Partial Substitution of Fishmeal and Fish Oil in a Semi-Purified Diet for Noble Crayfish, Astacus astacus (Linnaeus, 1758)

Abstract

Continuous environmental disturbances and the crayfish plague have restricted freshwater crayfish populations in Greece. Therefore, the need for the establishment of a repopulation policy in Greece and the increasing commercial interest for the species, dictated in the Thessaly County, have imposed the investigation of the optimum husbandry and dietary requirements of Astacus astacus in culture conditions. Hundred and five adult crayfish were placed in cement tanks for 60 days and fed a semipurified diet, whereas 90 adult crayfish were placed in similar cement tanks for the same time period and fed a control diet consisting of fresh fish and carrots. The semipurified diet had a Protein: Energy ratio of 21.29 mg Prot. kJ–1, a protein level of 37.95%, and a lipid level of 9.6% (on a Dry Matter basis). By the end of the experiment, crayfish fed the semipurified diet gained almost 5 g of weight with acceptable survival rates. Despite the total substitution of corn oil by soy oil and the partial substitution of fish oil (by 3%) and fishmeal (by 7%) with other plant-derived materials, in comparison with their levels in the semipurified diet of a previous experiment, dietary linoleic, and linolenic acids have been substantially high whereas dietary arachidonic acid and EPA, DHA have been somehow lower compared with the respective ones of the semipurified diet of a previous experiment. Although EPA tail muscle tissue has been progressively augmented throughout the experiment, DHA respective levels seemed to stay unaffected and at similar levels throughout the experiment. These results dispute the ability of noble crayfish for bioconversion of EPA to DHA and call for further investigation.