herring and alewife?'s

[smallmouth420]

i've got a few questions about the life cycle of blueback herring and alewife. i live in ma. and we have a heavy amount of herring and alewife that end up in our coastal ponds in the spring.i know they migrate in the spring up rivers and lay their eggs then they move out to deep water.do the adults migrate back to salt water in the fall?do the yearlings also migrate to salt water?i always read about shad dying off in the winter.is there a similar situation with the herring/alewife.any general info would be appreciated.thanks.