What question did this study set out to answer?

This study aims to document the anisakid nematodes infecting thread herrings and assess food safety implications.

May 9, 2026Open Access

Anisakid nematodes in thread herrings from the Gulf of California: food safety considerations and spatial patterns in parasite assemblages

DLDania López-MorenoAutonomous University of Sinaloa JCJosé A. Cruz-BarrazaUniversidad Nacional Autónoma de México EMEmigdio Marín‐EnríquezAutonomous University of Sinaloa

Key Points

This study aims to document the anisakid nematodes infecting thread herrings and assess food safety implications.
Examined 306 Opisthonema libertate, 25 O. medirastre, and 89 O. bulleri from various fishing grounds between 2022 and 2023.
Molecular analyses of ITS rDNA region confirmed anisakid species and assessed spatial patterns in parasite assemblages.
Utilized multivariate analyses to evaluate infracommunity structure across fishing grounds.
Identified 140 third-stage anisakid larvae from O. libertate, with rare infections in other species.
Confirmed presence of Contracaecum bioccai and an unidentified Contracaecum species.
Observed significant spatial variation in parasite assemblages, reaffirming reproducible patterns in the Gulf of California.

Abstract

Thread herrings (Opisthonema spp.) are ecologically and economically important small pelagic fishes in the Gulf of California, yet their parasitic fauna remains poorly documented. Given their role in regional fisheries and marine food webs, clarifying the identity of anisakid nematodes infecting these fishes is relevant for food safety surveillance. In this study, we examined 306 individuals of Opisthonema libertate, 25 of O. medirastre, and 89 of O. bulleri collected from multiple fishing grounds between 2022 and 2023. A total of 140 third-stage anisakid larvae were recovered from O. libertate, whereas infections were rare in the other two host species. Molecular analyses of the ITS rDNA region confirmed the presence of Contracaecum bioccai and revealed an additional Contracaecum species that could not be assigned to species level. Although infection intensities were low, the occurrence of anisakid nematodes belonging to a genus that includes species associated with anisakidosis highlights the importance of continued monitoring of small pelagic fishes in the region. In addition to anisakids, the parasite assemblage of O. libertate was dominated by digeneans, and multivariate analyses revealed significant spatial variation in infracommunity structure across fishing grounds. Similar spatial patterns reported previously were also detected in the present survey, indicating reproducible interannual differences within the Gulf of California. These findings provide the first molecular confirmation of anisakid species infecting O. libertate in the region and underscore the complementary value of parasitological research for food safety and fisheries science.

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