Anisakis disease in commercial fish
The extent of Anisakis disease in commercial species such as anchovy and hake in the north-west Atlantic is an indicator of its response to sea warming, due to its preference for warm, temperate waters. This indicator describes the presence of Anisakis in commercial species from 1998 to the present day. It is an important application index for fisheries and health.
- The distribution of the incidence of the different Anisakis species depends on the habitat of their hosts, which include fish and marine mammals, and the temperature of the sea.
- The incidence of Anisakis spp. in fish of commercial interest in the last two decades has increased in the north-west Atlantic.
Relationship of the indicator to climate change
Anisakis is a genus of parasitic nematodes whose life cycle affects fish and marine mammals, in which it can cause damage to the digestive tract. The consumption of fish that have been infected by Anisakis poses a risk to human health and is one of the factors that affect the quality of fish products on European markets.
Climate change may alter the distribution of species that are vectors of disease, increasing or decreasing their range and distribution, depending on whether conditions are favourable or unfavourable for their breeding sites. In the case of Anisakis, the reproductive cycle is complex and depends on its host species of zooplankton, fish and marine mammals; consequently, the range of its distribution is strongly dependent on the range and distribution of its hosts and on future changes in their habitats caused by ocean warming (Kuhn et al. 2016).
Prevalence and abundance
Trend in the abundance and prevalence of Anisakis spp. in fish in the Atlantic between 1998 and 2019. Source: Díez et al. (2022).
The trend analyses carried out show an increase in the incidence of Anisakis in fish over the last two decades (1998-2020) in the north-west Atlantic at an annual rate of 32 nematodes per specimen examined (Figure 2) (Díez et al. 2022).
Figure 1. Probability of the presence of Anisakis spp. Source: Díez et al. (2022).
The incidence of Anisakis spp. parasites in pelagic species of commercial interest (anchovy and hake) can be measured by two indicators:
- Prevalence of infestation (%): percentage of the number of infested specimens of the species examined in relation to the number of specimens examined.
- Abundance of infestation: ratio of the total number of nematodes in relation to the total number of specimens of the species examined.
Data on occurrence from the GBIF public biodiversity database (GBIF.org (2021) https://www.gbif.org/) and data on incidence compiled and analysed for hake and anchovy by AZTI (Díez et al., 2022) were used to carry out the trend analysis on the incidence of Anisakis. The relationship between the presence of Anisakis and sea temperature was also studied using habitat models in order to interpret the trends (see Figure 1) (Díez et al., 2022).
Kuhn, T., S. Cunze, J. Kochmann, and S. Klimpel. 2016. Environmental variables and definitive host distribution: a habitat suitability modelling for endohelminth parasites in the marine realm. Scientific Reports 6:30246.
Diez, G., G. Chust, E. Andonegi, M. Santurtún, C. Abaroa, E. Bilbao, A. Maceira, and I. Mendibil. 2022. Analysis of potential drivers of spatial and temporal changes in anisakid larvae infection levels in European hake, Merluccius merluccius (L.), from the North-East Atlantic fishing grounds. Parasitology Research. https://doi.org/10.1007/s00436-022-07446-2.
North-west Atlantic
32 nematodes
Per specimen examined per year