What are the reasons for the collapse of the west coast fishery?

The collapse of the east coast fishery had several causes.

1. Pollution. Pouring untreated sewage into the east coast waters killed a large number of fish.

2. Habitat loss. Many of the fish use the wetlands and streams as places to lay their eggs and as nurseries for their young. When the meadowlands are filled in they are no longer the nurseries for little fish. Little fish can no longer leave home to grow up to become big fish. Simply because no one saw the tons of little fish produced by the meadowlands every day did not mean they would not miss the tons of big fish they would become as they were eaten and as a few grew into those big fish.

When streams are dammed, Atlantic Salmon and other fishes can not swim upriver to lay their eggs. (Enough were already killed trying to swim upstream in polluted rivers.)

3. Over fishing. When entirely too many big fish are caught, not enough little fish will be produced to replace them. It still takes one large male and one large female fish to produce fertilized eggs. Enough of those must grow up for the fishery to recover. Right now that is difficult.