Dam… The Atlantic Salmon Are Gone

 

They start out looking like little, orange colored, tapioca balls, floating in large bundles at the bottom of a steadily moving river. These Atlantic salmon eggs, born in the Connecticut River, are at the very beginning stages of their life, having just been fertilized by a fully mature male Atlantic salmon. They will continue to grow and develop within the freshwater river into parr, or adolescent salmon, for two to four years, before they leave their home tributaries in the spring months and begin a journey that will take them downriver, through estuaries, and hundreds or thousands of miles to ocean feeding areas (Hendry & Cragg-Hine, 2003, p. 4 and McCormick, S. D., Hansen, L. P., Quinn, T. P., & Saunders, R. L., 1998, p. 77). When the developing salmon finally reach the ocean they are known as smolt, and they will then migrate to the coasts of New England, Canada, Greenland, and even Spain, France and the UK, where they will live for around a year before they return to their birthing grounds to spawn the next generation of Atlantic salmon (Hendry & Cragg-Hine, 2003, p.3). Along with long migrations, smolt now face finding new food sources, diseases, parasites, and predators in the vast ocean they have arrived at (McCormick et al., 1998, p. 77). The smolt that survive and thrive in their new environment for one winter now earn the title of grilse (Miramichi Salmon Association [MSA], 2015). Because development, winter survival, and sexual maturation require high levels of stored energy, feeding and growth are of prime importance during freshwater residence (McCormick et al., 1998, p. 78).

Unfortunately, this hasn’t happened within the Connecticut River system since the early 1800’s. With the construction of Turners Falls dam in Massachusetts in 1800, the last recorded spawning of Atlantic salmon was in 1809 and there has been no historical population return since (Benson, Hornbecker, & Mckiernan, 2011, p. 11). Compared to an average of 100-200 Atlantic salmon in the Connecticut River in 1967, there were only about 75 salmon that returned in 2009 (Benson, Hornbecker, & Mckiernan, 2011, p. 12).

Atlantic salmon are important for supporting the ecology of the Connecticut River system and surrounding habitats. Developing fry and parr salmon offer ecological benefits to the Connecticut River system by feeding on and controlling populations of aquatic invertebrate larvae within the river, such as mayfly, stonefly, and caddis (Hendry & Cragg-Hine, 2003, p. 7). In addition, Atlantic salmon that spawn in the Northeast American river systems are also crucial to sustaining the Atlantic Ocean salmon population at large. Not only do they offer food for other species surrounding the Connecticut River, they also function as enormous pumps that push vast amounts of marine nutrients from the ocean to the rivers inland (Rahr, G., 2017). These nutrients are incorporated into food webs in rivers and surrounding landscapes by a host of over 50 species of mammals, birds, and other fish that forage on salmon eggs, juveniles, and adult salmon (Rahr, G., 2017). In Alaska, spawning salmon contribute up to 25% of the nitrogen in the foliage of trees (Rahr, G., 2017). With this information, we can infer that Atlantic salmon populations have the ability to contribute increased percentages of nitrogen to foliage surrounding the Connecticut River system.

A sustainable salmon population also offers economic advantages to the communities surrounding the Connecticut River system. High numbers of salmon bring an increase in public participation in fishing clubs like the Fish Creek Atlantic Salmon Club (Carey, 2017). With increased participation in fishing clubs and throughout fishing season, professional and recreational fishers spend a substantial amount of money on fishing trips. Aside from joining fishing clubs, in 2014, marine anglers in the US spent $4.9 billion on fishing trips and $28 billion on fishing equipment (National Oceanic and Atmospheric Administration [NOAA], 2017). In 2006, there were about 2.8 million recreational anglers in the New England region who took 9.7 million fishing trips (NOAA, 2006, p. 51). These anglers, in total, spent $438 million on recreational fishing trips and $1.44 billion on fishing-related equipment (NOAA, 2006, p. 51).  Retired Senator Elizabeth Hubley claims that the value of wild Atlantic salmon was once $255 million and the value to the surrounding areas in the gross domestic product was about $150 million (Atlantic Salmon Federation [ASF], 2017: Hubley, 2017). Increased Atlantic salmon populations also supported 3,872 full-time equivalent job in 2010, and about 10,500 seasonal jobs depend on wild Atlantic salmon (ASF, 2017; Hubley, 2017). These jobs include salmon angling and related tourism, food services, and accommodation sectors in the area (ASF, 2011, p. 54).

New England communities were built along banks of rivers so dams have been a central component since the beginning to provide water for irrigation, power generation, industrial operations, and provide clean drinking water. Specifically, the Connecticut River remains among the most extensively dammed rivers in the nation with 756 dams in place following the floods of 1932 and 1955 (American Rivers, 2017; & Benson, Hornbecker, & Mckiernan, 2011, p. 2 & 3). Two of the first dams on the Connecticut River system that prevent Atlantic salmon from migrating into tributaries are the Leesville Dam on the Salmon River and the Rainbow Dam on the Farmington River (Benson, Hornbecker, & Mckiernan, 2011, p. 20 & 22). The Leesville Dam was built in 1900 and is used for recreational purposes today. The second dam on the Connecticut River, the Rainbow Dam, was the first dam on the Farmington River, which is the largest tributary of the Connecticut River. This river is supposed to provide access to 52 miles of historic spawning habitat (Benson, Hornbecker, & Mckiernan, 2011, p. 22).

Now, Atlantic salmon face the biggest obstacle, figuratively and literally, they have ever encountered before. The Leesville and Rainbow dams are preventing Atlantic salmon from entering their respective tributaries and spawning each season. Dams are preventing upstream salmon passage, reducing water quality, altering substrate within the river, and alter flow regime of the river.

Dams placed on the Connecticut are the primary reason for the lack of returning Atlantic salmon to the Connecticut River system. Dams fragment habitat and ultimately prevent upstream salmon migration, which not only limits their ability to access spawning habitats, but also limits their ability to seek out essential food resources, and return downstream to the ocean (American Rivers, 2017). As a result, major dams on the in the Connecticut River watershed have blocked fish passage and caused significant decreases in Atlantic salmon migration and spawning rates (Daley, 2012, p. 1). A fish count was taken in 2010 and only found 1 Atlantic salmon was recorded above the Leesville Dam (Benson, J., Hornbecker, B., & Mckiernan, B., 2011, p. 20). Another fish count was taken above the Rainbow Dam and only showed 4 Atlantic salmon above the dam site (Benson, J., Hornbecker, B., & Mckiernan, B., 2011, p. 22).

Not only do dams physically prevent salmon from migrating upstream to spawn each season, they also slow down water velocities in large reservoirs which can delay salmon migration downstream (U.S. Fish & Wildlife Service, 2017). Additionally, dams can block or impede salmon spawning by creating deep pools of water that, in some cases, have inundated important spawning habitat or blocking access to it (U.S. Fish & Wildlife Service, 2017).

The water quality of the Connecticut River is very important in order to sustain Atlantic salmon populations because they require very good water quality, including high dissolved oxygen and low nitrates, non-ionized ammonia, and total ammonia content (Hendry & Cragg-Hine, 2003, p. 11). Although Atlantic salmon have a higher tolerance to warm temperatures than other salmon species, warm temperatures can reduce egg survival, stunt growth of fry and smolts, and increase susceptibility to disease (Klamath Resource Information System [KRIS], 2011). The chemical, thermal, and physical changes which flowing water undergoes when it is stilled can seriously contaminate a reservoir and even the water downstream (McCully, 2001). Water released from deep in a reservoir behind a high dam is usually cooler in the summer and warmer in the winter, while water from outlets near the top of the reservoir will tend to be warmer than river water year round. Unnatural or inverted patterns of warming or cooling of the river affect the ideal concentration of dissolved oxygen and adversely influences the biological and chemical reactions driven by temperature flux (McCully, 2001).

One experiment was conducted on the Colorado River in Glen Canyon, where pre-dam temperatures were obtained in varied seasons. The pre-dam temperatures varied seasonally from highs of around 27 ºC (80 ºF) to lows near freezing (McCully, 2001).  The maximum temperature of the river water that developing salmon can take is around 27 ºC (80 ºF) (KRIS, 2011). However, the temperatures of the water flowing through the intake of Glen Canyon Dam, 70 meters (230 feet) below the full reservoir level, varied only a couple of degrees around the year (McCully, 2001). The Colorado River is now too cold for the successful reproduction of native fish as far as 400 kilometers (250 miles) below the dam (McCully, 2001). This experiment is transferable to the Leesville and Rainbow dams because they are similar in size to the Glen Canyon Dam, therefore we can infer that both the Leesville and Rainbow dams impede fish populations because of drastic water temperature fluctuations year round.

The dams also stagnate downriver water flow, which is disadvantageous to the salmon because they cannot use the current of the river to guide them to the ocean to continue their life cycle before returning to spawn (American Rivers, 2017). Furthermore, dams that divert water for power also remove water needed for healthy in-stream ecosystems as well as directly affecting dramatic changes in reservoir water level, which can lead drying systems downriver (American Rivers, 2017). Furthermore, flow regime dictates substrate composition, or what makes up the bottom of a river channel. Slower moving water results in a riverbed of fine material, while faster flowing water tends toward a rockier or even bouldered substrate (Claeson, S. M., & Coffin, B., 2016). Research finds Atlantic salmon seem to prefer this rougher substrate, a habitat type that leads to an increase of 80% of individuals in a given area of 70% or more rocky or bouldered, substrate cover in studies of post partial or total dam removal. Researchers hypothesize the rocky substrate mitigates flow speed at greater depths, thereby facilitating salmon passage and providing refuge for salmon eggs and young (Lii-Chang, C. et al., 2008). Thus, a dam’s effect on flow regime and subsequent substrate composition is very detrimental to existing and future generations of Atlantic salmon.

In summary, the implementation of dams on the Connecticut River is harmful to Atlantic salmon populations in more ways than one. Connecticut River dams prevent salmon from migrating properly during their spawning periods. It became such a substantial problem that the National Fish Hatchery System (NFHS) of the U.S. Fish and Wildlife Service stocked Atlantic salmon in the Connecticut River at one point in time. Unfortunately, after poor returns back into the Connecticut River and its tributaries, the NFHA discontinued stocking Atlantic salmon in 2012 (U.S. Fish & Wildlife Service, 2017). In addition to impeding salmon migration, dams that were constructed also reduce water quality and alter the flow regime of the river and its tributaries.

Given the evidence dams present a steep hurdle for migratory, anadromous fishes, the natural evolution of the question then becomes; can we somehow mitigate that hurdle without removing the dam itself? Enter an attempt to do just that with the implementation of fishways around a dam. A fishway is a manmade path that allows for fish to safely pass around a dam without affecting the purpose of the dam (hydroelectricity, flood prevention etc.) (Harrison, 2008). There are two main types of fishways used today: fish ladders and fish lifts. A fish ladder is a system in which fish manually swim up and around the impending dam through a series of ascending pools (Edmonds, 2008, p. 1). Among the most common, pool and weir fish ladders utilize the flow of water over the ascending pools to encourage fish to jump up and into the next highest pool (Edmonds, 2008, p. 2). Another basic design called vertical slot fish ladder utilizes a small vertical slot in which the water flows into a pool. The angles of the entrance and exit slots create a holding area in each pool that the fish can rest in before battling the current to get to the next pool (Federal Energy Regulatory Commission [FERC], 2005).  A fish lift, however, is a hydraulic lift that automatically carries fish up and over the dam. Fish congregate at the base of the dam where they find the entrance to the fish lift. They then swim through this entrance and congregate in a holding tank at the base of the dam. Once there are enough fish in the holding tank, the tank is lifted to the height of the dam where fish are safely released on the other side (Harrison, 2008; Church, 2016).

One significant flaw with fishways is that they are not consistently effective for all fish species, especially Atlantic salmon. A fish lift put in place at the Holyoke dam on the mainstream of the Connecticut River kept track of how many fish passed through the elevator and their species. In 2010, the dam successfully passed: 164,439 American Shad, 39,782 Sea Lamprey, and only 41 Atlantic salmon (Benson, Hornbecker, & Mckiernan, 2011, p. 29). The Rainbow dam, which blocks a main tributary to the Connecticut River, conducted a study measuring what types of fish utilized its fish ladder. They found that three months after its installation in 2010, the vertical slot fish ladder passed: 548 American Shad, 3,090 Sea Lamprey, and only 4 Atlantic salmon (Benson, Hornbecker, & Mckiernan, 2011, p. 22). This data begs the question, why are some fishways more effective to certain species than others? Well, the answer is a lot more complex than people think. Alex Haro, a fish passage engineer at the S.O. Conte Anadromous Fish Research Center noted in 2014 that most of the design decisions made about fish ladders overlooked critical information (Kessler, 2014). Since fish ladder technologies developed with little cooperative partnership between engineers and fish biologists (Calles & Greenberg, 2009), attempts at engineering fish passage was often in the form of a one-size-fits-all solution for the sake of cutting costs. Examples of fatal oversights include a failure to calculate for critical variables that create what is referred to as ideal hydraulic conditions, such as speed, directional chop, and the physical and chemical qualities of water affected by a given dam as it relates to a fish species’ size, resilience, and overall passage efficiency (Brown & Limburg et al., 2013). Furthermore, design emphasis favored upstream passage potential, with little regard for returning downstream passage (Calles & Greenberg, 2009). Though even when fishways were designed with a target species in mind, passage was ever more ambitious than successful. Swedish ecological engineers found salmon-specific fish ladders prevented as much as 30% of potential spawning salmon from passing at the first mainstem dam and ultimately leading to an overall decrease of 70% of potential spawning salmon to reach high-quality spawning tributaries (Rivinoja, 2005).

As a way to bring the salmon populations back to the Connecticut River system, we advise the Connecticut state government to remove the Leesville and Rainbow Reservoir dams from the Connecticut River watershed. This solution will allow the restoration of salmon populations in the Connecticut River communities and bring with it economic, recreational, and ecological benefits to the surrounding areas.

In fact, areas that prioritized dam removal for the sake of habitat restoration are quickly witnessing a substantial recovery in both target fisheries and surrounding ecosystems, to include their local salmon species. The 210-foot-high Glines Canyon dam of Washington State was removed in the year 2014, following the removal of the Elwha dam in 2011, collectively reopening 70 miles, or 90%, of high-quality spawning habitat for salmon (Mapes, 2016). These two dams prevented a whole host of river wildlife from upriver passage for over a century, but the local Lower Elwha Klallam Native American tribe persevered and collaborated with state and federal officials to restore the habitat for their culturally important Coho and Chinook salmon (Mapes, 2017). And while the project came with a $325 million price tag, the effort is producing immediate ecological payoffs. Just three days after the Elwha dam removal, Chinook salmon were documented upriver the removal site (Mapes, 2016). The same year, in the 11-mile stretch between the two dams of century-long impossible spawning potential, the Elwha produced 32,000 outgoing juvenile Coho salmon (Mapes, 2016). Now, Chinook and Steelhead salmon numbers are up 350% and 300% respectively, and previously landlocked Sockeye salmon are returning to sea (Mapes, 2016). But the salmon aren’t the only winners in this story, downstream ecosystems have benefited from nutrient connectivity. As well, resulting physical and chemical changes to the river environment post-dam removal are creating more complex, and thus biologically rich, habitat structure for native species such as otter, various crabs, and birds (Mapes, 2016). One study out of Ohio State University evaluating Washington state’s efforts to remove dams concludes that birds with access to rivers hosting salmon, and therefore marine-derived nutrients, increases survival rates up to 11%, encourages multiple broodings per season of up to 20x, and increases the overall likelihood to stay year-round of up to 13x (Crane, 2015).

Destroying two dams in the Connecticut River watershed could come with major negative effects to the local societies. Because the Rainbow dam provides electricity to Hartford, CT, demolition of the dam will come with negative power ratings for the city, but how much of an impact will dam removal make? According to an excel sheet put together by the Department of Energy and Environmental Protection (DEEP), the Rainbow Dam in Windsor, CT has a capacity of .004 megawatts (MW) (2017). The best performing dam in America, the Grand Coulee Dam on the Washington River, has a capacity of nearly 7,000 MW (National Park Service, 2013). To put this number into perspective, if Hartford replaced 100 of its light bulbs with new energy efficient ones, it would successfully negate the power lost from removing the dam (American Rivers, 2016). Converting to newer energy alternatives in Hartford is a cheaper alternative, and could very easily negate the electricity loss from removing the Rainbow Dam.

The main problem with removing the Leesville dam is the recreational value that it holds. However, those who enjoy the open water will actually find that there is more to do without the dams there. Yes, people who had boats on the water will no longer have the ability to enjoy open waters, but the local area should see an upturn in use of the river. Now that the lake behind the Leesville dam is a river, kayaking and rafting will increase as there is more river length to explore unobscured by a dam. Also, as stated before, with more fish in the river, there is likely to be an increase in recreational fishing as well (American Rivers, 2017)

It is also important to consider the costs associated with maintenance of the dams and cost of demolition. One would think that the owner of the dam stands to lose the most when dam removal is considered, but in reality, this is not the case. In fact, the dam owners often work together with local, state, and federal governments to help get rid of the dam. This is because ownership of a dam also comes with maintenance and safety costs, as well as payments related to fish and wildlife protection (American Rivers, 2016). Costs for dam removal range from thousands to millions of dollars depending on sediment buildup, size of the dam, and complexity of river environment. Grant money and taxpayer money covers most of these payments, with some money coming from private investors (Benson, Hornbecker, & Mckiernan, 2011, p. 34 & 41).

In sum, Atlantic salmon populations will likely never be self-sustaining while hundreds of dams exist in the Connecticut River watershed (American Rivers, 2017). Especially when dams block nearly every tributary that feeds into the Connecticut River. Starting at the bottom of the Connecticut River, with the Rainbow and Leesville dam, we can slowly return natural spawning to the bottom of the river. By removing just two dams we successfully open access to over 70 miles historic spawning habitat (Benson, Hornbecker, & Mckiernan, 2011, p. 29; American Rivers, 2017). Luckily we are in a time where dam removal is picking up support. Out of the 1,150 dams that have been removed in the U.S. since 1912, approximately 850 of them have been in the past 20 years (Kessler, 2014). This upward trend of dam removal will heavily influence natural spawning in the Connecticut, and slowly but surely, those little, orange colored, tapioca balls will return home.

AUTHORS

Ava Swiniarski – Pre Veterinary Science

Jonah Hollis – Environmental Conservation Science

Ben Smith – Building and Construction Technology

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Evan

One Comment

  1. Great info, but i don’t think that the picture up top showcases Atlantic salmon; If I’m correct those are Pacific salmon

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