Slide 16 of 20
Notes:
Migration is an important component of PVA models because it provides strong “rescue effects” that prevent populations from going extinct.
From a management standpoint, I see costs and benefits to utilities in treating river segments as parts of a larger metapopulation. The cost is that there will be no rescue effects if there is no movement between reaches. The benefit is that the habitat needs of different lifestages can be met in different river segments == that is to say, all kinds of habitat would not need to be provided in each reach.
Here you can see the downstream benefits of downstream migration. Moderate levels of balanced migration (upstream=downstream) had a positive influence on viability and genetic variation.