EVALUATING SUSTAINABILITY METRICS FOR MAINE RIVER HERRING POPULATIONS IN THE PENOBSCOT RIVER

There are two species of River Herring found throughout Maine watersheds, alewife (Alosa pseudoharengus) and blueback herring (A. aestivalis). River Herring hatch in inland lakes and rivers and migrate to the ocean until they are adults, returning inland annually to their natal waters in the spring to spawn. River Herring play a vital role in the overall function of several ecosystems, providing nutrients in river, lake, and ocean systems, a food source for larger fish, mammals, and birds, and a fishery for humans. For centuries, dams blocked access to rivers and streams in Maine, drastically reducing fish passage which led to population declines. Currently, efforts are underway to remove dams and improve passage. We investigated biological data of River Herring to understand how restoration efforts have changed populations dynamic. We collected 50 River Herring each week of the herring run from 2014 to 2024 at Milford Dam on the Penobscot River to collect biological data including, total length, weight, species, sex, age, and iteroparity. We prorated daily count data based on the biological samples taken. Counts of River Herring have increased from 400 thousand to over 5 million in the past 10 years. Species proportions have shown higher amounts of alewive than blueback herring in each year other than 2016 and 2022. In addition, we found that there were more older River Herring in recent years, with blueback herring up to age seven and alewife up to age eight. We observed a higher number of repeat spawners in recent years. We observed that the timing of the run appears earlier in 2021-2023 than in previous years. Our study is essential for understanding how River Herring species and their ecosystems are affected by improved habitat and fish passage.

Presentation Preference: Oral

Primary Presenter: Aileen McDonald, American University (aileenmcd2@gmail.com)

Authors:

Aileen McDonald, American University  (aileenmcd2@gmail.com)

Justin Stevens, Maine Sea Grant  (justin.stevens@maine.edu)

John Kocik, NOAA Fisheries  (john.kocik@noaa.gov)

Jason Valliere, Maine Department of Marine Resources  (Jason.Valliere@maine.gov)