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In Eurasian perch (Perca £uviatilis), the variability in spawning quality is a major limiting factor for successful production, especially when breeders are fed with an arti¢cial diet. The in£uence of the dietary DHA/EPA/AA ratio on the egg and larval quality and on the fatty acid and lipid class composition of eggs has been investigated in perch broodstock. Two experimental diets (16% lipids) with two di¡erent DHA/EPA/AA ratios, D1 (3/2/2) and D2 (23/9/1), were compared with a natural diet consisting of cultured carp juveniles, CC (10/10/1) and with a commercial diet for salmonids, CDS (14/16/1). Percentages of fertilization and hatching were comparable between ¢sh fed D1, D2 and CC, with the highest hatching rate observed for D1 (63.5 AE 3.8%). These diets supported better values than the CDS. Larval survival and TL50 observed after osmotic stress were higher for the D1 group, followed by larvae produced by ¢sh fed D2 and CC. Larvae from ¢sh fed D1, D2 and CC were signi¢cantly more robust than larvae from the CDS group. Di¡erences were observed regarding the fatty acid (FA) pro¢le in the eggs, which was related to the dietary FA composition. The results indicate that a ratio of 3/2/2 seemed to be e¡ective for obtaining eggs and larvae of good quality.

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The aim of this work was to study the fatty acid (FA) bioconversion ability in Eurasian perch fed with diets differing in their polyunsaturated fatty acids (PUFA) from n-3 and n-6 series content at two development stages: adults in exogenous vitellogenesis, and juveniles during the on-growing phase. Duplicate groups of adults and juveniles were fed for 12 weeks with four diets: D1 and D2, two diets prepared with fish oil partially or totally as the lipid source, and so containing long-chain PUFA (LC-PUFA). Those two diets differed by their n-3/n-6 FA dietary ratio (0.2 and 7.0, respectively), D1 being characterized by a high n-6 LC-PUFA level, while D2 had a high level of n-3 LC-PUFA. D3 and D4 were constituted only with vegetable oils, and were therefore devoid of LC-PUFA. D3 was characterized by a high level of 18:2 n-6 (n-6/n-3 ratio of 0.3), while D4 was characterized by a high level of 18:3 n-3 (n-3/n-6 ratio of 1.9). Both groups of fish were able to elongate and desaturate the 18:3 n-3 precursor into eicosapentaenoic acid and docosahexaenoic acid, regarding the FA profile of livers. Furthermore, total elongation/desaturation from [1-14C]18:3 n-3 of LC-PUFA was higher in fish fed with the high dietary 18:3 n-3 level compared to the diet rich in n-3 LC-PUFA. By opposition, the bioconversion of 18:2 n-6 into LC-PUFA was limited, regarding the elongation/desaturation activity of LC-PUFA from [1-14C]18:2 n-6. In view of the great ability for bioconversion of n-3 FA, linseed oil is a promising alternative to fish oil in formulating feed for juveniles perch as there were no differences in terms of specific growth rate between the treatments, but adults undergoing maturation should have at least partially LC-PUFA in their diet, particularly arachidonic acid (ARA) which is important during maturation, as breeders are not able to bioconvert 18:2 n-6 into ARA

The effects of docosahexaenoic, eicosaenoic and arachidonic acids (DHA, EPA and ARA, respectively) on sex-steroid and prostaglandin (PG) production were investigated in Eurasian perch (Perca fluviatilis) follicles using an in- vitro incubation technique. Only ARA was able to induce the production of 17,20β-dihydroxy-4-pregnen-3-one (DHP), the hormone produced by vitellogenic follicles undergoing final meiotic maturation, as well as the production of PGE2 and PGF2α by the follicles. This work also investigated, using a preliminary pharmacological approach, the presence of a functional PGE2-like receptor in fish follicles. Exogenous PGE2 and butaprost (specific agonist of the EP2 receptor) stimulated DHP production. A second experiment assayed the cyclic adenosine monophosphate (cAMP) production by the follicles after 24 h of incubation with the agonist and antagonist of the EP2 receptor. As observed in mammals, we concluded that the cAMP produced in response to PGE2 was probably mediated by an intracellular mechanism via a PGE2-like receptor. This is the first pharmacological indication of this type of receptors in fish follicles. This study also indicates that ARA, and its derivatives, PGE2 and PGF2α, may act on final follicle maturation in Eurasian perch.

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