In Ichkeul Lagoon there are 24 fish species belonging to 15 families. These fish were obtained from the commercial fishing fleet and from scientific collections made during experimental, fishery independent sampling. Most species are of marine origins and enter the Lagoon to feed. Among residential forms, there are two species of freshwater fishes(Barbus callensisandAphanius fasciatus).However, future plans to modify the water flow constitute problems for the Parc National de líIchkeul. Disturbance in the hydrological regime will inevitably have some repercussions on the fish biology and their population dynamics. The closing of the lock, installed on the Oued Tinja, may compromise the entering of migratory fish which will result in a total halt to fishing activity.