"The effects of dams on salmon in New England rivers are sobering."

Babcock's Rapids, Kennebec River, Augusta, Maine. June 2003. Restored to life after removal
of the Edwards Dam (two miles downstream) in summer 1999.
Photo by Timothy Watts.


In a long awaited research report, the National Academy of Sciences has declared that dams must be removed on Maine's Atlantic salmon rivers if the species is to be saved from extinction in the United States of America.

Excerpts from the Academy's 260 page report, Atlantic Salmon in Maine, are as follows:

"Dams are a major cause of salmon declines worldwide .... The committee regards dams as a serious problem for successful restoration of salmon on a statewide scale because the larger drainages have greater potential to support large salmon populations."

"Although fish-passage facilities can alleviate the difficulties that adults have in upstream migration, the effects of dams on the downstream migration of smolts has been recognized only recently, and they are more difficult to reverse. The slow-moving pools behind dams confuse smolts during migration, increase the energetic costs of their movement, and can increase predation on them. The dams can injure smolts or block their passage. Although smolts do swim, their travel time to the estuary can be greatly increased as a result of dams, as has been shown on the Columbia River system in the Pacific Northwest (NMFS 2000b). Although the western dams are larger than those in Maine, effects documented in the West are likely to occur to some degree on dammed streams in Maine.

"The second effect needs wider recognition. By creating pools behind them, dams change habitat by eliminating flowing water and riffles. They flood riparian habitats, and they change the patterns of sedimentation and erosion. Dams usually cause changes in water temperature and chemistry, and reservoirs behind dams are often stratified, while undammed rivers are usually not (American Rivers et al. 1999, Heinz Center 2002.) In addition, the large woody debris, gravel and sediment that were formerly carried down the river and that provided spawning and rearing habitat, as well as cues that helped adults to return home to their natal streams, are now stopped by dams. As a result, these altered habitats become less suitable for for spawning and juvenile rearing. Rivers behind dams become pools, more like lakes than rivers. Most anadromous salmonids are not adapted to such habitats. Other species of vertebrates and invertebrates that can thrive in lakes proliferate and thereby change the prey resources available to salmon, as well as the number and kinds of their competitors and predators."

"Findings and Recommendations

The decline of Atlantic salmon populations in Maine has been pervasive and substantial over the past 150 years, despite some periods in which they increased in numbers. The decline has brought them close to extinction in recent years. The combination and interaction of factors influencing salmon populations have been changing as well. Although salmon have declined over much of their natural range in Europe and North America in recent decades, suggesting that some factors affecting them operate over large areas, the severity of declines in Maine warrants special attention. Maine's rivers and streams once had the capacity to support much larger salmon populations than they do now, so the potential exists to substantially increase the populations of wild salmon in Maine. In other words, rehabilitating salmon populations in Maine is challenging but appears possible."

"Dams appear to be the single most important class of impediments to salmon recovery that can be influenced by human actions in the short and medium terms."

"The evidence from over 130 years of stocking leads to the conclusion that hatchery production has not rescued Atlantic salmon in Maine. The evidence does not allow an objective assessment of whether, or to what degree, hatcheries have slowed the decline of Atlantic salmon in Maine. There has never been an adequate assessment of whether stocked salmon, when they return to spawn in Maine's rivers, successfully contribute to the next generation. Reliance on hatcheries as the sole or primary intervention will not be sufficient to prevent extinction for very long.

"Urgently Needed Actions

There is an urgent need to reverse the decline of salmon populations in Maine if they are to be saved. Other than the Penobscot River, only 80 adult salmon were recorded to have returned to Maine's rivers in 2002. The serious depletion of salmon populations in Maine underscores the need to expand rehabilitation efforts to as many of Maine's rivers as possible. Since most Maine salmon are now in the Penobscot River, that population should be a primary focus for rehabilitating the species in Maine. The committee recommends the following urgent actions:

A program of dam removal should be started. Priority should be given to dams whose removal would make the greatest amount of spawning and rearing habitat available, which means that downstream dams should be considered for removal before dams upstream of them. In some cases, habitat restoration will likely be required to reverse or mitigate some habitat changes caused by a dam, especially if the dam is many decades old. The recent agreement to remove two Penobscot River dams (Richardson 2003) is encouraging."

 No anadromous Atlantic salmon of any life stage should be stocked in rivers that have populations of wild Atlantic salmon unless those rivers are specifically identified as part of a hatchery-recovery program that uses river-specific stocks. Stocking of non-native fish species and landlocked salmon also should be avoided in those rivers. Other rivers that once supported wild Atlantic salmon runs, but which lack them now, will probably become repopulated by strays from nearby streams if populations in those nearby streams recover. The advantages over stocking of such natural repopulation, which would be more likely to lead to local genetic adaptation, should be given serious attention before any decision is made to stock streams that currently lack wild Atlantic salmon runs."




Date: Jan. 20, 2004
Contacts: Bill Kearney, Director of Media Relations
Patrice Pages, Media Relations Officer
Christian Dobbins, Media Relations Assistant
Office of News and Public Information
202-334-2138; e-mail <news@nas.edu>


Urgent Statewide Action Needed to Address
Serious Depletion of Atlantic Salmon in Maine

WASHINGTON -- Urgent actions are needed if the once-abundant Atlantic salmon in Maine are to be replenished, says a new report from the National Academies' National Research Council. These rehabilitation efforts are needed statewide to preserve Maine's population of the fish, which constitutes most of the Atlantic salmon population in the United States.

"The decline of Atlantic salmon populations in Maine has been pervasive and substantial over the past 150 years, bringing them close to extinction in recent years," said Michael T. Clegg, chair of the committee that wrote the report, and professor of genetics, University of California, Riverside. "Comprehensive, statewide action should be taken now to ensure their survival. And a formalized decision-making approach is needed to evaluate options, establish priorities, and coordinate plans for conserving and restoring the salmon."

Populations of Atlantic salmon have declined drastically, from an estimated half million adult salmon returning to U.S. rivers each year in the early 1800s to perhaps as few as 1,000 in 2001. Atlantic salmon were listed in 2000 as endangered under the federal Endangered Species Act. Despite the intentional introduction of more than 100 million hatchery-raised salmon and the escape of an unknown number of pen-raised salmon into the wild over the past 130 years, salmon populations have never been smaller. The wild North American Atlantic salmon remain clearly genetically distinct from fish bred in captivity, according to an interim report from the committee in January 2002.

Atlantic salmon are adapted to two very different environments. The young hatch and grow for one to three years in freshwater rivers and streams before migrating to sea. At sea, the salmon mature for two to three years and then return to the same streams to lay their own eggs. While many of the adults die after spawning, some migrate back to sea and make another return trip to spawn again.

If these migrating salmon are to survive, a program of systematic dam removal should start immediately, the report says. Dams on Maine's rivers used for mills and other purposes hinder the passage of adult and juvenile salmon and alter the rivers' habitat. Some of the dams have also outlived their economic usefulness. The report estimates removal costs to be between $300,000 and $15 million per year, assuming a cost ranging from $100,000 to $3 million per dam and the removal of three to five dams per year.

There is a high natural mortality after young salmon migrate from fresh water to the ocean. Sulfates and other chemicals from the atmosphere that alter the water chemistry of streams may be harming young salmon and increasing mortality among fish making the transition from fresh water to salt water. The addition of limestone to rivers and streams, known as liming, is a well-established procedure that has had considerable success in counteracting acidification in streams. It should be tried in some Maine streams on an experimental basis as soon as possible, the reports says. It is estimated that the initial cost of liming each stream would be around $100,000, with subsequent costs of $50,000 to $100,000 per year for each stream treated.

Despite Maine's heavy reliance on hatcheries to increase its salmon population, these facilities should be used sparingly, the report says. The focus of hatcheries should be to preserve the genetic diversity of remaining wild salmon populations by providing them with a secure place to grow if necessary. Stocking rivers with hatchery-raised salmon remains an unproven way to boost the fish population, the report adds, and additional research and scientific guidance are needed.

The committee also recommended that Maine avoid stocking its streams with salmon or nonnative fishes that may mate with or crowd out wild salmon, or out-compete them for food. Improved monitoring of water quality and better efforts to prevent farmed salmon from escaping also are needed. In addition, a comprehensive decision-analysis approach should be established to prioritize and coordinate efforts to restore the salmon. Fishing has historically been a major source of mortality for Atlantic salmon, and fishing for this species should continue to be prohibited in Maine, the committee added.

The study was sponsored by the National Fish and Wildlife Foundation. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering. It is a private, nonprofit institution that provides science and technology advice under a congressional charter. A committee roster follows.

Copies of Atlantic Salmon in Maine will be available later this winter from the National Academies Press; tel. 202-334-3313 or 1-800-624-6242 or on the Internet at http://www.nap.edu. Reporters may obtain a pre-publication copy from the Office of News and Public Information (contacts listed above).

[ This news release and report are available at http://national-academies.org ]