World Fish Migration Day Awareness and the Challenges for the Sheepscot River’s Sea-Run Fish
On May 21st we celebrate World Fish Migration Day: a world-wide event highlighting the importance of migratory fish and free-flowing rivers. Our Sheepscot River hosts all 12 of Maine’s native sea-run fish during part of their life cycles, making it an incredibly important component of the local and regional ecosystem.
Prior to European settlement, the Sheepscot River and its tributaries flowed unobstructed, allowing migratory and resident fish to move freely throughout the watershed as their life cycles and needs required. With the arrival of European settlers, came European development; Dams were constructed, forests were cleared for farming and timber harvest, and the river was modified to facilitate log drives. Dams blocked sea-run fish from accessing their spawning grounds. Much of the forested riparian buffer providing shade that cooled the river was cleared. Log drives resulted in channelization or ‘straightening’ of the river and the removal of large wood and boulders. These modifications to the stream reduced the habitat complexity and degraded water quality that is necessary for migratory fish and other aquatic species. The legacy of dams, forest clearing, and logging practices have made it difficult for fish populations that rely on cold-water to survive. Today, the migratory fish runs in the Sheepscot River are at 1% of their historical abundance.
There are historical accounts of 44 dams on the Sheepscot River and its tributaries. Today, many of these dams have been removed. Those remaining are kept for a mix of historical, cultural, municipal, and recreational reasons. Some dams provide fish passage through fishways, while others still act as a complete barrier to fish. Remnants of many of the historical dams still exist in the river today, impairing the natural habitat and remaining potential barriers to fish passage.
Culverts at road crossings present a more modern barrier to fish passage that can be undersized, shallow, or perched. Undersized culverts restrict natural stream flow causing high flow velocities that fish cannot swim against. Culverts that are not placed appropriately within the stream bed can result in flow that is too shallow for fish to swim through and can also become perched above the stream, acting as a complete barrier to fish.
These fish passage issues are not unique to the Sheepscot watershed, or even Maine. The primary goal of World Fish Migration Day is to raise awareness of the importance of migratory fish and the rivers that they, and we, rely on. Through awareness, we can all make decisions to reduce streamflow barriers and take action to restore the rivers that support the activities and economy we depend on in Maine. Head to www.worldfishmigrationday.com to learn more and find World Fish Migration Day events near you!
