It depends on so many factors - it is a very dynamic system with potential trophic cascades.

Fully adult (older than 1 year depending on location)BG produce many more offspring than first spawning BG (1 year) and the males are much better at keeping them alive while nesting. Small differences like that cam make a big difference in year class size and thus population dynamics. Another example is hiding places for yoy BG ( xmas trees or plants near spawning grounds). Even increasing survival rates 1 to 2% for 90 days makes a large difference.