaction in diet K8. A decreased perimeter of hepatocyte nuclei was detected in all experimental diets when compared with the control. This study demonstrates that the optimal replacement of FM with SBM/BY in brown bullhead diets contains up to 50% of FM replaced with SBM in order to obtain advantageous growth performance and adequate health condition.

We have limited knowledge of determinants of consumer preferences for wild-caught versus farmed-raised fish, so this work aims to investigate the impact of sociodemographics, habits and frequency of fresh fish consumption, such as involvement in cooking, on the preferences for wild versus farmed fish. A survey was done on a sample of 1151 fish consumers in Croatia. Results showed that female, older consumers, consumers with higher income and those living in coastal parts of Croatia give higher preferences for wild fish and they detect differences between the taste of wild and farmed fish. Consumers with higher levels of habits of fresh fish consumption, who eat fresh fish often and are more involved in cooking, prefer wild-caught fish. These findings provide valuable information for the aquaculture sector, especially for planning marketing strategies for the promotion of farmed fish.

Due to the cyclic or systemic nature of both aquaponics and organic production, organic certification appears to be a natural step for a researcher, system designer or commercial-oriented aquaponics producer to engage in. However, the underlying principles and justifications of aquaponics and organic production differ considerably between respectively a technological- and a soil-based understanding of nutrient cycles and long-term sustainability in food production. These principles are confirmed in both the organic regulation regime of the EU and USA, and presently leave the question ambiguously open as to whether aquaponics as a food production system can be recognized and certified as organic. Despite an openness in the organic regulation for new knowledge, adaptations and innovations, the organic sector itself has shown a reluctance to recognize more knowledge-based intensive speciality crops and technologies. This is particularly difficult with respect to small organic sub-sectors such as horticulture and aquaculture production. Both are very specific subsystems of the agricultural sector, where aquaponics potentially would belong at the intersection between organic greenhouse horticulture and organic aquaculture. Organically certified aquaponics would therefore need to establish a niche within the organic sector. So in order to move forward, there is a great need for a more serious but open-minded exchange and discussion among the aquaponics and organic sub-sectors themselves to explore the potential but also limitations of their respective production models. However, between the two food production systems, there should be room for debate with a view to finding new and feasible roles for aquaponics in the organic community.