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Determining the macronutrient requirements for commercially valuable aquaculture species remains crucial for maximising production efficiency. Yet, such information is lacking for Australian hybrid abalone (Haliotis rubra × Haliotis laevigata), particularly with respect to life stage and water temperatures. The present study aimed to evaluate the effect of dietary protein inclusion level on the growth performance, nutrient utilisation and nutritional quality of juvenile (3·3 g) Australian hybrid abalone reared at three different temperatures representative of winter (12°C), average annual (17°C) and summer (22°C) grow-out periods and fed five diets containing graded dietary protein levels of 35, 38, 41, 44 and 47 %. Abalone growth increased with increasing water temperature with weight gains of approximately 100, 280 and 380 % of their initial weight at 12, 17 and 22°C, respectively. Furthermore, the present study clearly demonstrated that higher dietary protein inclusion levels (41 %) than those currently used commercially (35 %) would significantly improve the growth performance when water temperatures are ≥17°C without any adverse impacts on nutrient utilisation, nutrient deposition or nutritional quality of the abalone soft tissue. For example, at 22°C abalone fed a diet containing 41 % protein obtained a significantly higher weight gain percentage (421 %) compared with those fed a diet containing 35 % protein (356 %). Lastly, it is suggested that maintaining a dietary protein inclusion level of 35 % or implementing a 'least cost' feeding approach during cooler seasons, or where water temperatures are ∼12°C, may be beneficial, considering only marginal growth improvements were observed during these periods of slow growth. [ABSTRACT FROM AUTHOR]

The aims of this review are to describe the role of 'blue‐food production' (animals, plants and algae harvested from freshwater and marine environments) within a circular bioeconomy, discuss how such a framework can help the sustainability and resilience of aquaculture and to summarise key examples of novel nutrient sources that are emerging in the field of fed‐aquaculture species. Aquaculture now provides >50% of the global seafood supply, a share that is expected to increase to at least 60% within the next decade. Aquaculture is an important tool for reducing resource consumption in global protein production and increasing resilience to climate change and other global disruptions (i.e. pandemics, geo‐political instability). Importantly, blue foods also provide essential nutrition for a growing human population. Blue foods are helping to help the global goal of 'zero hunger' (United Nation's Sustainable Development Goal 2) while reducing the dependency on finite natural resources but further refinement and new solutions are needed to make the industry more 'circular' and sustainable, particularly with respect to sourcing raw materials for aquafeeds. This review describes the feed resources that are available or may be created within a circular bioeconomy framework, their role within the framework and in aquaculture and ultimately, how these resources contribute to de‐risking and establishing a resilient aquaculture production chain. [ABSTRACT FROM AUTHOR]

Developing an optimal heterotrophic feeding regime has the potential to improve captive coral growth and health. This study evaluated the efficacy of three exogenous diets: Artemia nauplii (ART), a commercially available coral diet (Reef Roids) (RR), and a novel, micro-bound diet (ATF), against a comparatively natural, unfiltered seawater treatment (RAW), and an unfed, ultra-filtered seawater treatment (CTL), in adult Acropora millepora and Pocillopora acuta nubbins. After 90 days, both species showed significantly positive weight gain in response to one treatment (A. millepora–RAW, P. acuta–ART), and comparatively low growth in response to another (A. millepora–ATF, P. acuta–RR). The results highlighted substantial differences in the nutritional requirements between species. The nutritional composition of A. millepora in the best performing treatment was dominated by high-energy materials such as storage lipids and saturated and monounsaturated fatty acids. In contrast, the P. acuta nutritional profile in the superior treatment showed a predominance of structural materials, including protein, phospholipids, and polyunsaturated fatty acids. This study demonstrates that Artemia nauplii can successfully replace a natural feeding regime for captive P. acuta, yet highlights the considerable work still required to optimise supplementary feeding regimes for A. millepora. [ABSTRACT FROM AUTHOR]

Heterotrophic feeding in newly-settled coral planulae can potentially improve survivorship and accelerate early development in some species; however, an optimal diet to facilitate this does not currently exist. This study evaluated the efficacy of three heterotrophic feeding regimes (enriched rotifers, unfiltered seawater, and a novel, particulate diet), against a wholly-phototrophic treatment on Acropora hyacinthus, A. loripes, A. millepora, and A. tenuis recruits, over 93 days post-settlement. The unfiltered seawater treatment recorded maximum survival for all species (A. hyacinthus 95.9±8.0%, A. loripes: 74.3±11.5%, A. millepora: 67±12.7%, A. tenuis: 53.2±11.3%), although not significant. Growth (% surface area gain) was also greatest in the unfiltered seawater, and this was significant for A. millepora (870±307%) and A. tenuis (693±91.8%) (p<0.05). Although total lipid concentration was relatively stable across treatments, the lipid class composition exhibited species-specific responses to each treatment. Lower saturated and higher polyunsaturated fatty acids appeared beneficial to recruit performance, particularly in the unfiltered seawater, which generally contained the highest levels of 20:5n-3 (EPA), 22:6n-3 (DHA), and 20:4n-6 (ARA). The present study demonstrates the capacity of a nutritionally adequate and readily accepted heterotrophic feeding regime to increase coral recruit survival, growth, and health, which can greatly reduce the time required in cost- and labour-intensive culture. [ABSTRACT FROM AUTHOR]

Information on the nutritional requirements and preferred diets of sea cucumber juveniles is extremely limited and this has hindered development of hatchery culture methods. This study assessed ingestion, cell wall digestion and relative nutritional values of two live micro-algae ( Isochrysis aff. galbana (TISO) and Chaetoceros muelleri ) and six concentrated micro-algae products (Instant Algae®, Reed Mariculture Inc.) for early juveniles of sandfish, Holothuria scabra . Seven of the eight micro-algae tested were ingested by juveniles with the exception of live TISO. Faeces excretion times varied between ingested diets that passed through the juvenile gut in less than 1 h. The cell walls of five of the eight micro-algae tested were partially or mostly digested ( Chaetoceros muelleri , TW1200®, Palova 1800®, Isochrysis 1800® and Shellfish 1800®), while the cell walls of Tetraselmis 3600® and 3H 1800® remained intact. Juvenile growth rates were significantly different between diet treatments over the duration of a 14 day growth trial. Mean (± SE) length of early juveniles at the end of the growth trial was highest for those fed live C . muelleri (4.10 ± 0.03 mm) followed by TW 1200® (3.49 ± 0.05 mm). Juvenile survival did not differ significantly between diet treatments and was highest for those fed C . muelleri (79.33 ± 6.11%) followed by TW1200® (78.33 ± 1.20%). Pearson's correlation tests were used to identify key correlations between the levels of specific nutrients and juvenile performance (growth and survival). A significant positive correlation between growth and dietary protein content ( P < 0.05), and a highly significant positive correlation between growth and dietary EPA:DHA ratio ( P < 0.01) provide new information to inform diet selection for juvenile sandfish that will help improve juvenile performance and support improved hatchery production. Use of commercially available micro-algae concentrates as a replacement for live micro-algae in sandfish hatcheries supports development of cheaper, simpler post settlement rearing protocols for this species. [ABSTRACT FROM AUTHOR]

Three Instant Algae® (Reed Mariculture Inc., Campbell, CA, USA, 95008) products: (1) mono-cultured Isochrysis sp. (Haptophyceae) (Isochrysis 1800®); (2) mono-cultured Pavlova sp. (Haptophyceae) (Pavlova 1800®); and (3) mono-cultured Thalassiosira weissflogii (Bacillariophyceae) (TW 1200®) were used to feed sandfish ( Holothuria scabra ) larvae both singly and in ternary combination to assess their nutritional efficacy. Two-day auriculariae were held at a starting density of 0.3 mL − 1 and were initially fed a daily ration equivalent to the dry weight of 10,000 cells mL − 1 of Isochrysis 1800®. This ration was increased by the dry weight equivalent of 1000 cells mL − 1 of Isochrysis 1800® per day as larval development proceeded. Post-settled larvae fed TW 1200® were significantly larger than those fed the ternary diet, Isochrysis 1800® or Pavlova 1800®. There were significant differences in the mean (± SE) survival of auriculariae and post-settled larvae between treatments and survival to settlement was significantly higher (P < 0.05) for larvae fed TW 1200® (13.7 ± 0.7%) alone. Laval development, competency and survival were significantly correlated with dietary levels of total protein, lipid and nitrogen-free extract (NFE), and with total polyunsaturated fatty acid (PUFA) content of the diets, and the levels of some specific fatty acids (FA). The proportion of late auriculariae with hyaline spheres (day 13), numbers of competent doliolariae (day 15) and the total length of post-settled larvae (day 21) were all positively correlated with dietary NFE and palmitic acid (16:0) contents, as well as dietary EPA: DHA ratio. This study is the first comprehensive assessment of the nutritional value of micro-algae concentrates for sandfish larvae based on their nutrient compositions. Our study confirms the feasibility of using commercially available microalgae concentrates as a sole food source for hatchery culture of sandfish, and is the first to report successful hatchery culture of H. scabra without using live micro-algae. All micro-algae concentrates used in this study proved nutritious for H. scabra larvae and supported normal growth and development and relatively high survival, through settlement. Use of commercially available micro-algae concentrates as a replacement for live micro-algae in sandfish hatcheries supports development of cheaper, simpler larval rearing protocols for this species. Statement of relevance Hatchery culture of sandfish using micro-algae concentrates, without the use of live micro-algae, is a significant finding that supports development of cheaper, simpler larval rearing protocols for this species. Our study provides detailed nutritional compositional data for the products used and on this basis we were able to deduce new information relating to key nutrients for sea cucumber larvae. [ABSTRACT FROM AUTHOR]

The closed-cycle rearing of palinurid lobsters in commercially relevant quantities currently represents one of the most difficult challenges facing modern-day aquaculture. The length and complexity of the larval life cycle exacerbate the problem, comprising the major bottleneck to their successful aquaculture. The general consensus is that developments in the key research area of nutrition will provide the necessary breakthroughs to make the closed-cycle rearing of lobster a reality. Due to the cryptic nature of feeding preferences and complex larval morphology, a commercially formulated feed for their culture does currently not exist. Nevertheless, there has been a wealth of research conducted to elucidate many of the unknowns concerning larval nutritional requirements. This review presents a synthesis of this information, ranging from investigations of larval morphology and feeding behaviour, hatchery nutrition practices, the elucidation of wild prey items and the nutritional content of wild-caught larval species. Based on the information available, this review culminates with a 'best guess' formulation for a larval spiny lobster diet, taking aspects concerning both the physical and chemical attributes of formulation into consideration. It is concluded that larval spiny lobsters are likely comparatively low in relation to other larval species with respect to their quantitative dietary requirements. Ultimately, the overall success of the larval cycle appears to be dictated by the stockpiling of lipids to fuel an energy-demanding metamorphosis and a subsequent nonfeeding puerulus phase. These insights provide valuable direction for the formulation of nutritionally complete feeds to permit the closed-loop culture of spiny lobster species. [ABSTRACT FROM AUTHOR]

Elucidation of the key nutritional requirements for complete larval development of the tropical spiny rock lobster, Panulirus ornatus , presents a major challenge for the development of robust commercial aquaculture for this crustacean. As a foundation study in this area, the chemical composition of early–mid stage P. ornatus phyllosoma (Stages I–VI) receiving a novel formulated diet was analysed immediately prior and post-ecdysis to provide insight into the crude nutritional trends during the larval development cycle. From the onset of moulting, cyclical patterns were evident in the proximate composition of phyllosoma, resulting in substantial restructuring between the pre- and post-moult stages of the moult cycle. Proportions of protein, lipid and ash were high at the premoult stage, reflecting growth and nutrient accumulation over the intermoult period, and reduced at the post-moult stage, reflecting the large uptake of water to facilitate subsequent growth. Polar lipid was the dominant lipid class, accounting for > 90% of the total lipid content. Conversely, triacylglycerol concentrations were low (< 5%), despite being the principal lipid class available in the formulated diet. Likewise, despite receiving high concentrations of eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) (9.2 and 7.6% of the dietary lipid source, respectively), levels of these fatty acids were comparatively low in phyllosoma (3.4 and 4.7%, respectively). In contrast, there is selective deposition of these fatty acids in wild caught phyllosoma. This finding suggests a poor assimilation of triacylglycerols by captive larvae and highlights the importance of future investigations into alternative sources of EPA and DHA. Ultimately, this study provides insight into the nutritional requirements of phyllosoma, providing valuable knowledge on diet formulation for commercially viable hatchery production of spiny rock lobsters. [ABSTRACT FROM AUTHOR]