Long-term monitoring on the occurrence of a myxosporean parasite Kudoa camarguensis (Myxosporean) on the common goby (Teleostei, Pisces) Pomatoschistus microps

The evolution of a host-parasite system composed of Pomatoschistus microps- Kudoa camarguensis was investigated in the Vaccares lagoon (Rhone river Del ta, France) from 1993 to 1997. During this long-term monitoring, centennial flooding of the Rhone river occurred, leading to an inrush of about 110 mi llion m(3) of freshwater in the Vaccares lagoon. The salinity drastically d ropped from 14 to 5 g l(-1) in 1 Wk. We observed that the annual prevalence and abundance of the myxosporean parasite decreased from 12.18 in 1993 to 3.7% in 1997 and from 1.10 in 1993 to 0.27 in 1997, respectively. Here, we discuss the possible reasons for the rapid decline of this host-parasite sy stem following the flood.