SEA WATER TEMPERATURE RECORDS GATHERED DURING EXPERIMENTAL BOTTOM TRAWL SURVEYS IN THE STRAIT OF SICILY (MEDITERRANEAN SEA)

Depth and sea water temperature values recorded by a Minilog system during several bottom trawl surveys carried out in the Strait of Sicily (Central Mediterranean Sea) in spring (MEDITS) and late summer (GRUND), were analyzed by using an ad hoc developed software (MiSeAT). Depth and temperature profiles were analyzed for each haul. Three sea water temperature (t°C) values were considered: the upper and lower water layers temperature, and the difference between them. Mean values by depth stratum and the corresponding standard deviations were estimated for the three parameters, then compared between the two seasons. Haul parameters recorded during the more heterogeneous GRUND surveys (due to the vertical waters stratification occurring in summer), were fed to a GIS system in order to produce thematic spatial maps by survey and variable. Data recorded support an ongoing warming up of the water masses in the Strait of Sicily (13.5°C representing the asymptotic temperature between 200 and 800m), and confirm the existence of the basic three layers structure (Atlantic, Levantine and Transitional waters) reported for the area by classic literature. In spite of the limitations related to the use of Minilog (i.e., short coverage in space and time, incidental loss of devices, lower precision and accuracy of data if compared to those recorded by other devices), present results strongly support the validity of the Minilog-system-obtained temperature values.