Aquaculture as a circular bio-economy model with Galicia as a study case: How to transform waste into revalorized by-products

Circadian rhythm in turbot (Scophthalmus maximus): daily variation of blood metabolites in recirculating aquaculture systems

INTRODUCTION

Animal welfare in aquaculture is becoming increasingly important, and detailed knowledge of the species concerned is essential for further optimization on farms. Every organism is controlled by an internal clock, the circadian rhythm, which is crucial for metabolic processes and is partially influenced by abiotic factors, making it important for aquaculture practices.

OBJECTIVE

In order to determine the circadian rhythm of adult turbot (Scophthalmus maximus), blood samples were collected over a 24-h period and plasma metabolite profiles were analyzed by 1H-NMR spectroscopy.

METHODS

The fish were habituated to feeding times at 9 am and 3 pm and with the NMR spectroscopy 46 metabolites could be identified, eight of which appeared to shift throughout the day.

RESULTS

We noted exceptionally high values around 3 pm for the amino acids isoleucine, leucine, valine, phenylalanine, lysine, and the stress indicator lactate. These metabolic peaks were interpreted as either habituation to the usual feeding time or as natural peak levels in turbot in a 24-h circle because other indicators for stress (glucose, cortisol and lysozymes) showed a stable baseline, indicating that the animals had no or very little stress during the experimental period.

CONCLUSION

This study provides initial insights into the diurnal variation of metabolites in adult turbot; however, further studies are needed to confirm present findings of possible fluctuations in amino acids and sugars. Implementing optimized feeding times (with high levels of sugars and low levels of stress metabolites) could lead to less stress, fewer disease outbreaks and overall improved fish welfare in aquaculture facilities.

Effects of eggshell and seashell powder as natural dietary calcium supplements on growth, molting frequency, and carapace calcium composition of juvenile red claw crayfish, Cherax quadricarinatus

The growth performance of red claw crayfish, Cherax quadricarinatus, fed diets with different sources and concentrations of natural calcium was evaluated. Formulated diets containing 30% protein and 8% lipid were prepared using supplementation of 0 (control), 3%, 6%, 9% eggshell, and 6% seashell. C. quadricarinatus juveniles with an average total weight of 0.21 ± 0.01 g and length of 25.0 ± 0.10 mm were obtained from ten ovigerous females bred in captivity. An aquarium with a size of 0.72 m² was divided into eight compartments with an area of 0.09 m² per compartment and was individually stocked with juvenile crayfish. A total of eight juvenile crayfish were used per dietary treatment. There were five dietary treatments in total and each of these treatments were replicated three times. The addition of eggshell and seashell powder exerted positive effects on the growth performance, molting frequency, and survival of the crayfish. Crayfish fed with a 6% eggshell-supplemented diet exhibited the best overall growth performance. The calcium percentage of the carapace increased with the increase in calcium content of the diets. Meanwhile, the performance of diets comprising eggshells and seashells was not significantly different (P > 0.05). Considering the low cost and abundance of eggshells, the addition of 6% of this product to the diet is recommended for the best growth of juvenile C. quadricarinatus.

Biometric and gonadosomatic indices and chemical constituents of edible tissues and exoskeletons of Callinectes amnicola and their potential for reuse in the circular economy paradigm

The study investigates some biological indices and chemical compositions of Callinectes amnicola and their potential for reuse in the context of the circular economy paradigm. The total of 322 mixed-sex C. amnicola collected over a period of six months was examined. The morphometric and meristic characteristics were estimated for biometric assessment. The gonads were obtained from the female crabs for gonadosomatic indices. The shell was obtained using the hand removal technique by detaching it from the crab body. The edible and shell portions were processed separately and subjected to chemical analysis. Our findings showed that females had the highest sex ratio across the six months. The slope values (b) for both sexes exhibited negative allometric growth across all months since the slope values obtained were less than 3 (b < 3). The values obtained for Fulton's condition factor (K) of crabs in all examined months were greater than 1. The edible portion had the highest moisture level at 62.57 ± 2.16% and varied significantly (P < 0.05). The high amount of total ash obtained in the shell sample showed that ash is the main mineral present in crab shells and showed a significant difference (P < 0.05). The shell sample had the highest concentrations of Na and CaCO₃. Based on the findings of this study, it was observed that the shell waste contains some essential and transitional minerals (Ca, CaCO₃, Na, and Mg) and can be utilized as catalysts in several local and industrial applications, such as pigments, adsorbents, therapeutics, livestock feeds, biomedical industries, liming, fertilization, and so on. Proper valorization of this shell waste should be encouraged rather than discarding it.

Circular Economy and Sustainable Recovery of Taiwanese Tilapia (Oreochromis mossambicus) Byproduct-The Large-Scale Production of Umami-Rich Seasoning Material Application

In this study, umami-rich seasoning powder was produced from the offcuts of Taiwanese tilapia (Oreochromis mossambicus) by cooking concentration and spray drying of granules while yielding an abundance of glutamic acid (0.23 mg/100 g), glycine (0.10 mg/100 g), aspartic acid (0.11 mg/100 g), lysine (0.10 mg/100 g), and 11 other aminic acids. It exhibited water content (3.81%), water activity (0.3), powder yields (68.83%), and a good water solubility index (99.89%), while the particle microstructure was a spherical powder. Additionally, it received the highest overall preference score (7.53) in the consumer-type sensory evaluation compared to commercially available seasonings. This study proves that offcuts may be part of the human diet after proper processing and can be widely used to flavor savory food. The producers involved could increase their economic returns while meeting the environmental challenges. The practical contribution could create incremental value for products to critical stakeholders at each point in the tilapia supply chain with an operational guide for transitioning from inefficient to innovative circular practices.

Marine Macroalgae in Rabbit Nutrition—A Valuable Feed in Sustainable Farming

Simple Summary

Commercial rabbit farming has faced critical challenges in the last few years, during which the ban on the prophylactic use of antibiotics in animal feed has added to the weakness of the production system and a decrease in consumption of rabbit meat. Considering the potential role of macroalgae as an alternative to the use of antibiotics in animal nutrition, this review paper aims to evaluate the use of macroalgae in rabbit farming. It specifically focuses on how macroalgae can be used sustainably to improve rabbit health as an economically viable alternative that could help guarantee the future of this high-value sector.

Abstract

The rabbit meat industry has faced critical challenges in the last few years, during which the ban on the prophylactic use of antibiotics in animal feed has added to the weakness of the production system and a decrease in consumption of rabbit meat. This review paper highlights the potential value of macroalgae in the rabbit farming sector as an alternative to the use of antibiotics to improve rabbit health. In line with sustainable agriculture programmes, the use of seaweed in rabbit nutrition may improve gut health according to the One Health approach, whereby consumers and the environment could receive tangible benefits. The inclusion of algae in animal feed has experimentally proven to help to reduce intestinal dysbiosis. However, further studies evaluating the prebiotic effects of algal components on gut health and also identifying the compounds directly responsible for the antimicrobial, antiviral, antioxidative and anti-inflammatory properties of algae are still needed. Furthermore, the inclusion of marine algae in rabbit food could potentially become a commercial marketing strategy that could attract new consumers who are concerned about environmental sustainability and who are looking for different, high-quality foods.

Adult European Seabass (Dicentrarchus labrax) Perform Well on Alternative Circular-Economy-Driven Feed Formulations

There is an increasing need in the aquaculture industry for more sustainable and functional feed concepts for marine finfish. This study provides results for the effect of alternative feed formulations on health status, welfare parameters, sensory analysis, and growth performance in European seabass (Dicentrarchus labrax) over an 83-day feeding trial. Fish were fed twice a day with five experimental diets. A control diet (control) and four different alternative feed concepts rich in processed animal proteins (PAP), other alternative ingredients (NOPAP), and a positive (NOPAP+) and negative (PAP−) formulation were tested. All alternative formulations contained hydrolysates from aquaculture by-products and macroalgae. The results indicate that the alternative feed concepts are more sustainable alternatives compared with the commercial diet. Equally interesting, the alternative formulations did not affect the sensory analysis of the fillet quality or the animal welfare. These are increasingly important factors in aquaculture products and, accordingly, also in the formulation of new feeds. Feed concepts that are not only more sustainable in their production, have shorter transportation distances, recycle the resources (usage of by-products), and have no adverse effect on growth or welfare parameters are highly needed. Therefore, the experimental diets tested in this study are a win-win concept for future seabass aquaculture production.

The Analysis of the Conceptual Framework of Green Port Implementation in Indonesia Using Circular Economy: The Case Study of Benoa Public and Fishing Terminals

Several public seaports and fishing terminals are located in the same port complex but have different fragmented operations such as waste management. It is possible to provide a new initiative to ensure sustainability for all entities in the surrounding port ecosystem through the application of Green Port using the circular economy approach and mixed linear programming model. Therefore, this study aims to explore the collaborative management of waste generated from different port activities such as the operators of the public seaport, fishing terminal, and a city authority in Bali–Indonesia using circular economy principles. It was discovered that the integration model has the potential to generate new energy by recycling waste from all related entities in the production of a few main fishing products such as tuna, sardine, and squid, as well as vessel traffic, facilities, and cargo flow interactions in addition to other port operations.

Advantage of Species Diversification to Facilitate Sustainable Development of Aquaculture Sector

Simple Summary

The aquaculture sector must be well-founded to undergo robust growth and sustainable development in the years ahead. Species diversity must reflect species compatibility and complementarity to manage the complexity in polyculture systems. There is a need for the implementation of innovative strategies that facilitate sustainable aquaculture development, enhance profitability, improve resilience, and support conservation and environmental protection. An aquaculture development scenario must look beyond the economic profitability and strategize aquatic food production systems to attain food and nutrition security and benefits for all stakeholders.

Abstract

Intensified agrochemical-based monoculture systems worldwide are under adoption to meet the challenge of human population growth and the ever-growing global demand for food. However, this path has been opposed and criticized because it involves overexploitation of land, monoculture of few species, excessive input of agrochemicals, and adverse impacts on human health and the environment. The wide diversity among polyculture systems practiced across the globe has created confusion over the priority of a single strategy towards sustainable aquaculture development and safer products. Herein, we highlight the significance of polyculture and integrated aquaculture practices in conveying the successful transition of the aquaculture industry towards sustainable development. So far, the established thought is that the precise selection of aquatic species and a focus on compatible and complementary species combinations are supposed to facilitate rapid progress in food production with more profitability and sustainability. Therefore, the advantages of species diversification are discussed from an ecological perspective to enforce aquaculture expansion. This account asserts that a diverse range of aquaculture practices can promote synergies among farmed species, enhance system resilience, enable conservation, decrease ecological footprints, and provide social benefits such as diversified income and local food security.