IMIS

In the framework of a PhD research regarding the study on the cause of skin ulcerations of common dab (Limanda limanda) in the Belgian part of the North Sea, two-monthly monitoring surveys were performed. These were conducted in the Belgian part of the North Sea on board of the research vessel Simon Stevin. The main goal of these surveys was to gather information on the prevalence of skin ulcerations. Moreover, information on environmental, anthropogenic and fish-related characteristics was gathered to allow a broad analysis of possible risk factors correlated with the presence of skin ulcerations. The monitoring surveys were organized every two months between March 2015 and December 2019. In each survey, various locations in the Belgian part of the North Sea were sampled. Between 2016 and 2019, eight sampling points were consequently sampled, if the weather conditions allowed it. In each location, the CTD was lowered to a few meters above the sediment and information was gathered on the temperature of the sea water, turbidity, salinity and much more (see MIDAS). Furthermore, a sample of the water was collected to measure the pH on board using a multiparameter. In each location, we trawled during 20 minutes against the current. The catch was sorted and sole (Solea solea), plaice (Pleuronectes platessa) and common dab were sorted out for further measurements. Of all flatfish, individual length and weight measurements were gathered. For common dab, the seks was also noted. All flatfish were checked for lesions and deformities. Fish with deformities were noted and sampled further if lesions were skin ulcerations.