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 the 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.
The evidence suggests that regional climate change in Maine—mainly winter warming—has increased the difficulties encountered by salmon populations. Climate change, along with probably associated changes in oceanic conditions, appears to be an important factor affecting salmon, and it cannot be directly influenced by human intervention over the short and medium terms. The question arises as to whether the climate changes are so great that attempts to restore salmon are futile. The committee cannot answer that question, but there is no doubt that the changes make it more urgent to improve other aspects of their environments if wild
salmon populations are to persist in Maine. In the absence of additional warming or other adverse climate changes, comprehensive efforts to rehabilitate salmon populations probably could be successful. Most of the measures designed to restore salmon populations would also benefit other native aquatic resources that depend on ecosystem services in these same watersheds.
Although genetic problems are important for Atlantic salmon in Maine, they appear to be less urgent than demographic problems. Given the choice of reducing an adverse genetic effect or reducing an adverse population effect, initial priority should be given to the population effect.
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. Although they are perhaps of smaller importance on the eight DPS streams than elsewhere in Maine, they are very important throughout the state.
Local populations of Atlantic salmon inhabiting different rivers and tributaries are demographically and genetically connected into so-called metapopulation systems through exchange of individuals. To the degree that this structure can be retained by maintaining or reestablishing salmon runs in many of Maine’s rivers, the evolutionary future of salmon in Maine will be enhanced.
Aquaculture also appears to have an important and generally adverse effect on wild salmon populations, although reliable data are not available for Maine. Elsewhere, aquaculture has been shown to affect native salmon populations through ecological competition from escaped farm fish and through a large increase in the population density of parasitic copepods (sea lice). Other diseases can become concentrated in netpens and affect wild fish as well. Even if the diseases are originally transferred to farms from wild fish, the concentration in the net-pens aggravates the problem. Although reliable data for such effects are lacking in Maine, similar effects are likely to occur there.
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 off-spring to the next generation. Reliance on hatcheries as the sole or primary intervention will not be sufficient to prevent extinction for very long.
Additionally, large releases of hatchery fish can have adverse effects on natural populations, as reviewed in Chapter 3. Current procedures for management of DPS river and Penobscot brood stock and offspring at the
Craig Brook National Fish Hatchery commendably avoid some of these hazards and could reduce additional hazards with feasible modifications. Some of the known hazards, however, are inherent to hatchery operations and cannot be fully avoided or substantially reduced. The committee concludes that hatcheries should be used sparingly in rehabilitation of natural populations and that published guidelines for reducing the adverse effects should be followed.
Survival of salmon at sea appears to be significantly depressed below that required to maintain robust populations. Other than the possible adverse effects of salmon farms and fishing, the factors involved, such as predation, competition, and adverse water temperatures, are not well understood and do not appear to be accessible to human control, at least for the short or medium terms.
The use of deep groundwater wells and storage ponds to irrigate agricultural crops (principally blueberries) does not appear to adversely affect stream flow and Atlantic salmon. By contrast, direct water withdrawals from streams, interacting with climate-induced changes in stream flow, could substantially degrade salmon habitat.
Timber harvesting does not currently appear to be a substantial problem for salmon. However, some forest practices (inappropriate road construction and deferred maintenance) have the potential to adversely affect salmon habitat quality and availability.
Some research that entails the collecting or trapping of fish appears to increase the risk of salmon mortality in streams with very small populations. Given the urgency of demographic problems, the committee questions the value of obtaining detailed genetic and physiological data on wild fry, parr, and smolts from such depleted populations.
Fishing has historically been a major source of mortality of Atlantic salmon. Currently, directed fishing for Atlantic salmon is prohibited in Maine and in most of the ocean that Maine salmon use. The Greenland salmon fishery is currently operated at a low level, but if it increased, it probably would affect Maine Atlantic salmon adversely. Recreational angling for brown and rainbow trout and landlocked salmon in waters that harbor wild anadromous Atlantic salmon is likely to add to the mortality of Atlantic salmon through bycatch. The amount of bycatch of Atlantic salmon in ocean fisheries is not known.
Water-quality degradation caused by atmospheric deposition (and subsequent acidification and metals mobilization) and pesticides (irrigation return or aerial drift) may threaten Atlantic salmon in subtle and pervasive ways. Historical and current monitoring programs are not sufficient to detect and evaluate these threats.
Many recommendations have been made for the rehabilitation of Atlantic salmon populations in Maine. Most of them are sound, but there are too many recommended actions to take at once. Moreover, not all of them are equally urgent. Most of the actions have been recommended by others, such as the Maine Atlantic Salmon Task Force, but here an attempt is made to set priorities for them and to recommend those actions most likely to be effective.
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 salmon that returned to 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, meaning 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.
The problem of early mortality as smolts transition from freshwater to the ocean and take up residence as post-smolts needs to be solved. If, as seems likely, that the difficulty of the transition is due in part to water chemistry, particularly acidification, the only methods of solving the problem are changing the water chemistry and finding a way for the smolts to bypass the dangerous water. Liming has had considerable success in counteracting acidification in many streams, and the techniques are well known. Examples of its application are in nearby Nova Scotia. Liming should be tried experimentally on some Maine streams as soon as possible. Bypassing the dangerous water is best achieved by rearing smolts and acclimating them to seawater in controlled conditions. This approach is not appealing because of the degree of human intervention required and because of the adverse selection that must result from it.
Given the extreme depletion of salmon populations, however, desperate measures are called for.
Hatcheries need to continue to be used, at least in the short term, to supplement wild populations and to serve as a storehouse of fish from the various rivers. There is an urgent need to understand the relative efficiency of stocking of different life stages in the rivers in terms of adult returns per brood-stock fish and their reproductive success. Additional research on hatcheries and scientific guidance for their use is needed, because hatchery-based restoration of wild salmon populations remains an unproven technology. Indeed, hatcheries themselves should be used adaptively as scientific tools for obtaining additional information.
The approximate costs of these options are discussed in Chapter 5.
Actions Important over the Longer Term
Over the longer term, the committee recommends a comprehensive decision analysis approach to the rehabilitation of Atlantic salmon populations in Maine. The analysis should be conducted along the lines of the examples in Chapter 5 of this report but in more detail and with all major groups of stakeholders involved. Taking a Maine-wide view is more likely to be successful than focusing only on some rivers.
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 nonnative 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.
The current prohibition of commercial and recreational fishing, including catch-and-release fishing, for salmon in Maine should be continued. Any further reduction in the take of Maine salmon at sea would be helpful. Maximum and minimum size limits for trout and landlocked salmon should be established in rivers that have anadromous Atlantic salmon. The minimum size for retention should be large enough to protect Atlantic salmon smolts, and the maximum size should be small enough to protect adult Atlantic salmon. Any fishing that might take a wild Atlantic salmon constitutes an additional risk to the species. This risk should be carefully evaluated for all Maine rivers with Atlantic
salmon and additional measures should be taken if the risk is judged to be important. Habitat zones most heavily used by Atlantic salmon young and adults should be closed to fishing for all species until salmon populations have recovered.
Research that increases the risk of death to wild fish should be curtailed. The value of any information obtained needs to be weighed against the likelihood of increased death of wild fish subjected to handling.
Every effort should be made to further curtail the escape of salmon from farms. If accumulation of parasitic copepods (sea lice) or other pathogens is found to be a problem for wild salmon, the aquaculture facilities should be moved to a place where they will not adversely affect wild salmon.
Hatchery practices should be evaluated in an adaptive-management context to further reduce adverse genetic and ecological effects, and modified as needed.
The monitoring of water quality and gauging of streams should be augmented. A network of metereological-monitoring, stream-gauging, water-quality-monitoring, and biological-monitoring sites should be linked to a geographic information system and an online database within 2 years.
Government, industry, and private organizations and landowners should cooperate to evaluate forestry best-management practices and forest-road networks. Mitigation and pollution prevention should be organized on a priority basis to maximize the effectiveness of stormwater management and sediment control and the removal of barriers to fish passage.
The State Planning Office should conduct a systematic governance assessment to see whether there are gaps in authority, overlapping authority, conflicts of goals and interests among agencies, and adequate cooperation among agencies.
The State Planning Office, in cooperation with all other agencies, should implement adaptive management to monitor performance of governance activities related to Atlantic salmon, to experiment with alternative institutions for salmon recovery, and to systematically learn and adapt to the results of new information.
The Maine Atlantic Salmon Commission should consider shaping governance structures so that they are consistent with salmon biology. That could involve developing multistakeholder governance institutions for each drainage basin, each nested within larger-scale governance bodies to address effects, such as climate change and aquaculture, that are larger than individual basins.
The suite of conservation options with multiple environmental ben-
efits outlined in Chapter 5 should be adopted. Those strategies are likely to help Atlantic salmon in Maine, and they will have other environmental benefits even if they do not help salmon. The energy and commitment of the members of many local watershed and river-specific groups focused on restoring salmon and their habitats is an important asset and should be included in any overall approach to rehabilitating Atlantic salmon and their habitats in Maine.