Parasites of Argentine anchovy in the south‐west Atlantic: latitudinal patterns and their use for discrimination of host populations

Abstract

Four stocks of Argentine anchovy Engraulis anchoita in the south‐west Atlantic, south of 34°S were identified by the use of parasites as biological tags. A total of 671 fish were examined for parasites and 19 parasite species were found in 664 Argentine anchovies. The parasite populations and both infra‐ and component communities showed marked latitudinal gradients. Cluster analyses allowed the identification of four groups, one composed of autumn samples (35–37°S) and three of spring ones. Among the latter, a Patagonian group (43–46°S) was clearly separated from a Bonaerense group, which was divided into two groups: North Bonaerense (34–40°S) and South Bonaerense (40–43°S). Autumn samples were characterized by low values of prevalence for most parasite species. Among spring samples Pseudanthocotyloides heterocotyle, Lecithochirium microstomum, Parahemiurus merus, Scolex polymorphus and Corynosoma australe were characteristic of the northern region, whereas Cardiocephaloides sp., Anisakis simplex, Contracaecum sp. and Hysterothylacium aduncum were more prevalent in southern waters. Latitudinal environmental gradients and their influence on the distribution of both zooplankton and definitive hosts, could be determinants of the clines observed.