In the index of The Silmarillion Salmar is described as a Maia, but it is unknown whether that entry was written by J.R.R. Tolkien or his son Christopher Tolkien. While there is no other text describing Salmar as one of the Maiar his status as a spirit who accompanied Ulmo but was not listed amongst the Valar would make that the logical conclusion.
Other Versions of the Legendarium
Quenya noun inflection
|Eönwë · Ilmarë · Ossë · Uinen · Salmar · Sauron · Melian · Arien · Tilion · Gothmog|
Curumo (Saruman) · Olórin (Gandalf) · Aiwendil (Radagast) · Alatar · Pallando · Durin's Bane