Chronic Ulcerative Dermatopathy (CUD) is a newly described disease affecting the lateral line organ of freshwater and marine cultured fish, including meagre. The disease is directly associated with the use of borehole water, although the aetiological factor is still unknown. High mortalities are not associated with CUD, although it results in severe disfigurement of the fish, especially around the head where the lateral line canals are located, making the fish unacceptable for marketing. The lesions resolve when fish are transferred to surface water, either fresh or marine depending on the species. Chronic Ulcerative Dermatopathy has been reported in several marine fish, amongst which meagre seems to be one of the most vulnerable. Here, we propose the study of the development of the disease using two parallel rearing systems with different water sources; natural seawater and borehole water. Lesion resolution will be studied following transfer of CUD-affected fish in natural seawater. The study will involve advanced histological techniques and measurements of the abiotic factors in order to identify the causes of the disease.