Approximately 70% of the aquatic-based production of animals is fed aquaculture, whereby animals are provided with high-protein aquafeeds. Currently, aquafeeds are reliant on fish meal and fish oil sourced from wild-captured forage fish. However, increasing use of forage fish is unsustainable and, because an additional 37.4 million tons of aquafeeds will be required by 2025, alternative protein sources are needed. Beyond plantbased ingredients, fishery and aquaculture byproducts and insect meals have the greatest potential to supply the protein required by aquafeeds over the next 10-20 years. Food waste also has potential through the biotransformation and/or bioconversion of raw waste materials, whereas microbial and macroalgal biomass have limitations regarding their scalability and protein content, respectively. In this review, we describe the considerable scope for improved efficiency in fed aquaculture and discuss the development and optimization of alternative protein sources for aquafeeds to ensure a socially and environmentally sustainable future for the aquaculture industry.

This study investigated the biochemical suitability of Australian native microalgal species Scenedesmus sp., Nannochloropsis sp., Dunaliella sp., and a chlorophytic polyculture as nutritional supplements for human health. The four microalgal cultures were harvested during exponential growth, lyophilized, and analysed for proximate composition (moisture, ash, lipid, carbohydrates, and protein), pigments, and amino acid and fatty acid profiles. The resulting nutritional value, based on biochemical composition, was compared to commercial Spirulina and Chlorella products. The Australian native microalgae exhibited similar, and in several cases superior, organic nutritional properties relative to the assessed commercial products, with biochemical profiles rich in high-quality protein, nutritious polyunsaturated fats (such as α-linolenic acid, arachidonic acid, and eicosapentaenoic acid), and antioxidant pigments. These findings indicate that the microalgae assessed have great potential as multi-nutrient human health supplements.

Using data collected from more than 1,000 tourists on live-aboard dive boats operating in the Cairns/Cooktown management area of the Great Barrier Reef, this paper estimates the regional economic impact of that live-aboard industry. It also uses a subset of these data (247 respondents) to investigate some of the relative ‘values’ of key marine species seen on the trips that included the Coral Sea location of Osprey Reef and which targeted multiple species of wildlife. The authors find that (i) each year, the live-aboard dive boats are directly responsible for generating at least AU$16 million worth of income in the Cairns/Port Douglas region; (ii) visitors participating in different types of trips gain their highest levels of ‘satisfaction’ from interacting with different types of species; and (iii) visitors to Osprey Reef would be willing to pay more for a ‘guaranteed’ sighting of sharks than they would for a ‘guaranteed’ sighting of large fish, marine turtles or a ‘wide variety of species’.

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The green alga Haematococcus pluvialis is able to produce and accumulate large amounts of astaxanthin under stress conditions, but not every strain has such a capability. At present, there is little information on how strains differ for astaxanthin production. In this study, three Australian strains of H. pluvialis (New South Wales (NSW), South Australia (SA) and Queensland (QLD)) were cultured and exposed to 0.17 M NaCl for 10 days, to compare their molecular profiles for astaxanthin accumulation and carotenogenesis. After 10 days of salinity stress, the astaxanthin contents of strains NSW, SA and QLD increased up to 16.2, 5.6 and 17.7 mg g −1 dry weight (DW), respectively. Astaxanthin accumulation was more efficient in H. pluvialis QLD, followed by strain NSW and then SA. The transcript abundance of seven carotenogenesis genes (ipi-1, ipi-2, psy, lyc, crtR-B, bkt2 and crtO) was upregulated with different patterns and incremental expression levels amongst the three strains. The early upregulation of the rate-limiting genes, psy, lyc, bkt2, crtR-B and crtO, was more pronounced in the superior astaxanthinaccumulating QLD and NSW strains. Although the increased transcript level of carotenoid genes was not correlated to the different astaxanthin accumulation between the three strains, expression patterns of these genes likely are strain-specific. Overall, H. pluvialis strains QLD and NSW showed good potential to produce high astaxanthin contents, and the former strain displayed a higher productivity upon salinity stress.