Samples of Atlantic herring from fourteen locations (Area) shown clockwise from Kragerø in southern Norway to Balsfjord in northern Norway along the coast of Norway (see also Fig 1).

ID: Population abbreviation, Lat: latitude (N), Lon: longitude (E), N/W/S: N: populations in northern Norway, W: populations in western Norway, S: populations in southern Norway, System: type of habitat where the herring were sampled, Month: month of spawning, Year: sampling year, Spawn: some in spawning condition (+), none in spawning condition (-), Length: mean length in cm and length range for each age range 3–5 years, 6–8 years, 9–12 years, n: total number of samples for each age range, ntot: total number of samples from each area.Samples of Atlantic herring from fourteen locations (Area) shown clockwise from Kragerø in southern Norway to Balsfjord in northern Norway along the coast of Norway (see also Fig 1).