During each spring alewife and blueback herring return to their natal stream to spawn. After spending four years in ocean these fish return to the river where they were born to spawn.
Several rivers in Maine and throughout New England contain alewife and blueback herring. Counting the numbers that return to each individual stream or river is difficult because they arrive at approximately the same time each year. Through the use of video data capture biologists are able to record fish ascending these rivers and streams but determining exactly how many arrive in each river each year is a huge task.
However, with assistance from individuals willing to review selected video clips, biologist will be able to determine how well each population is doing in each individual river.