Full compliance with harvest regulations yields ecological benefits: Northern Gulf of California...

Full compliance with harvest regulations yields

ecological benefits: Northern Gulf of California case

study

Cameron H. Ainsworth1*†, Hem Nalini Morzaria-Luna2, Isaac C. Kaplan3, Phillip S. Levin3

and Elizabeth A. Fulton4

1Marine Resources Assessment Group (MRAG) Americas Inc, 2725 Montlake Blvd, E. Seattle, WA 98112, USA;2Frank Orth and Associates, 2725 Montlake Blvd, E. Seattle, WA 98112, USA; 3NOAA Fisheries, Northwest Fisheries

Science Center, 2725 Montlake Blvd, E. Seattle, WA 98112, USA; and 4CSIRO Wealth from Oceans Flagship,

Division of Marine and Atmospheric Research, GPO Box Hobart, 7001 Tasmania, Australia

Summary

1. The Northern Gulf of California is an ecologically important marine area with a high degree of

biodiversity, endemism and productivity. Mounting conservation concerns have prompted

researchers to propose newmanagement regulations, restricting fishing and protecting sensitive spe-

cies. Compliance with existing regulations is poor. Rules that are currently in place, if followed,

may go a longway towards achieving the ecological goals of management.

2. We conduct a review of existing fisheries regulations in this area. Then, using a spatially explicit

marine ecosystem model (Atlantis), we estimate the benefits of compliance with existing fisheries

regulations.

3. Under a full compliance scenario, we find large increases in protected species biomass within

25 years and a slowed rate of ecosystem degradation because of fishing. However, full compliance

costs the fishing industry about 30%of its annual revenue.

4. We parse out the benefits offered by management instruments (including spatial management

protections, seasonal fishery closures, gear restrictions, cessation of illegal fishing and vessel buy-

out programmes) and conclude that a suite of measures is needed to address major conservation

objectives.

5. Synthesis and applications. This exercise quantifies the benefits of improved fisheries enforcement

and provides a benchmark by which the value of future regulatory amendments can be assessed.

Where compliance with existing regulations is poor, conservation goals may be better served by

strengthening enforcement than by enacting new rules and legislation.

Key-words: Atlantis, compliance, ecosystem model, ecosystem-based management, Gulf of

California, illegal fishing, IUU, marine protected area

Introduction

There is little question that declining integrity of marine eco-

systems is eroding the ability of these systems to provide the

goods and services that humans need (Worm et al. 2006). It is

less clear what to do to reverse this trend. In recent years, calls

for the implementation of new approaches to marine resource

management such as networks of marine protected areas

(MPAs), marine zoning schemes, catch share programmes or

systematic overhaul of governance structures have increased

(Costello, Gaines & Lynham 2008; Halpern, Lester &McLeod

2010). In many cases, such calls follow an indictment of exist-

ing management, but often this condemnation of management

lacks specificity. Management may fail for two very different

reasons.

First, the management approach may be inadequate. For

example, while both MPAs and traditional fisheries manage-

ment can preserve fish biomass,MPAsmay be superior at pro-

tecting the age structure of exploited populations (I. Kaplan,

unpublished data). Thus, when a management goal is to pre-

serve the age structure of stocks (e.g. Francis et al. 2007), a

management scheme without MPAs is likely to be insufficient.*Correspondence author. E-mail: [email protected]

†Present address: College of Marine Science, University of South

Florida, 140 7th Ave, S. St. Petersburg, FL 33701.

Journal of Applied Ecology 2012, 49, 63–72 doi: 10.1111/j.1365-2664.2011.02064.x

� 2011 The Authors. Journal of Applied Ecology � 2011 British Ecological Society

Second, implementation of the approach may fail. Terrestrial

management provides examples of where poor compliance

with conservation rules can be easily identified as the primary

factor limiting policy success (Hilborn et al. 2006).More often,

the degree to which non-compliance impedes management is

poorly understood because of difficulties in studying rule-

breaking behaviour directly, and because of the complex and

case-specific nature of the problem (Keane et al. 2008).

Because of the social and fiscal costs of implementing new

management schemes (e.g. Helvey 2004), it is helpful to distin-

guish between cases in which management has failed because

the approach is fundamentally flawed and those in whichman-

agement could succeed, but implementation has failed. We

explore this issue in theNorthernGulf of California,Mexico.

This region is ecologically valuable for its biodiversity, its

endemic species and for the critical breeding and feeding

habitat it provides for birds, turtles and marine mammals

(Enriquez-Andrade et al. 2005; Lluch-Cota et al. 2007).

Fisheries are the chief source of economic productivity in the

Northern Gulf, and they are critical for food security.

Unfortunately, overfishing and environmental degradation

during the last century have eliminated important fisheries and

jeopardized others (e.g. Lercari & Chavez 2007). Growing

conservation concerns regarding the vaquita porpoisePhocoena

sinus, sea lions and sea turtles now further limit the economic

options of coastal communities (e.g. Seminoff et al. 2003;

Jaramillo-Legorreta et al. 2007).

Since the 1990s, Mexico has attempted to address these con-

servation concerns through the issuance of fisheries regulations

(Hernandez & Kempton 2003), but most fisheries still operate

as de facto open access systems (Cinti et al. 2010). Newpropos-

als attempt to plug some gaps in the regulatory framework.

For example, the use of a catch shares programme has been

suggested for the Northern Gulf, akin to the one implemented

in the Sinaloan shrimp trawl fishery (J.Murrieta-Saldivar, per-

sonal communication). Other proposed measures would

expand the existing network of MPAs to include additional

juvenile fish habitat (Cudney-Bueno et al. 2009a) or to protect

reefs (Sala et al. 2002). However, promising these proposals

may be poor compliance threatens to scuttle benefits.

An aerial survey in 2006 found over 19 000 artisanal vessels

(pangas) actively fishing (Rodrıguez-Valencia et al. 2008),

while as many as 50 000 vessels may participate in fisheries

throughout the year (Cisneros 2001; SAGARPA (Secretarıa

de Agricultura, Ganaderıa, Desarrollo Rural, Pesca y Alimen-

tacion) 2002). This far exceeds the number of panga licenses.

There were 17 313 licenses administered in 2008 by states adja-

cent to the Gulf, and this includes the Pacific fleet (INEGI

(Instituto Nacional de Estadıstica, Geografıa e Informatica)

2010). Moreover, poaching is known to occur in marine

reserves (Cudney-Bueno et al. 2009b; Rodrıguez-Quiroz et al.

2010), and few fisheries in the Gulf completely respect seasonal

closures (Cinti et al. 2010).

In this article, we review existing rules and regulations gov-

erning marine fisheries and conservation in the Northern Gulf

of California. We divide fisheries regulations into these catego-

ries: (i) spatial management protections; (ii) seasonal fishery

closures; (iii) gear restrictions. Following regulations strictly,

we would also see (iv) elimination of all illegal fishing; (v) by

2012, further reductions in fishing effort and changes in fleet

structure as the Mexican fisheries authority carries out fishery

license buy-out and gear switch-out programmes (SEMAR-

NAT (Secretarıa del Medio Ambiente y Recursos Naturales)

2008; CONAPESCA 2010). Each of these five management

instruments represents potential limitations in where, when

and how fishing can occur. All of these measures are imple-

mented in current or impending regulations.

Using an ecosystem simulation model of the Northern Gulf

of California (Fulton et al. 2004; Ainsworth et al. 2011), we

modelled these five management measures independently to

examine their effects on the ecosystem. We then compared the

results to a status quo scenario, in which the current degree of

compliance and fishing effort is represented. Combining all five

management measures leads to a ‘full-enforcement’ scenario,

in which all fishing regulations are adhered to, all illegal fishing

is stopped and scheduled fleet reductions ⁄ changes are carriedout. The ecological and economic benefits or costs achieved by

this full-enforcement scenario provide a benchmark by which

we can evaluate the costs of non-compliance and judge the

value of proposed regulatory amendments. Policy success is

framed in terms of species recovery, maintenance of biodiver-

sity and fisheries value. With specific impacts of each policy

described, we can explore the trade-off space inherent between

economic and ecological costs and benefits.

Materials and methods

THE ATLANTIS ECOSYSTEM MODEL

Atlantis is a deterministic biogeochemical and biophysical modelling

system that simulates the functioning of marine food webs and fisher-

ies to serve as a policy exploration tool for ecosystem-based manage-

ment (Fulton et al. 2004; Fulton, Smith & Smith 2007; Fulton 2010;

Fulton et al. 2011). It is an ‘end-to-end’ model, in that it represents

ecosystem components from marine bacteria to apex predators and

human beings. We opted to use this framework because it allows test-

ing of highly articulated management scenarios involving spatiotem-

poral fishing restrictions and it offers a wide range of economic and

ecological outputs.

Fulton et al. (2004) provide a summary of the chief dynamics and

process equations. Sub-models include consumption, biological pro-

duction, waste production, reproduction, habitat dependency, age

structure, mortality, decomposition and microbial cycles. The spatial

domain is resolved in three dimensions using irregular polygons to

represent biogeographic features. Exchange of biomass occurs

between polygons according to seasonal migration and foraging

behaviour, while water movement, heat and salinity flux across

boundaries can be represented by a coupled hydrodynamic model.

Plaganyi (2007) and Rose et al. (2010) provide reviews of this and

other marine ecosystemmodelling approaches.

NORTHERN GULF OF CALIFORNIA MODEL

For simulations here, we utilize the model of Ainsworth et al. (2011).

The spatial domain encompasses approximately 57 800 km2 of sea

area and includes the Colorado River Delta in the Northern Gulf to

areas as far south as the northern tip of Baja California Sur (Fig. 1).

64 C. H. Ainsworth et al.

� 2011 The Authors. Journal of Applied Ecology � 2011 British Ecological Society, Journal of Applied Ecology, 49, 63–72

Functional groups used in the model are presented in Table S1

(Supporting Information).

Building an ecosystem model for this region required integrating

diverse types of information. These included data emerging from the

PANGAS project (http://www.pangas.arizona.edu), an effort by

universities and non-governmental organizations to characterize

small-scale fisheries and assess artisanal resources. Original field work

included diet sampling (Ainsworth et al. 2010), trawl and underwater

video surveys (Ainsworth et al. 2011), andfisher interviews to estimate

species relative abundance trends (Ainsworth 2011). We forced salin-

ity, water temperature and currents in Atlantis with output from a

regional oceanmodelling system (Lluch-Cota et al. 2010) for the years

1985–2008, looped into the future. Ainsworth et al. 2011 show how

thesedatawere used in the calibration andvalidationof themodel.

SCENARIO DEVELOPMENT

All model simulations presented in this article run from 2008 to 2033

(25 years). The 2008 model represents current ecosystem structure

and functioning. For these simulations, we assumed that targeting

preference of fishers remains constant. Therefore, changes in fishing

mortality rates result fromeffort differencesbetweenmanagement sce-

narios. The scenarios tested are as follows: (i) status quo (partial com-

pliance with regulations), (ii) full adherence to spatial management

protections, (iii) full adherence to seasonal fishery closures, (iv) full

adherence to physical gear restrictions, (v) no illegal artisanal fishing,

(vi) planned fishery buy-outs and gear switch-outs are implemented

and (vii) full enforcement (combined effects of scenarios ii–vi).

STATUS QUO

The status quo scenario represents our best understanding of present

fishing patterns in the Northern Gulf. We represent the activity of 33

fishing fleets (Table S2, Supporting Information). Based on literature

and discussions with local experts involved in the PANGAS project

(P. Turk-Boyer, R. Cudney, W. Shaw, T. Pfister, P. Raimondi,

L. Bourillon, J. Torre, M. Moreno, personal communication), we

have assembled the set of fishery regulations that are followed by fish-

ers in the Northern Gulf, partially or completely (Table S3, Support-

ing Information). These rules and level of compliance are

implemented in the 2008 ecosystemmodel.

We assume that fisheries catch in the status quo scenario corre-

sponds to the average catch from 2000 to 2007 (Table S4, Supporting

Information). This series was assembled using officialMexican fishery

statistics, port-level surveys with fishing cooperatives and various out-

puts of the PANGAS project. Complete references are provided in

Appendix Table E2 of Ainsworth et al. (2011). Catch by functional

group (in Table S4, Supporting Information) was allocated to each of

the 33 fleets according to Table S5 (Supporting Information); refer-

ences are in Table S6 (Supporting Information). Fishing areas are

defined for artisanal fleets using Moreno-Baez et al. (2010), and for

purse seine and squid fisheries using DOF (2006). Otherwise, fleet

activity follows hydrographic contours: we assumed longlines operate

to 150-m depth, shrimp trawls operate to 500 m and areas deeper

than 500 mwere exclusively used by pelagic fisheries.

SPATIAL MANAGEMENT POLIC IES

Spatial management includes MPAs, concessions and regulations

contained in Diario Oficial de la Federacion and other governmental

publications (Table S7, Supporting Information), as illustrated in

Fig. S1 (Supporting Information). Major spatial restrictions are

found within the Upper Gulf of California and ColoradoRiver Delta

Biosphere Reserve (hereafter called ‘Upper Gulf’), including a sea-

sonal closure for artisanal fleets and a slated halving in the number of

permitted shrimp trawlers (Table S7, Supporting Information), from

Fig. 1. Northern Gulf of California. Atlantis

polygon geometry andmain fishing ports.

Following fishery rules yields benefits 65


162 to 82 (SGPA (Subsecretarıa de Gestion para la Proteccion

Ambiental) 2009). This was simulated as a reduction in fishing mor-

tality to 51% (82 ⁄ 162) of the 2008 levels. Spatial restrictions also con-

sider the exclusion of gillnets from the vaquita distribution area, as is

planned for 2012 (SEMARNAT (Secretarıa del Medio Ambiente y

Recursos Naturales) 2008). We considered this implemented as of

2008 for ease of modelling. This simplification has little effect on the

long-term (25 year) simulations presented here.

SEASONAL CLOSURES

Seasonal closures are active for Cortez oyster (Crassostrea cortezien-

sis), spiny lobsters (Panulirus interruptus, Panulirus inflatus, Panulirus

gracilis), Curvina golfina (Cynoscion othonopterus) and mullets

(Mugil cephalus and Mugil curema) (Table S9, Supporting Informa-

tion). The spatial closures were simulated as partial or complete spa-

tial closures to specific model cells, with fishing effort reduced

proportionately to area closed.

GEAR RESTRICTIONS

The gear restrictions scenario combined both catch age structure reg-

ulations and effort restriction regulations (Table S8, Supporting

Information). Regulations that increase the minimum size of fish

caught were simulated by increasing the age at first capture by one

age class. Effort restrictions were simulated as either a total elimina-

tion of fishing mortality for protected species or minor or major

reductions in fishing mortality (i.e. a 20% or 50% reduction relative

to status quo on protected species). For sea turtle groups, we simu-

lated the enforcement of turtle excluding devices as a 66% reduction

in fishingmortality (Epperly 2003).

I LLEGAL FISHING

This scenario represents the elimination of illegal fisheries. We esti-

mated the proportion of small-scale vessels that operate legally as the

ratio of registered boats relative to the total number of boats present

in the area. There were 4085 active licenses in the Northern Gulf

based on the totals for Sonora (3778; INEGI (Instituto Nacional de

Estadıstica, Geografıa e Informatica) 2010), San Felipe (265; Acua-

corp de Hidalgo 2009) and Bahıa de Los Angeles (42; Danemann,

Torreblanca-Ramırez & Smith-Guerra 2007). The number of vessels

in operation (5720) is based on fly-overs by Rodrıguez-Valencia et al.

(2008). Catch of artisanal fleets was multiplied by the resulting ratio,

4085 : 5720 or 71%.

BUY-OUT AND SWITCH-OUT

This scenario represents the possible effects of an upcoming trawl

buy-out programme and an ongoing gear switch-out programme.

The shrimp trawl buy-out aims to reduce trawl effort by 30%

throughout Mexico by 2012 (CONAPESCA 2010). We therefore

reduced fishing mortality for shrimp and fish trawlers to 70% of sta-

tus quo for target and bycatch species in this scenario. The gillnet

buy-out and switch-out programme aims to eliminate gill nets and

driftnets from critical vaquita habitat or permanently substitute them

for gears that avoid vaquita bycatch as part of the species recovery

programme (SEMARNAT (Secretarıa del Medio Ambiente y Recur-

sos Naturales) 2008). Within this programme’s region, we assumed

that 51% of gillnet vessels would opt for a buy-out, while 49%would

shift to a light shrimp trawl (SEMARNAT (Secretarıa del Medio

Ambiente y Recursos Naturales) 2008; PRONATURA, CEC-CCA-

CCE, CEDO Intercultural, & NOS 2010). We assumed that light

shrimp trawls catch 80% less bycatch than the current trawl fleet and

eliminate vaquita bycatch, but are less efficient at capturing the target

species (catch is 56% of status quo levels; see Appendix S1 (Support-

ing Information) for details).

FULL ENFORCEMENT

The full-enforcement scenario assumes perfect compliance with each

of these five classes of regulations: spatial management policies, sea-

sonal closures, gear restrictions, elimination of illegal fishing and

reduction in fishing effort through buy-out and switch-out.

POLICY SUCCESS METRICS

We discriminate the outcomes of these scenarios by considering spe-

cies-level, fishery and ecosystem-based metrics. Species-level metrics

include changes in biomass, body size and the ratio of reproductively

mature individuals to juveniles. Fishery metrics include changes in

catch (total amount and distribution among fleets), landed value and

average trophic level (a proxy for ecosystem maturity, Cury et al.

2004). Ecosystem-based metrics include spatial distribution of bio-

mass and species biodiversity measured by Kempton’s Q index

(adapted for ecosystem models, Q90: Ainsworth & Pitcher 2006).

This metric represents the interdecile slope of the cumulative species

log-abundance curve, where functional group biomass, sorted into

bins, substitutes for abundance. The metric increases with species

richness and evenness and behaves consistently across a wide range of

model structures.

Results

SPECIES RECOVERY

Our model projects that species of conservation concern, oce-

anic turtles, pinnipeds, vaquita and totoaba (Totoaba macdon-

aldi) (see Ainsworth et al. 2011 for group definitions),

experience population increases once full compliance with fish-

eries regulations is achieved (Fig. 2a). The full-enforcement

scenario results in the highest biomass of threatened species in

all cases, and the status quo scenario results in the lowest.

Under the full-enforcement option, vaquita achieve an increase

in biomass 3Æ5 times over present-day (2008) levels; though,

they do not reach their population maximum within the span

of the simulations. Under the status quo scenario, they

decrease to 1 ⁄3 of their current biomass and stabilize. Totoaba

are predicted to recover under all policy simulations including

the status quo.Of the five regulatory instruments tested, spatial

management allows the largest increases in turtles, vaquita and

pinnipeds, while totoaba respond most positively to gear

restrictions (i.e. larger gillnetmesh sizes reduce juvenile mortal-

ity). The initial decrease in the biomass of the long-lived

groups, oceanic turtles and pinnipeds, reflects the lag time

between new recruitment and individual body growth.

Abundance of commercially exploited species shows a

steady increase throughout the 25-year simulation (Fig. 2b).

Full enforcement yields the greatest increase in biomass over-

all, while the status quo scenario projects a modest increase for

the first 15 years followed by stabilization. The increase in



commercial biomass under the status quo regime mainly

occurs in groups below trophic level (TL) 2Æ5; these increase

22% on average, while groups above TL 2Æ5 decrease by 49%.

This shunting of secondary production towards the lower food

web occurs in all scenarios to some degree, but it is moderated

by restrictive fishing policies. For example, under full enforce-

ment, the majority (64%) of predator groups above TL 2Æ5increase in biomass, while under status quo themajority (54%)

decrease.

High trophic level groups benefit the most from full enforce-

ment (Fig. 3). These tend to be large-bodied exploited species,

whose population abundance lies far below ecosystem carrying

capacity. The positive relationship between trophic level and

species recovery is pronounced under the full-enforcement sce-

nario (mean regression slope in Fig. 3 is 0Æ36), but spatial man-

agement alone also favours predator recovery to some extent

(slope = 0Æ19, not shown). Gear restrictions (0Æ07) and vessel

buy-outs (0Æ04) marginally increase the relative biomass of pre-

dators.

Spatial management alone allows an increase in exploitable

biomass to between 125% and 200% of the status quo

(Fig. 4a,b). The increase occurs broadly over the study area,

even though spatial management areas are restricted to the

coast and Upper Gulf (Fig. S1, Supporting Information).

There are smaller biomass increases in protected areas than in

unprotected areas, but this is an artefact of the simplifying

assumption regarding static spatial fishing effort. Biomass

accumulates in unprotected areas because fisheries do not

re-allocate effort appropriately, while biomass in protected

areas is kept low by the presence of fisheries. Factoring in all of

the current management regulations, the full-enforcement

scenario (Fig. 4c) achieves a dramatic increase in exploitable

biomass with the greatest improvements occurring in the delta

region and along coastlines.

FISHERIES

Total catch decreases under the full-enforcement scenario for

all gear types relative to the status quo (Fig. 5). However, for

(a) (b)

Fig. 2. Biomass trajectories from 2008 to 2033 under various management scenarios for species of conservation concern and for commercially

exploited species except small pelagics. For threatened species, we show the best scenario (full enforcement), the worst scenario (status quo)

and the second best scenario (varies).

Fig. 3. Benefit of full enforcement by trophic level. Biomass in 2033

under the full-enforcement scenario (BiomassFE) shows the greatest

increase relative to the status quo scenario (BiomassSQ) in high tro-

phic level groups. Light grey area shows interdecile range; dark grey

area shows interquartile range; solid line shows mean trend (herbivo-

rous fish, skates and vaquita are excluded). Open circles show

commercially exploited functional groups; closed circles show

non-commercial groups.



all fleets except diving, the reduced fishing effort mandated by

the full-enforcement scenario permits a steady increase in

exploitable biomass, so catch increases after an initial dip.

Catches by the gillnet fleets for fish and driftnet fleet for shrimp

are reduced immediately to 21% of the status quo amount,

mainly because of spatial management rules that restrict fish-

ing in the Upper Gulf and the vaquita refuge. Those controls

reduce total effort of pelagic gillnets by 66% inshore and 78%

offshore. The initial drop in fishing effort reduces annual catch

value (see Table S10, Supporting Information for prices) for

pelagic gillnet fisheries from $0Æ9 million (US dollars) under

the status quo to around $0Æ25 million (US dollars) under the

full enforcement.

Trap fisheries are impacted the least: total catch is reduced

to 74% of the status quo initially but recovers almost com-

pletely. Total value from fisheries in 2009 (i.e. 1 year after full

enforcement is effected) is reduced for most fleets relative to

status quo. The biggest losers are the following: shrimp drift-

nets )95%, pelagic gillnets )74%, demersal gillnets )61%,

diving )57% and seine )47%. This lost revenue is likely to be

an overestimate as we have not factored in adaptive behaviour

from fishermen. The only winning fleets are fish trawl +2Æ6%and sport fisheries+15%.

TRADE-OFFS BETWEEN FISHERIES AND

CONSERVATION

Scenarios that take a large amount of catch tend to result in

lower end-state species biodiversity (Fig. 6a). Spatial manage-

ment regulations appear apt at preserving biodiversity. In fact,

no additional benefit is realized by the full-enforcement sce-

nario in our simulations. The shrimp trawl buy-out pro-

gramme, which reduces incidental mortality on a broad range

of species, also improves ecosystem biodiversity as measured

by the Q90 metric from 5Æ42 (initial 2008 value) to 5Æ93.Average fish body size and average trophic level of artisanal

catch are at their maximum values under the full-enforcement

scenario (Fig. 6b,c). The trade-off frontiers suggest there may

be convex relationships between catch and some ecological

proxies, indicating that joint benefits are maximized bymoder-

ate fishing solutions. Translating catch into landed value by

the price matrix in Table S10 (Supporting Information), the

full-enforcement scenario could cost fishers $230 million (US

dollars) annually from lost revenue (about 30% of gross

revenue).

Each of the regulatory instruments shows high performance

in at least one economic or ecological policy criterion (Fig. 7).

For example, seasonal closures maximize shrimp landings,

gear restrictions preserve elasmobranch biomass and spatial

management protects biodiversity and vaquita biomass. No

one regulatory instrument achieves exceptional results across

all criteria, but layering these regulations together in the full-

enforcement scenario yields outstanding conservation benefits

to the detriment of fisheries revenue.

Fig. 4. Biomass distribution of commercially

exploited species in 2035 except small pela-

gics. Absolute biomass is presented for the

status quo scenario; change in biomass rela-

tive to the status quo is presented for spatial

management and full-enforcement scenarios

to highlight policy impacts.

Fig. 5. Catch by fishing fleet under full-enforcement scenario relative

to status quo. Catch under full enforcement (CatchFE) is reduced ini-

tially to 20–80% of status quo (CatchSQ) depending on fleet (because

of reductions in fishing effort), but increases slowly over time as target

populations increase in biomass.



Discussion

The Northern Gulf of California demonstrates a case where

management regulations are likely to be sufficient to achieve a

broad range of conservation objectives, but management falls

short because implementation is lacking. The full-enforcement

scenario offers significant ecological benefits including

increased ecosystem biodiversity and recovery prospects for

depleted species. We did not attempt to estimate the costs of

achieving compliance, but they are likely to be substantial. In

addition to enforcement costs, we know that fisheries would

suffer economic losses under strict implementation of existing

rules, perhaps losing 30% of revenue. Moreover, we recognize

that it would require an organizational feat to improve compli-

ance significantly, addressing issues like coordination between

agencies, stakeholder education, regulatory oversight, legality

and corruption (Moreno, Recio-Blanco &Michel 2010). Nev-

ertheless, conserving this ecologically rich area may offer a

cost-effective means to protect global biodiversity, as has been

suggested by cost-benefit analysis of conservation in tropical

terrestrial systems (Balmford et al. 2003).

A TOOLBOX APPROACH

Regulatory instruments excel at different aspects of resource

management. Seasonal closures increase shrimp landings as

they restrict harvests during breeding periods. Gear restric-

tions, aimed at reducing incidental capture of juvenile fish and

Fig. 7.Multivariate comparison of scenario performance. These radar plots show socioeconomic and ecological benefits accrued in each scenario

measured in terms of ecosystem biodiversity (Biodiv.) (Q90 metric), mean trophic level of fisheries landings (Troph.), the ratio of mature to juve-

nile fish numbers (Mature ⁄ Juv.), shrimp landings (Shrimp), vaquita biomass (Vaq.) and elasmobranch biomass (Elasmo.). There is no inherent

comparability between these metrics (in absolute or relative change), so we have scaled the simulation outputs to show the worst results observed

(a) and the best results observed (b); the range in between (c) shows the scope of possible outcomes. The total shaded area represents a multivari-

ate criterion of performance.

Fig. 6. Relationship between total catch and three ecological indicators. Q90 biodiversity statistic is based on Kempton’s Q index and summa-

rizes species richness and evenness (Ainsworth & Pitcher 2006). We fit a polynomial curve ad hoc to illustrate a potential convex relationship

between total catch and average trophic level of catch of artisanal fisheries (broken line). Initial (2008) conditions: catch 278 000 tonnes; biodiver-

sity 5Æ42, individual weight 0Æ412 g N; trophic level of catch 3Æ41. Status quo (SQ); spatial management (SM); seasonal closures (SC), gear restric-

tions (GR); illegal fishing (IF); buy-outs (BO); full enforcement (FE).



non-target species, help increase commercial biomass. Cessa-

tion of illegal fishing has only minor ecological and economic

effects at the ecosystem scale, although benefits to legitimate

operators could be substantial; for instance, in the south-east

of the study area where unregulated trap operations are com-

mon (Bourillon-Moreno 2002). The buy-out programme for

shrimp trawlers has a positive effect on biodiversity and

reduces bycatch, but the benefits of buy-outs and spatial man-

agement are not additive because the main areas of effect clo-

sely overlap. The buy-out may help to reduce benthic habitat

damage, but this was not modelled. Spatial management pro-

tections assist in the recovery of predatory fish and vaquita,

and they preserve biodiversity because of the wide umbrella of

protection offered across ecological communities. However,

no single instrument can match the combined protections

offered by the full-enforcement scenario.

FISHERIES PROGNOSIS

All of the tested scenarios, including the status quo scenario,

projected an increase in commercially exploitable biomass over

the next 25 years, but this does not indicate species recovery.

When fisheries deplete piscivore populations, trophic chains in

the ecosystem are shortened overall and this can lead to bio-

mass increases in the lower food web (Casini et al. 2009).

Indeed, there are economic reasons to allow this type of reor-

ganization (Pauly et al. 2000). However, the decision to do so

should be made with care as simplification of the ecosystem is

akin to a ratcheting effect (in that it is one-way process) and

may be difficult to reverse for ecological and socioeconomic

reasons (Pitcher 2005). Also, such ecosystems can be prone to

collapse (Nystrom, Folke & Moberg 2000). Policies with

increased enforcement slow this degradation process.

SPECIES RECOVERY

The Atlantis model predicts that vaquita are not yet doomed

to extinction as some policies can elicit an increase in numbers.

This is the tacit consensus among researchers who call for

immediate management protections (e.g. Jaramillo-Legorreta

et al. 2007; Aragon-Noriega et al. 2010). However, our model

has not considered the effects of genetic bottlenecks, which

could become a significant obstacle to recovery after prolonged

population depression (Rojas-Bracho & Taylor 1999). The

driftnet switch-out and gillnet buy-out initiatives included as

part of the species recovery programme (SEMARNAT (Secre-

tarıa del Medio Ambiente y Recursos Naturales) 2008) appear

to be insufficient to permit recovery even under perfect compli-

ance, which is not to be expected (Aragon-Noriega et al.

2010). Recovery is achieved only under the spatial manage-

ment and full-enforcement scenarios, both of which assume

gillnets are excluded entirely from the vaquita distribution area

(Fig. S1, Supporting Information). A coordinated approach

involving spatial protections seems necessary. This will surely

impact the profitability of fisheries in nearby communities like

San Felipe, Golfo de Santa Clara and Puerto Penasco (Aragon-

Noriega et al. 2010).

Totoaba are predicted to recover under all policy variations

including the status quo. However, as there has been little

change in stock status since the fisherywas banned in 1975, it is

likely that we have missed or underestimated an important

source of mortality. The impacts of poaching and environmen-

tal stress were not included in themodel but theymay be signif-

icant (Lercari &Chavez 2007). Juvenile bycatch seems to be an

important influence judging from the success of simulated gear

restriction policies; however, severitymay be underestimated.

Conclusions

There has been amazing progress made in the last 15 years in

the use of end-to-end and ecosystem modelling approaches.

These tools can play an important role in providing the quanti-

tative evaluation and synthesis needed to support ecosystem-

based management. In particular, end-to-end models are

useful for evaluating the impacts of management policies that

affect numerous species and ecosystem processes, like those

tested in this study. However, the inclusivity of end-to-end

models comes at a price as they incorporate processes that are

poorly understood.Wemust therefore use caution in interpret-

ing predictive results (Rose et al. 2010). Moreover, the slow

run-times of complex end-to-end models affect our ability to

explore uncertainty surrounding projections through sensitiv-

ity analysis. Current efforts to parallelize code aim to overcome

this limitation (e.g. in Atlantis: E. Fulton, personal communi-

cation, and Ecospace: C.Walters, personal communication).

Several general conclusions can be drawn from this study.

First, improving compliance with existing fisheries regulations

(e.g. through improved education, monitoring and enforce-

ment) might offer great conservation benefits. As newmanage-

ment policies are developed for this region, there must be a

concurrent attempt to improve compliance. Second, no one

regulatory instrument is able to address all major conservation

and fishery concerns; an effective regulatory framework must

include a suite of measures. Third, conservation costs money,

and this cost will be borne unevenly among fishing communi-

ties in theNorthernGulf of California.

Acknowledgements

This project was funded by the David and Lucile Packard Foundation. PAN-

GAS members provided useful input on scenario development: J. Torre (COBI

A.C.), W. Shaw, M. Moreno Baez and T. Pfister (The University of Arizona),

R. Cudney-Bueno (Packard Foundation), P. Turk-Boyer, R. Loaiza-Villanu-

eva and I. Martinez-Tovar (CEDO Intercultural), A. Cinti (The University of

Arizona), P. Raimondi (University of California-Santa Cruz), E. Torreblanca

and G. Danemann (PRONATURA A.C.). M. Moreno-Baez and C. Moreno

provided data on fishers’ interviews and logbooks. The Gordon and Betty

Moore Foundation supported improvements to theAtlantis code base.

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Received 22April 2011; accepted 26 September 2011

Handling Editor: NickDulvy

Supporting Information

Additional Supporting Information may be found in the online ver-

sion of this article.

Fig. S1. Spatial restrictions used in the management scenarios. Infor-

mation on specific spatial restrictions is found in Table S7.

Table S1.Functional groups used in the Atlantismodel.

Table S2. Fishery fleets for Atlantis model. Number of functional

groups targeted out of 61 in themodel.

Table S3.Non-spatial regulations assumed followed under the status

quo scenario.

Table S4. Catch by functional group used as baseline (status quo)

summed across fleets.

Table S5.Catch per fleet under status quo (average of 2000–2007).

Table S6.Citations and assumptions referred to in Table S5.

Table S7. Spatial management of fishing areas in the northernGulf of

California used in the spatial management scenario; DOF date (Dia-

rio Oficial de la Federacion) indicates publication in the official regis-

try.

Table S8.Regulations used in gear restrictions scenario.

Table S9.Regulations used in seasonal closures scenario.

Table S10. Prices by functional group in USD.

Appendix S1.Additional information on scenario parameterization.

As a service to our authors and readers, this journal provides

supporting information supplied by the authors. Such materials

may be re-organized for online delivery, but are not copy-edited or

typeset. Technical support issues arising from supporting infor-

mation (other than missing files) should be addressed to the

authors.



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