Marine Policy 36 (2012) 389–392

Contents lists available at ScienceDirect

Marine Policy

0308-59

doi:10.1

n Corr

E-m

Paul.Wa

Barbara

journal homepage: www.elsevier.com/locate/marpol

Management rules for marine mammal populations: A response to Lonergan

Justin Cooke a, Russell Leaper b,n, Paul Wade c, David Lavigne d, Barbara Taylor e

a CEMS. Hollenbergstr. 7, 79312 Windenreute, Germanyb School of Biological Sciences, University of Aberdeen, Tillydrone Avenue, Aberdeen AB24 2TZ, UKc National Marine Mammal Laboratory, Alaska Fisheries Science Center/NOAA, 7600 Sand Point Way NE, Seattle, WA 98115-6349, USAd International Fund for Animal Welfare, 40 Norwich Street East, Guelph, Ontario, Canada N1H 2G6e Southwest Fisheries Science Center, 8604 La Jolla Shores Drive, La Jolla, CA 92037-1508, USA

a r t i c l e i n f o

Article history:

Received 8 May 2011

Received in revised form

30 June 2011

Accepted 30 June 2011Available online 25 August 2011

Keywords:

Management procedure

RMP

PBR

Management Strategy Evaluation

7X/$ - see front matter & 2011 Elsevier Ltd. A

016/j.marpol.2011.06.009

esponding author. Tel.: þ44 1397772544.

ail addresses: jgc@cems.de (J. Cooke), r.c.leap

de@noaa.gov (P. Wade), dlavigne@ifaw.org (

.Taylor@noaa.gov (B. Taylor).

a b s t r a c t

The development of management rules for decisions regarding marine mammal populations, which

resulted in the Revised Management Procedure (RMP) of the International Whaling Commission and

Potential Biological Removal (PBR) within the US Marine Mammal Protection Act is well documented.

The description by Lonergan (Potential biological removal and other currently used management rules for

marine mammal populations: a comparison, in Marine Policy) of RMP and PBR, and the origins of the

management policy choices that they are designed to implement, is not accurate. The policy decisions

relating to conservation targets, and the balance between conservation and utilisation, were made by

governments and legislators, not by scientists as claimed by Lonergan. Based on the original sources the

key aspects of the two procedures, including the way they incorporate policy choices, are explained.

Some misconceptions by Lonergan regarding Canada’s Atlantic Seal Management Strategy are also

addressed. The Management Strategy Evaluation approach used in the development of RMP and PBR

has since become increasingly widely used in fishery management. It provides a means to assess the

short- and long-term consequences of different policy choices in the context of realistic levels of

uncertainty over the status and dynamics of the populations concerned. An alternative approach

suggested by Lonergan has been found wanting in the past and would likely also fail in the future.

& 2011 Elsevier Ltd. All rights reserved.

1. Introduction

The article ‘‘Potential biological removal and other currently usedmanagement rules for marine mammal populations: a comparison’’by Lonergan [1] from the UK Sea Mammal Research Unit purports todescribe and compare a number of proposed procedures for themanagement of marine mammal populations, including the RevisedManagement Procedure (RMP) [2] of the International WhalingCommission (IWC) and the Potential Biological Removal (PBR) [3]method used in the implementation of Marine Mammal ProtectionAct (MMPA) in the USA [4]. The author’s thesis is that proceduressuch as the RMP involve fixed choices of management objectives,choices which he argues should not be built into a scientificprocedure but instead made by policy makers.

Unfortunately Lonergan’s descriptions of the various proce-dures are factually inaccurate. He also misrepresents the legal andpolitical origin of the various management policy choices, whichhe erroneously attributes to scientists. Lonergan’s aim to push the

ll rights reserved.

er@abdn.ac.uk (R. Leaper),

D. Lavigne),

decision about conservation targets back from scientists to policy-

makers, where it belongs implies that scientists have been makingsuch decisions. However, the author has shown no instancewhere scientists have in fact made policy choices and this wasnot the case for RMP or PBR.

Although Lonergan’s paper is in part an opinion piece, itpresents a considerable amount of material as if it were a fact.In the spirit of ‘‘everyone is entitled to their own opinion, but not to

their own facts’’ (a quote that has been attributed to the lateSenator for New York, D.P. Moynihan) this response aims tocorrect the record by summarising the main features of RMPand other proposed management procedures, with reference tooriginal sources, and by pointing out some of the misconceptionsin Lonergan’s article. Finally, some of the main issues facingmanagers dealing with marine mammal populations that proce-dures such as RMP and PBR were designed to address and wherethe alternative approach proposed by Lonergan would likely failare reiterated.

2. The Revised Management Procedure (RMP)

The Revised Management Procedure (RMP) is a formallyspecified procedure for determining sustainable catch limits for

J. Cooke et al. / Marine Policy 36 (2012) 389–392390

baleen whale populations developed by the IWC Scientific Com-mittee [2,5]. The RMP was the successor to the so-called NewManagement Procedure (NMP) that was adopted by the IWC in1975, with the aim of putting the management of whaling on asustainable basis [6]. The NMP, based on the principle of max-imum sustainable yield (MSY), was a deterministic rule thatassumed perfect knowledge of the key population parameters.Because the required information was lacking for real whalepopulations, the procedure proved difficult to apply in practise [7].The NMP was operated until 1986 when a moratorium oncommercial whaling came into effect, a decision that was in parta response to the deficiencies of the NMP [8].

Following the moratorium, simulation studies of the operationof the NMP under hypothetical conditions showed that, even withrelatively good data, it could not be expected to provide manage-ment leading to stable whale populations [9]. Work started on theRevised Management Procedure that would, at least in simulationtests, perform satisfactorily and overcome the deficienciesof NMP.

The process of evaluating the RMP involved the construction ofa broad range of hypothetical, but realistic, scenarios, designed tocover the plausible span of alternative possibilities for thedynamics of whale populations and whaling operations [10].The RMP was tested by simulating its operation in these scenar-ios, and recording its performance against different managementobjectives. This approach, while novel at the time, has sincebecome more widely used in fishery management, under thename Management Strategy Evaluation (MSE) [11]. The approachcan be used whenever the specification of the managementstrategy is sufficiently explicit that its performance in hypothe-tical scenarios can be simulated [12]. The ensemble of testscenarios should be sufficiently comprehensive to cover the rangeof phenomena that might plausibly arise in practice, but no singlescenario is assumed to approximate ecological reality.

The IWC Scientific Committee presented a preliminary versionof RMP to IWC in 1991 [13]. In contrast to its predecessor, theRMP contains an algorithm for determination of catch limitsdirectly from data, without attempting to estimate the para-meters or status of a population. Issues of uncertainty are handledautomatically. The inputs to the RMP are a time series of one ormore abundance estimates (with associated confidence limits),and a series of annual historical catches, as far as these are known.The output is a catch limit. The simulation trials of the procedureshow that, compared to its predecessor, it is expected to achievemodest but stable continuing yields, while maintaining popula-tions above their maximum sustainable yield level most of thetime, and with a low risk of accidental depletion [7,13].

The committee noted that any management procedureinvolves a trade-off between the level of catches on one handand the risk of population depletion on the other, and that thebalance is not entirely a scientific matter [10,13,14]. Therefore thecommittee did not itself choose a specific tuning of the RMP, butinstead presented the IWC with several alternative versions of theprocedure [13]. The yield/risk trade-off was illustrated graphicallyso that delegates could see the expected consequence of theirchoice of tuning level [15]. The IWC then selected a tuning levelby majority vote [16].

2.1. Errors in Lonergan’s description of RMP

Lonergan states (without citing a source) that ‘‘Part of thereason the RMP lacks a tuning parameter y was the perceivedneed to provide a fixed, scientific, system whose results would beunaffected by any subsequent horse-trading’’. As described pre-viously, the RMP does have an adjustable tuning parameter,whose value was selected by regulators from a range presented

by scientists. It is not surprising that different managementauthorities, answerable to different constituencies, have chosendifferent balances between catch and risk. For example, theNorwegian Ministry of Fisheries and Coastal Affairs, in applyingthe RMP to manage the national whaling industry, currently usesa different tuning from the one selected by the IWC [17,18] inorder to allow higher catches.

Lonergan repeats a common misconception that the RMP‘‘aims, in most cases, to maintain populations at 72% of their carrying

capacity’’ which has been described as erroneous by the IWCScientific Committee [19]. The RMP does not contain the notion ofa target level; instead it aims at achieving the maximum con-tinuing yield consistent with controlling risk. For catches setaccording to the RMP the expected mean population size, as afraction of carrying capacity, is scenario-dependent.

Lonergan’s cites an equation from the RMP, stating that it is‘‘essentially’’ the catch limit algorithm. Attempting to representthe RMP as a single equation leads to a number of misconcep-tions. For example, Lonergan asserts that the RMP ‘‘does not

permit any commercial whaling in populations below 54% of their

pre-exploitation levels’’. In fact the simulation tests of the RMPshowed that in some scenarios, populations can be exploited thatare still well below 54% of their pre-exploitation levels [15].

Lonergan also states that ‘‘once RMP could be interpreted as

permitting commercial catches of minke whales (Balaenoptera acu-

torostrata[sic]) in Antarctic waters, any agreement about the appro-

priateness of its targets evaporated’’. For this assertion he cites tworeferences [20,21], neither of which mentions either targets orAntarctic minke whales (Balaenoptera bonaerensis). The IWCScientific Committee provided specific recommendations for theimplementation of the RMP to Antarctic minke whales in its 1993report [22]. No record was found of RMP target or tuning levelshaving been discussed in the context of Antarctic minke whales.

3. Potential Biological Removal (PBR)

PBR is an approach designed to ensure that populations bemaintained at or restored to an optimum sustainable population,to meet legal requirements under the US Marine MammalProtection Act (MMPA). It uses a single formula of the productof a minimum population estimate, one-half of the maximum netproductivity rate (RMAX), and a recovery factor [3,4]. However, indescribing PBR Lonergan claims that ‘‘The term Optimal[sic]

Sustainable Population (OSP) was introduced to describe population

levels that did not qualify as depleted. It is often used to mean the

lowest point of this range, also known as the Maximum Net

Productivity Level (MNPL)’’. No reference is provided for theassertion that OSP is ‘‘often used to mean the lowest point of this

range’’. The definition of OSP in the MMPA clearly specifies that itis a range between the population, which is the largest suppor-table within the ecosystem and MNPL. The subsequent assertionsby Lonergan that OSP is ‘‘half the carrying capacity’’ and that ‘‘PBR

effectively aims for half the carrying capacity’’ are not correct in thecontext of the MMPA or for the specific goals when PBR wasdeveloped for allowing each stock to reach or maintain a popula-tion level above MNPL [3]. MNPL for marine mammals is believedto be towards the lower part of the range between 50% and 85% ofcarrying capacity [3,23]. MNPL will be higher in the case wheredensity dependence effects only occur close to environmentalcarrying capacity but Lonergan is not correct to state that ‘‘the

equilibrium will be above OSP’’ in these situations, since OSPincludes the range up to the maximum numbers the environmentwill support.

PBR was developed to provide a workable implementation ofthe management objectives that were already enshrined in law.

J. Cooke et al. / Marine Policy 36 (2012) 389–392 391

The developers of the PBR did not invent new objectives of theirown but devised a procedure that could be implemented simplyby stakeholders, for example allowing them to examine theimplications of different recovery factors. The formulation givesa precise benchmark but takes into account uncertainty by usinga minimum estimate of abundance rather than the point estimate.No marine mammal population numbers can be estimated withabsolute precision, but Lonergan uses this unrealistic example tosuggest that PBR aims at a target level. Instead the developmentof PBR proceeded on broadly similar lines to that of RMP:the procedure was simulated in a range of hypothetical scenariosand adjustments made until satisfactory performance wasachieved [24].

Lonergan states that the selection of a recovery factor for PBRis subjective. Different criteria are used for the value of therecovery factor for different populations, but these were basedon simulation testing [25]. The ‘‘standard’’ PBR was specifiedbased on the criterion of a 95% probability in simulations thatpopulations would recover to or remain above MNPL (and thus bewithin OSP), with a recovery factor of 1.0. Robustness of thestandard PBR to potential biases in estimation of abundance andhuman-caused mortality, RMAX, and other factors was testedthrough simulation, with the result that a recovery factor of0.5 would still allow for achievement of the goal of a 95%probability of being above MNPL for the levels of bias investi-gated. Therefore, 0.5 is used as a default value for the recoveryfactor in the US. The recovery factor may be increased up to1.0 for populations where there is reasonable scientific evidencethat there are no large biases in estimates of abundance, mortal-ity, RMAX or in the definition of population structure.

The standard PBR described above applies to populations ofunknown status relative to OSP. For populations with differentstatus, different criteria apply. For species listed as ‘‘Endangered’’under the US Endangered Species Act, a recovery factor waschosen to ensure that the time to recovery (to MNPL) is notdelayed by more than 10% by human-caused mortality. Thisapplies the simple concept of allowing these populations toincrease at a rate approaching their maximum so that they canincrease rapidly away from the small population size that createsa risk of extinction. Through simulations a value of 0.1 for therecovery factor was found to accomplish this. It is not correct tosuggest that endangered populations will recover to a higherfraction of carrying capacity than others since when a populationchanges status (e.g. it is removed from the endangered specieslist), its recovery factor is also changed.

4. Canadian objective-based fisheries managementfor harp seals

Lonergan is also mistaken about Canada’s objective-basedfisheries management (OBFM) approach, which is now appliednot only to harp seals (Pagophilus groenlandicus) but also tohooded seals (Cystophora cristata) and grey seals (Halichoerus

grypus) [26]. While he suggests that the approach ‘‘sidesteps the

difficulties in determining carrying capacities’’ OBFM simply pro-vides arbitrary reference points against which estimates ofcurrent population size may be compared , including estimatesfrom models that in some cases incorporate carrying capacity[27,28]. In the case of harp seals, OBFM model did not incorporatedensity dependence but Lonergan’s assertion that the approachset ‘‘thresholds as proportions of the maximum numbers of indivi-

duals observed during surveys of the population’’ is inaccurate. Thethresholds were actually set based on estimates of abundancederived from population models that incorporated survey esti-mates of pup production together with life-history parameters

[29]. There are different implications, including time delays andlevels of uncertainty, between setting catch limits based onsurveys that estimate total population as used in RMP or PBR oron models based on pup production [30]. Lonergan also arguesthat it is ‘‘unclear’’ whether the lack of an explicit and transparentalgorithm for calculating takes ‘‘is any more problematic than the

subjective choice of recovery factor within PBR’’. This ignores thekey difference that Canada’s approach is untested, and that thelimited simulations that were possible suggested that objectivesmay not be met [30], whereas PBR has been subjected toextensive well documented simulation testing [3]. The subse-quently released Integrated Fisheries Management Plan for Atlan-tic Seals for 2011–2015 moves even further from a fully specifiedmanagement procedure designed to meet agreed objectives bysuggesting that the objectives (in this case a reference point),rather than the procedure, may be adjusted based on modelsimulations [26].

5. Lonergan’s alternative proposal

Lonergan’s proposal is to base management advice on theeffects of exploitation on the population as predicted by adeterministic population model, all the parameters of which areassumed to be known. In this respect his proposal is similar toNMP, which has long since been found wanting and ignores thelessons learnt during the process of replacement of the NMP bythe management procedure approach [31]. He claims that underhis proposal regulators would be presented with the conse-quences of alternative options. In fact, they would be presentedwith only the theoretical consequences of management optionspredicated on all models and assumptions being correct.

This is in contrast to the choices offered to regulators underMSE approach (such as the IWC in the context of the tuning ofRMP), where information on the actual range of consequences thatmight occur in realistic scenarios is provided, such that regulatorscan be confident that the proposed procedure would not subjectpopulations to undue risk under plausible circumstances. As withsimilar attempts in the past, Lonergan’s proposed approach wouldlikely fall at the instance of data which did not fit the assumedmodel. For example, if the next population survey shows apopulation reduction that is substantially greater than had beenpredicted, what is the regulator to do? The decisions would bewide open from revising estimates, abandoning the approach orstopping the source of mortality. The regulators would not be in aposition to judge which of these responses would be compatiblewith sustainable management without first having formulated thealternative responses in the form of rules whose performance canbe simulation-tested in realistic scenarios.

A workable management approach necessarily includes anelement of contingency planning. This is achieved in proceduressuch as the RMP through a full specification of the managementrules. This does not imply that rules are fixed forever but it doesensure that at each point in time the decision-maker has a defaultcourse of action available, namely to continue with the pre-specified rules. Because the default policy will have been shownto perform robustly in all plausible scenarios, this remains a fail-safe option.

Lonergan suggests that stochastic simulations would mainlybe required for small populations. However, large populations arealso subject to variability. Indeed both theory and experiencewith pinnipeds and cetaceans suggest such that variability tendsto increase as populations get larger, due to higher incidence ofepisodes of disease or nutritional distress [32,33]. It is still anopen question as to how much of the variability seen in marinemammal populations is real (process variance) and how much is

J. Cooke et al. / Marine Policy 36 (2012) 389–392392

simply variation in the data (observation variance), but it appearsthat in most cases both factors can be important [34]. Evaluationsof management strategies need to allow for both kinds ofvariability.

6. Concluding remarks: the role of science in decision making

According to Lonergan ‘‘Scientists can advise on consequencesand identify contradictory aims, but have no special prerogativefor making the actual decisions. Unfortunately no one else reallywants to make these hard choices.’’

On the contrary, these ‘‘hard choices’’ have been negotiated,agreed and incorporated into law at various levels from the globaldownwards. The case of the IWC, and the development of theRMP, is just one such example. The United Nations Convention ofthe Law of the Sea (UNCLoS), concluded in 1982 after many yearsof negotiations, in force since 1994 and ratified by 161 countries,is universally applicable throughout the High seas and ExclusiveEconomic Zones [35]. It requires that states take measures thatare designed, on the best scientific evidence available, to maintainor restore populations of exploited species at levels that canproduce the maximum sustainable yield, as qualified by variousfactors, including the interdependence of species. In the case ofmarine mammals, UNCLoS authorises states and internationalorganisations to adopt more conservative measures. Some inter-national conventions, such as the Convention for the Conservationof Antarctic Marine Living Resources (CCAMLR), go further inspecifying how MSY targets are to be defined in the context ofinteracting species [36]. In the US the Marine Mammal ProtectionAct contains similar policy objectives, as noted above. In theEuropean Union, objectives are provided by the CommissionDecision on Standards for Good Environmental Status under theMarine Strategy Framework Directive [37].

The role of scientists is to develop workable implementationsthat reflect the intent of the agreed objectives, and to design, testand explain strategies that meet these objectives. To the extentthat competing objectives have been specified, scientists shouldshow how the trade-offs are likely to play out in realisticsituations that take account of typical levels of uncertainty andvariability. Managers and stakeholders can then try to agree a setof rules based on science that reach an acceptable compromisebetween different interests. The clearer the rules, the more likelythey are to be respected.

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