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Aquafeeds are formulated to contain all the essential nutrients that fishes need to keep healthy. They are highly dependent on marine ingredients: fish meal and oil. Hence, alternative ingredients which successfully replace these marine ingredients are required to result in sustainable and economical feeds. In this context, brewers' spent grain and yeast arise as alternative potential ingredients for aquafeed due their availability and nutritional content. However, reducing aquaculture's dependence on marine resources depends not only on developing alternative ingredients but also on improving their feed efficiencies.In this context, Life Brewery project (LIFE16ENV/ES/000160) proposes an enzymatical hydrolysis step prior to the stabilization process to improve the digestibility of brewers' by-products and, therefore, increases the assimilation of nutrients by fishes. Hence, optimum hydrolysis conditions for both brewers' spent grain and yeast have been defined by comparing different enzymes combination and hydrolysis conditions at laboratory scale. Afterwards, selected enzymes and conditions have been validated at industrial scale. Finally, the digestibility of different experimental diets containing both hydrolysed and un-hydrolysed ingredients from brewers' waste has been determined with positive results.Based on obtained results, it can be concluded that both hydrolysed and un-hydrolysed brewers' spent grain and yeast are suitable as alternative ingredients which successfully replace marine ingredients. Nevertheless, hydrolysis step improves ingredients efficiency and involves higher digestibility than un-hydrolysed ingredients.

Purpose The purpose of this study was to evaluate the environmental impacts linked to fish extraction on a temporal basis, in order to analyze the effect that stock abundance variations may have on reporting environmental burdens. Inventory data for the North-East Atlantic Mackerel (NEAM) fishing season were collected over an 8-year period and used to carry out a life cycle assessment (LCA). The selected fishery corresponds to the Basque coastal purse seining fleet. Materials and methods The functional unit (FU) was set as 1 t of landed round fish in a Basque port during the NEAM fishing season for each of the selected years. The selected data for the life cycle inventory were gathered from personal communication from ship owners and from a fish first sale register in the Basque Country. A series of fishery-specific impact categories and indicators were included in the evaluation together with conventional impact categories. Results and discussion Conventional LCA impact categories showed that the environmental impact is dominated by the energy use in the fishery, despite of the low fuel effort identified with respect to other purse-seining fisheries. Nevertheless, strong differences were identified between annual environmental impacts, attributed mainly to remarkable variations in NEAM stock abundance from 1 year to another, whereas the fishing effort remained relatively stable throughout the assessed years. Fishery-specific categories, such as the discard rate or seafloor impact showed reduced impacts of this fishery respect to other small pelagic fish fisheries. Finally, the fishery in balance (FiB) index identified the evolution of NEAM stock abundance for this particular fishery. Conclusion To our knowledge, this is the first fishery LCA study in which there is sufficient inventory data in order to conduct the methodology throughout a wide period of time. The outstanding variance in environmental impacts from one season to another evidences the need to expand fishery LCAs in time, in order to attain a more integrated perspective of the environmental performance of a certain fishery or species.The extension of LCA inventories in the timeline may be an important improvement for activities that rely entirely on the extraction of organisms from wild ecosystems. For instance, future research will have to determine the importance of increasing the timeline in fishery LCAs for species that do not show large stock abundance variations through time, unlike NEAM.