The Friends of the Presumpscot River, the Conservation Law Foundation and Sappi North American say more than 50,000 river herring ascended a fish ladder at the Cumberland Mills dam last year.

The Portland Press Herald reports that it’s a big jump. The year before, just 810 river herring were counted at the fishway. But the numbers tend to vary from year to year.

The fish ladder at the Cumberland Mills dam was built in 2013 as a result of a settlement agreement between the three parties. The parties say river herring are considered to be a “keystone” species that play a critical role in maintaining the river’s ecosystem for fish, aquatic life and birds.