Els Sorell (Trachurus trachurus): estudi dels paràsits i la seva conservació i durabilitat

Abstract

The aim of this work was to study the factors that affect the quality and preservation of the horse mackerel (Trachurus trachurus, F. Carangidae), for the consumer and also in order to extend its commercial life. The study was divided into three sections: the study of parasites; the migration process and excapsulation of these parasites after the death of the fish; and degradation of the fish through the study of quality indices. Parasitic nematodes belonged to two different genera of F. Anisakidae: Anisakis and Hysterothylacium. In the case of Hysterothylacium, there were always larvae of the species H. aduncum: larva 3 (L3) L4 (last stage before the adult) and step 3 to 4 larvae (L3-L4). Regarding Anisakis, we differentiated between type I and type II level (specific determination requires molecular studies), always at larval stage 3 (L3). The presence of Anisakis was observed mainly in medium-sized fish, while H. aduncum was detected more frequently in larger fish. This differential distribution of parasites was related to a change in diet depending on the size of fish. Crustaceans being the main prey of young ones and instead, fish, were the dominating prey on the old ones. Mindful that anisakids nematodes can cause problems in allergic consumers, it raised the need to know the location of these parasites in the host, not only in fresh fish but also once time had passed. Both the analysis of the distribution of the parasites and the excapsulation and migration process were done with medium-sized individuals. All the parasites were Anisakis type I. In fresh fish, parasites were observed mainly in the digestive tract. As the days passed, their presence could be observed, especially, in the visceral cavity. Parasites were never observed encapsulated in the muscles, but instead, there was penetration of parasites in the meat from the third day on.

Finally, the "Quality Index Method" (QIM) showed no significant differences in the overall analysis of all attributes and organoleptic quality of tissues, including the whole fish and the fish without viscera (gutted). Nevertheless, aspect and colour analyses of the flesh showed significant differences. Additionally there was a personal test of acceptability, which gave significant differences between the samples of whole fish and without viscera (gutted)