External lesions and flesh parasites in commercial fishes of Nigerian inshore waters

Abstract

Commercial fish species from the east Nigerian Coast were cxamined for extcrnal lesions and flcsh parasitic infections that may affect thcir consumahility. Altogether, 2 886 specimens from 43 species representing 34 genera werc sampled. The occurrence of lymphocystis disease in the pleuronectiform Cynoglossus senegalensis is here rcported for thc first time from an African marinc teleost. Other external lesions of fishcs cncountered were fin rot, granulomas, pseudotumours and ulcers with total prevalences not exceeding 1 %. The following commercial fish spccics were infectcd by muscle parasites at thc given prevalcnces: Cynoglossus brouni (mctaccrcariae, 18%, Capilluriu b pino osa cggs, 27%; Echinocephalus sinensis L3 larvae, 9%; Philomerru beninensis, 27%); C. senegulensis (Kudou sp., 10%; metacercariac, 87%); Pseudotolirhus bruchygnuthus (Hysterothylucium sp. larvae, 2%); P. srnegulensis (Poeciluncistrum cf caryophyllum plerocercoid, 1 %; Philometru beninensis, 1 %); P. typus (Kudou sp., 3%); Synapturu cadenati (Echinocephalus sinensis, 12%); Stromuteus jÏutola (trypanorhynch plcrocer- coid, 44%); Epinephelus aeneus (didymozoid trematode, 44%; Hy~terothyluciunz sp. larvae, 6%). Cupillrr- ria and Echinocephalus, representing helminths with zoonotic potential, present low risks to public health due to their low prcvalences and the local methods of preparing fish for consumption. Apart from C. spinosa eggs in soles and trypanorhynch plerocercoids in S. fiutola, none of the other flcsh parasites are likely to affect the market value of thcir hosts at the rccorded levels of occurrence. Carcharhinid sharks influence the occurrence in the locality of most flesh-parasitic helminths for which they serve as definitive hosts. The absence of the third stage larvae of zoonotic Anisakidac common in marine fishes from many other parts of the world is related to the unavailability of suitable hosts. Compared to the results from most temperate locations whcre similar studics have been earried out, the present study shows remarkably low prevalences and diversity for external lesions and flesh parasites in West African marine fishes.