Recent advances and future directions in practical diet formulation and adoption in tropical Palinurid lobster aquaculture

The spiny lobsters Panulirus ornatus and Panulirus homarus are important developing tropical aquaculture species, with high demand and limited supply. The established industry in Vietnam relies on wild-caught mixed seafood bycatch as feed, a practice linked to water quality degradation and potentially disease proliferation in lobster aquaculture, necessitating formulated feed development. The emerging Indonesian and Australian industries lack the crustacean and mollusc component of the seafood bycatch used in Vietnam, increasing the need for manufactured feeds. Development of such feeds is reliant on knowledge of nutrient requirements, ingredient quality, physical feed requirements, and the link between feeding behaviour and feeding methods. This review will elaborate on the development of these knowledge areas to date and outline the two main reference diet recipes that are available as the basis for future research. Research to date has focused on developing a feed recipe that will be consumed and supports adequate growth rather than steering commercial least-cost formulation practices. Future research is clearly needed to inform formulation, but equally an understanding of the disparate emerging lobster farming industries and their drivers for adoption of formulated feeds is required to ensure that such research is applied. This will require engagement throughout the supply chain to ensure that research is implementable and to address farmer perception toward formulated feeds. Technical aspects of feed manufacture and scale-up of feed developments will be critical to adoption of research results, while validation though semi-commercial benchmarks and demonstration farm models are expected to increase commercial uptake of developed feeds

Digesting the Indigestible: Microplastic Extraction from Prawn Digestive Tracts

Microplastics (MPs) have become ubiquitous in the marine environment, and are likely ingested by a broad cross-section of marine life. The extent to which marine organisms ingest MPs is uncertain due to limitations in analytical methods. Effective identification and analysis of ingested MPs is a precursor to understand their impact on marine organisms and their human consumers. This is particularly challenging for crustaceans, due to the chitin present in their exoskeleton and digestive systems, which is resistant to chemical degradation. This study presents a novel application that can efficiently break down the stable organic tissue of banana prawns (Penaeus merguiensis), and subsequently isolate putative MP polymers from the digestive tract without damaging their integrity. Five treatments were examined for their capacity to break down chitin from the prawn digestive system; namely acid, alkaline, oxidant, enzyme and microwave assisted oxidant digestion. Gravimetric and image analysis revealed that the organic tissue of the prawn gastrointestinal tract can be effectively removed by acid, oxidant, and microwave assisted oxidant digestion methods. However, testing on seven reference polymers (polyamide (PA), polyethylene (PE), polyester (PES), polypropylene (PP), polystyrene (PS), polyvinyl chloride (PVC), and rayon) revealed significant degradation when exposed to acid digestion. Overall, microwave assisted oxidant digestion achieved the best recovery rate of spiked MPs ( > 90%) with minimal size, shape, and Fourier transform infrared (FTIR) spectral changes for all polymers except for rayon. These results highlight a new direction for tissue removal and MP extraction in crustacean ingestion studies

Reducing dietary wild derived fishmeal inclusion levels in production diets for large yellowtail kingfish (Seriola lalandi)

Further research to understand the effect of dietary wild derived fishmeal (WD-FM) substitution with commercially relevant alternative ingredients for large yellowtail kingfish (Seriola lalandi; YTK) was investigated. This 36-week study was designed to replace dietary inclusions of WD-FM with alternative protein ingredients including poultry meal, soy protein concentrate and by-product fishmeal (PM, SPC and BP-FM) and measure the effect on the growth performance, feed utilisation, and health of large YTK (2.5 kg initial weight) at ambient water temperatures (average 16.6 °C). Six diets were formulated on a digestible basis to contain 39% digestible protein (∼45–46% crude protein), 23% digestible lipid (∼24–25% crude lipid), and a digestible energy level of 17 MJ kg−1 (∼19 MJ kg−1 gross energy level). Fish were fed to apparent satiation once daily at 10:00 h. Substitution of fish meal with alternative ingredients did not significantly impact fish growth, feed utilisation, gastrointestinal health, blood haematology or measured biochemistry indices. Results from the current study will allow reductions to the dietary WD-FM inclusion levels, with tangible sustainability benefits. The inclusion of the alternative protein sources resulted in improvements in the fish in-fish out ratios of up to 35.1%. This study suggests formulation criteria for large YTK should include a minimum of 10% WD-FM. Further to this, at least 30% of the diet should consist of a combination of poultry meal, soy protein concentrate and fishmeal (both wild and by-product). Our data further support the use of BP-FM up to ∼20% inclusion, while PM and SPC should be limited to ∼10% inclusion until further data is available on these raw materials in YTK feeds. These recommendations will facilitate formulation flexibility for large YTK feeds, enabling formulators to adapt to changes to extrinsic factors such as raw material availability, and sustainability while minimising cost and performance impacts

Exploring the physiological plasticity of giant grouper (Epinephelus lanceolatus) to dietary sulfur amino acids and taurine to measure dietary requirements and essentiality

Giant grouper (Epinephelus lanceolatus) is an economically important yet under-researched species, still reliant on ‘trash fish’ or generic aquafeeds. The transition toward sustainable formulations is contingent on establishing requirements of target species for limiting nutrients, among which the sulfur amino acids (methionine and cysteine) commonly limit fish growth. Further, there remains significant conjecture around the role of the sulfonic acid taurine in marine aquafeed formulation and its relationship to sulfur amino acids. To develop a species-specific feed formulation for giant grouper, dietary methionine was modulated in a dose-response experiment to achieve five graded levels from 9.5 to 21.5 g/kg, including an additional diet with methionine at 18.6 g/kg supplemented with 8 g/kg taurine. The mean (±SD) cysteine level of the diets was 4.5 ± 0.3 g/kg. Each diet was randomly allocated to triplicate tanks of 14 fish (83.9 ± 8.4 g). The best-fit regression for growth showed that the optimal dietary methionine content was 15.8 g/kg and the total sulfur amino acid content was 20.3 g/kg. Inadequate dietary methionine content triggered physiological responses, including hepatic hyperplasia and hypoplasia at 9.5 and 21.5 g/kg, respectively, and high aspartate transaminase levels at 18.9 g/kg. Moreover, inadequate dietary methionine contents resulted in higher densities of mixed goblet cell mucin and reduced absorptive surface area of posterior intestinal villi. Our results suggest that adequate levels of methionine, but not taurine, improved posterior intestinal conditions and liver homeostasis. These findings may aid in formulating aquafeeds to optimize gastrointestinal and liver functions in juvenile giant grouper

Dietary supplementation of astaxanthin modulates skin color and liver antioxidant status of giant grouper (Epinephelus lanceolatus)

Giant grouper (Epinephelus lanceolatus) is an emerging aquaculture species in Southeast Asia and Australia with limited knowledge of its nutrient requirements and effects of supplements on its physiology. The present study investigated the effects of astaxanthin, vitamin E, and combinations on growth performance, body coloration, and the antioxidant status of juvenile giant grouper. Nine isonitrogenous (crude protein = 65 % ± 0.7 %) and isolipidic (crude lipid = 10 % ± 0.3 %) diets were formulated using a 3 × 3 factorial design, including three levels astaxanthin (0, 75, and 150 mg/kg) and vitamin E (0, 250, and 500 mg/kg), respectively. Each of the nine diets was fed to triplicate groups of 15 giant grouper (18.04 ± 0.92 g) for 30 days. Giant grouper fed the different diets exhibited no significant differences (p > 0.05) in specific growth rate (4.87 %/day - 5.21 %/day). However, dietary astaxanthin supplementation significantly enhanced the redness (a*), yellowness (b*b*), chroma, and hue values of the fin, regardless of the dose supplemented. Giant grouper fed astaxanthin at 75 and 150 mg/kg diet were more yellow and had three times higher b* values than fish fed non-supplemented diets. Further, total antioxidant capacity (TAC; mmol Trolox equivalent) in liver tissues was significantly increased in fish fed any of the astaxanthin-supplemented diets (p ≤ 0.05). In contrast, TAC levels were not affected by vitamin E supple-mentation. Malondialdehyde (MDA) levels were not significantly (p > 0.05) affected by astaxanthin or vitamin E. Findings from this study will contribute toward a better understanding of the dietary effects of antioxidant and pigment in juvenile giant grouper. We present that dietary treatment can modulate giant grouper pigmentation and may be used in the live fish trade. Further, this study contributes to narrowing the knowledge gap in formulating appropriate diets for giant grouper, which to date is fed diets formulated for other species

Phosphorus nutrition in farmed Atlantic salmon (Salmo salar): life stage and temperature effects on bone pathologies

Bone health is important for a viable and ethically sound Atlantic salmon aquaculture industry. Two important risk factors for vertebral deformities are dietary phosphorus and water temperature. Here, we explore the interplay between these two factors during a full production of Atlantic salmon. Salmon were fed one of three diets (low 4.4–5.0 g kg−1, medium 7.1–7.6 g kg−1, or high 9.0–9.7 g kg−1 soluble phosphorus) from 3 to 500 g body weight, followed by a common diet of 7.3 g kg−1 soluble phosphorus until harvest size at 4 kg. Additional groups were included to investigate the effects of water temperatures of 10 vs 16 °C (low and high diets only) and the switching of dietary phosphorus levels (from low to medium or high, from medium to low or high, from high to low or medium), starting at seawater transfer (~100 g body weight) and lasting for 4 months (~500 g body weight). During the experimental feeding period, the low phosphorus diet caused reduced bone mineralization and stiffness and a greater prevalence of vertebral deformities, compared to the medium and high phosphorus diets. However, the prevalence of severely deformed fish at harvest was reduced by switching from the low to either the medium or high phosphorus diets for 4 months after seawater transfer, followed by rearing on the standard commercial feed. Concurrently, switching from either the medium or high to a low phosphorus diet for the same period following seawater transfer had no effect on vertebral deformities at harvest. The higher water temperature for 4 months following seawater transfer increased the severity of deformities at harvest, irrespective of dietary phosphorus. Finally, low dietary phosphorus was associated with increased fillet damage, due to ectopic connective tissue around the spine, at harvest. In conclusion, dietary phosphorus levels of 5 g kg−1 for the initial 4 months in seawater are more of a risk factor for vertebral pathologies if preceded by low, but not medium or high, dietary phosphorus in freshwater. However, dietary phosphorus levels may not play a role in temperature induced radiologically detectable vertebral pathologies. Under the reported growing conditions and diet compositions, a combination of 7.5–7.6 g kg−1 soluble phosphorus during freshwater and 5.0 g kg−1

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

How are some fish able to change colour or complexion depending on their mood?

[Extract] FISH come in a dazzling array of colours, which is no doubt part of their appeal. One aspect of fish colour that may initially go unnoticed is that it is not always fixed but may change, at times quite quickly. So how do fish become the colour that they are, and why does it change