Atlantic Salmon in Maine (2004) / Chapter Skim
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5 Addressing the Threats to Atlantic Salmon in Maine
5 Addressing the Threats to Atlantic Salmon in Maine
Pages 138-187
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From page 138... ...
The 1997 Conservation Plan (Maine Atlantic Salmon Task Force 1997) provides the foundation for wide range of current efforts in Maine.
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From page 139... ...
It would also be helpful to adapt earlier assumptions and goals to current conditions and scientific knowledge. Immediate Goals The goal of hatcheries in response to the extinction crises in Maine should be to conserve genetic quality -- a broad term that includes the concepts of genes adapted to local conditions, complementary and coadapted genes, and appropriate genetic diversity -- in the remaining wild populations of Atlantic salmon, allowing these survivors to persist.
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From page 140... ...
Clearly, current hatchery operations in Maine cannot support recreational or commercial fisheries for anadromous Atlantic salmon. It is possible to establish a small recreational fishery for salmon by rearing fish to adulthood in a hatchery and then releas
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From page 141... ...
Hatchery fish phenotypes commonly differ in ways that will influence ecological interactions between them and wild fish. A meta-analysis of hatchery effects on pre-spawning behavior shows strongly that hatchery rearing results in increased pre-adult aggression and decreased response to predators that may, in part, explain their decreased subsequent survival in the wild (in 15 of 16 case studies)
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From page 142... ...
; and appropriate genetic diversity, which confers evolutionary potential by allowing for a variety of genotypes to be produced from various matings but does not counteract other aspects of genetic quality. For example, domestication selection is a well-known hazard of supportive breeding programs (Fleming and Gross 1989; McGinnity et al.
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From page 143... ...
. The current DPS-river supportive breeding and propagation program at the Craig Brook hatchery reduces the risk of purely demographic extinction by bringing only a portion of a river's parr or returning adults into captivity (Buckley 2002a,b)
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From page 144... ...
For instance, the high fecundity of salmon fosters a temptation to produce large numbers of progeny from a few parental fish in each breeding season, artificially creating a "genetic bottleneck" that significantly reduces genetic variability among the progeny. Current protocols at the Craig Brook hatchery for DPS river brood stocks appropriately avoid this obvious pitfall (Buckley 2002a,b)
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From page 145... ...
Most Atlantic salmon populations in Maine are severely depleted and continue to decline, and for such populations, the positive effects of increasing the actual population size outweighs the potential short-term genetic drawbacks caused by reductions of the Ne. Thus, the need for supportive breeding is urgent.
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From page 146... ...
. The dashed line indicates the effective size in the absence of supportive breeding.
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From page 147... ...
Loss of Genetic Variability among Populations (Population Identity) Crosses made among fish from multiple populations result in loss of genetic distinctness of each individual population (that is, population identity)
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From page 148... ...
While Sheehan's study is not definitive, because of design limitations, it is suggestive of the kind of local adaptation that is common in wild populations of salmonids and that forms the basis of the concern for maintaining the remnants of the natural metapopulation structure of wild salmon in Maine. Low amounts of migration can counter the inevitable loss of genetic variability in isolated populations without overwhelming local forces of adaptation.
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From page 149... ...
A recent modification to the DPS brood-stock mating protocol at the Craig Brook hatchery (to mate only 4-year old adults) could increase the risk of this kind of domestication selection, because there probably is a partial genetic basis (heritability)
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From page 150... ...
Both genetic hazards cannot be reduced simultaneously. At present, practices at Craig Brook hatchery focus on reducing the loss of genetic variability within populations and ignore the risk of domestication selection that is due to loss of sexual selection.
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From page 151... ...
and wild salmon is very likely bidirectional. It has been extremely difficult to determine the incidence of disease transmission from hatchery to wild fish, as well as the impacts such transmission would have on wild stocks (Flagg et al.
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From page 152... ...
. Sea lice are more common in wild fish in areas with sea cages (PFRCC 2003)
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From page 153... ...
The authors concluded that small wild populations and hatchery populations with lowered genetic variability would have increased susceptibility to pathogens. With small wild populations, disease susceptibility is not directly controllable or even necessarily the most important concern, but the protocols described above (also Flagg and Nash [1999]
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From page 154... ...
Altered behaviors of hatchery-reared fish may disrupt or harm the reproductive success or survival of wild fish. Although releases of hatchery fish are often implemented to compensate for reduced production caused by human-induced habitat degradation, a range of potential ecological problems may be associated with this practice.
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From page 155... ...
Increasingly, evidence shows that the altered behaviors of hatchery fish are maladaptive, resulting in poor survival and reproductive success in the wild. Hatchery fish experience reduced survival, compared with wild fish (15 of 16 studies reviewed by Einum and Fleming 2001, metaanalysis p 0.001)
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From page 156... ...
Of those, current procedures at Craig Brook hatchery are appropriate for reducing the probability of extinction, loss of genetic variability within populations, and domestication selection. The recent move to mate DPS brood stock only at age 4 may increase the genetic risk of domestication selection.
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From page 157... ...
Additionally, any stocking of hatchery fish should include direct monitoring of their performance and their effects on wild fish. Genetic marking based on inherent allelic differences between families (see Eldridge et al.
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From page 158... ...
. Recently, the Craig Brook hatchery appears to have initiated genetic marking, at least for a portion of the matings made in the Dennys River and Penobscot River brood stock, that could be used later to distinguish returns from fry versus smolt releases (Buckley 2002a,b)
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From page 159... ...
. Under certain circumstances, for example, if the wild population seems about to disappear or if rehabilitation or other events seem to have substantially improved available habitat in a stream without a surviving run of salmon, the wild fish could be used as brood stock for reintroducing fish into the population.
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From page 160... ...
Lacking other approaches to salmon recovery, gene banking alone would ultimately be ineffective. Disadvantages of this option include expense, risk of losing entire banked populations through disease or system failure, the need to periodically tap wild populations for new juveniles, the inevitable loss of genetic quality that would occur, and the difficulty of gaining political support.
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From page 161... ...
Given the small population sizes, genetic markers could be used to develop estimates of the genetic contribution of hatchery versus wild adults to subsequent generations. It would be reasonable for a gene bank to contain representative samples of juveniles from all the unstocked rivers, as described in the Gene Banking section.
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From page 162... ...
With the removal of Edwards Dam on the lower Kennebec, the possibility of salmon recovery in the upstream Kennebec main stem has become a matter of considerable interest. Viable populations of Atlantic salmon are in Togus Stream and Bond Brook tributaries, both joining the main stem below Edwards Dam.
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From page 163... ...
The Kennebec also provides an excellent opportunity for fishery managers and biologists to determine whether dam removal will be sufficient to allow recolonization and expansion of the wild fish populations upstream of previous impediments. A review of accumulated experience in the Bond Brook and the Togus Stream suggests that some recolonization of the upstream Kennebec main stem can be expected.
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From page 164... ...
This option allows for the relocation of cage sites away from important Atlantic salmon populations. The magnitude of most environmental impacts on wild salmon diminishes as distance is increased between the cage site and the natal rivers and migratory routes.
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From page 165... ...
Physical tagging or marking could be used to identify farm salmon in the wild and facilitate their separation from wild fish. This option can be used to determine the source of escapes and to assess the interactions of escaped farm salmon with wild populations.
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From page 166... ...
Cooperative agreements with Canada should be implemented to reduce the impacts of salmon farming on wild salmon, especially in the Cobscook and Passamaquoddy Bay areas. Some of the measures that provide opportunities for coexistence between cultured and wild fish are initially costly to the industry.
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From page 167... ...
To the degree that socioeconomic factors associated with the industry are understood, it will be less difficult to adapt the industry to reduce risks to wild salmon. Even if it does not change, many socioeconomic factors related to aquaculture have not been quantified, and better knowledge of them could be used to the benefit of Maine's residents and the industry itself.
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From page 168... ...
However, several approaches short of total prohibition could be helpful. Stocking gamefish that resemble anadromous Atlantic salmon or compete with or prey on them in streams with imperiled anadromous Atlantic salmon populations is probably detrimental to Atlantic salmon and should be carefully evaluated wherever it occurs.
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From page 169... ...
At the Maine Atlantic Salmon Task Force (1997) pointed out, "Despite careful handling, fish may die from trauma when fisheries biologists capture salmon to collect necessary growth and population data." In most cases, the number of fish killed by research is so small that it is not a serious consideration, but in several Maine rivers there are so few wild salmon that killing even one parr or smolt could affect the population.
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From page 170... ...
If noninvasive sampling is infeasible or too costly at present, the committee suggests that until wild fish numbers rebuild substantially, invasive sampling be limited to counting smolts migrating down river with minimal holding time when rotary screw traps are used and that the collection of blood and other tissues be discontinued. That would reduce further stress to wild fish.
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From page 171... ...
Additionally, the committee sees a need for the State Planning Office, or other legitimate authority, to conduct a systematic assessment of governance to determine whether there are gaps in authority; overlapping authority; conflicts of goals, interests, and values among agencies and groups; and adequate cooperation among government agencies as well as between these agencies and NGOs. Among other things, the study should determine whether the current ecology of governance contains disincentives or incentives for experimentation or other forms of learning; it should also determine the extent to which the public processes used to date have contributed to the development of effective strategies for conservation and rehabilitation of salmon habitat and salmon populations that are perceived as legitimate and credible by the different interest groups affected by these strategies.
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From page 172... ...
To date, this appears to have been the central component of efforts to diagnose the problem of Atlantic salmon in Maine. To be effective, risk characterization requires diverse and sustained participation by the full range of interested and affected parties throughout the process of diagnosing the situation, characterizing risks, risk assessment, decision analysis, and implementation of the recovery program (NRC 1996b)
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From page 173... ...
This section provides detailed examples of strategies that relate to spatial data and management information systems, roads, irrigation withdrawals and return flow, agricultural chemicals, riparian forest buffers, forest management planning, forestry best management practices (BMPs) , and recreational use and that reduce the adverse impacts of residential, commercial, and industrial development.
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From page 174... ...
After completing the first iteration of the watershed assessment, a more detailed functional inventory of dams and other obstructions (culverts, bridges, channelized reaches, waterfalls, any hydraulic conditions or structures that inhibit fish passage) to fish passage could be developed to evaluate cumulative effects and design optimal conservation strategies.
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From page 175... ...
careful route planning to keep roads on resistant terrain and minimize the number of road-stream crossings, (2) bridge and culvert designs with hydraulic characteristics that permit fish passage in both directions for different life stages, (3)
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From page 176... ...
Agricultural Chemicals Low-bush wild blueberry (Vaccinium angustifolium) is a small woody shrub that once grew in the understory of sparse forests, openings created by wildfires, or larger patches when soil and site conditions were too poor to support trees.
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From page 177... ...
Riparian Forest Buffers The riparian area is the transition between terrestrial and aquatic ecosystems (NRC 2002d)
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From page 178... ...
Forest Management Planning A brief summary is needed to explore the potential interaction of forestry and Atlantic salmon in Maine. Contemporary forest management involves the harvesting of trees to generate a sustainable supply of wood fiber for paper, lumber, and other forest products while avoiding or mitigating adverse impacts on other resources -- water, fisheries, wildlife, recreation, aesthetics, and spiritual values.
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From page 179... ...
There are several ways that state-of-the-art forest management planning could help to conserve Atlantic salmon populations in Maine. The first is simply by using terrain (digital elevation model)
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From page 180... ...
or exceed thresholds at the subwatershed scale. In the latter case, the influence of timber harvesting near smaller tributaries with unobstructed, high-quality salmon habitat could be substantial even though they are protected with riparian forest buffers.
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From page 181... ...
5. Timber harvesting, road construction, road reclamation, and postharvest site stabilization efforts should be adjusted to terrain and weather conditions.
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From page 182... ...
· Temporary bridges or brush mats to cross ephemeral streams or wetlands. · Seeding of exposed soil with annual winter rye to ensure rapid revegetation while limiting the permanent introduction of exotic grasses and herbaceous plants (the rye dies and adds organic matter to soil as native species recolonize the site)
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From page 183... ...
But for the others, the hidden or indirect costs and benefits can be substantial. For example, if a dam that blocks fish passage is retained, the dam's owners benefit from any net revenues generated by the dam and property owners adjacent to the pool behind the dam benefit from owning waterfront property.
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From page 184... ...
An additional complication is the uncertainty surrounding the effect of an option on salmon and its effect on other species of interest. There is no guarantee that implementing any of the options the committee recommends, or even all of them together, will lead to a recovery of wild salmon populations in Maine.
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From page 185... ...
They paid the city of Augusta, a co-licensee, $100,000 to make up for lost revenue. Bath Iron Works, a shipbuilder, agreed to contribute $2.5 million in exchange for favorable consideration of its request to expand its shipyard on the river, and the Kennebec Hydro Developers Group of upstream dam operators contributed $4.75 million in return for extra time allowed for the installation of fish passage devices at their dams (Associated Press 1998)
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From page 186... ...
The bearers of the cost would have to be determined by negotiation, legal action, or other processes. More information on estimating costs of dam removal is provided by the Heinz Center (2002)
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From page 187... ...
A properly conducted research program involving paired streams might require additional employees and support and equipment. Salmon Farms The cost of many of the committee's suggested modifications of salmon farming cannot be reliably estimated because the costs of salmon farming operations are proprietary and because many factors -- for example, the willingness of employees to move to work at a new site, the costs of various permitting and other legal and political requirements-are unknown.
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