We assessed the presence of fatty acid (FA)-sensing mechanisms in hypothalamus of Senegalese sole (Solea senegalensis) and investigated their sensitivity to FA chain length and/or level of unsaturation. Stearate (SA, saturated FA), oleate (OA, monounsaturated FA of the same chain length), α-linolenate [ALA, a n-3 polyunsaturated fatty acid (PUFA) of the same chain length], and eicosapentanoate (EPA, a n-3 PUFA of a larger chain length) were injected intraperitoneally. Parameters related to FA sensing and neuropeptide expression in the hypothalamus were assessed after 3 h and changes in accumulated food intake after 4, 24, and 48 h. Three FA sensing systems characterized in rainbow trout were also found in Senegalese sole and were activated by OA in a way similar to that previously characterized in rainbow trout and mammals. These hypothalamic FA sensing systems were also activated by ALA, differing from mammals, where n-3 PUFAs do not seem to activate FA sensors. This might suggest additional roles and highlights the importance of n-3 PUFA in fish diets, especially in marine species. The activation of FA sensing seems to be partially dependent on acyl chain length and degree of saturation, as no major changes were observed after treating fish with SA or EPA. The activation of FA sensing systems by OA and ALA, but not SA or EPA, is further reflected in the expression of hypothalamic neuropeptides involved in the control of food intake. Both OA and ALA enhanced anorexigenic capacity compatible with the activation of FA sensing systems.

Oyster reefs are among the most threatened marine habitats globally. In Europe, oyster reefs have been extirpated from most locations within their historical range. Active restoration of the native oyster (Ostrea edulis) in Europe has grown substantially in recent years. In sharing experiences between oyster restoration projects in Europe at the Native Oyster Restoration Alliance conference, NORA2, in Edinburgh in May 2019, it became apparent that a number of similar barriers are experienced. This study identified the top 40 questions, which, if answered, would have the greatest influence on the policy and practice of oyster restoration in Europe. Initially 71 people were consulted across 28 institutions and 11 European countries to generate 194 questions. An established process of one round of pre‐workshop voting followed by a one‐day online workshop and two post‐workshop rounds of voting resulted in the final 40 questions. Questions were broadly grouped into the following 10 themes: baselines, site selection, restoration methods, quantifying benefits, disease management, biosecurity, genetic diversity and population differentiation, policy and management, novel technologies, and current and future threats. We anticipate that this list will provide a starting point for developing collaborative projects across the NORA network, as well as assisting policy makers and funders with identifying key areas that need to be addressed in order to overcome existing barriers to scaling up oyster restoration in Europe.

The Native Oyster Restoration Alliance (NORA) supports the protection and ecological restoration of the native European oyster, Ostrea edulis, and its habitat across its current and historical biogeographical range. NORA works to overcome barriers to the conservation, restoration, and recovery of the European oyster by providing a platform for the NORA community to collaborate and participate in knowledge exchange. NORA seeks to support responsible restoration practice, in compliance with biosecurity and sustainability. Against this background, the NORA community formulated a series of specific recommendations, the Berlin Oyster Recommendation, to support native oyster restoration by developing and applying best practice with the aim to recover healthy and resilient marine ecosystems. In combination with the Standards for Ecological Restoration (SER) and the Restoration Guidelines for Shellfish Reefs, the Berlin Oyster Recommendation is a relevant tool for successful and sustainable oyster restoration in Europe. The establishment of NORA working groups will support the implementation and further development of the six corresponding recommendations. Current NORA working groups cover site selection, biosecurity, production, and monitoring. The site selection working group will address the identification of suitable sites for oyster restoration to support policy relevant decision making and the conservation, reinforcement, or reintroduction of native oysters. The biosecurity working group will develop biosecurity guidelines for native oyster restoration in Europe. The production working group will assess the potential of standards for seed oyster production and supply in order to enhance production appropriate for restoration purposes. In close collaboration with the Native Oyster Network – UK & Ireland (NON), the monitoring working group will produce a monitoring guidelines handbook to provide metrics and methods that will be suitable across the range of O. edulis projects in Europe for the documentation of restoration success and ecosystem recovery. The Berlin Oyster Recommendation was examined and interpreted by NORA experts in the context of the further development of joint guidelines for the practice of successful and sustainable native oyster restoration.

No abstract

The study of digestive physiology is an important issue in species that have been introduced in aquaculture like the spotted rose snapper (Lutjanus guttatus). The aims of this study were to describe the expression of digestive enzymes (trypsinogen, chymotrypsinogen, α-amylase, lipoprotein lipase, phospholipase A and pepsinogen) and their relation with orexigenic (neuropeptide Y, NPY) and anorexigenic (cholecystokinin, CCK) factors during the larval development and to evaluate the effect of weaning in their expression. The results showed that the transcripts of all the assayed digestive enzymes, with the exception of pepsinogen, and NPY and CCK were already present in L. guttatus from the hatching stage. The expression of all the enzymes was low during the yolk-sac stage (0-2 days after hatching, DAH), whereas after the onset of exogenous feeding at 2 DAH, their expression increased and fluctuated throughout larval development, which followed a similar pattern as in other marine fish species and reflected changes in different types of food items and the progressive maturation of the digestive system. On the other hand, weaning of L. guttatus larvae from live prey onto a microdiet between 25 and 35 DAH significantly affected the relative expression of most pancreatic digestive enzymes during the first weaning days, whereas chymotrypsinogen 2 and lipoprotein lipase remained stable during this period. At the end of co-feeding, larvae showed similar levels of gene expression regardless of the diet (live prey vs. microdiet), which indicated that larvae of L. guttatus were able to adapt their digestive capacities to the microdiet. In contrast, feeding L. guttatus larvae with live feed or microdiet did not affect the expression of CCK and NPY. The relevance of these findings with regard to current larval rearing procedures of L. guttatus is discussed.