Due to the high mortality rates and poor growth generally observed in Octopus vulgaris paralarval rearing experiments, it was decided to organize a working group in order to formulate recommendations to tackle this problem. Over a dozen scientists representing the most active current research groups related to this subject attended the meeting in Vigo, Spain, in November 2005. The aim of this working group was to determine the bottlenecks that prevent success in paralarval rearing, define the most appropriate rearing conditions, and identify required future research. This paper describes rearing techniques for the O. vulgaris paralarvae used by the different research participant teams, with regard to tank systems, feeding environment, and diets (Artemia, crustacean zoeae, sandeel flakes, copepods, etc.). Additionally, it includes other related themes such as the culture of Artemia and copepods, organisms that are commonly used in paralarval rearing. When embarking on O. vulgaris rearing it is advised to use prey rich in DHA (docosaenoic acid, 22:6n-3) and EPA (eicosapentaenoic acid, 20:5n-3), and with high DHA/EPA ratio. Such prey could be enriched Artemia, accompanied or not by crustacean zoeae or any microdiet. It is also recommended that, in future studies, values of growth and survival rates are recorded at the beginning of the benthic phase, in order to compare them to successful previous studies. Dry weight and DHA/EPA ratio of paralarvae may also be good criteria to define paralarval viability and evaluate success of the rearing system.

The ability of juvenile turbot, Scophthalmus maximus (L.), to elongate and desaturate various polyunsaturated fatty acids (PUFA) was examined in relation to their lipid composition. Triacylglycerols were the most abundant lipid class present in the fish and phosphatidylcholine was the predominant phospholipid. In all lipid classes examined the levels of (n-3) PUFA exceeded that of (n-6) PUFA. 18C PUFA were minor components in comparison with 20:5(n-3) and 226(n-3). 20:4(n-6) was present in highest concentration in phosphatidylinositol in which it accounted for 16.9% of the fatty acids. When the fish were injected with either i4C-labelled 18:2(n-6), 18:3(n-3), 20:4(n-6), 20:5(n-3) or 22:6(n-3) the highest percentage recovery of radioactivity (69%) in body lipid was observed with 22:6(n-3). With all labelled substrates free fatty acids contained only a small proportion of the total recovered radioactivity whereas triacylglycerols were highly labelled. Phosphatidylcholine/sphingomyelin was the most highly labelled polar lipid fraction. With W-20:4(n-6) as injected substrate, 23.2% of the radioactivity recovered in total lipid was present in phosphatidylinositol in comparison with less than 6% with the other substrates. Only small proportions of radioactivity from "CC-18:2(n-6) and '%-18:3(n-3) were recovered in the 20 and 22C fatty acids of triacylglycerols and total polar lipid. With I4C-20:5(n-3) as substrate, 27 and 33% of the total radioactivity recovered in the fatty acids of triacylglycerols and polar lipids respectively was present in 22C fatty acids. The corresponding values for '%-204(n-6) as substrate were 19 and 18%. The results confirm the limited capacity of turbot to convert 18C PUFA to longer chain PUFA but demonstrate their ability to synthesize 22C PUFA from 20C PUFA. They also suggest a small but specific requirement for 20:4(n-6).

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Blackspot seabream, Pagellus bogaraveo (Brunnich), has been identi¢ed as a potential species to diversify European aquaculture production. Although rearing aspects have been widely investigated, little information exists on the nutritional requirements for this species. The aim of this study was to build up information on the activity of digestive enzymes at certain developmental stages of blackspot seabream in order to understand the nutritional needs of larvae and post larvae. Fish larvae were reared from hatching to 55 days after hatching (dah), and the feeding plan consisted in rotifers (5^35 dah), Artemia naupli (303 5 dah) metanaupli (35^45) and Gemma microdiet (45^55 dah). At 7, 11, 21, 45 and 55 days after hatching (dah), pooled samples of ¢sh larvae were collected for analysis of trypsin, amylase, lipase, alkaline phosphatase and leucine^alanine peptidase activity. Up to 21dah, the whole larvae body was used for enzymatic analysis, whereas in older larvae only the dissected abdominal cavity was used. Blackspot seabream body dry weight growth was exponential, increasing from 60 mg at 5 dah to 30 AE 9.7 mg at 55 dah. Amylase speci¢c activity decreased signi¢cantly during development, exhibiting at 11dah (0.6 U mg À1 protein) an average value 2.7 times lower than at 7 dah, and remaining stable between 45 and 55 dah (0.7 U mg protein À1 ). Trypsin speci¢c activity remained constant until 21dah (between 38 and 44 mU mg protein À1 ), which could be related to the larvae feeding regime. At later stages of development, lipase-speci¢c activity exhibited a signi¢cant increase (Po0.05), being three times higher at 55 dah (8 U mg protein À1 ) than at 45 dah. The total activity of the studied digestive enzymes increased signi¢cantly during larval development (until 21dah), whereas afterwards only lipase and leucine^alanine peptidase increased signi¢cantly between 45 and 55 dah. The pattern of digestive enzymes activity was related to organogenesis and the type of food used at di¡erent developmental stages. Digestive enzyme activity during P. bogaraveo development L Ribeiro et al.