Search

The high worldwide amount of residues derived from the banana harvest is an opportunity to create synergies between the banana industry and aquaculture, from a circular economy perspective. The present work objective is to evaluate the inclusion of banana by-products, such as banana pseudo-stem and banana flower in tilapia feeds, and to explore the extracts from the banana flower on the development and health in tilapia juveniles. Three consecutive feeding trials were performed to evaluate the test by-products inclusions: Experiment I) with 0%, 2.5%, 5%, 15% and 20% of banana pseudo-stem; Experiment II) with 0%, 0.2%, 0.5%, 1% and 3% of banana flower; and Experiment III) with 3% of banana flower against its correspondent organic extract and residue of the extraction. Salinity stress challenges were conducted after the feeding trials in Experiments II and III. From the obtained results, up to 5% of banana pseudo-stem and 3% of banana flower inclusion were suitably regarded the fish growth and the liver health, also, as the essential fatty acids proportion in the muscle, despite the reduction in total lipid percentage. Regarding the stress challenges, the flower and more specific, the remaining residue from its organic extraction, appears to regulate the levels of plasma cortisol and glucose and reduce the oxidation parameters in fish liver and muscle, which may be due to the polyphenols present in both, the whole banana flower and in its organic extraction residue.

The sustainable expansion of aquaculture relies on a sufficient supply of eggs and larvae, which are the first step of life cycle management. However, marine fish larval rearing generally depends on live feed production, which needs additional facilities and labor. The flathead grey mullet (Mugil cephalus), a promising species for aquaculture diversification, has a precocious digestive system development, supporting the feasibility of early weaning strategies. For these reasons, this study evaluated survival, growth, proximate and fatty acid composition, and gene expression of Mugil cephalus larvae reared under three different weaning protocols. Three co-feeding treatments, two with different Artemia sp. concentrations (A100 and A50, 2 and 1 Artemia sp. mL−1 day−1, respectively) and one with only rotifers administered as live feed along the feeding trial (A0), were assessed from 22 to 36 days post-hatching (dph). The A0 treatment performed better in survival (64.79 ± 7.40%) than the A100 protocol (32.46 ± 12.82%). In contrast, the larvae of the A100 treatment presented significantly higher final length (15.51 ± 0.86 mm) than those of the A0 treatment (12.19 ± 1.45 mm) and higher final weight (41.28 ± 1.48 mg) than those of the A50 and A0 treatments (31.23 ± 3.65 mg and 24.03 ± 7.99 mg, respectively). On the other hand, the expression of digestive enzyme- and somatotropic factor-related genes did not show differences between treatments. The present results support the convenience of treatment A0 in maximizing survival, as rotifers should be maintained until 30–32 dph (until a total larval length of at least 10 mm). However, to improve growth and minimize size dispersion, Artemia sp. addition is recommended from day 26 to day 29 post-hatching (total larval length of 8 to 9 mm).

Mullets (Mugilidae) present significant potential for sustainable aquaculture diversification due to their eurythermal, euryhaline, and low-trophic nature. However, the physiological differences and optimal cultured conditions among the diverse mullet species are quite unknown. For these reasons, the present study aimed to address two main objectives: (1) to characterize the differences in digestive biochemistry, somatic indexes, and body composition between two mullet species (Liza aurata and Chelon labrosus); and (2) to evaluate the interactions of two different feeding frequencies (one against three meals per day) on the above-mentioned parameters, and also on the potential bioavailability of nutrients determined using in vitro assays. The results evidenced higher protease and amylase activities for Chelon labrosus than for Liza aurata, while the latter species presented a higher percentage of eviscerated weight and muscle lipids. Furthermore, the results from in vitro assays supported the higher enzyme activity of Chelon labrosus by an observed increase in the release of amino acids and reducing sugars measured for this species. Regarding feeding patterns, the results of the in vitro assays simulating enzyme: substrate (E:S) ratios corresponding to one or three meals per day point to a clear increase of nutrient bioavailability when the daily ration is split into several meals. The present results improve the physiological knowledge of mullet species and define criteria to develop better management protocols by producers.

Among of the actual challenges for the sustainable aquaculture development are to lower the trophic level of the cultured species, and to increase the use of by-products from the primary sector. The golden mullet (Liza aurata) is a marine low trophic level consumer present in the Mediterranean and in the Canary Islands, where there was a significant consumption in the past. On the other hand, Aloe vera plant, which production in Canary Islands is highly world representative, contains more than 70 biologically active components which have aroused the interest for its use in aquaculture, although the enormous quantity of the generated by-products has no use at all, and has never been tested for aquaculture purposes. The objective of this study was to run the first controlled feeding test with Liza aurata in the Canary Islands, as a target species to promote its cultivation, and to evaluate the use of pure Canarian Aloe vera against different levels of the by-product, to determine the effects in growth, health, and quality parameters. Therefore, 5 diets were formulated to contain 0% of aloe inclusion (diet control), 2% of pure form of aloe (diet P2), and 2, 4 and 6% of aloe by-product (diets BP2, BP4 and BP6). At 91 days of feeding, growth, proximal and fatty acid composition of liver, muscle and whole body, serum lysozyme, serum antibacterial activity, and malonaldheyde content of liver and whole body, were measured. According to obtained results, up to 6% of the aloe by-product could be included in diets for this species, without any rejections in growth or quality parameters, although no improved results compared to the control fish could be observed. Further studies are on the way to determine the sustainability and bioeconomic impact of present results, to gain knowledge on their direct industrial applications.