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Using stable isotope analysis, we assessed the relative contributions of the main protein contributors fishmeal, soya and sunflower meal to mature abalone muscle and gonad tissue over 1 year. Prerequisites for the use of stable isotope mixing models were established in this species. The δ13C and δ15N discrimination factors and turnover rates were influenced by diet composition, and there were tissue‐specific and sex‐specific differences. Abalone were fed the two combination diets (fishmeal–soya and fishmeal–sunflower meal) grew at similar rates. However, feed was most efficiently utilised in abalone fed a combination of fishmeal and soya. The relative contribution of fishmeal, soya and sunflower meal to female and male abalone tissue growth fluctuated throughout the 1‐year study. Overall, fishmeal contributed over 50% of the gonad (54%–82%) and muscle (54%–84%) tissue growth in females. Similarly, fishmeal contributed over 50% of gonad tissue growth of male abalone, ranging from 59% to 87%, while the contribution to meat tissue growth in males ranged from 44% to 94%. These findings support the importance of laboratory studies when using stable isotope analysis and mixing models for nutrient allocation in aquaculture. [ABSTRACT FROM AUTHOR]

The effects of adding a probiotic mixture of Bacillus subtilis and B. licheniformis to an aquaponics system on water quality, fish growth and digestive enzyme activity in Mozambique tilapia, Oreochromis mossambicus, were tested. The fish (36.4 g fish−1 ± 0.10; 3.64 kg m−3 tank volume, 10 fish per tank) were kept in 386-L systems and fed 2% of body mass day−1 for ten weeks. The Bacillus product (Sanolife®PRO-W; 5.0 × 1010 CFU g−1) was added twice weekly. Each treatment was duplicated. The product reduced total dissolved solids and electrical conductivity levels and increased weight gain of Mozambique tilapia. There was no difference between treatment and control in the proximate analysis of the fish. In the Bacillus treatment the activity of the digestive enzymes α-amylase, alkaline protease and alkaline phosphatase was higher than in the control. The probiotic used in this study improved water quality and increased fish growth. [ABSTRACT FROM AUTHOR]

ABSTRACT Ammonia is a toxic metabolite of protein catabolism that can limit growth and health of aquatic animals. This study investigated the effect of dietary protein level on the average [...]

Purpose: Aquaponics is a technology that has minimal impact on the environment and which is often promoted as a solution for sustainable food production. Developing aquaponics sustainably requires a thorough understanding of the biological components of the system. Recent reports on the bacterial populations of aquaponics systems using new DNA sequencing technologies are revealing a complex and diverse microbial ecosystem. The purpose of this review is to present information on microbial composition and various factors affecting bacterial activity in aquaponics systems. Approaches for establishing a bacterial ecosystem during the setup of an aquaponics system, and microbiological safety of aquaponics products are also highlighted. Methods: This review was developed by evaluating and synthesising current literature of peer-reviewed publications related to aquaponics and microbial communities. Based on the results from credible academic journals, publications were categorised into five groups: methods used to characterise microbiomes, biofiltration microorganisms, bacterial diversity, biofilter establishment, and safety of aquaponics products. Results: The microbial ecosystem is essential for biological filtration of water through the mineralisation of nutrients required for plant growth in an integrated system. The aquaponics microbiome is complex, and bacterial composition varies between the different compartments of these systems. Establishing these bacterial ecosystems is essential for optimal functioning of aquaponics. At the phylum level, Proteobacteria and Bacteroidetes are dominant in aquaponics systems. Despite bacteria being fundamental to aquaponics, there are currently no reports of human pathogens in aquaponics products. Conclusion: Knowledge of the composition of bacterial populations in aquaponics systems will enhance understanding of relationships and functions within the microbiome. This in turn will allow for the establishment of sustainable and healthy aquaponics systems for food production. [ABSTRACT FROM AUTHOR]

The development of environmentally sustainable plant and fish production in aquaponic systems requires a complete understanding of the systems' biological components. In order to better understand the role of microorganisms in this association, we studied the bacterial communities in the dry, root, and mineralized zones of a flood-and-drain media bed aquaponic system. Bacterial communities were characterized using metabarcoding of the V3-V4 16S rRNA regions obtained from paired-end Illumina MiSeq reads. Proteobacteria, Actinobacteria, and Bacteroidetes accounted for more than 90% of the total community in the dry zone and the effluent water. These phyla also accounted for more than 68% of the total community in the root and mineralized zones. The genera Massilia, Mucilaginibacter, Mizugakiibacter, and Rhodoluna were most dominant in the dry, root, and mineralized zones and in the effluent water, respectively. The number of shared operational taxonomic units (OTUs) for the three zones was 241, representing 7.15% of the total observed OTUs. The number of unique OTUs in samples from dry zone, root zone, mineralized zone, and effluent water was 485, 638, 445, and 383, respectively. The samples from the root zone harbored more diverse communities than either the dry or mineralized zones. This study is the first to report on the bacterial community within the zones of a flood-and-drain media bed. Thus, this information will potentially accelerate studies on other microbial communities involved in the bioconversion of nitrogen compounds and mineralization within these types of aquaponic systems. [ABSTRACT FROM AUTHOR]

Predation is a pervasive force that structures food webs and directly influences ecosystem functioning. The relative body sizes of predators and prey may be an important determinant of interaction strengths. However, studies quantifying the combined influence of intra‐ and interspecific variation in predator–prey body size ratios are lacking.We use a comparative functional response approach to examine interaction strengths between three size classes of invasive bluegill and largemouth bass toward three scaled size classes of their tilapia prey. We then quantify the influence of intra‐ and interspecific predator–prey body mass ratios on the scaling of attack rates and handling times.Type II functional responses were displayed by both predators across all predator and prey size classes. Largemouth bass consumed more than bluegill at small and intermediate predator size classes, while large predators of both species were more similar. Small prey were most vulnerable overall; however, differential attack rates among prey were emergent across predator sizes. For both bluegill and largemouth bass, small predators exhibited higher attack rates toward small and intermediate prey sizes, while larger predators exhibited greater attack rates toward large prey. Conversely, handling times increased with prey size, with small bluegill exhibiting particularly low feeding rates toward medium–large prey types. Attack rates for both predators peaked unimodally at intermediate predator–prey body mass ratios, while handling times generally shortened across increasing body mass ratios.We thus demonstrate effects of body size ratios on predator–prey interaction strengths between key fish species, with attack rates and handling times dependent on the relative sizes of predator–prey participants.Considerations for intra‐ and interspecific body size ratio effects are critical for predicting the strengths of interactions within ecosystems and may drive differential ecological impacts among invasive species as size ratios shift. [ABSTRACT FROM AUTHOR]

Detailed molecular data of Artemia (Crustacea, Anostraca) from South Africa are scarce. Here, we provide for the first time genetic data on the species status and phylogeography of Artemia from this region after an extensive sampling expedition. Our 16S rRNA RFLP analysis of 27 Artemia populations, including seven from South African sites, provides evidence for the presence of a mixed bisexual and parthenogenetic component in this area. Phylogenetic and network analyses reveal that three (out of seven) Artemia populations from South Africa belong to the invasive A. franciscana, two of them belong to A. salina while the last two contain both parthenogenetic and bisexual (A. salina) individuals. From a total of 18 haplotypes identified, seven were recorded from South Africa. To our knowledge, this is the first confirmed report of A. franciscana in this region. Its invasiveness is reaffirmed by evidence for the complete replacement of the native A. salina population from Velddrif Saltworks. However, in other cases, parthenogens seem to modify the capacity of A. franciscana to replace natives. Results on the genetic identification of South African Artemia provide insights into the dynamics of invasion and co-occurrence and highlight effects on species interactions and on biodiversity in inland aquatic invertebrates. [ABSTRACT FROM PUBLISHER]

The farming of abalone, Haliotis midae L., can be intensified in serial-pass systems, but water re-use increases the concentration of NH3 (free ammonia nitrogen, FAN) and reduces water pH. Changing the percentage dietary protein from 33% to 26% reduced the concentration of FAN (F42, 252 = 2.79; P < 0.0001) in a serial-pass system and did not reduce weight gain (F1, 12 = 1.09; P = 0.31) or length gain (F1, 12 = 1.08; P = 0.31). Low water pH was the most important variable to contribute to a reduction in abalone growth (weight gain: F1, 19 = 64.5; P < 0.0001; r2 = 0.76; length gain: F1, 19 = 41.9; P < 0.0001; r2 = 0.67). In addition, supplemental oxygen (103% saturation) improved length gain (t = 3.45, P = 0.026) in abalone exposed to an average FAN concentration of 2.43 ± 1.1 μg L−1) and an average pH value of 7.6 ± 0.13, relative to a treatment with no oxygen supplementation. Thus, in an abalone serial-use raceway with three passes, FAN was not the first growth-limiting variable. It is suggested that future studies should examine the major causes of reduced water pH in serial-use systems and their effect on the growth and health of H. midae. [ABSTRACT FROM AUTHOR]

To quantify the effects of serial-use of water on abalone growth and feed conversion, this study describes water quality in a serial-use raceway with seven passes. A flow index of 7.2-9.0 L h kg was estimated as the minimum value at which to grow 60-70 mm Haliotis midae, as weight gain (analysis of variance; F=13.9, P<0.0001) and feed conversion ratio (Kruskal-Wallis test; H=16.3, P=0.012) were significantly reduced at lower values. pH and dissolved oxygen concentration were positively correlated with the flow index (pH, r=0.99; P<0.001; dissolved oxygen, r=0.99; P<0.001), while free ammonia nitrogen (FAN) and nitrite were negatively correlated with the flow index (FAN, r=0.99, P<0.001; Nitrite, r=0.93, P<0.001). The concentration of nitrite increased throughout the experiment and may reflect the colonization of Nitrosomonas bacteria as water re-use increased. Based on comparisons with growth and toxicity tests, it is suggested that low pH combined with growth-limiting levels of FAN were the first variables limiting abalone growth in the serial-use raceway. [ABSTRACT FROM AUTHOR]

One function of aggression in animals is to gain access to mates. Aggression may therefore be favoured by sexual selection, the strength of which can be assessed using repeatability of aggressive behaviour. Here, we tested the hypotheses that male swordtails, Xiphophorus sp., are consistent in the aggressive and mating behaviours exhibited and in the time spent at a close distance to females (female attendance), and that aggressive males gain increased opportunity to attempt copulation compared to their less aggressive conspecifics (sneak frequency). As predicted, aggression between males, and male display and sneak frequency were repeatable. However, male aggression was not significantly correlated with sneak frequency. The function of aggression in this species is not clear-cut and may have an indirect female access function through formation of dominance hierarchies or defence of resources. A surprising finding highlighted by this study was the contradictory results for consistency in female contact, with high repeatability scores indicating consistency in behaviour but the within-subjects component of repeated measures ANOVA showing differences in female contact between trials. The possible reasons for this discrepancy are discussed. [ABSTRACT FROM AUTHOR]

The article presents an experiment that compared the effect of two cryoprotectants, glycerol and dimethyl sulfoxide, on post-thaw membrane integrity of Austroglossus pectoralis sperm after cryopreservation. Findings suggests that Austroglossus pectoralis spermatozoa can be cryopreserved using glycerol as a cryoprotectant with up to 61% of spermatozoa maintaining their nuclear membrane integrity.

Fresh vegetables harbour diverse bacterial populations on their surfaces which are important for plant health and growth. Information on epiphytic bacteria is limited to only a few types of vegetables and it is unknown how the lettuce epiphytic bacterial community structure may respond when a probiotic product is added to an aquaponic system. In this study, we evaluated lettuce growth and analysed epiphytic bacterial communities of lettuce based on metabarcoding analysis of the V3-V4 region of the 16S rRNA gene obtained from paired-end Illumina MiSeq reads. The addition of Bacillus probiotics resulted in a significant increase of nitrate and phosphate in the deep-water culture solution, as well as increased vegetative growth of lettuce. Metabarcoding analysis revealed that the most abundant phyla on lettuce leaf surfaces were Proteobacteria, Bacteroidetes, Firmicutes, and Actinobacteria. The in-depth bacterial composition analysis indicated that genera Chryseobacterium, Bacillus, Pantoea, Pseudoduganella, Flavobacterium, Paludibacter, and Cloacibacterium were dominant in leaf samples obtained from Bacillus-treated systems. Analysis of lettuce epiphytic bacterial communities of the fresh lettuce leaf surfaces also indicated the presence of food-borne pathogens belonging to the Shigella and Aeromonas genera, which were less abundant in the probiotic treated systems. This study provides the first characterization of the epiphytic bacterial community structure and how it can be modulated by the addition of a probiotic mixture to the nutrient solution of aquaponic systems. [ABSTRACT FROM AUTHOR]

The effects of temperature on growth, food-conversion ratio (FCR) and feeding intensity of juvenile dusky kob Argyrosomus japonicus (23.7±2.6 g fish−1) were assessed over the temperature range 17.5–28.5 °C in a 42-day growth trial. Growth increased with increasing temperature up to an optimum after which it declined. Specific growth rates were 2.05% and 1.2% day−1 for the fastest (25.3 °C) and the slowest (17.5 °C) treatments respectively. Food-conversion ratio peaked at a lower temperature than growth. Optimal (0.72 kg kg gain−1) and least efficient (1.40 kg kg gain−1) FCR were found at 21.7 and 17.5 °C respectively. Feeding intensity was linearly related to temperature within the range of 17.5–28.5 °C. These results corresponded to the thermal preference (25–26.4 °C) and natural temperature distribution (12–28 °C) of South African dusky kob. Determination of the temperature range that does not limit growth is a prerequisite to assess the relationship between growth and environmental variables such as light intensity, feeding regime and stocking density. Consequently, experiments to determine the effects of these environmental variables on growth and aquaculture potential of dusky kob should be conducted at 24–26 °C. [ABSTRACT FROM AUTHOR]

South African juvenile dusky kob Argyrosomus japonicus are more abundant in turbid estuaries than in clear marine-dominated estuaries. Turbidity can reduce light penetration into the water and create an environment different from that experienced by fish under culture conditions in mechanically filtered clear water. In order to optimize rearing conditions of this species, the effects of light intensity (23–315 lx) and feeding method (restricted ration vs. feeding to apparent satiation) on growth and food conversion ratio (FCR) of juvenile A. japonicus were assessed in a 56-day growth trial. Fish weight increased from 7.2±1.6 to 41.9±10.2 g fish−1 at a growth rate of 3.25% body weight day−1. Light intensity did not significantly affect growth or FCR. Feeding method did not significantly affect growth rate, but average FCR was significantly better in treatments fed a ration of 3.6% body weight day−1 than in treatments fed to apparent satiation. Therefore, a light intensity range of 23–315 lx can be used to culture dusky kob juveniles. The better FCR in fish fed a restricted ration suggests that a ration of 3.6% body mass day−1 allowed good growth of juvenile dusky kob. [ABSTRACT FROM AUTHOR]

Newborn (i.e. neonate) swordtail Xiphophorus helleri Heckel attempted to escape cannibalization attempts in a downward direction more frequently than in any other direction. The downward escape response is likely to be anti-predator behaviour. In addition, neonates were often able to escape cannibalization at the time of birth, despite no previous exposure to predators, which suggests that this anti-predator behaviour is innate. However, neonates at the time of birth were more vulnerable to cannibalism than older juveniles, which supports the hypothesis that anti-predator behaviour is, at least in part, further developed as a result of previous experience (i.e. learning). [ABSTRACT FROM AUTHOR]

The post-parturition behavioural patterns of adult Xiphophorus helleri (Heckel) were described and quantified by recording their duration and/or frequency in glass tanks. All births occurred in the dark. Female behaviour might increase the chance of newborn juvenile survival: at the top of the tank, where juveniles are more vulnerable to predation, the females gave birth in the artificial refuge, while no parturition took place in the refuge at the bottom. Birth-giving females were no less cannibalistic than males and other females. There was a reduction in cannibalism and the frequency of secondary attacks with time, even though the number of juveniles in the tank continued to increase due to ongoing parturition. Most adults were found at the bottom of the water column during the first 500 min of parturition, after which they were distributed equally in the water column. The movement of adults, away from the bottom and consequently away from the juveniles corresponded with an increase in feeding on alternative food and a reduction in cannibalism. Thus, cannibalism in swordtail might be opportunistic predation. [ABSTRACT FROM AUTHOR]

The nematode Panagrellus redivivus (Linné) has been suggested as a source of live food in the rearing of larval fish and shrimp species. This study tested the use of P. redivivus in the early rearing of the bottom-feeding catfish Synodontis petricola (Matthes). A comparison of feeding rates of 5000–10 000 nematodes larva−1 day−1 showed that fish receiving 5000 nematodes larva−1 day−1 grew faster than those fed a dry diet, but slower than treatments fed 200 and 600 Artemia larva−1 day−1. Enrichment of nematodes with SuperSelco® improved fish growth relative to a non-enriched control treatment, with both treatments receiving 5000 nematodes larva−1 day−1. In the first two trials, feeding commenced 2 days after hatching. In the third study, fish were fed nematodes 6 days after hatching and there was no difference in growth between Artemia-fed fish (600 Artemia larva−1 day−1) and fish fed 5000 nematodes larva−1 day−1. Thus, it is suggested to feed S. petricola at a nematode density of at least 10 000nematodes larva−1 day−1 in order to achieve growth comparable to that of fish fed Artemia, or, alternatively, to feed 5000 nematodes larva−1 day−1 to improve growth relative to that achieved with a dry diet. Furthermore, nematodes may be enriched with essential fatty acids to improve the growth of S. petricola larvae. [ABSTRACT FROM AUTHOR]

The Knysna seahorse, Hippocampus capensis, is an endangered teleost confined to three South African estuaries. Its abundance within these systems is low and distributions are patchy. Consequently, monitoring population sizes is labour-intensive. The aim of this study was to establish if Knysna seahorses are associated with specific regions within the estuaries, on which conservation efforts could concentrate. The relationship of Knysna seahorses with aquatic vegetation was analysed in the Knysna Estuary (the largest of the three estuarine systems inhabited by H. capensis) to determine whether this species shows a preference for a particular plant species, vegetation density or vegetation height. Seahorses were associated with five dominant aquatic plants: Zostera capensis, Caulerpa filiformis, Codium extricatum, Halophila avails and Ruppia cirrhosa. Together, these comprised 96% of the submerged objects with which seahorses were associated. The relative abundance of plant species changed along the estuary, but seahorses were present throughout the system, except at the estuary mouth, which was characterized by low plant densities and strong currents. No significant difference was found between the proportion of plant species present in a particular region of the estuary and the proportion of plants that seahorses used as holdfasts. However, when Z. capensis and C. filiformis were present at the same sites, adult seahorses preferred C. filiformis as holdfast. Adult seahorse density (individuals/m²) was significantly correlated with percentage vegetation cover and with holdfast length, but juvenile seahorse density was not. Nonetheless, significantly more adult and juvenile seahorses were found at sites characterized by high vegetation cover (> 75%) than at sites with lower cover. Our results indicate that although there is some evidence that Knynsa seahorses prefer certain plant species over others, they are likely to be encountered anywhere in the estuary where aquatic plants are present. Conservation efforts in the Knysna Estuary should thus concentrate on such vegetated areas, which comprise approximately 11% of the total submerged surface area. [ABSTRACT FROM AUTHOR]

Owing to the problem of antibiotic resistance and subsequent reluctance of using antibiotics, the use of probiotics in larviculture is becoming increasingly popular. During the early stages of development, manipulation of the larval digestive system seems possible through the addition of probiotics either through the culture water or via the livefood. Well-studied probiotics used in human medicine and terrestrial agriculture have proved to be successful in aquaculture and therefore reduce the need for extensive biosafety trials. The selection of probiotics requires various in vitro screening experiments, which assay for the production of antagonist compounds, their growth in and attachment to fish intestinal mucus, and the production of other beneficial compounds such as vitamins, fatty acids and digestive enzymes. Further information regarding probiont suitability can be obtained from its identification, interaction with livefood and host pathogenicity. Finally, pilot-scale in vivo tests need be performed, after which a production cost–benefit analysis to determine its economic viability needs to be undertaken. [ABSTRACT FROM AUTHOR]

The selection of probiotics for aquaculture is usually based on their antagonism towards pathogens. However, other criteria such as growth, attachment to intestinal mucus and production of beneficial compounds should also be considered. We suggest a protocol for the isolation and selection of potential probiotic bacteria based on their in vitro growth characteristics and propose a ranking index (RI) to screen potential aquaculture probionts. We suggest that the lag period and doubling time are the most important criteria for the comparison of growth curves, hence the RI is based on the doubling time (td) and lag period (λ) obtained from the growth profile of each bacterium. Bacteria were isolated from the gut of the common clownfish, Amphiprion percula, and screened for antagonistic activity towards seven aquatic pathogens. All five candidate probiotics showed antagonism to various aquatic pathogens. When grown in intestinal fish mucus no probiotic had a RI higher than the two tested pathogens (Aeromonas hydrophila and Vibrio alginolyticus). However, candidate probiont AP1 had a faster specific growth rate (μ) (0.05) than the pathogens (0.049 and 0.047 respectively), while AP5 grown in marine broth had a shorter lag period than the pathogens. Strategies to increase probiotic concentration include the inoculation of high concentrations and the preconditioning of these bacteria to reduce the lag period. It should be tested whether or not such strategies will allow the probiotic bacteria to dominate initially and thereby gain a competitive advantage. This could become an important aspect under in vivo conditions where both attachment and nutrient supply differ from that found in in vitro studies. [Copyright &y& Elsevier]

The relationship between condition and population growth of the rock anemone, Aiptasia, was determined after exposure to different copper levels ranging from 0 to 199 µg/L Cu. Coinciding with an increase in mortality, most specimens exposed to Cu had retracted heads and a reduced base and exhibited loss of symbiotic photosynthesizing algae. Population growth was affected at 106 µg/L Cu and mortality of adult Aiptasia was first observed at exposure to 154 µg/L Cu for 3-4 weeks or 199 µg/L Cu for at least 18 days. Since the effect of Cu on marine organisms is difficult to predict due to its interactions with other water quality parameters, it is suggested that behavior and condition of Aiptasia could be used as an indicator to predict their population growth in marine hatchery systems. [ABSTRACT FROM PUBLISHER]

Six growth-related variables were measured or calculated to evaluate two feeding methods for reducing the growth of the steelhead (Oncorhynchus mykiss). The two feeding methods were reduced continuous daily feeding and intermittent feeding. After eight 14-d growth periods, there were no significant treatment-related differences in size variation and size distribution within populations of fish in either treatment. Rates of growth among all groups – continuously fed and intermittently fed – were comparable, as were feed conversions. There were no apparent adverse effects, such as fin erosion, attributable to either treatment. [ABSTRACT FROM PUBLISHER]

The integration of probiotics in aquaponics systems is a strategy for mitigating environmental impacts and for promoting sustainable agriculture. In order to understand the role of probiotics, we investigated the effect of a commercial probiotic mixture of Bacillus subtilis and B. licheniformis on the growth of lettuce (Lactuca sativa L.) under deep-water culture integrated with Mozambique tilapia (Oreochromis mossambicus). We determined plant growth, water quality parameters, and leaf mineral analysis, and assessed the influence of a probiotic mixture on the microbiota. Bacterial communities were analyzed by high-throughput 16S rRNA gene sequencing. Compared to the control systems, the addition of the probiotic Bacillus significantly increased the concentration of nitrate and phosphate in deep water culture solution, which contributed to improved lettuce growth. In both the growth trials, the Fv/Fm, the mean shoot dry weight, and the mean fresh weight of the harvested shoots from the Bacillus treatment were significantly higher than those observed for the control plants. Higher concentrations of phosphorus, potassium, and zinc in the lettuce leaves were found in systems that received the Bacillus. Although differences were observed at the phylum level, Proteobacteria and Bacteroidetes were predominant in both the Bacillus-treatment and the control systems. At the genus level, however, the communities present in the two types of systems were heterogeneous with Bacillus-treated systems, containing significantly higher numbers of Chryseobacterium, Bacillus, Nitrospira, Polynucleobacter, and Thermomonas. The results indicate that Bacillus supplementation can effectively alleviate nutrient deficiencies, improve water quality, and modify the composition of bacterial communities in aquaponics systems. [ABSTRACT FROM AUTHOR]