Protozoan Co-Infection Drives Fish Mortality Event in Crete's Karteros River.

Abstract

In August 2024, a significant fish kill involving hundreds of flathead grey mullet (Mugil cephalus) was reported in the delta region of the Karteros River, Crete, Greece. The investigation identified the primary cause of mortality as severe parasitic infections, specifically from the protozoan parasites Amyloodinium ocellatum and Trichodina sp., both of which heavily affected the gills of the fish. Concurrently, poor water quality in the area, likely due to reduced water volume and limited water renewal, created favourable conditions for parasite proliferation while weakening the fish's natural defences. This event raised concerns due to the location of the fish kill in the Karteros River delta, a highly protected area designated as a small island wetland.