Improve Aquaculture Production Research Articles

Do climate change, access to electricity and renewable energy consumption matter in aquaculture production in Africa?

AbstractThe contribution of aquaculture to economic development cannot be overemphasized. Several factors affect aquaculture production. However, few studies document the impact of climate change, electricity and other macroeconomic covariates on aquaculture production in Africa. The present research's objective is to examine the impact of rainfall, temperature, access to electricity, per capita national income, renewable energy consumption, employment in agriculture, and carbon emissions on aquaculture production in 32 African countries. We rely on panel data using rigorous estimation techniques involving the fixed effects and method of moment quantile regression approaches. Our fixed effects model result indicates that an increase in temperature reduces aquaculture production, while renewable energy consumption, net per capita income, employment in agriculture, and carbon emissions increase aquaculture production. Similarly, the 75th and 90th quantiles of the method of moment quantile regression results indicated that both rainfall and temperature decrease aquaculture production, while renewable energy consumption, employment in agriculture, and carbon emissions increase aquaculture production. The study provides useful insight into the climate, economic, and technological factors that might increase or decrease aquaculture production in Africa and similar contexts. Overall, our findings are important for improving aquaculture production in Africa, particularly with the current low production relative to the global north. The results have implications on the current and future climate action that calls for increased reliance on renewable energy and targeting improvements in agricultural employment, and net national income. Additional efforts are needed to achieve carbon neutrality while ensuring sustainable aquaculture production in Africa.

A traits-based approach to assess aquaculture's contributions to food, climate change, and biodiversity goals.

Aquaculture has the potential to support a sustainable and equitable food system in line with the United Nations Sustainable Development Goals (SDG) on food security, climate change, and biodiversity (FCB). Biological diversity amongst aquaculture organisms can drive diverse contributions to such goals. Existing studies have assessed the performance of a limited number of taxa in the general context of improving aquaculture production, but few explicitly consider the biological attributes of farmed aquatic taxa at the FCB nexus. Through a systematic literature review, we identify key traits associated with FCB and evaluate the potential of aquaculture to contribute to FCB goals using a fuzzy logic model. The majority of identified traits are associated with food security, and two-thirds of traits linked with food security are also associated with climate change or biodiversity, revealing potential co-benefits of optimizing a single trait. Correlations between FCB indices further suggest that challenges and opportunities in aquaculture are intertwined across FCB goals, but low mean FCB scores suggest that the focus of aquaculture research and development on food production is insufficient to address food security, much less climate or biodiversity issues. As expected, production-maximizing traits (absolute fecundity, the von Bertalanffy growth function coefficient K, macronutrient density, maximum size, and trophic level as a proxy for feed efficiency) highly influence a species' FCB potential, but so do species preferences for environmental conditions (tolerance to phosphates, nitrates, and pH levels, as well as latitudinal and geographic ranges). Many highly farmed species that are typically associated with food security, especially finfish, score poorly for food, climate, and biodiversity potential. Algae and mollusc species tend to perform well across FCB indices, revealing the importance of non-fish species in achieving FCB goals and potential synergies in integrated multi-trophic aquaculture systems. Overall, this study provides decision-makers with a biologically informed assessment of desirable aquaculture traits and species while illuminating possible strategies to increase support for FCB goals. Our findings can be used as a foundation for studying the socio-economic opportunities and barriers for aquaculture transitions to develop equitable pathways toward FCB-positive aquaculture across nuanced regional contexts.

Genome-Wide Identification of Trachinotus ovatus Antimicrobial Peptides and Their Immune Response against Two Pathogen Challenges.

Golden pompano, Trachinotus ovatus, as a highly nutritious commercially valuable marine fish, has become one of the preferred species for many fish farmers due to its rapid growth, wide adaptability, and ease of feeding and management. However, with the expansion of aquaculture scale, bacterial and parasitic diseases have also become major threats to the golden pompano industry. This study, based on comparative genomics, shows the possibility of preferential evolution of freshwater fish over marine fish by analyzing the phylogenetic relationships and divergence times of 14 marine fish and freshwater fish. Furthermore, we identified antimicrobial peptide genes from 14 species at the genomic level and found that the number of putative antimicrobial peptides may be related to species evolution. Subsequently, we classified the 341 identified AMPs from golden pompano into 38 categories based on the classification provided by the APD3. Among them, TCP represented the highest proportion, accounting for 23.2% of the total, followed by scolopendin, lectin, chemokine, BPTI, and histone-derived peptides. At the same time, the distribution of AMPs in chromosomes varied with type, and covariance analysis showed the frequency of its repeat events. Enrichment analysis and PPI indicated that AMP was mainly concentrated in pathways associated with disease immunity. In addition, our transcriptomic data measured the expression of putative AMPs of golden pompano in 12 normal tissues, as well as in the liver, spleen, and kidney infected with Streptococcus agalactiae and skin infected with Cryptocaryon irritans. As the infection with S. agalactiae and C. irritans progressed, we observed tissue specificity in the number and types of responsive AMPs. Positive selection of AMP genes may participate in the immune response through the MAPK signaling pathway. The genome-wide identification of antimicrobial peptides in the golden pompano provided a complete database of potential AMPs that can contribute to further understanding the immune mechanisms in pathogens. AMPs were expected to replace traditional antibiotics and be developed into targeted drugs against specific bacterial and parasitic pathogens for more precise and effective treatment to improve aquaculture production.

Design of a Smart Biofloc Monitoring and Controlling System using IoT

In this paper, an IoT based real-time monitoring and controlling system have been designed and developed for an eco-friendly aquaculture system namely a biofloc fish farm. Currently, technology has a vital role in improving aquaculture production which leads to attaining sustainable development. The microorganisms in the biofloc fish tank are utilized for detoxifying the toxic waste materials by recycling as well as transforming them into fish food e.g. protein cells. Hence, it not only manages good water quality in the biofloc system but also produces additional feed for the fish. Water quality monitoring of biofloc fish tanks is a significant aspect to guarantee a better environment for producing fish. This paper focuses on developing an IoT based device for biofloc fish tanks to monitor various water quality parameters as well as control water temperature and air pump. Using this device, users can monitor the water quality data received from sensors and control the actuators accordingly from any remote location through the graphical user interface (GUI).

Salmonidae Genome: Features, Evolutionary and Phylogenetic Characteristics

The salmon family is one of the most iconic and economically important fish families, primarily possessing meat of excellent taste as well as irreplaceable nutritional and biological value. One of the most common and, therefore, highly significant members of this family, the Atlantic salmon (Salmo salar L.), was not without reason one of the first fish species for which a high-quality reference genome assembly was produced and published. Genomic advancements are becoming increasingly essential in both the genetic enhancement of farmed salmon and the conservation of wild salmon stocks. The salmon genome has also played a significant role in influencing our comprehension of the evolutionary and functional ramifications of the ancestral whole-genome duplication event shared by all Salmonidae species. Here we provide an overview of the current state of research on the genomics and phylogeny of the various most studied subfamilies, genera, and individual salmonid species, focusing on those studies that aim to advance our understanding of salmonid ecology, physiology, and evolution, particularly for the purpose of improving aquaculture production. This review should make potential researchers pay attention to the current state of research on the salmonid genome, which should potentially attract interest in this important problem, and hence the application of new technologies (such as genome editing) in uncovering the genetic and evolutionary features of salmoniforms that underlie functional variation in traits of commercial and scientific importance.

Measuring the Green Total Factor Productivity in Chinese Aquaculture: A Zofio Index Decomposition

Aquatic products are important sources of protein and food consumption, which are pivotal to solving the problem of food shortage. As the world’s largest producer of aquatic products, China’s aquaculture has developed rapidly. However, a large quantity of pollutants has also been generated in the fish farming process, which is detrimental to the sustainable development of China’s aquaculture. Therefore, under double constraints with regard to resources and the environment, fishery development must achieve cleaner production. Measuring green total factor productivity in aquaculture is fundamental to improving aquaculture production efficiency and reducing pollution emissions. This paper investigated the green total factor productivity in China using the SBM-ML method and analyzed the dynamic evolution of fish farming, measuring its change characteristics with regard to time and spatial differences. The results indicated that the total factor productivity indexes of mariculture and freshwater aquaculture in China are 1.050 and 1.060, respectively. Regionally, mariculture in the East China Sea region has the highest green total factor productivity of 1.072, followed by the South China Sea region with 1.056, and the green total factor productivity in the Yellow Sea region is the lowest—only 1.030. The results of the freshwater aquaculture calculations showed the opposite geographical distribution characteristics in China, with the highest in the western region (1.098), followed by the central region (1.046), with the lowest being in the eastern region (1.038). Evidently, both mariculture and freshwater aquaculture have noticeable spatiotemporal heterogeneity. Relevant policy recommendations are provided to improve the green production efficiency of fishery.

Nanoparticles (NPs) in aquaculture industry: current status and future perspectives

The fastest-growing aquaculture industry plays a crucial role in fulfilling the increased demand for animal protein. However, the outcomes of the sectors are greatly hindered by unexpected disease prevalence, environmental degradation, organic and inorganic pollutants in aquaculture operations, and ineffective feed exploitation to achieve the global food security goal. There has been little research on the impact of nanotechnology on fish nutrition and improved health, despite the fact that the application of nanotechnology in food production systems is being studied globally. In this respect, scientists are generating and inventing new potential ideas and technology to cope with these challenges in aquaculture. Among them, the use of nanoparticles (NPs) has grown in popularity due to their numerous attractive and distinctive features and also tremendous potential to improve aquaculture production. New ideas regarding the application of NPs in fish medicine, drug delivery techniques through NPs, diet formulation to enhance feed efficacy, and as an antiviral or antimicrobial agent to control disease prevalence in aquaculture systems to augment overall production have been discussed. Commercially cultured fish species, including shrimp, Thai koi, Common carp, Grass carp, and Tilapia, have been shown to respond favorably to a variety of nanoparticles (eg. silver, gold, iron, copper, zinc, selenium, and chitosan). Thus nanoparticles researched-based information in finfish and shellfish aquaculture have short-term or long-term prospects and can be used as a potential candidate for nanomedicines combined with fish feed. These new ideas can be studied further before being utilized commercially in the aquaculture fish feed industries and it has huge merit in the future aquaculture need to be considered. Ann. Bangladesh Agric. (2022) 26 (1) : 113-125

Mechanistic model based optimization of feeding practices in aquaculture

Fish feed accounts for more than 50% of total production cost in intensive aquaculture. Feeding fish with low-quality feed or adopting inappropriate feeding strategies causes not only food waste and consequent loss of income but also lead to water pollution. The aim of this study was to develop a mechanistic model based optimization method to determine aquaculture feeding programs. In particular, we integrate a fish weight prediction model and a requirement analysis model to establish an optimization method for designing balanced and sustainable feed formulations and effective feeding programs. The optimization strategy is necessary to maximize the fish weight at harvest, while constraints include specific feed requirements and fish growth characteristics. The optimization strategy is re-solved with new available fish weight measurement by using the error between measurement and model prediction to adjust the requirement analysis model and update feeding amount decision. The mechanistic models are parameterized using the existing nutritional data on gilthead seabream (Sparus aurata) to demonstrate the usefulness of proposed method. The simulation results show that the proposed approach can significantly improve aquaculture production. This particular simulation study reveals that when “Only prediction” method is considered as benchmark, the average improvement in fish weight of proposed method would be 13.25% when fish weight is measured once per four weeks (mimicking manual sampling practice), and 38.43% when daily measurement of fish weight is possible (e.g. through automatic image-based methods). Furthermore, if feed composition (460 g protein kg feed−1; 18.9 MJ kg feed−1) is adjusted, the average improvement of proposed method could reach 46.85%. Compared with traditional feeding methods, the improvement of proposed method could reach 36.36% of the final fish weight at harvest. Further studies will consider improving the quality of feed plus executing more appropriate mathematical prediction models to optimize production performance.

Scenario analysis and land use change modelling reveal opportunities and challenges for sustainable expansion of aquaculture in Nigeria

This study explores the critical factors of pond aquaculture development in Nigeria, and opportunities and challenges for sustainable expansion of the sector. Aquaculture’s role in food security especially in developing countries has been recognized, including its growth potential. However, Nigeria’s aquaculture development remains slow. Using Delphi technique, key factors influencing aquaculture were identified: availability/cost of aquafeed, land use change, government policy and climate change. Then scenario planning was used to develop four alternative but plausible pathways (scenarios) for Nigerian aquaculture development to 2035, depicting baseline, favourable, somewhat favourable, and unfavourable situations. For each scenario, future pond aquaculture production was estimated by modelling future changes in land use and pond yield potential. Government estimates suggest a potential of producing 2.5 million metric tonnes (t) of fish annually, but our results suggest Nigeria is unlikely to reach this estimate by 2035 without interventions. While the qualitative scenarios are useful to enhance discussions on potential interventions for improving aquaculture production and sustainability, the quantitative projections can be used for evaluating these interventions.

A Solution for Sustainable Utilization of Aquaculture Waste: A Comprehensive Review of Biofloc Technology and Aquamimicry.

Biofloc technology (BFT) is gaining traction as a strategic aquaculture tool for boosting feed conversions, biosecurity, and wastewater recycling. The significant aspect of BFT is aquaculture with highest stocking density and minimal water exchange. It not only improves the water quality of a system by removing inorganic nitrogen from wastewater but also serves as a suitable feed supplement and probiotic source for cultured species. This technology is commonly used for shrimp and tilapia culture and can be used for both semi-intensive and intensive culture systems. Biofloc, when combined with formulated diets, forms a balanced food chain that improves growth performance. Nutrients in this system are continuously recycled and reused and form an efficient alternative system in aquaculture. In addition to the reduction in water exchange, it is also considered as a bio-security measure, since it prevents entry of disease from outside sources. Aquamimicry is an innovative concept that simulates natural estuarine conditions by developing copepods that act as supplementary nutrition especially for shrimp culture. The review highlights the process, significance, and development of BFT, its microbial interactions, nutritional value, transition from biofloc to copefloc, and concept of aquamimicry to sustainably improve aquaculture production.

Reviewing Pseudoloma neurophilia infections in the popular zebrafish model

AbstractZebrafish is a worldwide used animal model to better understand cultured fish species; thus, in the last two decades, zebrafish facilities have been created in many aquaculture research centres. However, and despite the attempts of rigorous aseptic conditions for animal husbandry in wet laboratory facilities, the presence of parasites cannot be underestimated. The microsporidium Pseudoloma neurophilia, which mostly affects the central nervous system, has been listed as the most prevalent parasite in reared zebrafish. The emergence of P. neurophilia is usually detected when the individual presents irreversible morphological and/or behavioural symptoms, and consequently, the spread of the disease is inevitable, indicating that the infection is expanded across rearing tanks. This review attempts, for the first time, to collect and discuss the current information on P. neurophilia life cycle, target tissues and symptomatology of the infection occurred in zebrafish. Due to its vertical transmission together with the increasing presence of zebrafish as a model in reproduction‐related problems found in aquaculture, it is highlighted, among others, the sexual dimorphism of the pathogenic effects and the possible transgenerational implications of parasitic infections. Further, to date none effective treatments have been described, so here we provide in detail available diagnostic methods, discussing the importance of the early detection, giving safety‐rearing recommendations to decrease the presence of P. neurophilia. Our intention is to minimize parasite outbreaks in zebrafish facilities, which, on the one hand, can compromise zebrafish welfare, and on the other hand, could interfere furtively in the resulting research previously designed for improving aquaculture production but also other biomedical‐related research.

Temperature induced changes in physiological traits and expression of selected candidate genes in black tiger shrimp (Penaeus monodon) larvae

Temperature is an important abiotic factor influencing growth, development, metabolic performance and sex determination of aquatic organisms. The present study was conducted to test the effect of six different temperature levels (24℃, 26℃, 28℃ as control, 30℃, 32℃ and 34℃) on the physiological (growth, developmental durations, survivability, sex ratios and O2 consumption) and genetic (changes in expression pattern of seven candidate genes: three male sex determining genes, three female sex determining genes and a single thermal stress response gene) aspects of black tiger shrimp (Penaeus monodon) larvae. Temperature treatments significantly altered the growth performance of shrimp individuals (P < 0.05) with the highest growth performance obtained at 32℃, moderate levels were obtained at 28−30℃ and the lowest levels were obtained at the remaining temperatures. Temperature treatments significantly shortened the larval developmental durations at 28℃, 30℃ and 32℃ (required 44–46 days for sex differentiation) while 52–63 days were required at 24℃, 26℃ and 34℃. Temperature treatments also altered sex ratios of experimental P. monodon individuals; significantly higher (P < 0.05) proportions of males (coupled with higher expression levels of male sex determining genes) were obtained at lower temperatures (24℃ and 26℃) while larger proportions of females (with higher expression levels of female sex determining genes) were obtained at higher temperature levels (30℃, 32℃ and 34℃). The thermal stress response gene, heat shock protein (HSP70) showed constant expression levels at 28℃ but higher expression levels were obtained at other temperatures. Results imply that higher temperature can significantly increase the expression of female sex determining genes to produce larger proportions of females in P. monodon that in turn can help to improve aquaculture production.

What determines aquaculture fish production? empirical evidence from South Aceh Regency, Indonesia

This study empirically assesses the determinants of aquaculture fish production in South Aceh District using multiple linear regression analysis. The study documented that, except for the number of fish seeds, the factors of land area, the number of workers, and capital had a significant positive effect on aquaculture production. These empirical findings suggest that to improve aquaculture production, fish farmers should possess adequate capital, land area, and the number of workers. The government must assist in providing soft loans by coordinating with provincial government-owned banking institutions, providing sufficient land areas by initiating conversion programs for vacant land into fish ponds. Various free of charges of the training program should be undertaken by the government regularly and continuously to enhance the capacity of aquaculture farmers to produce professional fish farmers who enable to ensure an increase in aquaculture fish production throughout the years.

Status of genetic and genomic approaches for delineating biological information and improving aquaculture production of farmed rohu, Labeo rohita (Ham, 1822)

AbstractFarmed rohu, Labeo rohita, is an economically important freshwater aquaculture species in south Asia. Consumer preference for this species has driven researchers to develop genetically improved rohu (Jayanti) for important traits such as growth and disease resistance. The feeding and breeding biology of rohu is well‐studied, but the physiological responses to stress or climate change at the molecular level are less understood. We summarized the genetic and advanced molecular tools used for biological insights into farmed rohu. Recently, next‐generation sequencing technology (NGS) and genome informatics have helped to identify biological questions in fish using genome, transcriptome, metagenome, proteome and epigenome sequencing. We briefly reviewed past rohu research using traditional selective breeding methods for genetic improvement, as well as the other molecular tools that have been utilized to understand the fish’s physiology, health, nutrition, stress and reproduction. We discuss the molecular techniques used in rohu, such as gene cloning and expression profiling, DNA markers, NGS, metagenomics, epigenomics, proteomics, cell culture/cell line development and transgenics. Finally, we address the future perspectives of rohu research, which may be driven by NGS and other advanced techniques like genome editing to improve rohu aquaculture production. The comprehensive information presented here will provide insights for the carp aquaculture research community.

Application of meta‐analysis towards understanding the effect of adding a methionine hydroxy analogue in the diet on growth performance and feed utilization of fish and shrimp

AbstractMethionine hydroxy analogue (MHA) has been widely used and shows positive effects on growth in poultry, swine, ruminant and aquatic animals. Nevertheless, the utilization efficiency of methionine hydroxy analogue remains controversial considering the wide variation in effects across studies, feeding parameters and environmental culture conditions. Meta‐analysis can quantify the effect of adding MHA on animal performance. Here, we analysed the effect of MHA‐supplemented diets on the final weight (FW), per cent weight gain (WG), protein efficiency ratio (PER), feed conversion ratio (FCR) and feed efficiency (FE) in common, diverse aquaculture taxa. To conduct the meta‐analyses, twenty‐three published studies were included that accounted for 249 effect sizes estimated across eight fish and one shrimp species. The effect size (measured as the standardized mean difference; Hedges’ g) of response parameters between MHA level in a diet formulation and an MHA‐less control condition was calculated. Based on these results, adding MHA in the diet can significantly improve FW, WG, PER, and FE and decrease FCR for fish rather than shrimp. Using meta‐regression analysis, there was a significant quadratic linear relationship between MHA addition and effect size for FW (P = 0.002 for MHA, P = 0.042 for MHA2), and significant linear relationships between MHA addition and effect size for WG (P = 0.0005) and FCR (P = 0.002). There was no significant relationship, linear or non‐linear, between the MHA addition and effect size for FE (P = 0.985) and PER (P = 0.461). In all, when properly dosed in diets, MHA can significantly improve aquaculture production for fish.

Biofloc technology as a promising tool to improve aquaculture production

AbstractGiven that the expansion of the aquaculture industry is associated with increased environmental impact and its strong dependence on fishmeal in the diet, the use of biofloc technology can reduce these problems. This technology absorbs inorganic nitrogen from aquaculture wastewater and improves water quality as well as produces microbial protein that is directly used as a suitable feed supplement for aquatic animals. Furthermore, this technology reduces the feed conversion ratio and subsequent production cost. Biofloc is available to aquatic animals throughout the day and provides the necessary nutrients, fatty acids and minerals. Biofloc along with formulated diets provides a complete food chain for aquatic animals’ growth and thus improves growth performance. Since feed constitutes a major part of the aquaculture cost, having accurate information about biofloc system in aquatic animals’ nutrition can be beneficial and helpful. Compared to traditional aquaculture techniques, biofloc technology provides a more sustainable approach with minimal water exchange along with reduced feed intake and transforms it into a low‐cost sustainable technology for sustainable aquaculture development. Overall, this study highlights the significance of developing biofloc technology to improve aquaculture production and could be an alternative system for cultivation of important commercial species in aquaculture.

Fatty Acid Composition of Hepatopancreas and Gonads in Both Sexes of Orange Mud Crab, Scylla olivacea Cultured at Various Water Flow Velocities.

Nutritional quality of the hepatopancreas and gonads of orange portunid mud crab, Scylla olivacea was evaluated for each gender under four treatment of different water velocities (0, 20, 40 and 60 cm s−1), in terms of nutrient reserve and nutrient for reproduction. About 56 crabs were used in this study in which fatty acids composition was analysed using gas chromatography mass-spectrometry (GC-MS). For hepatopancreas analysis, monounsaturated fatty acids (MUFAs) were present in the highest fatty acids concentration, followed by polyunsaturated fatty acids (PUFAs) and, saturated fatty acids (SFAs). However, long-chain polyunsaturated fatty acids (LC-PUFAs) were displayed in low concentration in the hepatopancreas. Total fatty acid (TFAs) composition was significantly higher at moderate velocity of 20 cm s−1 compared to other water velocity treatments. For gonad analysis, 20 cm s−1 showed the highest TFA concentration of 93.34 mg g−1 while, the lowest concentration of 3.90 mg g−1 occurred at 0 cm s−1. There were significant differences in male and female crab’s fatty acids contents of gonads at all flow velocities challenged (p < 0.05). PUFAs and MUFAs were dominant while, SFAs were observed at low concentration. This study revealed that, concentration of PUFAs increased as gonad maturation increased. The decreasing concentration of hepatopancreas fatty acids over the culture period indicated that nutrient was shifted from the hepatopancreas, to be used as energy reserved to gonads for further growth of eggs and offspring. The linkages between water flow strength, hepatopancreas, and gonad fatty acids concentrations, is fundamental knowledge useful in establishing efficient habitat velocities selection which will improve aquaculture production of mud crabs with high quality broodstock.

Atlantic salmon (Salmo salar L.) genetics in the 21st century: taking leaps forward in aquaculture and biological understanding.

SummaryAtlantic salmon (Salmo salar L.) is among the most iconic and economically important fish species and was the first member of Salmonidae to have a high‐quality reference genome assembly published. Advances in genomics have become increasingly central to the genetic improvement of farmed Atlantic salmon as well as conservation of wild salmon stocks. The salmon genome has also been pivotal in shaping our understanding of the evolutionary and functional consequences arising from an ancestral whole‐genome duplication event characterising all Salmonidae members. Here, we provide a review of the current status of Atlantic salmon genetics and genomics, focussed on progress made from genome‐wide research aimed at improving aquaculture production and enhancing understanding of salmonid ecology, physiology and evolution. We present our views on the future direction of salmon genomics, including the role of emerging technologies (e.g. genome editing) in elucidating genetic features that underpin functional variation in traits of commercial and evolutionary importance.

Effects of flow velocity on growth, food intake, body composition, and related gene expression of Haliotis discus hannai Ino

This study investigated the effects of different flow velocities in a circulating aquaculture system on growth, food intake, and related gene expression of the abalone Haliotis discus hannai Ino. Abalones (shell length: 41.39±2.85mm, body weight: 8.19±0.66g) were cultured at three flow velocities; high-velocity (400L/h), medium-velocity (300L/h), and low-velocity (200L/h) during the course of the experiment. Four repeats of each flow velocity were conducted over an experimental cycle of 90days. Results showed that the survival and specific growth rate of abalones in the 200L/h group were significantly lower than in any other group at the end of the experiment, while total ammonia nitrogen and NO2‑N concentration in the water was significantly higher than that in any other group (P<0.05). Food intake, food conversion efficiency, protein content, pepsin, and α-amylase activity of abalones in the 300L/h group were significantly higher than in the 200 and 400L/h groups (P<0.05), but there was no significant difference identified between 200 and 400L/h groups (P>0.05). Although no significant difference was identified between 300 and 400L/h groups with respect to cellulase activity or the expression levels of Hdaly, both were significantly higher than in the 200L/h group (P<0.05). In the 400L/h group, hexokinase and pyruvate kinase activity, and lactic acid content were significantly higher compared with in the 300L/h group (P<0.05). The ash and fat contents of abalones in the 200L/h group were significantly lower than in any other group, but moisture content was significantly higher (P<0.05). At Day 90, the expression levels of Hdamyl, Hdlam, and Hdcel in the 300L/h group were significantly higher than in any other group (P<0.05), and compared with Day 45, the expression levels of were Hdamyl significantly increased (P<0.05). Although no significant difference was identified between 200 and 400L/h groups with respect to the expression levels of Mn-SOD and CAT, both were significantly higher than those in the 300L/h group (P<0.05). Therefore, control of flow velocity at 300L/h will not only stimulate the food intake and growth of abalones, but also reduce energy consumption to resist against water flow impact and avoid oxidative damage due to water quality deterioration. This will be beneficial for abalone health and will improve aquaculture production.

Biofloc technology application in aquaculture to support sustainable development goals.

SummaryBiofloc technology (BFT) application offers benefits in improving aquaculture production that could contribute to the achievement of sustainable development goals. This technology could result in higher productivity with less impact to the environment. Furthermore, biofloc systems may be developed and performed in integration with other food production, thus promoting productive integrated systems, aiming at producing more food and feed from the same area of land with fewer input. The biofloc technology is still in its infant stage. A lot more research is needed to optimise the system (in relation to operational parameters) e.g. in relation to nutrient recycling, MAMP production, immunological effects. In addition research findings will need to be communicated to farmers as the implementation of biofloc technology will require upgrading their skills.