Montpelier, Vt. (AP) — A top U.S. Fish & Wildlife Service official says a 45-year effort to restore Atlantic salmon to the Connecticut River is being abandoned.

Regional assistant director for fisheries Bill Archambault says that last year the service spent about $2 million on the Connecticut River program and only about 50 adult fish returned to the basin to reproduce.

He says officials are beginning a three-year process to determine if a similar program should continue in the Merrimack River basin of Massachusetts and New Hampshire.

The only bright spot for Atlantic salmon in the region is Maine's Penobscot River, where hundreds of fish returned last year.

Archambault says the problem is the small number of salmon that survive in the North Atlantic. Scientists don't understand what's causing the low survival rate.