The results of bioeconomic analysis informed by a survey of 80 small-scale mud crab farmers in Vietnam are presented in this paper. Mud crab farming in Vietnam is profitable, with net revenue being approximately 135 and 41 million VND/year (USD 7000–USD 2100 per year) in the central and southern regions, respectively. Profitability was significantly higher in the centre compared with the north, as almost three times the biomass is harvested in the centre compared with the south (in turn, due to higher aquaculture area and survival rates). The benefit–cost ratio (the ratio between total revenue and total costs) is 3.55 in the centre and 1.97 in the south. The crabs are fed almost exclusively on low-value finfish in the centre and the south. Feeding rates were found to be low, with 95% of biomass gain coming from natural feed in the environment rather than supplementary feeding by the farmer. If pellets are to be adopted widely by mud crab farmers, negative perceptions regarding the poor adaptability of mud crab to pellets (northern farmers only), relatively slow growth rates compared with low-value finfish and lack of availability of pellets need to be overcome.

Bioeconomics of mud crab, Scylla paramamosain, culture in Vietnam

This study investigated the antioxidant activity and functional properties of fractionated cobia skin gelatin hydrolysate (CSGH) at different molecular weights (10, 5 and 3 kDa). Antioxidant activities studied included reducing power, ferrous ion chelation, DPPH (1, 1diphenyl-2picrylhydrazyl) radical scavenging, and superoxide anion scavenging. Functional properties studied included emulsifying and foaming properties as well as fat and water binding capacity. Results showed significant differences (p <0.05) between the chelating activity of ferrous and superoxide anions for 5 kDa and other fractions, while the highest DPPH radical scavenging activity was presented by the 3 kDa fraction. The 10 kDa fraction had the highest fat binding capacity (28 ± 2%) while functional properties were not affected by lower molecular weight. Lower outcomes obtained for functional properties from smaller molecular weights may have been due to enzymatic hydrolysis and the fractionation process to which the hydrolysate was subjected. Hence, varied CSGH molecular weights appeared to benefit different functions.

Antioxidant activity and functional properties of fractionated cobia skin gelatin hydrolysate at different molecular weight.

The high cost and limited availability of fish oil makes plant-derived lipids attractive for aquafeed manufacturing, but replacing fish oil with these lipids can result in long-chain polyunsaturated fatty acid (LC-PUFA) deficiencies. Fatty acid metabolism, specifically the efficiency of LC-PUFA utilization, may be influenced by the dietary saturated fatty acid (SFA) content versus that of C18 polyunsaturated fatty acids (PUFAs). We assessed the growth and tissue composition of Cobia Rachycentron canadum (55.3 ± 0.2 g initial weight [mean ± SE]; 10 fish/tank, 3 tanks/diet) fed diets (∼49% protein, ∼10% lipid) containing fish oil; 22:6(n-3)–amended standard, partially hydrogenated, or fully hydrogenated soybean oil; and these same soybean oils supplemented with soybean lecithin for 8 weeks. Although survival (range = 97–100%), final weight (160–189 g), and feed conversion ratio (1.40–1.52) were unaffected by diet, differences were observed in weight gain (185–241%), specific growth rate (1.87–2.19%...

Saturated Fatty Acids Limit the Effects of Replacing Fish Oil with Soybean Oil with or without Phospholipid Supplementation in Feeds for Juvenile Cobia

We examined growth performance and the lipid content in juvenile cobia, Rachycentron canadum, fed a taurine supplemented (1.5 %), plant protein based diet with two fish oil replacements. The first fish oil replacement was a thraustochytrid meal (TM + SOY) plus soybean oil (~9 % CL) and the second was a canola oil supplemented with the essential fatty acids (EFA) docosahexaenoic acid (DHA) and arachidonic acid (ARA) (~8 % CL). The diet using the thraustochytrid meal plus soybean oil performed equivalently to the fish oil diet; both resulting in significantly higher growth rates, lower feed conversion ratios, and higher survival than the supplemented canola oil diet, even though all three diets were similar in overall energy and met known protein and lipid requirements for cobia. The poor performance of the canola oil diet was attributed to insufficient addition of EFA in the supplemented canola oil source. Increasing levels of EFA in the supplemented canola oil above 0.5 g EFA kg−1 would likely improve results with cobia. When fish fed either of the fish oil replacement diets were switched to the fish oil control diet, fatty acid profiles of the fillets were observed to transition toward that of the fish oil diet and could be predicted based on a standard dilution model. Based on these findings, a formulated diet for cobia can be produced without fish products providing 100 % survivorship, specific growth rates greater than 2.45 and feed conversion ratios less than 1.5, as long as taurine is added and EFA levels are above 0.5 g EFA kg−1.

Taurine Supplementation of Plant Derived Protein and n-3 Fatty Acids are Critical for Optimal Growth and Development of Cobia, Rachycentron canadum

The project WISEFEED received funding by the European Union's H2020 programme (Marie Sklodowska-Curie grant No 691150). Additional funding from project EFISHDIGESTAGL2014-52888 (MINECO, Spain + FEDER/ERDF contribution). S.E. acknowledges a Foundation for Science and Technology of Portugal (FCT) investigator grant IF/00482/2014/CP1217/CT0005 funded by the European Social Fund, the Operational Programme Human Potential and FCT. This work also received national funds through FCT through project UDI/Multi/04326/2013 and Norwegian Agency for Development Cooperation NORHED, No. QZA-0485 SRV-13/0010.

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Effect of increased rearing temperature on digestive function in cobia early juvenile.

Cobia Rachycentron canadum aquaculture in Vietnam: Recent developments and prospects

Harvesting procedures, welfare and shelf life of ungutted and gutted shortfin pompano (Trachinotus falcatus) stored in ice

Topics covered in this symposium includes resources, trends and strategies illustrated by regional case presentations; experiences and opportunities in shrimp farming; ecological constraints on the sustainability of bivalve aquaculture.

Sustainable aquaculture : food for the future? : proceedings of the second international symposium on sustainable aquaculture, Oslo, Norway, 2-5 November 1997

Niels Svennevig

Papers

Cobia Rachycentron canadum aquaculture in Vietnam: Recent developments and prospects

Harvesting procedures, welfare and shelf life of ungutted and gutted shortfin pompano (Trachinotus falcatus) stored in ice

Sustainable aquaculture : food for the future? : proceedings of the second international symposium on sustainable aquaculture, Oslo, Norway, 2-5 November 1997