Lipid profiles of Mediterranean moray, Muraena helena, European conger, Conger conger, and European eel, Anguilla anguilla (Actinopterygii: Anguilliformes)

Background. The current topics in fish fatty acid (FA) research include qualitative comparisons, trophic transfer as nutritive sources of FA, evolutionary comparison of synthesis pathways, and potential application of most efficient fish desaturases and elongases. FA are scarcely investigated in Elopomorpha and Anguilliformes, except for common- and Japanese eels. In this study determines the differences in lipid composition of FA between species of the order Anguilliformes, representing three families, Mediterranean moray, Muraena helena Linnaeus, 1758; European conger, Conger conger (Linnaeus, 1758); and European eel Anguilla anguilla (Linnaeus, 1758) (thereafter moray, conger, and eel, respectively). These are the first results on FA for the moray. Materials and methods. The fishes were collected in September 2011 on the Croatian coast of the Adriatic Sea, including the Neretva River estuary. Total lipids were extracted and the fatty acid profile in total lipid isolates were determined by gas chromatography of the corresponding methyl esters, obtained by acid methanolysis. A Hewlett Packard HP 5890A capillary gas chromatograph equipped with flame ionization detector (FID) was used. Results. Both moray and conger were less fatty than eel but had higher ω FA content, especially ω-3. Moray and conger, contained more proteins than lipids, while in eel, lipids exceeded the crude protein content. Conger was the leanest fish among the three. The qualitative SFA, MUFA, and PUFA were species specific (myristic FA characteristic for moray). PUFA were higher in moray and conger, due primarily to DHA. Moray showed the most favourable qualitative lipid content and profile and best ratio of ω-3 to ω-6 FA. Moray had 7.6- and conger 11-fold more DHA than eel. Approximate ratios along ω-3 biosynthesis pathway, show that there was 6-fold more EPA than α-LNA in moray and conger, and only 1.64- in eel, 5.63-fold, and 11.27-fold more DHA than DPA in Mediterranean moray and conger, respectively, and only 1.03-fold more in eel Approximate ratios along ω-3 biosynthesis pathway, show that there was 6-fold more EPA than α-LNA in moray and conger, and only 1.64-fold in eel. DHA was 5.63-fold, and 11.27-fold more abundant than DPA in moray and conger, respectively. In comparison, eel had only 1.03-fold more DHA than DPA. Conclusion. Although trophic status and environment are the most determined, the differences in individual FA ratios might indirectly suggest different physiological utilization of elongation pathways in each species. Presently reported results draw focus on Muraena helena and Conger conger to be included in the studies elongase and desaturase pathways in teleost fish

Sustainable large‐scale production of European flat oyster ( Ostrea edulis ) seed for ecological restoration and aquaculture: a review

The conservation and active restoration of European flat oyster (Ostrea edulis) populations are a major focus of ecological restoration efforts to take advantage of the wide‐ranging ecosystem functions and services this species provides. Accordingly, additional and new demands for seed oysters have arisen. In commercial aquaculture (mariculture), the production of O. edulis is still largely based on natural seed collection. Considering the specific requirements, related to ecological restoration, such as the absence of pathogens and the preservation of high genetic diversity, the current supply is insufficient. Despite the development of breeding and controlled reproduction techniques for this species since the late 1930s, seed production today is mainly based on empirical concepts. Several of the issues that producers still face are already subjects of research; many others are still unanswered or even unaddressed. This review provides a summary of all available knowledge and technologies of O. edulis seed production. Furthermore, it provides a detailed reflection on implications for restoration, future challenges, open questions and it identifies relevant research topics for sustainable seed supply. The study covers the following aspects on (i) biology of the species, (ii) stressors – including pathogens and pollutants, (iii) genetics, (iv) history of production technologies, (v) seed production in polls, (vi) seed production in ponds and (vii) seed production in hatcheries. Future research needs on sex determinism, gametogenesis, cryopreservation, nutrition, selective breeding, pathogens and disease, and the development of reliable protocols for production are highlighted