Three points on the Megunticook River:

Not all dams are bad

The Molyneaux Dams provide multiple benefits to our community. They allowed the previously disconnected habitat at Fernald’s Neck to be contiguous with the habitat of Megunticook Lake, offering the largest freshwater ecosystem in Knox county. Because these dams are well-maintained, they can perform their job of flood protection flawlessly.

In our 100-year flood last October, they reduced our flood exposure by over a billion gallons and worked in concert with the systems in place downstream to slow the breakneck speed of rushing water by diverting it in a zig-zag pattern through the Megunticook’s system of mill ponds — similar to hiking down a steep hill using switchbacks versus running straight down.

Over time, the dams have modified the river downstream towards further flood prevention. Since dams trap sediments, the water they release carves deeper into the river’s bed, creating a more generous channel that can hold more water, thus preventing future and greater flood waters from spilling over riverbanks. In a 2020 U.S. study by Zhao and colleagues, dams — like the Molyneaux, Seabright, and Knox Mill — were found to reduce flood exposure by 9%. In a more robust 2022 study by Boulange and colleagues, dams like ours were found to reduce flood exposure in 100-year flooding scenarios by 20%, providing a significant level of protection to people living downstream.

Not all fish ladders are good

Fish ladders are not natural and have not evolved with organisms or the natural environment. They are manmade and, as such, are a form of environmental manipulation, placing them in the same category as dams and bridges. Fish are often injured or killed swimming up ladders. They can become stressed and exhausted by the warmer temperatures and even if they reach their destination, may not spawn successfully.

Fishways have been documented to introduce invasive species and to increase predator-prey encounters, harming the very fish populations they are supposed to be helping. The most effective fishways are designed for one type of fish to navigate and are not all-purpose. Like dams, fish ladders are a human-engineered piece of infrastructure. There’s nothing restorative about them. They require a regular operator, ongoing maintenance, and have a lifespan. The average lifespan of a dam is 56 years in the U.S. The average lifespan of a fish ladder is, well, it’s uncertain given the data aren’t widely available.

In a Yale study that ran across three decades, fish run sizes were found to be 10% of stated goals some years and as low as 2% other years. Another study of fish ladder effectiveness showed the percentage of fish that successfully navigated a fish run diminished with every ladder they were required to navigate.

From Camden Harbor to Megunticook Lake, a minimum of four fish ladders would be required, two of these because of dams that serve an important function for our community and cannot be removed, and at least two more because regardless of whether we choose to restore and maintain other dams, the elevation gain is far too great for anadromous fish — those that migrate from the ocean to freshwater to breed — to navigate without environmental manipulation from us. Another 2021 meta-study found their effectiveness to be 60%. Add two ladders for a fish to navigate and that effectiveness drops to 36%, or just 13% for a series of four ladders. How many millions should be spent to serve 13% of a particular fish population? (That difference by the way between 13% and 60% means about half of the fish that entered the first passage aren’t making it through the fourth.)

Our Megunticook River is the only one in the state of Maine the ocean doesn’t enter due to its height. Even though fresh and saltwater merge at the head of the harbor when the water cascades down the bedrock, there’s no brackish water — where seawater and freshwater mingle. The elevation gain is simply too great for fish to navigate naturally.

All living organisms live at the expense of others

Because energy and matter can neither be created, nor destroyed, only transformed, every living thing survives in an intricate web with all other life and sometimes at the expense of others. Some would argue human life is better or more important than nonhuman life. Others would argue that’s not the case. Either way, in order for us to live we must take energy from other life forms, whether that’s the tofu on your plate that once existed as a living edamame plant, or the deer shot last season that’s nourished you for many meals.

There’s a notion removing dams creates a net positive effect on the wildlife and this is often true, particularly when there’s good evidence a fish species previously spawned there in abundance. After the immediate removal of a dam, however, the sediments are released causing death by burial and suffocation to algae, invertebrates, and fish eggs. The stream bed becomes unstable and is not suitable as a habitat for many living organisms. The turbidity can negatively affect fish, causing abrasions, reducing their ability to forage for food, clogging gills, and interfering with their orientation skills. Lower fish populations can persist for 15 years after a dam is removed.

Our river’s sediments contain toxic levels of mercury, lead, and arsenic. If released, these bioaccumulates that affect vertebrate reproduction would flow into our harbor, affecting future fish and bird populations for an indeterminate amount of time. Even the act of trying to responsibly remove these toxins by hauling them elsewhere releases volatile compounds and has unintended consequences — not to mention this raises the question of the ethics of moving toxins from location A to location B.

In summary, dams can provide many benefits, fish ladders are not a remedy for every river, and dam removal can have long-term negative consequences on the very ecosystem we’re trying to protect. The Molyneaux Dams, having received the ongoing care they need, are prepared to tackle the challenges they were built to handle, but much of the rest of our river infrastructure is crumbling before our eyes. Will we continue to neglect our infrastructure causing unintended changes to habitat and reducing our flood protection or will we rise to the challenge of stewardship?

SL Gathers grew up in Maine, lives in Rockport three seasons of the year while spending the summer on Megunticook Lake, and worked as a senior medical and science writer for 14 years.