Instrument: YSI Sonde 6-Series
YSI 6-Series water quality sondes and sensors are instruments for environmental monitoring and long-term deployments. YSI datasondes accept multiple water quality sensors (i.e., they are multiparameter sondes). Sondes can measure temperature, conductivity, dissolved oxygen, depth, turbidity, and other water quality parameters. The 6-Series includes several models. More from YSI.
A YSI model 650 MDS (YSI Inc., Yellow Springs, OH, USA) was used to measure salinity. See the description from the manufacturer.