The yellow mullet fish oil from the Banc d’Arguin Imrâguens in Mauritania: an example of polyunsaturated fatty acids transfer from diatoms to the fish within the alimentary chain

Abstract

The Banc d’Arguin National Park (PNBA) in Mauritania is listed by the UNESCO World Heritage. It is characterized by an exceptionnal marine biodiversity with numerous endemic species and it provides a major site of reproduction for western Africa fish. The Imrâguens form fisherman communities established at Banc d’Arguin, who live upon fishing the yellow mullet (Mugil cephalus) during its migration and derived products. The fish oil produced by Imrâguens from mullet heads is rich in omega 3 polyunsaturated fatty acids (37.7 % of total fatty acids). The main fatty acid is eicosapentaenoic fatty acid (EPA ; 20.18 ± 0.01 %). This fatty acid is particularly abundant in diatoms, that contribute to 20- 30% of mullet feeding. The identification of 16:4n-1 also provide a good trophic marker for yellow mullet feeding on diatoms. The lipases potentially involved in the mobilization of these fatty acids in the course of digestion of diatoms were identified from the analysis of Mugil cephalus genome. Genes encoding a lipase homologous to gastric lipase and four lipases homologous to pancreatic carboxylester hydrolase or bile-salt stimulated lipase were identified. These later could be involved in the lipolysis of galactolipids, the main lipids present in diatom photosynthetic membranes which are rich in EPA. These data provide an added value to the traditional fishing practice of Imrâgens and highlight the nutritional value of the fish oil they produce.