The clear split into two clusters and the population parameters obtained
fromprevious calculations indicated a kind of permanent barrier
effected by environmental conditions like salinity gradient and intrinsic
factors like spawning time. Petereit et al. (2014) have shown the absence
of density layers for successful eastward drift of non-feeding
early-life stages from the western cod population. This would explain
the strong population divergence (based on passive life-stages only)
along the west–east axis.