Health assessment of grey mullet Mugil cephalus based on interrelationship between parasite co‐infections and relative condition factor

Abstract

This study aimed to assess the health status of grey mullet Mugil cephalus by means of relative condition factor under the coexisting parasite groups within seasons. Fish were captured monthly in the Lower Kızılırmak Delta in Samsun, Turkey, from December 2011 to November 2012. A total of five taxonomic groups containing 13 parasite species were constituted: Trichodina (Trichodina puytoraci, T. lepsii), Monogenea (Ligophorus cephali, L. mediterraneus, Gyrodactylus sp., Microcotyle mugilis), Digenea (Ascocotyle (Phagicola) longa, Diplostomum spathaceum, Tylodelphys clavata, Posthodiplostomum sp., Haplosplanchnus pachysomus), Acanthocephala (Neoechinorhynchus agilis) and Copepoda (Ergasilus lizae). Only one mullet was not parasitized and 13.8%, 36.3%, 29.2%, 16.2% and 4.5% were infected by one, two, three, four and five parasite groups respectively. Health assessment of mullets was performed by means of relative condition factor based on weight–length relationship estimated by robust regression methods. General linear modelling was employed to investigate any effect of season and infection load on this condition measure. Potential impacts of multiple parasitism on the community, which have been largely overlooked in the literature, were first visually revealed by relating the levels of co‐infections (in terms of prevalence and intensity) to the seasons. Then, a correlation analysis was carried out between condition estimates and the log‐ratios of relative abundances of parasite groups. The results showed that mullets suffering from Monogenea–Digenea–Acanthocephala (M–D–A) and also along with Copepoda (M–D–A–C) co‐infection had weights less than expected (Kn < 1) under winter conditions. However, Trichodina involved co‐infections appeared to prefer large sized hosts (Kn > 1) particularly in autumn.

Oxidative stress biomarkers in the African sharptooth catfish, Clarias gariepinus, associated with infections by adult digeneans and water quality

“…For instance, Lagrue and Poulin (2015) obtained a positive correlation between digenean parasite load and body condition in Gobiomorphus cotidianus McDowall, 1975. Conversely, Özer et al (2016) reported an opposite pattern in Mugil cephalus Linnaeus, 1758 suffering from infections by monogeneans, digeneans and acanthocephalans; whereas in the present study, the correlation between body condition and digenean infections/intensities was insignificant. Inconclusive data on this matter is likely due to direct interactions between hosts and parasites, as well as, external factors affecting both host condition and parasite infection independently.…”