leading to economic losses in first-sale and retail services, as well as posing a risk to public health. Therefore, it is considered very important to implement measures aimed at reducing/minimizing the parasite load in fish, acting across the entire product chain, from the extraction and storage of fish, to marketing and sale to consumers. The removal and discarding of viscera on board commercial fleets is a widely used method for preventing postmortem migration of nematode larvae from the viscera to the muscle when the fish are stored onboard; this approach helps reduce the presence of larvae in the product in fish auctions and markets [17]. According to some authors, discarded infested viscera can be ingested by other predator fishes and thus re-enter the life cycle [18; 19; 20]. However, a recent experiment with farmed seabasses free of _Anisakis_ larvae showed that only a very small proportion of the nematodes ingested reinfected the host, and most of them were rapidly digested and defecated [21]. With respect to the removal of viscera, certain technological treatments aimed at inactivating _Anisakis_ larvae before discarding them into the sea have been promoted [22], but the equipment necessary on board is often expensive and bulky. The space limitations on board and the lack of economic incentives for fishermen result in the viscera being thrown to the sea. Moreover, the presence of high infestation levels of _A. simplex_ in the viscera casts doubt on this practice due to the unknown impact it may have in the trophic chain and the possibility of recovering the viscera with other fish processing byproducts as raw material for feed. Total EU aquaculture production increased by 6% from 2011 to 2020 and is expected to increase from 13 to 32% between 2018 and 2030 [23]. Fishman and oil are the preferred sources of highly digestible essential nutrients for aquaculture species. A growing share of fishmeal and fish oil for aquaculture feeding, estimated at 25-35%, is produced from fish processing byproducts. However, previous studies have detected trace amounts of _Anisakis simplex_ allergens in samples of sushi and slaughter-ready farmed salmon [24], suggesting a possible origin in the feed, and further studies have shown that _Anisakis_ allergenic peptides can withstand aquaculture feed processing and be transferred to fish tissue, with the risk of causing symptoms in sensitized consumers [25]. The European hake (_Merlucius merlucius_) is a target species caught mainly by bottom trawlers in European multi-specific fisheries and by demersal and bottom gillmetters [26]. In the Basque Country, landings of European hake reached 4983 tons in 2021; medium-large individuals are normally gutted on board and marketed fresh. According to the total visceral weight relationship in hakes [27], the production of hake viscera in Basque ports was estimated at 438.5 tons in 2021. However, hake (_Merlucius merlucius_) captured on the Atlantic coast of Spain exhibits high infestation levels of _Anisakis_[28; 29]. A simple and economically feasible processing method that can inactivate or destroy _Anisakis_ allergens, allowing the use and exploitation of fish viscera, would be highly useful for the Basque fleet. Although some studies have evaluated the resistance of _Anisakis simplex_ allergens to human gastric enzymes [30; 31], there are no previous studies on how acid autolysis, known as silage, can affect _Anisakis simplex_ and its allergenic potential. Although a serine protease inhibitor similar to the trypsin inhibitor found in soya beans has been identified in _Anisakis_ larvae [32] and may play a role in the defense against host digestion, it should not inhibit the acid aspartic protease (pepsin) present in the viscera, and the effect of long-term treatment has not yet been observed. Thus, the objective of this work was to study the silage of hake viscera as an alternative for the use or exploitation of discarded viscera to reintroduce them into the food value chain.