Great Question!
They travel the open bottom and they move regardless of water temp when it is time to spawn. They move according to their biological clocks once they are ticking they go.
Do they make stops along the way? Yes those are called transition areas.
These are my opinions. Could I be wrong? Sure, but a migrating fish is a migrating fish... so I tend to believe they all act the same when migrating.
I would love to hear from others and what they think!
