Fisheries management planning and support for strategic and tactical decisions in an ecosystem approach context

Fisheries Research 100 (2009) 6–14

Contents lists available at ScienceDirect

Fisheries Research journal homepage: www.elsevier.com/locate/fishres

Fisheries management planning and support for strategic and tactical decisions in an ecosystem approach context Stratis Gavaris ∗ Fisheries and Oceans Canada, 531 Brandy Cove Road, St. Andrews, NB E5B 2L9, Canada

a r t i c l e

i n f o

Article history: Received 28 January 2008 Received in revised form 15 September 2008 Accepted 2 December 2008 Keywords: Ecosystem approach Management planning Decision support Conservation strategies Fisheries management

a b s t r a c t Management planning is a hierarchical process that translates objectives to strategies, ‘what’ will be done, and strategies to tactics, ‘how’ it will be done. A strategy specifies what will be done about a human pressure using a reference to signal when the pressure is unacceptable. The reference is established from consideration of the response by valued attributes to alternative references. Two types of management decisions are invoked by the planning process, strategic decisions that establish a suitable reference for the pressure and tactical decisions that identify levels of a management measure that keep the pressure acceptable relative to the reference. An Ecosystem Approach for Management can be made operational through a progressive evolution of traditional fisheries management that extends strategies beyond consideration of productivity for only the harvested resources to productivity, biodiversity and habitat of the ecosystem and then integrates the cumulative effects across managed human activities. The consideration of more pressures and attributes will require some sort of triage to identify priorities for first attention. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved.

1. Introduction Traditional fisheries management gave first attention to regulating the impact of fishing on the utilized resources. This is not surprising, as the removals by the fishery are the most obvious direct effect of that activity. In recent years, some attention has also been directed towards the impact of fishing on the non-retained species that are caught incidentally and on the impact of fishing on habitat. While the considerations about impacts from this single activity, fishing, were broadening, there was a parallel development recognizing that the cumulative effects from the multiple human activities that were impacting marine ecosystems needed to be considered in an integrated way. These notions have culminated into the Ecosystem Approach for Management (EAM), a philosophy that has gained much popularity. An EAM extends traditional management in two important ways; taking into account the impact of an activity on all ecosystem components, not just those resources utilized by that activity, and accounting for the cumulative effects of all activities impacting the ecosystem. An EAM does not manage the ecosystem. It manages human activities while considering ecosystem implications. Controlling the impacts of managed human activities on the ecosystem is the intent of an EAM, but it must also recognize how

∗ Tel.: +1 506 529 5912; fax: +1 506 529 5862. E-mail address: [email protected].

other forces affect ecosystem dynamics and what the implications of these forces effects are for the way the human activities are managed. While these general principles for an EAM have gained popularity, ways of making EAM operational are still in development (de la Mare, 2005). Some have speculated that revolutionary changes to management may be required to implement an EAM for fisheries (Hall and Mainprize, 2004; Francis et al., 2007). The mainstream view though, is that traditional fisheries management approaches are among the best developed management tools and that we can build on that experience (Hall and Mainprize, 2004; Garcia and Cochrane, 2005; de la Mare, 2005). Some contend that management ‘best practice’ for an EAM is already emerging from these incremental experiences (Murawski, 2007). This paper embraces the latter philosophy and explores a way of making EAM operational by examining how traditional fisheries management can be extended to incorporate the emerging concerns about ecosystem impacts. The elements of management planning and of the associated decision support required for controlling fishery exploitation of utilized resources are analyzed to elucidate the general structure. This general structure is then used to show how other ecosystem impacts can be addressed in an analogous way. The implications of EAM for fisheries management are outlined. Challenges and pragmatic steps that can be taken to make progress on implementing an EAM are discussed. The paper offers a framework for making EAM operational. Examples illustrate elements of the framework and how it can be used, but a systematic application

0165-7836/$ – see front matter. Crown Copyright © 2008 Published by Elsevier B.V. All rights reserved. doi:10.1016/j.fishres.2008.12.001

S. Gavaris / Fisheries Research 100 (2009) 6–14

7

is not yet available. Development of methods that apply the general structure to emerging ecosystem considerations require further research and are beyond the scope of this work. 2. Management planning 2.1. Traditional fisheries management An objective of traditional fisheries management was to regulate the fisheries in a manner that did not cause a reduction in the productivity of the harvested resources. The reason for engaging in management was the concern that the mortality imposed by fishing could adversely impact productivity. The productivity of a resource was considered to be reflected by the sustainable yield that could be extracted in perpetuity. The idea therefore was to regulate the fishing mortality rate, F, in order to control the impact on sustainable yield. The general strategy was to keep F moderate. To make this operational, it was necessary to develop a model that described the relationship between the sustainable yield and a level of F that would be applied in perpetuity. Based on the modeled response of yield, a suitable reference fishing mortality rate, Fref , was selected. The explicit operational strategy was to keep F at or below Fref . F cannot be directly monitored. However, the fishery catch could be monitored and there is a relationship between the catch and the imposed F. The resulting management approach controlled catch quotas to regulate F so that sustainable yield was not adversely impacted. In principle, exploiting a resource using a harvest strategy prescribed by a constant Fref should conserve productivity. Such a harvest policy may not perform satisfactorily in practice however, because the rate of recovery for depleted populations may be slow and it affords little latitude for errors of assessment or environmentally driven fluctuations of productivity, particularly if these are temporally correlated (Shepherd, 1981). Strategies that reduce exploitation when the biomass is low perform better in relation to both long term yield and conservation of the resource (Shepherd, 1981; NRC, 1998; Restrepo et al., 1998; DFO, 1999). Many forms of such a harvest strategy are possible, but the simplest form, where Fref is reduced in proportion to biomass when the biomass drops below a threshold, suffices for illustration. With a constant Fref , sustainable yield is roughly a constant fraction of sustainable biomass. When Fref is not constant, this proportionality breaks down and sustainable biomass has to be considered explicitly along with sustainable yield when evaluating the conservation performance of alternative values of Fref . The following features of the example give insight on properties that are important when generalizing ideas to extend traditional fisheries management for an EAM: • The management plan objective incorporated conservation by specifying sustainability, but it framed the goal in the context of utilization. Conservation in the absence of utilization has little pertinence to the management of most human activity, and in particular, fisheries. • Management action was motivated because fishing imposed a force, F, that was of consequence to the objective. While a fishery may be perceived as a homogeneous activity, it is comprised of multiple events from diverse fleets. F is the common currency for the imposed force that integrates the cumulative effect from all these events. • The ecosystem property that was used to reflect the productivity objective, yield, had to be responsive to alternative choices of Fref . • Modeled response of yield, not the realized yield, was used to select Fref . There are two reasons for this. First, forces other than F will affect the realized yield. In the models used to select Fref these forces are kept comparable. The models allow comparison

Fig. 1. Explicit reference to F and Fref in the management approach links yield and catch quota.

•

•

•

•

•

of sustainable yield for alternative values of Fref assuming ‘all other things being equal’. Second, even in the absence of these other forces, it would take many years for a harvested population to equilibrate to each alternative level of Fref so that the response of sustainable yield could be characterized. A reference was specified for F but not for sustainable yield. While there may be expectations for yield, these are conditioned on assumptions about future recruitment, future growth and the future natural mortality rate. These parameters are not known; therefore a reference for yield would not be particularly useful for management purposes. On the other hand, F is directly related to human actions that can be regulated. A reference for F has direct application in management. While a reference for yield was not specified, persistent departures from expected yield could however trigger a re-evaluation of the relationship between yield and Fref . Explicit reference to F and Fref in the management approach was the key for the link between yield, which reflects the objective, and the catch quota, which is monitored and controlled (Fig. 1). The two relationships, one between yield and Fref and the other between F and quota, were fundamental for making the plan operational. The ecosystem property biomass played two distinct roles. The modeled sustainable biomass was used along with modeled sustainable yield to evaluate alternative values of Fref . The transient realized biomass was used as a co-variate to modulate Fref . In strategies where Fref is not a constant value, thresholds for biomass designate when Fref changes. However, specifying how Fref changes when these thresholds are reached is fundamental to the strategy because it is F that is being regulated. Consideration of both yield and biomass in the selection of Fref necessitated balancing the two properties, e.g. lower yield for higher biomass, which means reduced benefits but greater resilience to adverse environmental forces.

2.2. General structure The management planning described for this example can be generalized as a hierarchical process (Halliday and Pinhorn, 1985) that translates objectives into strategies, ‘what’ will be done, and specifies tactical management measures to implement the strategies, ‘how’ it will be done (Fig. 2). Objectives are general statements about the goals of management. In the example, the objective pertained to productivity of the utilized resources. Attributes, yield and biomass in the example, are valued ecosystem components or properties that reflect the objectives. Strategies state what will be done about a pressure, a force induced by a managed activity. The pressure in the example was F. A generic statement like ‘keep F moderate’ is sufficient for communicating the intent of the strategy and acknowledges that some levels of F have unacceptable impacts. In any particular plan, the generic strategy is made operational by

8

S. Gavaris / Fisheries Research 100 (2009) 6–14

placed greater emphasis on the conservation aspects. Accordingly, much of the development to date on EAM has focused on conservation and this trend is reflected here. Nevertheless, as noted in the example, conservation must be considered in the context of utilization and utilization derives economic, social and cultural benefits from the ecosystem. The EAM broadens the scope of conservation concerns. A tacit consensus is emerging, recognizing three principal conservation objectives: maintaining productivity, preserving biodiversity and protecting habitat (e.g., Jamieson et al., 2001; Sinclair et al., 2002). These objectives can be stated in a manner to emphasize that it is the human activities that are managed and not the ecosystem:

Fig. 2. The hierarchical management planning process is illustrated with the strategy for controlling exploitation.

specification of a reference for the pressure which signals when the pressure attains a level that has unacceptable impacts, i.e. ‘keep F below Fref ’. The term reference is used preferentially instead of the more common expression, reference point, to specifically acknowledge that a reference need not be a constant value, as in the example where Fref was a function of biomass. Also, in this paper, the term reference is only used in relation to pressures to avoid confusion with thresholds for co-variates like biomass that trigger a change to the pressure reference. Following the example, explicit specification of a pressure and its respective reference in the strategy is the key for the link between the attributes, which reflect the objectives, and the tactics, which are monitored and controlled (Fig. 3). The relationships between attributes and references and the relationships between pressures and tactics are fundamental for making the plan operational. It is generally advantageous to have relationships that quantify the responses, but in the absence of such knowledge, a qualitative understanding of associations may assist management decisions. In the next section this general structure is considered for other ecosystem impacts. It is noteworthy that while all steps in the hierarchical process should be considered, a linear implementation sequence is not implied. In particular, since the attributes must be responsive to alternative values of pressure references, it is practical and more efficient to identify the pressures pertaining to the objectives first and use them as an aid to determine which ecosystem components and properties are impacted by them. Accordingly, the next section describes the objectives and then discusses strategies for pressures before considering attributes. 2.3. Ecosystem Approach for Management Objectives have conservation, economic, social and cultural facets. However, the prevailing concern about worldwide depletion of fisheries resources and degradation of marine ecosystems has

Fig. 3. The strategy is the key to the framework and establishes the linkage between attributes and tactics through explicit specification of the pressures and their associated references.

• Do not cause unacceptable reduction in productivity so that components can play their role in the functioning of the ecosystem. • Do not cause unacceptable reduction in biodiversity in order to preserve the structure and natural resilience of the ecosystem. • Do not cause unacceptable modification to habitat in order to safeguard both physical and chemical properties of the ecosystem. The qualification ‘unacceptable’ recognizes that any human activity will have some impact. Standards of what is unacceptable are established by the references for the pressures. There is a correspondence between these three broad objectives and the Ecologically Sustainable Development hierarchy framework adopted by FAO (Garcia and Cochrane, 2005) which considers ecosystem well being to be comprised of interest in retained species (productivity concerns), non-retained species (biodiversity concerns) and habitat. To extend traditional fisheries management to an EAM, additional strategies were required to specify what will be done about other pressures induced by human activities that are of consequence to the three conservation objectives. Through consultation with scientists, fisheries managers and industry stakeholders involved with Canadian fisheries on the Scotian Shelf, Bay of Fundy and Georges Bank, a suite of strategies was developed under the three conservation objectives (Table 1). The strategies in Table 1 address emerging concerns about ecosystem impacts in a comprehensive framework that includes the “traditional” management considerations using a parsimonious suite of pressures associated with common ocean activities. Classification of a strategy under one of the three objectives simply reflects the dominant association, as pressures may have implications for more than one objective, e.g. population component mortality has implications for productivity as well as biodiversity. Productivity strategies address fishing mortality, spawning escapement, spawning disturbance, and nutrient concentrations affecting algal production. Managing discards and rebuilding depleted biomass, important aspects of many plans, are considered elements of the fishing mortality strategy as they relate to controlling exploitation. Under biodiversity there is provision for mortality of non-harvested species, spread of invasive species, and genetic diversity within populations. Note that discarding of harvested resources is considered with respect to the productivity objective while discarding of non-harvested species is considered under the biodiversity objective. Habitat strategies pertain to benthic habitat disturbance, pollutants, physical hazards and disturbances from physical stimuli. The suite of strategies may be revised as experience is gained. Perhaps some new activity will be started that introduces a different pressure, or it is discovered that one of the existing activities induces a pressure that was not previously recognized. There are many ecosystem components and properties that emanate from the three objectives. To be relevant to the management planning process though, attributes must exhibit an appreciable response to alternative reference levels of a pressure.

Table 1 A strategy specifies what will be done about a pressure and a reference, determined on the basis of impact on attributes, signals when the pressure is unacceptable. Explicit references, which are case specific, for the pressures are required to make the strategies, expressed generically here, operational. Tactics, specific to the nature of the activity (those shown are for fishing activities), are used to implement the strategy. An Ecosystem Approach for Management expands the scope of pressures and attributes considered and addresses the cumulative effects.

S. Gavaris / Fisheries Research 100 (2009) 6–14 9

10

S. Gavaris / Fisheries Research 100 (2009) 6–14

Having established the suite of strategies, the associated pressures were used to assist with compilation of candidate attributes by considering how the pressures impact the ecosystem. While the attributes in Table 1 are thought to be impacted by the identified pressures, they are designated ‘candidate’ here because the relationships between them and the pressures that impact them have not all been established. The candidate attributes include single species aspects like yield, biomass, recruitment, size/age structure, spatial distribution and population or genetic richness. There is also concern about community attributes like requirements for predator forage, composition of assemblages, size spectrum and trophic structure. Attributes associated with habitat features include the spectrum of bottom habitats and stimuli induced behavior changes. For some attributes, a suitable way to measure the ecosystem property has also not been developed. Notably, the least well determined attributes are community assemblage and trophic structure. As experience is gained with measuring attributes and understanding the relationships with the pressures that affect them, the attributes may be refined. Attributes can have linkages with more than one pressure. For example, the spatial distribution of a species may be impacted by both fishing mortality and by habitat disturbance caused by fishing. The suite of strategies and associated pressures may also be used to evaluate which tactics would be effective for regulation of the pressure. Pressures and attributes are fairly generic and apply to all human activities. Tactics are generally specific to the nature of the activity. Tactics used for fisheries management generally pertain to catch controls, effort controls, spatial/temporal closures and gear specifications. Multiple tactics may be used to implement a strategy and some tactics may be effective for more than one strategy. For example, the incidental mortality on non-retained species may be managed through both area/season closures and gear specifications, e.g. requirement for escape features on gear. Cumulative effects are manifested in relation to both pressures and attributes. When several managed human activities contribute to a pressure in an area, their cumulative effect must be regulated relative to the reference. The initial challenge is to identify a common currency for the pressure that integrates the contributions to the force from all impacting activities. Some, like fishing mortality, will be obvious and natural while developing an acceptable common currency for others, like habitat disturbance, may be more complicated. The cumulative effect on the pressure from multiple activities may not be simply additive. Integrating across all activities may require development of techniques specific to the pressure for that strategy, e.g. inclusion of all landings and discards in the computation of an instantaneous fishing mortality rate. The second manifestation of cumulative effects arises because some attributes are affected by more than one pressure. This necessarily applies to community attributes like trophic structure which can be affected by the set of fishing mortality and incidental mortality references, e.g. the trophic structure is affected by fishery removals of both forage species and predators. The response of an attribute must be evaluated with respect to alternative references for all the pressures that impact it appreciably. These cross linkages between pressures and attributes are a complicating feature that should be accommodated by the relationships and models used to evaluate references. Analytical solutions for these more complex models may not be feasible and reliance may have to be placed on simulation results. It is notable that the cumulative effects of activities on attributes is decomposed into cumulative effects of activities on pressures and cumulative effects of pressures on attributes. This decomposition facilitates management because it is the pressures that are regulated. The broader scope of conservation strategies, expanded number of pressures and consideration of a wider range of attributes for an EAM places greater demands for decision support. Judicious

direction of efforts towards those things that matter most is needed to achieve effective progress. The list of strategies was intended to be parsimonious but comprehensive for common ocean activities. Not all strategies are pertinent to all fisheries though. For example, impacts on bottom habitat are not a consideration for pelagic longline fisheries. Also, not all pertinent strategies may be of equal importance. For instance, discarding by fisheries is generally given greater priority than noise and light disturbance caused by fishing operations. There is a requirement therefore to sift through concerns by identifying issues and prioritizing these using risk assessment (Fletcher et al., 2002, 2005; Astles et al., 2006). The initial triage may simply be informed identification of the key pressures for an activity, e.g. pelagic longlines do not impact bottom habitat. If risk is determined, i.e. there is an appreciable contribution to the pressure by an activity and a relationship describing the impact of the pressure on an attribute has been established, the choices are to manage that risk or to conduct subsequent, more involved evaluations to better assess the risk. It may be more cost effective to manage the risk indicated by a rough metric than to refine the measure of risk with more involved analyses. Further, it would be precautionary to manage the risk, as determined by the initial triage, until such time as the more involved evaluation is completed. 3. Decision support 3.1. Traditional fisheries management The fishery example illustrates the nature of decisions in management. There are two types of decisions with respect to the fishing mortality strategy; ‘What is a suitable Fref to control the impacts on sustainable yield and biomass?’ and ‘What level of catch quota will keep F below Fref ?’. Selection of Fref was informed by comparing how sustainable yield and biomass responded to a range of alternative values of Fref . The decision support was comprised of describing the responses as a function of Fref . To characterize these responses, models that incorporated recruitment, somatic growth, mortality and fishery selectivity processes were considered. Given an established Fref , decisions concerning the catch quota are perhaps more straight forward, in principle. This decision support was comprised of determining the F resulting from a range of contemplated catch quotas for a coming fishing season. The resulting F is in fact a function of both the catch quota and the realized population biomass. If an absolute biomass estimate were available, say from a survey, F could simply be obtained as the ratio of the catch quota to observed survey biomass. Complicated population and ecosystem dynamics do not have to be invoked in order to determine F. More typically though, only relative trend indices of biomass or abundance are available, not absolute estimates. It is necessary then to scale the relative indices to an absolute magnitude. One common way of doing this calibrates the indices and the fishery catch (e.g. Deriso et al., 1985; Gavaris, 1988; Patterson and Melvin, 1996; Shepherd, 1999). Also, typically the advice is needed for 1 or 2 years ahead of the terminal year of observation for fishery or survey data, necessitating some form of short term projection. Calibration and projection introduce technical complication but population and ecosystem dynamic processes, such as recruitment and growth, that involve tenuous assumptions can still be avoided. 3.2. Ecosystem Approach for Management Generalizing from the traditional fisheries management experience, support is required for two types of management decisions; decisions about the strategy and decisions concerning the tactic, (Fig. 4). While some analytical tools, e.g. biomass dynamics models

S. Gavaris / Fisheries Research 100 (2009) 6–14

Fig. 4. There are two types of decisions for management. Strategic decisions establish a suitable reference for the pressure and tactical decisions identify levels of a management measure that keep the pressure acceptable relative to the reference.

(Schaeffer, 1954; Pella and Tomlinson, 1969), may produce results to inform both types of decisions, the advice needed to support tactical and strategic decisions is different. Decisions about tactics, consideration for a catch quota that kept F below Fref in the example, require determination of an appropriate level of a management measure to achieve the strategy. The decision support for tactics should inform when the pressure is unacceptable, relative to its reference, for alternative levels of the tactic. It is desirable to avoid population and ecosystem dynamic processes that involve tenuous assumptions when providing tactical advice. Tactical advice relies on the relationship between a pressure and the regulating tactic(s). Obtaining the necessary information to parameterize those relationships for ‘new’ pressures in the EAM framework may place additional demands for fishery and ecosystem monitoring. Decisions about strategies, selection of an appropriate Fref in the example, require evaluation of suitable references. The decision support for strategies should facilitate comparison of attribute outcomes for alternative reference choices. Strategic advice depends on understanding the relationships that link pressure references to attributes and the dynamics of other forces affecting the attributes. Parsimonious selection of only those candidate attributes that show appreciable dynamic range in their response to make them useful for evaluation of references will make strategic decision considerations more tractable. Unlike the case for tactical advice, understanding of population and ecosystem dynamics is central to the development of strategic advice. Parameterizing these population and ecosystem models for the expanded suite of strategies associated with EAM may also place further demands for fishery and ecosystem monitoring. The frequency of advice for strategic and tactical decisions is typically not the same. Decisions about strategies are founded on equilibrium, or at least long term, dynamics and generally only need updating periodically. A reference controls the impact of an activity on the ecosystem in the context of how prevailing or forecast environmental conditions and forces, external to the managed activity, affect ecosystem and population dynamics. Therefore, the frequency for provision of strategic advice is dictated by the need to account for changes in dynamics or demographics. References are updated periodically when such changes are detected. References may also be updated when there is discovery of alternative models that are more suitable for describing the linkages between the attributes and the pressure references. In contrast, decisions about tactics are generally made on a more regular schedule. Tactics are regulatory measures that can provide feedback and can be adjusted to achieve the strategy. The frequency for provision of tactical advice is dictated by the nature of the tactic, e.g. catch quotas may need to be updated annually while area/season closures may need to be altered only when a change in spatial distribution is detected. Performance evaluation of management is related to, but distinct from decision support. Performance evaluation and decision support both employ the same underlying population/ecosystem

11

dynamics. However, performance evaluation is retrospective and considers if past management has been effective while decision support is prospective and aids the determination of appropriate future management actions. As with decision support, performance evaluation can be profitably decomposed into strategic and tactical elements. The tactical effectiveness of the implementation can be evaluated from the retrospective performance for each pressure in relation to the respective references. For example, estimating the time series of F for the recent past and comparing to Fref is routine when assessing the status of exploited stocks. The performance evaluation could include a decomposition of the contribution to a pressure by each contributing activity. The strategic effectiveness of management is more difficult to assess as it involves analysis of the effects of the pressure and of other forces when evaluating if the realized state of attributes satisfies the conservation objectives. In essence, this is an evaluation of competing models for describing the relationships between pressures and attributes where their concordance with past events and their robustness to assumptions is compared. 4. Ecosystem approach for fisheries management The extension of traditional fisheries management planning and decision support for an EAM requires common currencies to measure the cumulative force of all activities on pressures, development of relationships between pressures and tactics, metrics for attributes impacted by the pressures and development of relationships between the attributes and pressure references. It is practical to give first attention to these implications of an EAM on the three key pressures from fishing; the direct deaths associated with the harvest, the deaths from unintentional catch and the physical disturbance caused by the gear (Gavaris et al., 2005). Only a subset of the candidate attributes are implicated in the choice of references for these key pressures. Suggested linkages deserving first attention are shown in Fig. 5, but only a few of the relationships between the attributes and the pressure references are well established and in wide use. Regulating fishing mortality of harvested resources remains an important consideration. Existing methods for measuring the pressure, F, are well established, as are relationships between F and common tactics. Regulation of F generally requires monitoring of catch even when output controls like catch quotas are not used as tactics. The catch is comprised of landings and discards. Though EAM recognizes the potential for improving the determination of F by accounting for discards, documentation of accurate landings remains an issue in fisheries. All of the candidate attributes except habitat type spectrum are thought to respond to alternative values of Fref . However, Fref for many if not the majority, of fisheries has been established on the basis of consideration for only yield and

Fig. 5. Each of the three key pressures from fishing may have an effect on several of the attributes. The response of all impacted attributes is considered when establishing a reference for the pressure. Solid lines represent relationships that are well established and in wide use.

12

S. Gavaris / Fisheries Research 100 (2009) 6–14

biomass. The relationship between Fref and size/age structure is readily extracted from existing models and could be incorporated in strategic decision support if the stock recruitment relationship was appreciably affected by consideration of age structure (Marteinsdottir and Thorarinsson, 1998). Convincing relationships between Fref and the other attributes will need to be developed if the harvest strategies are to account for impacts on them. ‘Ecosystem’ or ‘multi-species’ models incorporating dynamic interactions, e.g. yield for a species of interest is a function of fishing mortality on its prey and predators, have been developed but have not been widely applied for management yet (Walters et al., 2005; Plagányi, 2007). These models aim to account for perceived deficiencies in the prevailing, so-called ‘single-species’ models used to evaluate Fref , including biomass dynamics models (Schaeffer, 1954; Pella and Tomlinson, 1969), yield per recruit (Beverton and Holt, 1957) and age-structured dynamic pool models (Beverton and Holt, 1957; Sissenwine and Shepherd, 1987), which assume that interactions in population and ecosystem dynamics can be adequately characterized by stationary processes. For example, yield and biomass for a species of interest is based on constant natural mortality and therefore assumed to be independent of fishing mortality on its prey and predators. It is not apparent if the greatly increased monitoring demands for general application of multi-species models can be satisfied. Nor is it evident that the adjustment to Fref will be appreciable when these dynamical interaction terms are included. Cases may be found where selected impacts relating to consumption requirements of important competitor species or to dominant predator prey interactions have been taken into account when establishing strategies (Hollowed et al., 2000; Bogstad and Gjosaeter, 2001). At present, best practice is exemplified by such pragmatic approaches. Determination of incidental mortality for non-harvested resources can follow well established practices for determining F, but requires monitoring of discards. The high cost of enhanced atsea monitoring of discards will dictate strategic deployment and effective use of technology to achieve adequate coverage of fishing activities that is affordable. As with F, incidental mortality is a function of both the discarded catch and the abundance of that species. Estimates of absolute abundance for non-harvested species are difficult to obtain. In the absence of absolute estimates of abundance, proxies that measure relative trends in mortality (Sinclair, 1998), in combination with trends in abundance from surveys, may be used in the early stages of triage to determine if the by-catch poses an appreciable impact. More involved analyses to calculate incidental mortality may subsequently be used to refine the risk assessment (Zhou and Griffiths, 2008). If catch limits are employed as the tactic to regulate incidental mortality, relationships used for F may be borrowed. If alternative tactics are entertained, e.g. area/season closures or gear modifications, relationships between these tactics and incidental mortality will need to be established. Of the candidate attributes, biomass, spatial occupancy and trophic structure are thought to be affected by incidental mortality references. As with fishing mortality though, quantitative relationships linking the attributes to the incidental mortality reference have only been developed for biomass. However, reduced spatial occupancy has been used qualitatively to indicate that incidental mortality is excessive. Measuring mortality rate and establishing suitable references, either absolute or relative, is particularly challenging for data limited situations, typical of non-harvested species. In the absence of sound information on a particular species, references might initially be based on analogy to exploited species with similar characteristics and subsequently refined using assumptions consistent with the life history and demographics of the species. Approaches for limiting the impact of fishing activities on habitat are still in the early stages of development and not well established yet. Both fishing mortality and incidental mortality were concerned with population dynamics, therefore the popula-

tion was a natural management unit. Management units for habitat will likely involve areas with similar characteristics. Thus, effective management of habitat disturbance will require classification of habitat with respect to resilience and recoverability (Kostylev et al., 2005) into operational management units. Developing a common currency for the pressure will likely involve some combination of bottom area contacted, frequency of contact and intensity of disturbance by diverse fishing activities. No single metric has yet gained popularity and most studies only consider impact by particular gear types separately. Quantification of the pressure requires monitoring of location fished. While traditional fishery monitoring techniques may be used for this purpose, they often pose limitations (Gavaris and Black, 2004). The availability of satellite monitoring systems for fishing vessels greatly improves accessibility to the kind of information needed. Little consideration has been given to comprehensive tactics for managing habitat impact or to the relationship between tactics and the pressure. Most management actions have been limited to restricting activity in areas of highly structured bottom. Habitat type and spatial occupancy by species are the attributes thought to respond to references for the area disturbed pressure, but relationships between these that are useful for management have not been established. Few attempts have been made to synthesize habitat classification and the quantification of habitat disturbance using models that can be investigated for evaluation of references in a pragmatic strategy. In a recent promising approach, Hiddink et al. (2006) used bottom contact intensity to measure the pressure on habitat disturbance and developed relationships linking it to benthic invertebrate biomass and production on a 9 km2 grid as the basis for evaluating and establishing practical references. 5. Discussion The wisdom of extending traditional fisheries management practice to an EAM may be questioned given the state of many fisheries subject to such management. Potential reasons for poor performance of fisheries management with respect to conservation include ignoring important pressures, tactics failing to keep the pressures within respective references, ignoring important attributes, references failing to adequately account for impacts on attributes, flawed relationships linking pressures to tactics and references to attributes, inadequate monitoring for measuring pressures or parameterizing the relationships and insufficient precaution in the face of uncertainties. Poor performance due to such causes does not implicate the framework for management planning and support of strategic and tactical decisions. Indeed, the extensions of traditional fisheries management for an EAM address several of the possible causes for poor performance. A fundamentally different way that fisheries management may fail to achieve conservation objectives is by favoring immediate economic, social or cultural benefits at the expense of longer term conservation. This can occur if the balance of weight across impacted attributes when evaluating their responses to alternative references is risk prone with respect to conservation. As an EAM increases the number of attributes considered for selection of references, it can be more susceptible to balancing attributes in a manner that puts sustainable conservation at risk. In reaction to this threat, some attention has been given to the specification of explicit goals for realized states of attributes (e.g., Jamieson et al., 2001). The goals often aim to keep the state of these attributes within ‘a normal range of variation’. In effect, the bounds of the normal range of variation act as thresholds that trigger changes to pressure references, analogous to the way Fref was reduced when biomass declined below a threshold. As noted earlier, the way the reference changes when a threshold is reached is fundamental to the strategy. However, selecting a ‘changed’ reference to apply when the threshold is reached involves balancing the modeled response of attributes. Thus, specifying

S. Gavaris / Fisheries Research 100 (2009) 6–14

explicit goals for attributes does not circumvent any tendency for risk prone strategic decisions but does implies a non-constant reference. The added complexity associated with non-constant references should be justified by the dynamics governing the populations and ecosystem, not on the basis of averting risk. Balancing attributes inevitably invokes societal values about risks to conservation versus the benefits from utilization. The important challenge for EAM, as it was for traditional fisheries management, is to achieve transparency about how the consequences and implications to the ecosystem are balanced by the accountable governing institutions when references for the pressures are selected. Extension of the framework to include specification of explicit social, economic and cultural pressures (e.g. transfer of harvesting entitlements out of a community or the harvest exceeding market demand) and attributes (e.g. coastal community vitality or economic viability of an industry) will greatly facilitate proper balancing of these considerations when selecting references. The procedure advocated here prescribes identification of the key pressures induced by human activities and managing their impact on attributes. Another tact is to identify ‘critical’ attributes, e.g. keystone species, forage species, special habitat, etc., which, if perturbed, would have far greater impact than the direct effects, and managing the pressures that impact those attributes. In practice, a hybrid approach may be employed. For example, traditional fisheries management in the Canadian Atlantic Maritimes has focused on managing a key pressure, fishing mortality, but that strategy was complemented with tactical measures to prohibit fishing on key forage species like krill and to protect vulnerable habitat like tree corals. Generally however, limitations in knowledge hinder development of convincing arguments for reaching consensus on what the critical attributes are. While addressing known critical attributes is pragmatic, placing emphasis on identifying and managing key pressures is advocated as the cornerstone of management planning for EAM. It may be assumed that the boundaries of an ecosystem management area need to be delineated in order to implement an EAM. While this concept is appealing, establishing unequivocal boundaries that apply to all ecosystem components, from geological and oceanographic characteristics through primary producers and lower trophic levels to top predators has proven to be generally intractable. Ecosystem features are often intrinsically continuous and ecosystem dynamics operate at diverse spatial scales. Accordingly, management units are a compromise between population/ecosystem structure for attributes, the scales at which pressures are naturally integrated and administrative convenience. They generally form a patchwork of overlapping and/or nested areas. de la Mare (2005) has argued convincingly that establishing ecosystem boundaries is unnecessary if a ‘hierarchical control’ paradigm is taken for the EAM. A hierarchical control paradigm is consistent with the way the EAM was developed here and operates at diverse spatial scales reflective of the management units for the pressures. Fisheries managers, stakeholders and scientists will need to work cooperatively to make an EAM operational. The immensity of the task is more conducive to progressive evolution of existing management institutions with incremental advances as knowledge and experience is gained. The fundamental elements of such a process are: • Review and reform management institutions that support the deliberation required for decisions, to reflect the nested structure of management units in an EAM framework. • List human activities contributing to pressures, identify management units and the managing authorities and prioritize the key pressures induced by each activity. • Revise activity management plans to incorporate strategies that address all key pressures imposed by the activity.

13

• Develop practical approaches for measuring pertinent pressures, establish references for those pressures, put in place the necessary monitoring, routinely provide advice required for tactical decision support and implement the measures. • Put in place the monitoring required for evaluation of strategic decisions and periodically review the attributes and the models describing the relationships between pressures and attributes to refine the strategies and references. Management authorities will be challenged to distribute limited resources to maintain infrastructure for monitoring and decision support of presently perceived important pressures and to develop ways of addressing emerging concerns for impacts from other pressures and on other attributes. The framework described here provides an integrated way to organize and prioritize support for making EAM operational. Acknowledgements I thank two anonymous reviewers and Dr. Gordon Kruse, the managing editor of this issue, for their constructive criticisms of an earlier draft. I am grateful to my colleagues and to members of the fishing industry for discussions that shaped these ideas. This paper was first presented at the Topic Session on “Ecosystem approach to fisheries: Improvements on traditional management for declining and depleted stocks” held at the 2007 PICES Annual Meeting in Victoria, Canada. References Astles, K.L., Holloway, M.G., Steffe, A., Green, M., Ganassin, C., Gibbs, P.J., 2006. An ecological method for qualitative risk assessment and its use in the management of fisheries in New South Wales, Australia. Fish. Res. 82, 290–303. Beverton, R.J.H., Holt, S.J., 1957. On the Dynamics of Exploited Fish Populations. Fisheries Investigations Series 2, vol. 19. UK Ministry of Agriculture and Fisheries, London. Bogstad, B., Gjosaeter, H., 2001. Predation by cod (Gadus morhua) on capelin (Mallotus villosus) in the Barents Sea: implications for capelin stock assessment. Fish. Res. 53, 197–209. Deriso, R.B., Quinn II, T.J., Neal, P.R., 1985. Catch-age analysis with auxiliary information. Can. J. Fish. Aquat. Sci. 42, 815–824. DFO, 1999. Proceedings of a workshop on implementing the Precautionary Approach in Canada. In: Haigh, R. (Ed.), Canadian Stock Assessment Proceedings Series 98/18, 73 pp. Fletcher, W.J., Chesson, J., Fisher, M., Sainsbury, K.J., Hundloe, T., Smith, A.D.M., Whitworth, B., 2002. National ESD reporting framework for Australian Fisheries: the ‘How to’ guide for wild capture fisheries. Fisheries Research and Development Corporation Final Report, Project No. 2000/145, Canberra, Australia, ASBN 1877098019. Fletcher, W.J., Chesson, J., Sainsbury, K.J., Hundloe, T.J., Fisher, M., 2005. A flexible and practical framework for reporting on ecologically sustainable development for wild capture fisheries. Fish. Res. 71, 175–183. Francis, R.C., Hixon, M.A., Clarke, M.E., Murawski, S.A., Ralston, S., 2007. Ten commandments for ecosystem-based fisheries scientists. Fisheries 32 (5), 217–233. Garcia, S.M., Cochrane, K.L., 2005. Ecosystem approach to fisheries: a review of implementation guidelines. ICES J. Mar. Sci. 62, 311–318. Gavaris, S., 1988. An adaptive framework for the estimation of population size. CAFSAC Res. Doc. 88/29, 12 pp. Gavaris, S., Black, J., 2004. Area trawled on Georges Bank by the Canadian groundfish fishery. DFO Can. Sci. Advis. Sec. Res. Doc. 2004/018, 7 pp. Gavaris, S., Porter, J.M., Stephenson, R.L., Robert, G., Pezzack, D.S., 2005. Review of management plan conservation strategies for Canadian fisheries on Georges Bank: a test of a practical ecosystem-based framework. ICES CM 2005/BB:05, 21 pp. Hall, S.J., Mainprize, B., 2004. Towards ecosystem-based fisheries management. Fish Fish. 5, 1–20. Halliday, R.G., Pinhorn, A.T., 1985. Present management strategies in Canadian Atlantic marine fisheries, their rationale and the historical context in which their usage developed. In: Mahone, R. (Ed.), Toward the Inclusion of Fishery Interactions in Management Advice. Can. Tech. Rep. Fish. Aquat. Sci. 1347, pp. 10–33. Hiddink, J.G., Jennings, S., Kaiser, M.J., 2006. Indicators of the ecological impact of bottom-trawl disturbance on seabed communities. Ecosystems 9, 1190–1199. Hollowed, A.B., Ianelli, J.N., Livingston, P.A., 2000. Including predation mortality in stock assessments: a case study for Gulf of Alaska walleye pollock. ICES J. Mar. Sci. 57, 279–293.

14

S. Gavaris / Fisheries Research 100 (2009) 6–14

Jamieson, G., O’Boyle, R., Arbour, J., Cobb, D., Courtenay, S., Gregory, R., Levings, C., Munro, J., Perry, I., Vandermeulen, H., 2001. Proceedings of the National Workshop on Objectives and Indicators for Ecosystem-based Management, Sidney, British Columbia, 27 February–2 March 2001. DFO Canadian Science Advisory Secretariat Proceedings Series, 2001/09, 140 pp. Kostylev, V.E., Todd, B.J., Longva, O., Valentine, P.C., 2005. Characterization of benthic habitat on northeastern Georges Bank, Canada. In: American Fisheries Society Symposium, vol. 41, pp. 141–152. de la Mare, W.K., 2005. Marine ecosystem-based management as a hierarchical control system. Mar. Policy 29, 57–68. Marteinsdottir, G., Thorarinsson, K., 1998. Improving the stock-recruitment relationship in Icelandic cod (Gadus morhua) by including age diversity of spawners. Can. J. Fish. Aquat. Sci. 55, 1372–1377. Murawski, S.A., 2007. Ten myths concerning ecosystem approaches to marine resource management. Mar. Policy 31, 681–690. National Research Council (NRC), 1998. Improving Fish Stock Assessments. National Academy Press, Washington, DC, 177 pp. Patterson, K.R., Melvin, G.D., 1996. Integrated Catch at Age Analysis Version 1.2. Scottish Fisheries Research Report 58, 60 pp. Pella, J.J., Tomlinson, P.K., 1969. A generalized stock production model. Bull. Inter-Am. Trop. Tuna Comm. 13, 419–496. Plagányi, É.E., 2007. Models for an ecosystem approach to fisheries. FAO Fisheries Technical Paper 477, 108 pp. Restrepo, V.R., Thompson, G.G., Mace, P.M., Gabriel, W.L., Low, L.L., MacCall, A.D., Methot, R.D., Powers, J.E., Taylor, B.L., Wade, P.R., Witzig, J.F., 1998. Technical guid-

ance on the use of precautionary approaches to implementing National Standard 1 of the Magnuson-Stevens Fishery Conservation and Management Act. NOAA Technical Memorandum NMFS-F/SPO-31, 54 pp. Schaeffer, M.B., 1954. Some aspects of the dynamics of populations important to the management of commercial marine fisheries. Bull. Inter-Am. Trop. Tuna Comm. 1, 27–56. Sinclair, A.F., 1998. Estimating trends in fishing mortality at age and length directly from research survey and commercial catch data. Can. J. Fish. Aquat. Sci. 55, 1248–1263. Sinclair, M., Arnason, R., Csirke, J., Karnicki, Z., Sigurjonsson, J., Rune Skjoldal, H., Valdimarsson, G., 2002. Responsible fisheries in the marine ecosystem. Fish. Res. 58, 255–265. Sissenwine, M.P., Shepherd, J.G., 1987. An alternative perspective on recruitment overfishing and biological reference points. Can. J. Fish. Aquat. Sci. 44, 913–918. Shepherd, J.G., 1981. Cautious management of marine resources. Math. Biosci. 55, 179–187. Shepherd, J.G., 1999. Extended survivors analysis: an improved method for the analysis of catch-at-age data and abundance indices. ICES J. Mar. Sci. 56, 584–591. Walters, C.J., Christensen, V., Martell, S.J., Kitchell, J.F., 2005. Possible ecosystem impacts of applying MSY policies from single-species assessment. ICES J. Mar. Sci. 62, 558–568. Zhou, S., Griffiths, S.P., 2008. Sustainability Assessment for Fishing Effects (SAFE): a new quantitative ecological risk assessment method and its application to elasmobranch bycatch in an Australian trawl fishery. Fish. Res. 91, 56–68.