Suggested Citation:"Appendix J." National Research Council. 1998. Improving Fish Stock Assessments. Washington, DC: The National Academies Press. doi: 10.17226/5951.
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J— Excerpts from the Food and Agriculture Organization Report Precautionary Approach to Fisheries*
4.3 Assessment Methods and Analysis
- Biological reference points for overfishing should be included as part of a precautionary approach.
- A precautionary approach specifically requires a more comprehensive treatment of uncertainty than is the current norm in fishery assessment. This requires recognition of gaps in knowledge, and the explicit identification of the range of interpretations that is reasonable given the present information.
- The use of complementary sources of fishery information should be facilitated by active compilation and scientific analysis of the relevant traditional knowledge. This should be accompanied by the development of methods by which this information can be used to develop management advice.
- Specifically the assessment process should include:
- scientific standards of evidence (objective, verifiable and potentially replicable) should be applied in the evaluation of information used in analysis;
- a process for assessment and analysis that is transparent, and
- periodic, independent, objective and in-depth peer review as a quality assurance.
- A precautionary approach to assessment and analysis requires a realistic appraisal of the range of outcomes possible under fishing and the chances of these outcomes under different management actions. The precautionary approach to assessment would follow a process of identifying alternative possible hypotheses or states of nature, based on the information available, and examining the consequences of proposed management actions under each of these alternative hypotheses. This process would be the same in data rich and data poor analyses. A precautionary assessment would, at least, aim to consider: (a) uncertainties in data; (b) specific alternative hypotheses about underlying biological, economic and social processes, and (c) calculation of the response of the system to a range of alternative management actions. A checklist of issues for consideration under these headings is found in the following paragraphs.
Suggested Citation:"Appendix J." National Research Council. 1998. Improving Fish Stock Assessments. Washington, DC: The National Academies Press. doi: 10.17226/5951.
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- Sources of uncertainty in data include: (a) estimates of abundance; (b) model structure; (c) parameter values used in models; (d) future environmental conditions; (e) effectiveness of implementation of management measures; (f) future economic and social conditions; (g) future management objectives, and (h) fleet capacity and behavior.
- Specific alternative hypotheses about underlying biological, economic and social processes to be considered include (a) depensatory recruitment or other dynamics giving rapid collapse; (b) changes in behavior of the fishing industry under regulation including changes in coastal community structure; (c) medium term changes in environmental conditions; (d) systematic under-reporting of catch data; (e) fishery dependent estimates of abundance not being proportional to abundance; (f) changes in price or cost to the fishing industry; and (g) changes in ecosystems caused by fishing.
- In calculating (simulating) the response of the system to a range of alternative management actions, the following should be taken into account:
- short term (1-2y) projections alone are not sufficient for precautionary assessment; time frames and discount rates appropriate to inter-generational issues should be used, and
- scientific evaluation of management options requires specification of operational targets, constraints and decision rules. If these are not adequately specified by managers then precautionary analysis requires that assumptions be made about these specifications, and the additional uncertainty in the consequences resulting from these assumptions should be calculated. Managers should be advised that additional specification of targets, constraints and decision rules are needed to reduce this uncertainty.
- Methods of analysis and presentation will differ with circumstances, but effective treatment of uncertainty and communication of the results is necessary in a precautionary assessment. Some approaches (see the Appendix to this section) that could prove useful are:
- where there are no sufficient observations to assign probabilities to different states of nature that have occurred, decision tables could be used to represent different degrees of management caution through the Maximin and Minimax criteria;
- where the number of different states of nature and the number of potential management actions considered is small, but probabilities can be assigned, then decision tables can be used to show the consequences and probabilities of all combinations of these, and
- where the range of states of nature is large the evaluation of management procedures is more complex, requiring integration across the various sources of uncertainty.
- A precautionary approach to analysis would examine the ability of the data collection system to detect undesirable trends. When the ability to detect trends is low, management should be cautious.
- Since concerns regarding the reversibility of the adverse impacts of fishing are a major stimulus for a precautionary approach, research on reversibility in ecosystems is an important part of developing precautionary approaches.
