Aplicaciones de los anfípodos (Crustacea: Peracarida: Amphipoda) en acuicultura

Abstract

Coastal protection, nutrient cycling, erosion control, water purification, and carbon sequestration are ecosystem services provided by salt marshes. Additionally, salt ponds offer coastal breeding and a nursery habitat for fishes and they provide abundant invertebrates, such as amphipods, which are potentially useful as a resource in aquaculture. Fishmeal and fish oil are necessary food resources to support aquaculture of carnivorous species due to their omega-3 and omega-6 long-chain polyunsaturated fatty acids (LC-PUFA). Currently aquaculture depends on limited fisheries and feed with elevated n-3 LC-PUFA levels, but the development of more sustainable food sources is necessary. Amphipods are crustacean with high nutritional quality and great potential to be reared as food for species of aquaculture interest. They play a fundamental rol in energetic exchange of trophic chain as predators’ resource. They appear to be a potential high quality alternative feed resource for aquaculture. The present thesis tries to explore the next questions: i) How important are amphipods in diet of species of commercial interest in aquaculture; ii) What nutritional composition have the amphipods species terrestrial ponds?; iii) How can be cultured and what nutritional value have the amphipods fed with different diets under laboratory conditions? and iv) Is it possible use the amphipod as alternative food recourse with species of commercial interest?. Hence, a nutritional study was carried out for several main amphipod species -Microdeutopus gryllotalpa, Monocorophium acherusicum, Gammarus insensibilis, Melita palmata and Cymadusa filosa- in terrestrial ponds in the South of Spain. These species showed high protein content (up to 40%), high n-3 PUFA and phospholipid levels, and high levels of phophatidylcholine (PC), phosphatidylethanolamine (PE) and triacylglycerols (TAG). Isoleucine, glycine and alanine were the dominant amino acids in all species. In addition, amphipods collected from ponds showed low levels of heavy metals. Therefore, pond amphipods are good candidates to be used as feed and are proposed as a new sustainable economic resource to be used in aquaculture. Of the five studied species, G. insensibilis may be the best for intensive culture as an alternative feed resource because it shows: 1) adequate n-3 PUFA and phospholipids composition; 2) high levels of glycine, alanine, tyrosine, isoleucine and lysine; 3) high natural densities; 4) large body size (≥1 cm), and 5) high concentration of calcium. Moreover, a combined culture of amphipods and fishes in these marsh ponds seems a promising and environmentally sustainable way to develop Integrate Multi-Trophic Aquaculture (IMTA) in these ecosystems. Two models of amphipod were used to be cultured, caprellids (Caprella equilibra and C. scaura) and gammarideans (Gammarus insensibilis). In both experiment Artemia, Phytoplankton, Detritus were used as food. In addition, Ulva was added in G. insensibilis experiment. Caprellids showed an adult survival rate significantly higher for caprellids fed with Detritus, and those fed with Phytoplankton and Detritus were richer in polyunsaturated fatty acids, especially DHA. Interestingly, caprellids fed with Detritus were also a rich source of LA (18:2-n6), considered to be an essential fatty acid in vertebrates. It was found that detritus based mainly on fish faeces and uneaten feed pellets can be considered an adequate food for adult caprellids, providing a source of both omega-3 (DHA) and omega-6 (LA) fatty acids. In the study with gammarideans, G. insensibilis was cultured for 21 days. When fed with Detritus and Ulva gammarideans also showed interesting survival rates and contributed to high concentrations of palmitic acid (16:0), oleic acid (18:1n9), arachidonic acid (20:4n6) (ARA), eicosapentaenoic acid (20:5n3) (EPA) and docosahexaenoic acid (22:6n3) (DHA). Furthermore, Gammarus insensibilis could play a key role as biorremediator being cultured with detritus and Ulva getting an adequate biochemical composition to be used in aquaculture. This amphipod could replace partial or totally the formulated diet with two consequences, no dependence of fish oil and reduction of economic costs. Finally, two experiments were done with Seriola dumerili larvae (model of commercial aquaculture species) of 22 and 44 days after hatchery. They were feed with the amphipod Gammarus insensibilis, collected from a terrestrial pond, and one formulated diet. Survival, biometry measures and chemical profile were measured. In the first experiment, G. insensiblis treatment showed better survival, although the other parameters were no different. On the other hand, in the second experiment the survival was similar, the growth was better in formulated diet but those fed with amphipod had the best chemical profile. Juveniles fed with G. insensibilis showed higher values of ARA (5.53±0.18%) and DHA (19.07±0.19%), low level of TAG (2.18±0.5%) and a coloration more similar to wild juveniles of S. dumerili. In conclusion, this thesis shows the high nutritional value of amphipods both in the wild and cultivated, and its great potential to be used as new trophic resource in aquaculture. It is interesting to explore future initiatives in the context of Integrated Multitrophic Aquaculture, where amphipods appear to be a very suitable resource, since their use as biofilters and a large-scale production can be combined at a very low cost.