ICES Journal of Marine Science: Journal du Conseil Advance Access originally published online on April 5, 2007
ICES Journal of Marine Science: Journal du Conseil 2007 64(4):775-778; doi:10.1093/icesjms/fsm033
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The dual role of indicators in optimal fisheries management strategies
1 Canadian Science Advisory Secretariat, Fisheries and Oceans, Government of Canada, 200 Kent Street, Ottawa, Ontario, Canada K1A 0E6
2 Ecosystem Science, Fisheries and Oceans, Government of Canada, 200 Kent Street, Ottawa, Ontario, Canada K1A 0E6
Correspondence to J. C. Rice: tel: +1 613 9900288; fax: +1 613 9900807; e-mail: ricej{at}dfo-mpo.gc.ca
Rice, J. C., and Rivard, D. 2007. The dual role of indicators in optimal fisheries management strategies. – ICES Journal of Marine Science, 64: 775–778.Indicators are used in two different ways in the assessment and advisory cycle. One is to audit performance of the management plan relative to achieving the objectives for the fishery. The second is to trigger control rules to manage the subsequent harvest. Traditionally, the assessment and management community has used spawning-stock biomass and fishing mortality for these functions, and as management strategies are being developed, generally continues to test the same indicators in both the audit and control functions. There is no reason to use the same indicators in both functions, and management of a few specialized commercial fisheries has recognized this, using different indicators in different roles for many years. That different indicators may be optimal for both roles presents a richer range of opportunities for exploring robust management strategies, and will be essential as ecosystem considerations and integrated management tools are included in assessment and management.
Keywords: ecosystem approach, harvest control rules, indicators, integrated management
Received 30 June 2006; accepted 18 January 2007; advance access publication 5 April 2007.
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Indicators play two crucial but different roles in management. One is reporting on the effectiveness of past management actions to achieve the biological, social, or economic objectives set for the fishery (the "audit" function); the other is guiding decisions about the provisions of the management plan being developed (the "control" function). Jennings (2005) reviews how state and pressure indicators can contribute to management, but he does not focus specifically on these two different roles of indicators, perhaps because of the different emphasis placed on the two roles in different management cultures.
Environmental quality reporting (World Bank, 2002; Belfiore, 2003; Olsen, 2003) focuses on the audit function, where suites of indicators of ecosystem health are periodically provided to managers (Rice, 2003; Jennings, 2005). Environmental reporting forms the basis for consultation with diverse clients on the acceptability of the state of the ecosystem, and for the management of activities affecting the state. The more abstract features of the ecosystem, such as indices of biodiversity or biological integrity, are used almost exclusively in the audit role, helping managers decide whether or not the ecosystem is in an acceptable state (Hughes et al., 1998; Andreasen et al., 2001; McCormick et al., 2001).
In fisheries management strategies, the emphasis is on using indicators in their control function, incorporating them into harvest control rules or otherwise placing them within rule-based decision-making. The trigger for the control rule drives the science advice on next year's management actions directly through the discrepancy between the current value of the indicator and some biologically based or societal reference point (Garcia and Staples, 2000; Defra, 2002; Rice and Rochet, 2005). Within the fisheries management culture, control rule triggers and associated reference points are not usually referred to as indicators, but functionally they are.
Fisheries science advisors have been addressing both functions for many years, usually using the same set of indicators for both tasks, so here we look at the limitations imposed by this culture on the exploration of fisheries management strategies, particularly when working within an ecosystem approach or addressing integrated management, using tools such as spatial management measures.
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The dual function of indicators |
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In both fisheries and environmental quality advisory cultures, the indicators often serve both functions (Figure 1a). Many jurisdictions have set environmental quality standards in policy and legislation, particularly for ecosystem features such as contaminant levels or water quality (OECD, 1998; Talue-McManus et al., 2003). In such cases, the "environmental health indicators" have been given a control function by providing at least on/off guidance to managers for regulatory action. In fisheries, indicators used in control rules de facto have informed users about the state of the system and the effectiveness of past management, even if the emphasis is on guidance for future management.
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For more than half a century, fisheries management has focused on using a state indicator of spawning-stock biomass (SSB) and a pressure indicator of fishing mortality (F) as the core products of assessments and the basis for management advice (Beverton and Holt, 1957; Ricker, 1975; Jennings, 2005; ICES, 2006), with many variants of SSB and F used to account for special cases. Strictly speaking, it is only when managers have agreed on the use of a harvest rate or a more complex harvest control rule that the SSB and F indicators serve a rigorous "control" function. However, in the context of ICES scientific advice on what the harvest should be, the adoption of safe biological limits and, subsequently, formal reference points applied these indicators in the control function, although ICES has no management responsibility (Griffith, 2002). During this evolution, the currency of rules has remained usually SSB and F, and the dual but different functions of the indicators have not been obvious to many users.
The move to implementing harvest strategies forces us to take a much broader view of which indicators can serve what roles. It no longer suffices to monitor or audit solely the biological system through SSB and F. We now acknowledge the necessity of monitoring and controlling the management system as well, requiring an augmented set of indicators focusing on the human (or management) side of the "system". Our search for this augmented set of indicators has been hampered by not separating the two functions they address and seeking indicators appropriate to each task separately. Similarly, participatory approaches requiring greater engagement of stakeholders in decision-making may change the role of a given indicator, depending on how it is used in the harvest strategies underlying the decision process.
Suitability of an indicator in fulfilling a function
In practice, SSB and F have been used to serve both the audit and the control functions in fisheries management strategies. Absolute values, increases and decreases in these indicators are the basis for conclusions about whether management is successfully keeping the stock sufficiently large (state) and the fishing mortality sufficiently low (pressure), i.e. the audit function. The relationships between SSB and F and their respective precautionary and limit reference points have been the direct quantitative basis for harvest advice in the coming year, i.e. the control function. Their performance was evaluated recently (Piet and Rice, 2004). They generally work as intended, but there are limitations. Problems seen in retrospect in many assessments (Mohn, 1999) highlight weaknesses in the audit function, and many managers feel that the complexities of fisheries management are not captured well in the control function (ICES, 2004).
The move to harvest strategies is meant largely to correct some weaknesses in the control function of SSB and F. Examining the case histories reviewed by ICES (2006), however, with a single exception (Icelandic cod, Gadus morhua, where some control rules include prey biomass), these developing harvest strategies use the same two indicators for both audit and control functions. Although our traditional indicators served both roles reasonably well, there is no biological or operational imperative requiring indicators to serve both functions simultaneously. The audit and control functions are different, and harvest strategies should focus on selecting the most effective indicators for each function (Figure 1b). Failing to take the opportunity to seek optimal indicators for each function may lead unnecessarily to suboptimal choices for both.
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Pacific salmon
Several decades ago, the anadromous and nearly semelparous life history characteristics of Pacific salmon (Oncorhynchus spp.) required the use of different indicators for the audit and control functions (Figure 2) for these fisheries (Link and Peterman, 1998; Woodey, 1999; Hilborn, 2006). The success of a management plan at preventing overexploitation is judged by estimating escapement to the spawning grounds and, sometimes, production of fry or smolts in the following year(s). However, escapement or smolt numbers yield only a coarse forecast of expected adult returns of the brood year, and these estimates are not considered sufficient to manage fisheries on the returning adults up to several years later. Therefore, test fisheries have been designed to provide in-season estimates of the strength of the returning salmon runs. The catches from these test fisheries are the basis for harvest management on that same run, often used in quite formal control rules. Not only are the indicators used in the audit and the control functions different, but each would be unsuitable for the alternative function. Test fishery catches cannot be used as a basis for inference on the success of management to ensure sustainable use, because the bulk of the fishery has not yet taken place. Escapement estimates cannot be used to manage the fishery because, by the time the salmon reach the escapement grounds, they are no longer suitable for harvest. In this case, necessity forced experts to consider the two functions separately, and they chose indicators optimal for each.
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Marine fish
The realization that separate indicators may fulfil the two functions appears to emerge slowly, if at all, in marine fisheries management. The example in ICES Advisory Committee for Fisheries Management practice that comes closest may be the advice on capelin (Mallotus villosus) management at Iceland. Results of an assessment in early spring each year are augmented by the results of a survey of stock size carried out after the assessment, but before the fishery. However, the audit and harvest control functions of the two indicators are not really separated, because the initial assessment is considered a coarse estimate of both stock status and suitable harvest, and the subsequent survey serves as additional information for both functions (ICES, 2005).
Industry participants in a stewardship initiative in Canada have proposed the use of harvest rules to guide the management of some groundfish fisheries, such as southern Gulf of St Lawrence cod. The focus has been on expanding the types of indicators used in the control function. Catch rates in small-scale and closely monitored fisheries ("sentinel fisheries") are proposed for use in guiding decisions about suitable harvest levels for the upcoming season. The harvest rules being explored could be complex and involve several indicators (sentinel catch rates, surveys, etc.) combined within a rule-based decision-making framework (the control function). While SSB and F could be part of the indicator set, they are by no means the only consideration in the harvest rule.
Although focusing on the control function, this approach necessarily requires evolving into two different processes to achieve the audit and control functions. The audit function would be achieved through scientific assessments done at a given interval (say 3–5 years), the primary purpose being to evaluate the state of the biological system. Audit of stock status could use indicators such as SSB, but also age composition and productivity of the stock (Dutil and Brander, 2003), and even the status of other species (Swain and Sinclair, 2000). These could be complemented by social and economic status indicators, auditing how the fishery met its objectives, as outlined in the Canadian Atlantic Fisheries Policy Review (DFO, 2003). The control function could be achieved through a stakeholder-inclusive process whereby the decision rules are pre-agreed to guide the establishment of harvest levels before each fishing season. This process would use indicators of the type discussed in the preceding paragraph, whose performance has been validated by the audit function. The two processes would be independent, would aim at delivering the audit and control functions separately, and could be based on different (sets of) indicators. Interestingly, this proposal did not come from scientists, but from industry participants.
Two developments suggest that this change, i.e. separating the audit and control functions of indicators, and choosing optimal ones for each task will be important in many fisheries. One development is the pressure to change governance systems, allowing more inclusive management (e.g. the increasing role of Regional Advisory Councils in Europe; Fischler, 2005; Gray, 2005). Separating the two functions might allow more inclusive approaches to some tasks than others and could help manage the risks of bias and politicization of science. Another development is the move to an ecosystem approach to management (FAO, 2003; Pikitch et al., 2004). If the effects of environmental forcing are strong but measurable only after the assessment has been completed (as is true for recruitment-dependent fisheries on short-lived stocks; Borges et al., 2003; MacKenzie and Köster, 2004; Santos et al., 2004), the most effective audit of whether past management took proper account of the environmental influence on the stock might not provide much insight into the appropriate harvest for the coming year, whereas an indicator sensitive to the environmental forcer might be a useful part of scientific advice on the impending harvest, but provide little insight into the effectiveness of recent management.
In a few fisheries, bycatch caps on non-target species have already been used in the control function (e.g. halibut, Hippoglossus hippoglossus, in North Pacific trawl fisheries; Salveson et al., 1992). However, these caps were not considered tools to optimize performance of the overall suite of fisheries in an ecosystem context; instead, they were used as a tool to address a gear-sector allocation problem.
Finally, as the footprint of fisheries on the ecosystem becomes an important aspect of management, the pressure indicators effective in controlling the size of the footprint are unlikely to be the same as the ecosystem indicators auditing the effectiveness of management by measuring the size of the footprint. Managing the footprint will often include managing the spatial distribution of effort and require a number of indicators to evaluate the effect of the fishery on target species, bycatch species, and habitat features. Some indicators may represent suitable triggers for rules controlling where the fishery may operate, and others for controlling its intensity. Control rules affecting intensity or location may also use pre-fishery survey-based indicators, perhaps giving information on areas where catches of a protected species or undersized fish are expected to be particularly high. Selecting separate indicators might help to optimize both functions. At the very least, this would expand substantially the scope for indicators to be considered when investigating harvest strategies.
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As management moves towards greater stakeholder participation in decision-making, there will be a tendency to move from traditional population dynamics models to simpler decision models. Control rules used in management with multiple objectives and participatory governance will involve compromises among the objectives and the indicators linked to them. Separating the audit and control functions means that the same compromises do not need to be made with the indicators selected for the audit function. As management moves to an ecosystem approach, the audit function will become more complex.
State (audit) and pressure (control) indicators need to be linked to both reporting structures and decision rules that will properly capture the realities of the biological and management systems. It may be easier to meet this important challenge if we seek separate indicators that serve each function well, rather than a common indicator that serves both adequately.
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