Marine amphipods as a new live prey for ornamental aquaculture: exploring the potential of Parhyale hawaiensis and Elasmopus pectenicrus

Supplementary data from the scientific paper contribution " Marine amphipods as a new live prey for ornamental aquaculture: exploring the potential of Parhyale hawaiensis and Elasmopus pectenicrus". Marine amphipods are gaining attention in aquaculture as a natural live food alternative to traditional preys such as Artemia, as they are rich in essential nutrients such as the lipids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are an important natural diet of many marine fish of commercial interest, and are relatively easy to culture in large numbers. However, there are no established culture techniques and a deeper knowledge on the reproductive biology, nutritional profiles and culture methodologies is still needed to potentiate the optimization of mass production. The present study assessed for the first time the aquaculture potential of Parhyale hawaiensis and Elasmopus pectenicrus, two cosmopolitan marine gammarids (as per traditional schemes of classification) that naturally proliferate in the wild and in aquaculture facilities. For that purpose, aspects of the population and reproductive biology of wild populations were characterized and then a series of laboratory-scale experiments were conducted to determine the amphipod productivity, the time needed to reach sexual maturity by the newborns (generation time), cannibalism degree, the effects of sex ratio on fecundity and the effects of diet (shrimp diet, plant-based diet and commercial fish diet) on fecundity and the juvenile growth. P. hawaiensis, unlike E. pectenicrus, was easily kept and propagated in laboratory conditions, performing exceedingly better than E. pectenicrus. P. hawaiensis showed a higher total length (9.3 ± 1.3 mm), wet weight (14.4 ± 6.2 mg), dry weight (10.5 ± 4.4 mg), females/males sex ratio in the wild (2.24), fecundity (12.8 ± 5.7 embryos per female), and gross energy content (16.71 ± 0.67 kJ g-1) with respect to E. pectenicrus. Although the P. hawaiensis juvenile growth was slightly reduced (marginally significant) by the use of a plant-based diet compared to a commercial shrimp and fish diet, fecundity was not affected, supporting the possible use of inexpensive diets to mass produce amphipods as live or frozen food. Possible limitations identified were their quite long generation times (50.9 ± 5.8 days) and relatively low fecundity levels (12.8 ± 5.7 embryos per female). With an observed productivity rate of 0.36 ± 0.08 juveniles per amphipod couple per day,