Three additional what-if scenarios provide examples of issues where
modeling can play a constructive role by placing potential population-level
effects of mortality resulting from entrainment and impingement in a
broader ecological perspective. The first involves comparing the mortality from entrainment and impingement of early life stages with the
fishing mortality of older fish. This comparison can demonstrate that the
population-level consequences of increased mortality of early life stages
(that experience high natural mortality) are likely to be substantially less
than the consequences of comparable levels of increased mortality of older
fish (that experience low natural mortality). The second example involves
comparing the dynamics of fish species with different demographic characteristics. That comparison can illustrate that not all fish species are demographically equal. Consequently, it is likely that they will not respond in the
same manner to incremental mortality of early life-history stages (i.e., those
life stages most commonly experiencing mortality from entrainment and
impingement). The third example involves comparing the consequences of
negative and positive extreme events (e.g., droughts and floods) and can
demonstrate that such events may result in either missing or dominant year
classes. Such perturbations to the age structure of a fish population can
influence its dynamics, making it more difficult for scientists to interpret
past trends or to predict consequences of mortality from entrainment and
impingement.
The second role for modeling, using the modeling process to communicate with and educate decision makers and stakeholders, can be
part of the regulatory decision-making process itself. In the context of
permitting electric-power-generation facilities under Section 316(b), the
decision-making process involves the values and objectives of all stakeholders, only some of which deal directly with entrainment and impingement of fish. This broader decision-making framework can be
viewed as involving (1) information collection, analysis, and model development and application; (2) development of decision models or criteria; and (3) decision making (Figure 3.1) (Clemen 1991). As the decision
stakes and complexity of an assessment increase, each of these three
activities becomes more intense and challenging. Whether consciously
or not, most 316(b) decisions involve all these activities. The process is
iterative. As more is learned about a water body, decision options are
discovered or limited (e.g., whether mitigation measures, such as stocking
or protecting wetlands, are allowed or whether a protective technology
actually works). In the course of the process, facility owners, regulators,
and stakeholders establish negotiation positions (e.g., the maximum
amount to invest in impingement or entrainment protection before mitigation is considered and how to cost mitigation measures). Communication
between key individuals in the first column of Figure 3.1 (typically scientists) and key individuals in the third column (typically nonscientists) is
important.
3. Modeling Fish Entrainment and Impingement Impacts
51
modeling can play a constructive role by placing potential population-level
effects of mortality resulting from entrainment and impingement in a
broader ecological perspective. The first involves comparing the mortality from entrainment and impingement of early life stages with the
fishing mortality of older fish. This comparison can demonstrate that the
population-level consequences of increased mortality of early life stages
(that experience high natural mortality) are likely to be substantially less
than the consequences of comparable levels of increased mortality of older
fish (that experience low natural mortality). The second example involves
comparing the dynamics of fish species with different demographic characteristics. That comparison can illustrate that not all fish species are demographically equal. Consequently, it is likely that they will not respond in the
same manner to incremental mortality of early life-history stages (i.e., those
life stages most commonly experiencing mortality from entrainment and
impingement). The third example involves comparing the consequences of
negative and positive extreme events (e.g., droughts and floods) and can
demonstrate that such events may result in either missing or dominant year
classes. Such perturbations to the age structure of a fish population can
influence its dynamics, making it more difficult for scientists to interpret
past trends or to predict consequences of mortality from entrainment and
impingement.
The second role for modeling, using the modeling process to communicate with and educate decision makers and stakeholders, can be
part of the regulatory decision-making process itself. In the context of
permitting electric-power-generation facilities under Section 316(b), the
decision-making process involves the values and objectives of all stakeholders, only some of which deal directly with entrainment and impingement of fish. This broader decision-making framework can be
viewed as involving (1) information collection, analysis, and model development and application; (2) development of decision models or criteria; and (3) decision making (Figure 3.1) (Clemen 1991). As the decision
stakes and complexity of an assessment increase, each of these three
activities becomes more intense and challenging. Whether consciously
or not, most 316(b) decisions involve all these activities. The process is
iterative. As more is learned about a water body, decision options are
discovered or limited (e.g., whether mitigation measures, such as stocking
or protecting wetlands, are allowed or whether a protective technology
actually works). In the course of the process, facility owners, regulators,
and stakeholders establish negotiation positions (e.g., the maximum
amount to invest in impingement or entrainment protection before mitigation is considered and how to cost mitigation measures). Communication
between key individuals in the first column of Figure 3.1 (typically scientists) and key individuals in the third column (typically nonscientists) is
important.
3. Modeling Fish Entrainment and Impingement Impacts
51