DURHAM — For the first time in more than 200 years, river herring are traveling past the Wiswall Dam into the upper reaches of the Lamprey River thanks to a new fish ladder.

Durham got more than $1 million in grant funds from the National Resource Conservation Service under the U.S. Department of Agriculture to complete the project.

In addition to allowing anadromous fish species to pass to more freshwater habitat, the funds also helped to repair the Wiswall Dam, which is an integral part of the Durham and University of New Hampshire water supply, and has been in existence since 1912.

River herring, primary alewives, have already been using the ladder and volunteer counters have estimated that between 20,000 and 30,000 had already passed the dam as of May 7.

Town engineer David Cedarholm admittedly chokes up a little bit when he talks about seeing the thousands of fish find their way up the ladder.

Cedarholm said a fish way was first proposed at the Wiswall Dam in 1983 and went through many iterations before the final design of a denil fish way, a technical fish way that allows fish passage seasonally to allow for migration.

There are several species of fish, including herring, that spend most of their lives in the ocean, but swim up fresh water rivers to spawn. The juvenile herring live in the river for a couple of years and then swim out to the ocean themselves.

Cheri Patterson, supervisor for marine programs with New Hampshire Fish and Game, said until a fish way was built at the MacCallan Dam in Newmarket in the 1960s, anadromous fish species were unable to access the freshwater component of their life cycle, and their populations diminished or died off.

Passage at the Wiswall Dam now opens up the river for the fish to about Deerfield.

New Hampshire Fish and Game uses an automatic fish counter at the dam in Newmarket, and so far this year, more than 54,000 river herring have passed through.

“Now there is that much more habitat that herring can go up and spawn and become part of that habitat and become part of the whole eco-system all over again and support the whole system that has been there all this time,” Cedarholm said.

Cedarholm and Patterson said the river herring is an important food source throughout the habitat.

“River herring, or alewives, in this case, are a food source for just about anything from the minute they are born until the minute they die,” Patterson said. “They are bait, and they are a very, very important component of a food web. So … when you do restore these populations in these river systems then you are providing additional food sources within the food web of a river system, as well as the ocean and Great Bay estuary.”

Cedarholm said in total the Wiswall Dam project cost about $1.8 million, of which $800,000 was paid for through town Capital Improvement plans and $1 million through the federal grant.

“From my perspective, I am so glad to get the dam fixed and to have the New Hampshire Dam Bureau off my back about that sort of thing,” Cedarholm said. “I guess I don't think I anticipated how exciting it would be to get the fish moving up the river, and to have it strike this emotional chord every time I talk about it.”

The fish will head up river from now until early June, and will stay there for most of the summer before the adults head back out to sea.