Atlantic Salmon in Maine (2004) / Chapter Skim
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4 Setting Priorities for Action
4 Setting Priorities for Action
Pages 108-137
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From page 108... ...
Therefore, it is not obvious what actions should be taken and in what order to reverse those declines. The Atlantic Salmon Conservation Plan for Seven Maine Rivers (Maine Atlantic Salmon Task Force 1997)
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From page 109... ...
The committee similarly has not attempted to evaluate the range of responses to potential threats that could be induced by climate change, because that issue is much larger than conservation planning efforts in Maine can reasonably address. As noted earlier, the committee's initial work focused on understanding the genetic status of Atlantic salmon in Maine (NRC 2002a)
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From page 110... ...
Once the application of risk assessment and decision analysis methods was proposed by a small subset of our members, the entire committee was unified and energized by the prospect of breaking the impasse and fostering the use of the adaptive management paradigm for conservation of Atlantic salmon in Maine -- to help see the forest for the trees. It has been observed that all models are wrong, but some are useful.
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From page 111... ...
and account for all of the means by which humans affect the viability of a wild salmon population can give the appearance of an artificially high accuracy of assignment (nothing left unexplained; precise allocation to alternatives)
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From page 112... ...
. They include such items as water quality and quantity, obstructions to passage, changes in availability and quality of spawning and rearing habitat, presence of nonnative species that likely compete with or prey on HUMANS Dams Irrigation Roads Agriculture Acidity Logging Hatcheries Exotics Aquaculture 0.3 0.6 0.1 A 0.4 0.05 0.2 0.2 0.1 0.05 F B 0.6 0.15 0.15 0.1 C 0.02 0.02 0.3 0.05 0.65 E Level 1 0.85 0.11 0.15 0.05 0.80 D Water Quality Habitat Passage Pred./Prey Disease Competition A B C D E F Abiotic 0.28 0.28 Biotic 0.28 0.12 0.14 0.06 Level 2 ECOLOGY FIGURE 4-2 Subcategories of ecological impacts on wild salmon.
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From page 113... ...
They include inbreeding, domestication selection, breakdown of co-adapted gene complexes through lack of mate choice, genetic drift due to small population size, the incorporation of genes into the population from nonnative or nonlocal populations, and so on. Finally, direct factors are human actions that directly kill adult or juvenile fish.
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From page 114... ...
Given that more than half the original spawning habitat of Atlantic salmon in Maine is no longer available to them because of obstructions to passage, and given the presence of additional ecological factors, it seems clear that ecological factors contribute more than half of all sources of human-caused salmon mortality in Maine. The committee therefore assigned the ecological category a total contribution of 0.6.
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From page 115... ...
It did this by considering the various pathways outlined in the Figure 4-2 bubble diagrams. At level 2, the level that feeds directly into level 3, it was possible to identify three major abiotic factors (water quality, habitat, passage)
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From page 116... ...
Thus, to understand the full impact of dams on viable wild salmon through impacts on water quality, we take the value of 0.4 at level 1 (impact of dams on water quality) and multiply this by 0.14, which is the relative impact of water quality on ecology.
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From page 117... ...
Impact (Sum) Dams Water quality 0.4 0.14 0.6 0.0336 Habitat 0.6 0.28 0.6 0.1008 Passage 0.85 0.28 0.6 0.1428 Predator/Prey 0.15 0.12 0.6 0.0108 0.29 Withdrawal Water Quality 0.05 0.14 0.6 0.0042 Habitat 0.15 0.28 0.6 0.0252 0.03 Roads Water Quality 0.2 0.14 0.6 0.0168 Passage 0.11 0.28 0.6 0.0185 0.04 Agriculture Water Quality 0.2 0.14 0.6 0.0168 Habitat 0.15 0.28 0.6 0.0252 0.04 Acidity Water Quality 0.1 0.14 0.6 0.0084 0.01 Logging Water Quality 0.05 0.14 0.6 0.0042 Habitat 0.1 0.28 0.6 0.0168 Passage 0.02 0.28 0.6 0.0034 Predator/Prey 0.05 0.12 0.6 0.0036 0.03 Hatcheries Passage 0.02 0.28 0.6 0.0034 Disease 0.3 0.12 0.6 0.0216 Competition 0.3 0.06 0.6 0.0108 0.04 Exotics Predator/Prey 0.8 0.12 0.6 0.0576 Disease 0.05 0.12 0.6 0.0036 Competition 0.6 0.06 0.6 0.0216 0.08 Aquaculture Disease 0.65 0.12 0.6 0.0468 Competition 0.1 0.06 0.6 0.0036 0.05 Totals 0.6000 0.60
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From page 118... ...
This suggests that 29% of the total impact on viable wild salmon populations by humans is through dams, and we can now map the role that dams have on disrupting the ecology of salmon. The tables summarize similar kinds of analyses for all the possible impact factors that the committee identified.
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From page 119... ...
TABLE 4-3 Proportional Impacts of Genetics on Wild Atlantic Salmon Populations Based on Risk Assessment (refer to Figures 4-1 and 4-4) Level Level Level Level Level Product Impact Component 0 1 1b 2 3 (1bx2x3)
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From page 120... ...
Density-Dependence of Factors Perhaps the most difficult problem is knowing which factors are density dependent and to what degree. For example, there appears to be considerable scientific agreement -- if not complete consensus -- that poor marine survival during their first winter at sea has been a major factor in the recent declines of salmon populations (Maine Atlantic Salmon Task Force 1997)
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From page 121... ...
However, we do not know how many fish escape from farms, the exact reproductive success of hatchery and farm fish in the rivers, how well their offspring survive, and so on. The committee has therefore recalculated Table 4-3 using penetrance ratios for hatchery to farm fish of 1:1, which yields values of 6% for hatcheries and 14% for farm fish; 1:3, which gives 10% and 10%; and 1:27, which gives 18% and 2%.
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From page 122... ...
It can be difficult to understand the relationships among all these factors and to establish clear, measurable objectives that integrate them into the decision making process. Decision analysis tools originally developed for economic applications that are now being used in the natural resource arena help policy makers to organize these factors and to evaluate their impacts on different alternative strategies.
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From page 123... ...
Changing land-use patterns within watersheds may be predictable directionally, but their pace, scale, and distribution are often uncertain. Whether the uncertainty is caused by the influence of an irreducible probability factor, such as the chance that a coin will turn up heads or tails for any given toss, or whether it is based on incomplete knowledge of the factors affecting outcomes, decision analysis provides a method to weigh uncertainty elements against preferences for different outcomes (Keeney and Raiffa 1976)
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From page 124... ...
Explicit objectives are important because they provide benchmarks against which to evaluate the expected outcomes of different management options. Risks of Farm Fish An application of decision analysis could be for understanding the importance of various factors that might influence the success of various options for managing the impacts of Atlantic salmon raised in aquaculture pens on wild fish.
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From page 125... ...
No Implement the Chosen Alternative FIGURE 4-5 A decision analysis process flow chart. Source: Clemen 1991.
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From page 126... ...
This very low level of infection is impossible to measure because of small population sizes of returning adult salmon, so as a practical matter, it is a surrogate standard for eliminating parasite and disease transfer between farmed and wild fish. Several alternative approaches to farming discussed in Chapter 5 can be evaluated with respect to the likelihood of success in meeting objectives 1 and 2.
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From page 127... ...
Sterilize farm fish to minimize mating success between escapees and wild fish.
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From page 128... ...
, but would also eliminate employment and economic benefit. Enhancing Habitat Availability A more complex example of decision analysis concerns improving access to habitat blocked by dams.
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From page 129... ...
The process starts with developing an influence diagram (Figure 4-6) to show important variables and relationships affecting expected outcomes, in this case new habitat units.
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From page 130... ...
A decision table that represents the various uncertainties shown in the influence diagram can then be used to model the different strategies
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From page 131... ...
131 B) First First First; Dam Branch Dam Dam Simultaneously Downstream Removal Permitting Both (Sequence Upstream Downstream Work for Upstream Improve Access Survival Decisions Return Habitat No Used Research Research Adult New Competition/ Predation Interactions Juvenile Support salmon.
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From page 132... ...
In this case, the high number of habitat units gained by removing the dam on River A might be tempered by the effect of high costs and high economic impact on the political acceptability of the strategy and the longer time to implement it. The next step is to understand the critical uncertainties that need to be modeled in the subsequent phases.
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From page 133... ...
Even though hard data are often lacking, decision analysis allows decision makers to consider a range of values to gain a better overall picture of the effect of different uncertainty variables. One of the strengths of decision analysis is that making quantified judgments about uncertainties promotes clear communication (Clemen 1991)
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From page 134... ...
The decision tree provides a convenient way of ranking the alternatives according to their expected or "net" value. The technique is to weigh the base value of habitat units for each option by the probability factor at each branch of the tree corresponding to the three uncertainty variables.
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From page 135... ...
135 strategies. improvement habitat for tree Decision 4-8 FIGURE
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From page 136... ...
in Figure 4-8 and Table 4-5. If decisions about whether to implement a stocking plan or to conduct research in conjunction with the strategy to increase habitat availability might differentially affect strategic outcomes, they can be included in the decision tree as decision nodes with yes/no branches.
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From page 137... ...
In the above example, decision makers could be short-sighted if they decided to restrict water withdrawals in an effort to improve water quality above dams that limit access unless plans to improve habitat occupation were also in the works. These exercises are only illustrative.
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