Abstract
Background: Fish meat represents an essential source of animal protein worldwide and possesses a significant nutritive value, especially in Egypt. Anisakid nematodes are the most abundant parasites among various species of marine fishes. These worms could alter the chemical properties of fish tissue reducing their quality. Objective: The current study aimed to analyze the presence of larvae in marine fish frequently consumed in Egyptian supermarkets, and to measure the chemical traits of fish, inferring the risk of
infection and its impact on the fish quality. Materials and methods: In total 435 specimens of three of the most consumed marine fish species in Alexandria, Egypt; chub mackerel (Scomber japonicus), Spanish mackerel (Scomber commerson), and Atlantic herring (Clupea harengus) were examined for Anisakid nematodes. The degree of infestation was categorized into a control group (completely free from Anisakis), a mild infection group (up to 15 larvae/100 g), a medium infection group (>15-30 larvae/100 g), and the high or heavy infection group (>30-50 larvae/100 g). The larvae were isolated, counted then fish tissues were subjected to chemical and molecular analysis. Results: Analysis showed that the overall Anisakis infestation among the examined fish species was 27.1% (118/435). The Atlantic herring represented the highest parasitic infection with Anisakis larvae (37.3%), then came the chub mackerel (23.8%), and lastly the Spanish mackerel (23.5%). Regarding the chemical quality parameters of fish samples, Trimethylamine values of the heavy Anisakis-infested samples of all chub, Spanish and herring samples were higher (mean
values 11.38, 10.61, and 11.52 mg/100g, respectively) than the control and other groups with different degrees of Anisakis infestation. Also, histamine values followed the same manner in the highest infection group (mean values 4.38, 3.78, and 5.73 mg/100g, respectively). Conclusion: The degree of Anisakis infestation in marine water fish should be considered by marketers and consumers, as it has a crucial impact on the quality parameters of fish flesh.

Key words: Anisakis; Mackerel; Quality; Trimethylamine; Histamine.