The saithe (Pollachius virens) stock is known to be a single stock in the North Sea (ICES subarea 4), West of Scotland and Rockall (ICES subarea 6), and Skagerrak (ICES subdivision 3a). Due to the topography or distance, the stock structure and migrations are not entirely clear among broader areas, such as the NE Atlantic. Although, there is some evidence that Rockall may be a genetically distinct subpopulation (ICES, 2019). 

Genetic tagging studies have also provided some evidence that the North Sea saithe is distributed in the northern management boundary (62° N), and potentially extending as far as 65° N. There is evidence to show a clear mixing of stocks for the North Sea and NE Arctic stock units as well, which would be worth exploring in the future (ICES, 2019). 

Four assessment units are considered within the NE Atlantic region for evaluation of the stock condition as well as for management purposes:
1 – Barents Sea (Subareas I and II, Northeast Arctic) 
2 – Icelandic (Division Va)
3 – North Sea, Skagerrak, west of Scotland and the Rockall (Divisions IIIa, IV and Subarea VI) 
4 – Faroe Islands (Division Vb).

In general, the saithe tend to spawn offshore in the winter and spring approximately 100-200 meters deep, with juveniles remaining close to shore. Adults tend to migrate to deeper waters, forming small shoals. The lifespan of an adult saithe can range between 16-20 years.