Role of risk assessment in fish health policy and management

Transcription

1 ICES Journal of Marine Science, 58: doi: /jmsc , available online at on Role of risk assessment in fish health policy and management C. Stephen Stephen, C Role of risk assessment in fish health policy and management. ICES Journal of Marine Science, 58: Fish health management occurs in a complex ecological and socio-economic system, in an uncertain and uncontrollable environment, and with a lack of empirical data. Increasingly, regional, national, and international policies require some form of risk assessment to help make reasonable decisions. Despite its increasing use and popularity, there are many criticisms of risk assessment as a basis for fish health management decisions. Underlying these criticisms are three common elements: (1) unrealistic expectations of the ability of risk assessments to identify the right decision; (2) inadequate predictive ability of fish health risk assessment models; and (3) the lack of integration or consideration of management, societal, and scientific concerns. Rather than abandoning risk assessment as a basis for management because of its quantitative limitations, the concept should be fully explored and applied in order to facilitate socially and ecologically relevant fish health management decisions. Moreover, efforts should be undertaken to educate managers and stakeholders as to the role of risk assessment in decision support and in exploring additional models for describing and assessing the impacts of fish health management decisions International Council for the Exploration of the Sea Key words: assessment, decision, fish, health, management, risk. Received 16 October 1999; accepted 15 May C. Stephen: Centre for Coastal Health, 900 5th Street, Nanaimo, BC, Canada V9R 5S5; tel: ; fax: ; cch@mala.bc.ca Introduction The protection of fish health has been a major criterion for the development of aquaculture and transfer regulations in Canada (Leach and Lewis, 1991). Increasingly, regional, national, and international policies are requiring some form of risk assessment to ensure reasonable and equitable management decisions. The application of risk assessment to fish health is advocated in the Sanitary and Phytosanitary Measures as established by the World Trade Organization, the International Council for Exploration of the Sea protocols for fish movement, the Office International des Epizooties International Aquatic Animal Health Code, Fisheries and Oceans Canada draft policy on introductions and transfers, and a variety of state and provincial aquaculture regulations. Despite its increasing use and popularity, there are many criticisms of risk assessment as a basis for management decisions, particularly for issues such as fish health, where deficits in information and lack of a substantial history of risk-based decisions limit our predictive capacity. Risk assessment has been called a shot-gun marriage between science and the law which attempts to apply scientific methods and evidence to issues of administration and legislation, yet fails to fully satisfy the needs of either the legal or scientific communities (Russell and Gruber, 1987). In Canadian aquaculture, criticisms of risk assessment have been largely of two types. First, there are those who feel that risk assessments err on the side of caution to the point of complete inaction, tending to overestimate risks by failing to discriminate between those that are likely to occur from those that are merely possible, thus leading to excessive regulatory control. Other critics feel that risk assessments tend to be insufficiently cautious, failing to account for unknown, unexpected, or synergistic impacts. Underlying both these criticisms are three common elements: (1) unrealistic expectations of the ability of risk assessments to identify the right decision; (2) inadequate predictive ability of fish health risk assessment models; and (3) the lack of integration or consideration of management, societal, and scientific concerns. On the basis of recent reviews of Canadian and international policies, I discuss how these elements must be considered when applying risk assessment to fish health management /01/ $35.00/ International Council for the Exploration of the Sea

2 Risk assessment in fish health policy and management 375 Risk assessment and management decisions The concept of risk reflects our uncertainty as to the outcome of today s actions. Risk is a product of the potential outcomes of a hazard, how likely the adverse events are to occur and the consequence of their occurrence (Kaplan, 1981). A hazard results in a risk only if there is an exposure pathway and susceptible individual(s) that create the possibility of an adverse outcome. The Animal, Plant, and Food Risk Assessment Network (APFRAN) of the Canadian Food Inspection Agency defines risk assessment as the process of identifying a hazard and estimating the risk presented by the hazard (where risk is the likelihood of occurrence and the magnitude of the consequences of an adverse event). It includes estimates of uncertainty and is an objective, repeatable and scientific process. The US National Research Council suggested that misunderstanding the role of risk analysis in making regulatory decisions may be due to confusion between risk assessment (the use of scientific methods and evidence) and risk management (the process by which managers decide how to use the results of a risk assessment) (Russell and Gruber, 1987). Risk management is defined by APFRAN as the process of identifying, evaluating, selecting and implementing alternatives for mitigating risks. It is acknowledged that risk managers make implicit judgments about the safety of particular courses of action. Risk assessment and management can therefore be seen as a process rather than a precise set of methods. Most fish health policies fail to detail how risks are to be assessed. While this is understandable, and perhaps inevitable given the diversity of fish species and ecosystems involved in mariculture, the lack of specificity leads to confusion regarding how risks can be compared between jurisdictions or between different risk assessments. Often, stakeholders or government managers mistakenly look to risk assessment as a method to resolve uncertainty and point to the correct decision. Alone, risk assessments are insufficient, except in the simplest circumstances, to make decisions (Wilson and Crouch, 1987). Instead, they are intended to fully characterize the hazards and benefits at hand to facilitate open, systematic, and repeatable decisions. The ultimate decision on whether or not to accept a risk is a societal or political choice that involves an understanding of risk perceptions and social values as much as it requires an understanding of science. Risk analysis helps to identify significant hazards and the need to mitigate their effects, stimulates research by identifying important unknowns, and helps set policy goals and regulatory priorities. Impediments to prediction In risk prediction, it is important to gain an understanding of the nature and potential magnitude of a hazard (Wilson and Crouch, 1987). The estimate of risk will always be subject to error. Part of this error is due to the stochastic nature of risk, part is due to systematic variation in determinants of impacts and the rest is due to uncertainties in what variables to measure and how to measure them. Along the chain of events from exposure to the manifestation of a risk, several alternate and unpredictable factors can influence the likelihood and magnitude of undesired outcomes. One of the largest impediments to forecasting fish health risks is a lack of understanding of the complex relationships that modify the likelihood and impacts of specific hazards. Fish health policy has historically focused on the potential impacts of translocated pathogens and parasites as the primary hazard and has implicitly assumed that the effects of translocation would be unacceptable. When regulations assume that the introduction of a hazard is undesirable, probability, rather than magnitude of effects, more strongly influences risk assessments (Ahl et al., 1993). Relying chiefly upon the concept of probability as a basis for regulatory approval is problematic when considering fish health. It is virtually impossible to determine the true infection status of any particular fish or region (Stephen, 1995). Testing protocols established through regulations often requires that the health status of a fish be based upon the features of a sample of a fish s cohort. At the group or facility level, decisions are typically based upon sampling strategies that give a certain level of confidence of detecting at least one positive fish from populations at or above the prevalence of disease that is considered acceptable. If no positive animals are found, it is assumed, within a certain error, that no fish will be infected. A recent survey of fish diagnostic laboratories in Canada revealed that a homogeneous approach to screening fish is unlikely to achieve the same results for all species and all pathogens (Thorburn, 1996). Therefore, confidence in estimates of the probability of infection is modified on a case-by-case basis. Moreover, there is little information on the false-negative and false-positive rates of diagnostic tests used in fishes, preventing evidence-based modifications of screening protocols. We are also limited in the number and nature of risks to look for; when compared to terrestrial animal health, we know relatively little about the epidemiology of disease-causing agents in wild (Bakke and Harris, 1998) and captive fishes. It has been estimated that less than 2% of fish diseases are known and our understanding of the known diseases is incomplete (Kinne, cited in Stewart, 1991). This, in part, reflects deficits in surveillance of fish diseases. For example, there are reports where the initial discovery of what is considered to be an imported disease is later found to be an endemic disease that has previously gone undetected (e.g. Amos et al., 1998), an error which could substantially mislead risk assessors.

3 376 C. Stephen Many environmental, social, nutritional, or other stressors modify the impacts of specific hazards associated with mariculture (Stephen and Iwama, 1997). For example, confounding effects of high densities, high temperatures, low water flows, and aggressive interactions at spawning have prevented researchers from determining the nature and magnitude of negative impacts that furunculosis places on wild fish in Norway (Johnsen and Jensen, 1994), the impact of Ich outbreaks on returns of Canadian sockeye salmon (Traxler et al., 1998), or the effect of whirling disease on North American trout populations (Modin, 1998; Stephen, 1999). While many fish health protection efforts focus upon the prevention of disease outbreaks, there is good evidence that disease can have significant ecological effects beyond acute mortality. Basic physiological and ecological parameters, such as immune function, genetic diversity, behaviour, predator avoidance, mate selection, reproductive success, community structure, species diversity, and demography can be dependent on an animal s infection and disease status (Dobson and Hudson, 1986; Spalding and Forrester 1993). For example, parasitism was identified as one of the main determinants of death in fish in a Manitoba lake where parasitized fish were smaller than non-infested fish and, thus, more susceptible to predation (Szalai and Dick, 1991). Similarly, infections with Kudoa paniformis in Pacific hake (Merluccius productus) were associated with a dose-related depression of female fecundity (Alderstein and Dorn, 1998). To completely characterize the magnitude of effects of a hazard, risk assessors must begin to look not only at the potential for large-scale mortality, but also at how changing disease status can affect population and community dynamics. Risk assessment is further challenged by the need of managers to have a hazard dichotomously classified as hazardous or not. Health can be defined as a state characterized by: anatomical integrity; ability to perform expected individual, population, and community roles; ability to deal with physical, biological, and social stresses; and freedom from risk of disease and untimely death (adapted from Last, 1983). Historically, fish health regulations have focused on acute infectious disease impacts rather than on an evaluation of the broader determinants of health. In a recent literature review of fish health risks, no examples were found that followed a wild fish population after the occurrence of a new disease, either to assess medium- to long-term impacts or to evaluate impacts from an ecological integrity viewpoint (Stephen and Iwama, 1997). In mariculture, health risks are presented to a variety of species that inhabit or visit the culture facility. There is a substantial and growing body of knowledge that shows that hazards affect different species differently. For example, some pathogens once thought to be restricted to salmonids in fact have wide host ranges (Kent et al., 1998). In some cases these salmon pathogens cause significant disease in non-salmonids, whereas in other fish these agents result only in asymptomatic infections. When fish populations mix, interacting strains of the same disease or multiple hazards circulate within and between populations at the same time. The wide variety of immune and population responses that occur in the face of one disease makes it very unlikely those coexisting diseases will act independently (Adler and Brunet, 1991). For example, the virus responsible for erythrocytic inclusion body syndrome is thought to increase the susceptibility or effects of other disease agents in salmonids (Leek, 1987). Given the diversity of species and diseases that exist, it is reasonable to conclude that risk assessments that evaluate disease impacts by looking at single populations and diseases are unlikely to predict all relevant outcomes. Moreover, risk assessments that focus only on the probability of hazard introduction or limit their assessments to overt disease impacts will fail to provide managers with a complete risk analysis. Accurate prediction of risk requires an appropriate model, and one model that can be used is historical consistency: what will happen tomorrow is likely to be the same as happened yesterday. In Canada, there is currently no programme dedicated to collecting, archiving, synthesizing, and assessing fish health risks. There is limited literature on the results of fish health management decisions, and where there is it tends to focus only on issues of whether or not disease outbreaks occurred subsequent to decisions (Bartley and Subasinghe, 1996; Stephen and Iwama, 1997). In the absence of sufficient historical data or in novel situations, risks can be assessed by analysis of an event tree, which is the flow of events from an initiator to a final outcome, with probabilities and outcomes of the various steps solicited from historical data from other situations or by analogy (Wilson and Crouch, 1987). If there is insufficient information to accurately characterize the event tree, it is reasonable to critically question the role of risk assessment in policy planning and management. The current lack of specific methods for applying risk assessment, coupled with the lack of data on significant impacts, often results in decisions about fish transfers made on a political or short-term economic basis (Bartley and Subasinghe, 1996). Social and management needs Decisions made on animal health can rarely be based on biological information alone (Johnston, 1980). Risk means different things to different people because social values influence its perception. During an environmental review of the management of the British Columbia salmon farming industry, there were fundamental differences in the interpretation of risk amongst the various stakeholders involved in public consultations. While

4 Risk assessment in fish health policy and management 377 Fish health risk issues Disease of fish and aquatic organisms Ecosystem values and services Public health Social, cultural and economic values Elements of the program Health intelligence: proactively identify potential risks and hazards through regular and critical reviews of various sources of health information Scoping issues: information passively and activelly collected so that the risk assessors can appropriately and accurately describe hazards and factors affecting the likelihood and severity of associated outcomes. Risk assessment: systematically synthesize a wide variety of information to determine the key unknowns and potential risk of alternative actions. Information dissemination: ensure that the results can be used in decision making, be incorperated into action plans, and be effectively communicated to stakeholders. Critical review: follow-up risk management decisions to evaluate and record the outcomes. Problem identification and prioritization Assess severity and probability of adverse effects Determine level of uncertainty Support risk management and communication Management and policy priorities and planning Figure 1. A proposed framework for a fish health risk assessment programme. industry advocated balancing the low probability of environmental catastrophe with the high likelihood of economic benefits, opponents emphasized the potential magnitude of environmental impacts and their effects on social values. For technical experts, risk can often be described as a probability function or in measures of impact such as mortality rates. However, to others, judgments about risk are often related to the social characteristics of the hazards, such as how equitably the impacts are distributed, the dread of the outcome, how controllable the outcome is and impacts on future generations (Slovic, 1987). Regulatory actions often require trade-offs between competing risk perceptions and values. The key issue for fish health managers is the extent and quality of information about the outcomes of alternative management decisions, the incentives for manipulating the fish and the preferences of the stakeholders involved. To date, just as in monitoring of the effects of fish translocations (Bartley and Subasinghe, 1996), fish health considerations have not adequately been concerned with impacts on society and ecosystems. While one could argue that evaluations of benefits and social implications of an action are a function of the risk manager rather than within the scientific realm of the risk assessor, strict uncoupling of management and assessment can lead risk assessors to ignore the value implications of their judgments and, hence, not serve managers or society adequately. Discussion Fish health management often involves a complex ecological and socio-economic system, an uncertain and

5 378 C. Stephen uncontrollable environment, and a lack of empirical data. Despite this, managers are required to make a good decision. Anderson et al. (1977) defined a good decision as a considered choice based on a rational interpretation of the available information. Many jurisdictions have chosen to rely on risk assessment as a means by which to gather and present information to support good decisions. It can be anticipated that we will continue to be faced with fish health problems that require us to make a choice between a range of options. Compared to terrestrial agriculture, we are limited in our ability to rely on past experience or standard protocols to meet the demands of a growing and evolving mariculture industry. Moreover, the fact that there are increasing public concerns requires managers to incorporate evaluations of ecological and social values into their fish health management strategies. Effective decisions regarding health programmes require that one consider different components in a meaningful and simple way to facilitate the selection of appropriate action (Ngategize et al., 1986). While it must be conceded that what constitutes minimal or acceptable risk will ultimately be a subjective determination, a framework for acquiring probability or impact data can be specified, as can the degree of confidence we have in those estimates. Figure 1 presents an outline of the components of a fish health risk assessment programme. Unlike the current situation in many countries, the proposed programme does not uncouple risks to fish, economies, societies, and ecosystems. It also acknowledges the dependence of effective risk assessments on information-gathering and dissemination of results. Recent fish health decisions have benefited from such an integrated approach. Take, for example, the importation of tilapia into western Canada. A recent unpublished comparison of the risk associated with importation of tilapia to the pet, seafood, and culture markets was frustrated due to the lack of data on the nature and environmental viability of imported tilapia pathogens. Risk management options were restricted to the application of generic recommendations in anticipation of potential but unquantified risks. However, a review of social and ecological data was more informative. Significant determinants of risk were found in social data, such as human immigration patterns, that would effect demand for imported fish and the economic pressures that would affect how local culture operations would contribute to the market in live fish, rather than by an examination of fish health data. An understanding of how social changes and ecological constraints affected risk made a greater contribution to risk management decisions in this case than did the generic fish disease data alone. Rather than abandoning risk assessment as a basis for management because of its quantitative limitations, the concept should be more fully explored and applied in order to facilitate socially and ecologically relevant fish health management decisions. Although fish health risk assessments face several obstacles that impede their predictive value, risk assessment guidelines can foster a consistent approach to evaluating and managing risks in spite of these uncertainties (Russell and Gruber, 1987). An important step towards ensuring proper use and interpretation of the results of risk assessment, should be a campaign to educate managers and stakeholders as to the role risk assessment plays in decision support. Whether we call the process risk assessment, decision analysis or cost-benefit analysis, the goal is to have an explicit, rational, comprehensive, and flexible process that incorporates relevant inputs and values. Fish health risk assessors should work to develop an array of techniques that can be used to identify how decision options differ, which values are at risk in a given situation, and which determinants of risk need to be compared to help people make open and objective decisions. Nations supporting risk assessment as a foundation for fish health management must take steps to integrate risk assessment with surveillance and the warehousing of information on the outcomes of management decisions so as to facilitate the timely acquisition of relevant information. A focus on decision support, rather than the rigid application of risk assessment technique originally derived from toxicology, is apt to better meet the needs of fish health managers. References Adler, F. R., and Brunet, R. C The dynamics of simultaneous infections with altered susceptibilities. Theoretical Population Biology, 40: Ahl, A. S., Acree, J. A., Gipson, P. S., McDowell, R. M., Miller, L., and McElvanie, M. 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