Spatial variation of larval ascaridoid nematode (Nematoda: Chromadorea: Ascaridoidea) infections in the Black Sea anchovy (Engraulis encrasicolus)

Abstract

This study evaluates the Black Sea anchovy population infected by parasitic Ascaridoid Nematode larva in the Southern Black Sea. It assesses the larva?s effect on fish body condition, energy stored in the body, and anchovy growth. For this, anchovies sampled on July 10-31, 2018, from 30 different stations were examined, and 11.8% of the 825 anchovies were found infected. The observed infection rate was higher on the western side of the study area, suggesting that this rate may be used as a biomarker for the western stock. Age and size of the anchovies play a significant role in the prevalence. Both of the fish well-being indicators (condition and hepatosomatic index) were lower in the parasitized fish. It may support the view that the larva weakened its paratenic host against its predator to facilitate its transfer to a definite host. The observed low infection rate, which is not considered an economic threat to fisheries, is linked to the warm-affinity of the anchovy. Moreover, considering the trophic role of the anchovy in the ecosystem, it is very likely that the infestation rate at the upper trophic levels is higher than that of anchovy. Therefore, a better understanding of the life cycle of the Nematodes in the Black Sea, their hosts in their life cycle, and the consequences of climate change is essential.