Do I need to compensate for salinity variations on ODO measurements?

Yes. Salinity has a significant effect on the concentration of dissolved oxygen. For example, if you are at 5ºC and the salinity is off by 1 PSU your concentration is off by ~0.8%.

To compensate the dissolved oxygen concentration for salinity, Ruskin or the instrument will use the derived salinity value from the instrument if there is a conductivity sensor and stream this compensated value or present it in the RSK file.

If your instrument does not have a conductivity sensor on the same instrument as the ODO, you can input a constant salinity value in the parameters table (see image below) of the instrument to produce the compensated concentration. Alternatively, if you want to post-process your oxygen data using a salinity value provided by another instrument, you can set the salinity to '0' in the parameters table and perform the compensation described by Garcia and Gordon, 1992.