trophic flows, ecosystem structure and fishing impacts in the south catalan sea, northwestern...
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Journal of Marine System
Trophic flows, ecosystem structure and fishing impacts in the
South Catalan Sea, Northwestern Mediterranean
Marta Coll a,*, Isabel Palomera a, Sergi Tudela b, Francesc Sarda a
a Institute of Marine Science (CMIMA-CSIC), Passeig Marıtim de la Barceloneta, 37- 49, 08003, Barcelona, Spainb WWF Mediterranean Programme Office, Canuda, 37, 08002, Barcelona, Spain
Received 21 February 2005; accepted 15 September 2005
Abstract
An exploited ecosystem from the continental shelf and upper slope of the Northwestern Mediterranean Sea was described by
means of an Ecopath mass-balance model with the aim of characterising its functioning and structure and describing the ecosystem
impacts of fishing. This application included some complexities added to the general modelling methodology due to the high
biodiversity of the Mediterranean Sea and the multispecific nature of the fishery, and to the difficulties of working with fishing data
which are usually irregularly or imprecisely collected. The model comprised 40 functional groups including primary producers, the
main species of benthic, demersal and pelagic invertebrates, fishes and non-fish vertebrates and three detritus groups. In addition,
trawling, purse seine, longline and troll bait fishing fleets were included.
Results showed that the functional groups were organized into four trophic levels with the highest levels corresponding to
anglerfish, dolphins, large pelagic fishes and adult hake. The system was dominated by the pelagic fraction, where sardine and
anchovy prevailed in terms of fish biomasses and catches. Detritus and detritivorous groups also played key roles in the ecosystem
and important coupled pelagic-demersal interactions were described. Considering Odum’s theory of ecosystem development, the
ecosystem was placed on an intermediate-low developmental stage due, at least partially, to the impact of fishing activity. This
highlighted the high intensity of fishing in the ecosystem, in accordance with the general assessment of western Mediterranean
marine resources, and fishing fleets were ranked as top predators of the system. The low trophic level of the catch was in line with the
long history of exploitation in the area. However, the steady decline of pelagic landings between 1994 and 2003, coupled with a
decrease of the pelagic biomass within the system, underlined the low resistance of the system in front of perturbations. This decline
was reproduced under Ecosim dynamic simulations combining different scenarios of moderate increase of fishing effort and an
environmental forcing affecting the availability of preys to small and medium-sized pelagic fishes under wasp-waist flow control.
D 2005 Elsevier B.V. All rights reserved.
Keywords: Ecopath; Ecosim; Ecological modelling; Trophic web; Network analysis; Fishing impact; Environmental forcing; Mediterranean; Ebro
Delta
0924-7963/$ - see front matter D 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.jmarsys.2005.09.001
* Corresponding author.
E-mail addresses: [email protected] (M. Coll),
[email protected] (I. Palomera), [email protected] (S. Tudela),
[email protected] (F. Sarda).
1. Introduction
The Mediterranean region has been inhabited for
millennia and human settlements have been spreading
continuously along its coastal areas, reaching a total of
132–135 million people now settled there (Margalef,
1985). Ecosystems have thus been altered in many ways
s 59 (2006) 63–96
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9664
due to the overexploitation of biological resources,
direct habitat modification of sea and coastal areas,
introduction of exotic species, pollution and climate
change; with many species presently endangered and
some probably prone to extinction (Bianchi and Morri,
2000). Fishing activity has been proposed as the first
major human disturbance to coastal areas (Jackson et
al., 2001), and evidence of fishing activity going back to
ancient times can be found all around the Mediterranean
Sea (Margalef, 1985). This is emphasised by a much
lower starting value of the mean trophic level of the
catch in the past 50-year historical series for the Med-
iterranean Sea when compared to oceanic areas of the
world (Pauly et al., 1998a).
Two important features of the fishing activity in the
Mediterranean Sea are the multi-specificity of catches
and the absence of large single stocks, especially in the
demersal regime, comparable to those which inhabit
other seas (Farrugio et al., 1993). Moreover, although
artisanal gears are still important within the western
basin, most fleets have developed towards a nearly
industrial type of activity (or semi-industrial fleets)
fully exploiting continental shelves and upper slopes
of the basin. They are associated with the highest land-
ings and are mainly composed of bottom trawlers, purse
seines and longliners (Lleonart and Maynou, 2003). The
development of fishing technologies and overcapitaliza-
tion, with an increasing demand for marine resources, is
placing intensive pressure on marine resources in the
western basin, and the general assessment suggests that
most demersal stocks are fully exploited or over-
exploited, while some pelagic stocks also show overex-
ploitation trends (Farrugio et al., 1993; Aldebert and
Recasens, 1996; Sarda, 1998; Papaconstantinou and
Farrugio, 2000; Lleonart and Maynou, 2003; Bas et
al., 2003). Increasing concern about recruitment over-
fishing is related to the Northwestern Mediterranean
anchovy stocks, while growth overfishing affects some
demersal resources because for many species the sizes at
first catch are very similar to those at which the fish
recruit (Lloret and Lleonart, 2002; Sarda et al., 2005).
Moreover, the introduction of new fishing procedures
such as modern longlines, e.g., for adult hake Merluc-
cius merluccius, has eliminated the spawning refugia of
some species and has lead to an increasing concern for
recruitment overfishing of some demersal stocks (Lleo-
nart and Maynou, 2003).
Fishing activities are developed within a context, the
ecosystem, where target and non-target species interact
establishing complex relationships. Fishing will thus
have various direct and indirect impacts, additionally
to those induced by oceanographic features and other
anthropogenic and natural disturbances (e.g., Jennings
and Kaiser, 1998; Hall, 1999; Jackson et al., 2001;
Christensen et al., 2003; Myers and Worm, 2003). In
this context, there is a growing need to apply more
integrative approaches to fisheries management to un-
derstand how fishing activity is impacting complex food
web structures and functioning (FAO, 2002; Pauly et al.,
2002).
Therefore, an ecological model using the Ecopath
with Ecosim software (EwE) (Christensen and Walters,
2004; Pauly et al., 2000) was applied to describe a well
known area from the Northwestern Mediterranean Sea:
the exploited continental shelf and upper slope ecosys-
tem of the South Catalan Sea associated with the Ebro
River Delta. The mass-balance modelling approach has
been widely used to quantitatively describe aquatic
systems and to assess the impacts that fishing activities
and environmental factors have on marine ecosystems
(Christensen and Pauly, 1993a; Christensen and Wal-
ters, 2004). However, there are still few examples of
ecological modelling applied to the exploited ecosys-
tems of the Mediterranean Sea and most are concen-
trated in coastal and shallow areas (Orek, 2000;
Daskalov, 2002; Libralato et al., 2002; Pinnegar and
Polunin, 2004). The present application is the first
effort to study western Mediterranean exploited shelf
and slope ecosystems using a mass balance model. It
has enabled the description of the structure and func-
tioning of this ecosystem with the analysis of a broad
number of ecological indicators related with trophic
flow description, thermodynamic concepts, information
theory and network analysis (Muller, 1997; Christensen
et al., 2004). Moreover, fishing activities are considered
within the ecosystem context to assess the ecosystem
effects of fishing.
According to FAO (1995) dThe achievement of real
marine ecosystem-based management of fisheries
implies the regulation of the use of the living resources
based on the understanding of the structure and dynam-
ics of the ecosystem of which the resource is a part’. This
clearly demands a substantial improvement of our un-
derstanding of the structure and functioning of eco-
systems, and the interactions between ecosystem
compartments and their changes due to human and en-
vironmental factors.
2. Materials and methods
2.1. The study area
An Ecopath with Ecosim (EwE) trophic model
(Christensen and Walters, 2004; Pauly et al., 2000)
Fig. 1. The continental shelf and upper slope area of the South Catalan Sea related with the Ebro River Delta (Northwestern Mediterranean).
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 65
was described to represent an average annual situation
(1994) of the continental shelf and upper slope area
associated with the Ebro River Delta (South Catalan
Sea, Northwestern Mediterranean) (Coll et al., 2004)
(Fig. 1). The considered depth range was between 50
and 400 m, covering a total area of soft bottom
sediments of 4500 km2. The coastal area within 3
nm from the coast or down to 50 m depth, where
the artisanal fleet mainly operates and the trawling
fleet is not allowed to fish, was excluded.
This is an oligotrophic area, where enrichment
occurs due to regional environmental events, mainly
related to wind conditions, the existence of a temporal
thermocline and a shelf-slope current and river dis-
charges (Estrada, 1996; Salat, 1996; Agostini and
Bakun, 2002). These episodes greatly influence the
productivity and fishing activity of the area (Palo-
mera, 1992; Sabates and Olivar, 1996; Agostini and
Bakun, 2002; Lloret et al., 2004), which yields almost
half of the total landings of the Catalan coast (Lleo-
nart, 1990) and which is specially relevant for the
reproduction of small pelagic fishes, mainly the Euro-
pean anchovy Engraulis encrasicolus. Moreover, this
is also a strategic area for marine vertebrate conser-
vation, sheltering three quarters of the world’s
breeding population of the Mediterranean endemic
Audouin’s Gull (Larus audouinii) and important col-
onies of other terns and gulls (Zotier et al., 1998;
Abello et al., 2003). Some of these species forage
actively on the marine shelf and find a complementary
food source in the discards generated by the trawling
and purse seine fleets (Oro et al., 1997; Oro and Ruız,
1997; Arcos, 2001).
The area includes the fishing harbours from Tarra-
gona to Les Cases d’Alcanar (Fig. 1). Trawling (with
174 boats operating in the study area), purse seine (51
boats), longline (13 boats) and troll bait fleet (few
seasonal boats) were included in the model. Small
pelagic fishes, overcoat sardine (Sardina pilchardus)
and anchovy (Engraulis encrasicolus), constitute the
principal component of the catches in terms of biomass
and are mainly caught by purse seines and bottom
trawlers. The demersal fishery comprises mainly juve-
niles of several target species, e.g. hake (Merluccius
merluccius), red mullet (Mullus barbatus) and blue
whiting (Micromesistius poutassou), caught principally
by the trawling fleet. Large demersal fish (e.g., adult
hake) and large pelagic fish (e.g., Atlantic bonito Sarda
sarda, bluefin tuna Thunnus thynnus and swordfish
Xiphias gladius) are caught by longline and troll bait
fleets (Bas et al., 1985; Lleonart, 1990; Lloret and
Lleonart, 2002).
ig. 3. Total official landings (t), demersal landings and small and
edium-sized pelagic fish landings from the studied area (Institute of
arine Science, CMIMA-CSIC, and Generalitat de Catalunya data-
ases) (1994–2003).
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9666
Themodel represented the highly fished ecosystem in
1994, when official landings were at their highest his-
torical level. Official landings from the studied area
increased dramatically from the early 1960s to the
early 1980s, mainly due to governmental aids to the
fishing sector. Marked fluctuations in landings occurred
thereafter until catches progressively declined from 1994
to the present (Fig. 2). Total official landings from 2003
were similar to those reached in the late 1970s. From
1994 to 2003 a decrease of 55% on total official landings
has been observed (Fig. 3). This reduction is mainly
based on the pelagic fraction, which also exhibited
marked interannual fluctuations and underwent a reduc-
tion of 70.2% in the case of anchovy official landings and
a reduction of 70% in the case of sardine landings.
Demersal landings have been maintained at similar
levels since 1983 with a reduction of 18% in landings
and underwent smaller fluctuations over the period of
decline in the pelagic fraction. Pelagic and demersal
landings reached similar values for the first time in 2003.
2.2. Modelling approach
The Ecopath and Ecosim approach (EwE) version 5
(Christensen and Walters, 2004; Pauly et al., 2000;
http://www.ecopath.org) was used to ensure energy
balance of the model. EwE divides the production
(P) of each component, or functional group, (i), of
the ecosystem into predation mortality (M2ij) caused
by the biomass of the other predators (Bj); exports from
the system both from fishing activity (Yi) and other
exports (Ei); biomass accumulation in the ecosystem
(BAi); and baseline mortality or other mortality (1-EEi),
where EE is the ecotrophic efficiency of the group
within the system, or the proportion of the production
Fig. 2. Total official landings and pelagic and demersal fractions (t)
from the studied area (Institute of Marine Science, CMIMA-CSIC,
and Generalitat de Catalunya databases) (1973–2003).
F
m
M
b
of (i) that is exported out of the ecosystem (i.e., by
fishing activity) or consumed by predators within it.
Pi ¼Xj
BjdM2ij þ Yi þ Ei þ BAi þ Pid 1� EEið Þ:
ð1ÞEq. (1) can be re-expressed as:
BdP
B
��i
¼Xj
BjdQ
B
��j
dDCij þ Yi þ Ei þ BAj
þ BidP
B
��i
d 1� EEið Þ: ð2Þ
Where (P/B)i indicates the production of (i) per unit
of biomass and is equivalent to total mortality, or Z,
under steady-state conditions (Allen, 1971); (Q/B)i is
the consumption of (i) per unit of biomass; and DCij
indicates the proportion of (i) that is in the diet of
predator ( j) in terms of volume or weight units. EwE
parameterizes the model by describing a system of
linear equations for all the functional groups of the
model, where for each equation three of the basic
parameters: Bi, (P/B)i, (Q/B)i or EEi have to be
know for each group (i). The unassimilation rate (or
the fraction of the food consumption that is not assim-
ilated, U/Q) and the fate of detritus are also required.
The energy balance within each group is ensured when
consumption by group (i) equals production by (i),
respiration by (i) and food that is unassimilated by (i).
To ensure consistence between ontogenetic groups, the
multiple stanza representation (Christensen and Walters,
2004) was used for modelling European hake, a highly
commercial species for which dietary information is
available for the different population fractions (Bozzano
et al., 1997, in press). Two groups were defined, namely
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 67
juvenile hake (b2years old or 25 cm) and adult hake
(z2 years old or 25 cm) (Recasens, 1992; Recasens and
Lleonart, 1999). (P/B)i and diet composition were pro-
vided for both groups, while Bi and (Q/B)i were intro-
duced for the leading stanza group only, juvenile hake.
The Automatic Mass Balance Procedure (Kavanagh
et al., 2004) was used after having modified some
errors on diet composition (mainly on cephalopods
and medium-sized pelagic fish where available trophic
information was not from the studied area) and bio-
mass for those groups whose initial biomasses were
assessed by the swept area method (maximum bio-
masses were used in these cases). The automatic
procedure modified the diet matrix, and to a lesser
extent biomass data, as they were considered the
parameters with a higher associated uncertainty. The
model was considered balanced when: 1) realistic
estimates of the missing parameters of EE were cal-
culated (EEb1); 2) values of P/Q for functional
groups (GEi or the gross food conversion efficiency)
were between 0.1 and 0.35 with the exception of fast
growing groups with higher GEi and top predators
with lower values; and 3) values of R/B were consis-
tent with the group’s activities with high values for
small organisms and top predators (Christensen et al.,
2004). The Pedigree routine was used to describe the
origin and quality of the model, while a sensitivity
analysis routine was used to explore the uncertainty of
the parameter estimates and the impact of such uncer-
tainty on the mass balance model (Christensen and
Walters, 2004; Christensen et al., 2004).
Finally, various hypotheses were preliminarily tested
in relation to the decreasing trend of official pelagic
landings reported from 1994 to the present. To do this,
the Ecosim temporal dynamic module of the software
(Walters et al., 1997) was used. The Ecosim module
takes the previous equations and sets up a series of
differential equations:
dBi
dt¼ P
Q
��i
dX
Qji �X
Qijþ Ii
� Mi þ Fi þ eið ÞdBi ð3Þ
Where dBi/dt is the growth rate during the time
interval dt of (i) in terms of Bi; (P/Q)i is the gross
efficiency; Mi is the non-predation natural mortality
rate; Fi is the fishing mortality rate; ei is the emigration
rate; Ii is the immigration rate; and ei Bi� Ii is the net
migration rate. Calculations of consumption rates (Q)
are based upon the bforaging arenaQ theory where the
biomass of (i) is divided between a vulnerable and an
non-vulnerable fraction and the transfer rate (t) be-
tween the two fractions is what determines the flow
control (Walters et al., 1997; Christensen and Walters,
2004).
2.3. Model parameters and functional groups
The model represents an annual average situation of
the South Catalan Sea ecosystem in 1994. Pelagic bio-
masses and catches were thus related to this one year,
but, due to poor data availability for 1994, demersal
biomass data were used for an extended period from
1994 to 2000, so to cover a full year’s seasonality.
Biomass values were obtained from the swept area
method, the egg production method, acoustic surveys
and information available in the literature. Production/
biomass ratios (P/B) and consumption/biomass ratios
(Q/B) were taken from the literature or obtained from the
application of empirical equations using length and
weight data (Nilsson and Nilsson, 1976; Pauly, 1980;
Innes et al., 1987; Pauly et al., 1990; Christensen et al.,
2004), whilst diet composition and assimilation rates
where compiled from published information. In the ab-
sence of information, steady state conditions were as-
sumed with BAi =0 and Ei =0.
Migratory patterns of Atlantic bonito, large pelagic
fishes, fin whale and marine turtles were taken into
account within the model by modelling a proportion of
the diet composition of these groups as imports to the
system (De La Serna and A lot, 1990; Grannier, 1998;
Block et al., 2001; Sabates and Recasens, 2001; Tomas
et al., 2001; Christensen and Walters, 2004). The
microbial food web was not directly considered in
the model, but it was indirectly considered within the
zooplankton diet composition and detritus dynamics
(Calbet et al., 2002).
Official landings statistics from 1994 concerning
trawling, purse seine, longline and troll bait fleets were
corrected by considering discard information drawn
from the literature (including by-catch of vulnerable
species of cetaceans, seabirds and turtles) (e.g., Arcos,
2001; Belda and Sanchez, 2001; Caminas, 1988; Cami-
nas and De la Serna, 1995; Sanchez et al., 2004; Tudela,
2004) and new estimates of illegal, unregulated or unre-
ported (IUU) landings. In order to assess the extent of
IUU landings in the Catalan Sea, short surveys were
conducted in the main fishing ports during 2002 and
straightforward questionnaires were delivered to the
fishermen’s representatives. Average IUU estimates
amounted to 25% of the official landings on an annual
basis, while in some cases and for some species IUU
comprised 50% to 90% of the official data (Fig. 4).
Consumption of discards by scavenger species was con-
Fig. 4. Estimates of illegal unreported or unregulated (IUU) landings for target fishes and invertebrate species of the continental shelf and upper
slope (Catalan Sea) as a percentage of reported official landings.
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9668
sidered within the model by taking into account the main
results of research in the area (Bosch et al., 1994; Oro,
1996; Oro and Ruız, 1997; Oro et al., 1997; Granadeiro
et al., 1998; Arcos, 2001; Tomas et al., 2001; Bozzano
and Sarda, 2002).
Input data is listed in Table 1; main data sources and
estimation methods are compiled in Table A1. The
model included 40 functional groups spanning the
main trophic components of the ecosystem and including
target and non-target fish and invertebrate groups (Tables
1 and A1), and three detritus groups (natural detritus,
discards and by-catch of vulnerable species of cetaceans,
seabirds andmarine turtles). Definition of the groups was
based on similarities in their ecological and biological
features (e.g., feeding, habitat, mortality) and on the
importance of the species in terms of the fisheries. In
addition, dealing with the high biodiversity of the Med-
iterranean Sea implied a systematic analysis of available
ecological information. Factorial Correspondence Anal-
ysis (FCA) and Hierarchical Custer Analysis were ap-
plied to published stomach-content data for 44 fish
species to establish new mixed groups of benthic, de-
mersal and benthopelagic species. When defined, these
new groups where added to the rest of groups and input
data was integrated taking into account species compo-
sition and biomasses proportions within each group.
2.4. Model analysis
After balancing the model, ecological analyses
integrated in EwE were used to examine various
indicators based on trophic flow description, thermo-
dynamic concepts, information theory and network
analysis (Muller, 1997; Christensen et al., 2004).
Some of these results are related with the ecosystem
development theory sensu Odum (1969, 1971) (Lin-
deman, 1942; Odum and Heald, 1975; Finn, 1976;
Ulanowicz, 1986, Christensen and Pauly, 1993b;
Christensen, 1995a; Ulanowicz, 1995). The mixed
trophic impact routine, derived from economic theory
(Leontief, 1951; Ulanowicz and Puccia, 1990), allowed
the quantification of direct and indirect trophic interac-
tions among groups. In this analysis, the positive or
negative impact that a hypothetical increase in the
biomass of a group would produce on the other groups
of the ecosystem is provided, including the fisheries.
The primary production required to sustain the fishery,
the trophic level of total catch, the omnivory indices,
mortalities and the relative consumption of total pro-
duction, excluding plankton and benthic invertebrates,
and of fish production were analysed to place the
fisheries into their ecosystem context (Pauly and Chris-
tensen, 1995; Pauly et al., 1998a; Christensen and
Walters, 2004).
Dynamic simulations with Ecosim were carried out
using the 1994 model to test hypotheses to reproduce
the most recent intense decrease of pelagic landings in
the area from 1994–2003 (Fig. 2) and the low bio-
masses for sardine and anchovy; anchovy being more
abundant than sardine in recent years considering
results from stock assessments (Quintanilla et al.,
2004; Torres et al., 2004). Until the beginning of
Table 1
Input data of the South Catalan Sea model by functional group
Functional group Bi P/B Q/B U/Q Landings Discards
1 Phytoplankton 10.20 37.91 – – – –
2 Micro and mesozooplankton 7.79 20.87 48.85 0.40 – –
3 Macrozooplankton 0.54 20.41 50.94 0.20 – –
4 Jellyfish 0.39 28.51 50.48 0.20 – –
5 Suprabenthos 0.03 8.05 52.12 0.30 – –
6 Polychaetes 15.54 1.82 11.53 0.60 – –
7 Shrimps 0.03 3.08 7.20 0.20 0.035 0.012
8 Crabs 0.09 2.10 4.73 0.20 0.113 0.034
9 Norway lobster 0.03 1.20 4.56 0.20 0.013 0.001
10 Benthic invertebrates 8.87 1.02 3.13 0.43 0.009 0.003
11 Benthic cephalopods 0.13 2.34 5.30 0.13 0.221 0.011
12 Benthopelagic cephalopods 0.14 2.02 26.47 0.40 0.038 0.002
13 Mullets 0.06 2.29 6.90 0.20 0.106 0.005
14 Conger eel 0.03 1.56 2.88 0.20 0.042 0.002
15 Anglerfish 0.05 1.58 2.70 0.20 0.069 0.003
16 Flatfishes 0.04 2.10 7.53 0.20 0.061 0.003
17 Poor cod 0.02 1.52 6.97 0.20 0.014 0.004
18 Juvenile hake 0.02 1.30 7.37 0.20 0.020 0.001
19 Adult hake – 0.60 – 0.20 0.198 0.010
20 Blue whiting 0.66 0.66 5.93 0.20 0.132 0.040
21 Demersal fishes (1) 0.32 1.16 6.85 0.20 0.130 0.039
22 Demersal fishes (2) 0.01 1.00 7.17 0.20 0.005 0.002
23 Demersal fishes (3) 0.09 0.43 6.25 0.20 0.001 0.000
24 Demersal small sharks 0.06 0.42 5.43 0.20 0.005 0.001
25 Bentopelagic fishes 0.12 1.37 9.03 0.30 0.050 0.015
26 European anchovy 2.44 1.33 13.91 0.30 0.897 0.045
27 European pilchard 3.37 1.50 8.86 0.30 2.693 0.135
28 Small pelagic fishes 0.69 0.52 7.39 0.30 0.012 0.004
29 Horse mackerel 1.75 0.39 5.13 0.20 0.021 0.001
30 Mackerel 0.68 0.46 4.88 0.20 0.058 0.003
31 Atlantic bonito 0.30 0.35 4.36 0.20 0.011 0.0006
32 Large pelagic fishes 0.14 0.43 1.63 0.20 0.046 0.0018
33 Loggerhead turtle 0.03 0.15 2.54 0.20 – 0.0003
34 Audouins gull 0.001 4.64 70.00 0.20 – 0.00002
35 Other sea birds 0.001 4.56 73.20 0.20 – 0.00002
36 Dolphins 0.03 0.07 13.49 0.20 – 0.0014
37 Fin whale 0.40 0.04 4.11 0.30 – –
38 Detritus 70.00 – – – – –
39 Discards 0.38 – – – – –
40 By-catch 0.002 – – – – –
Table A1 lists main data sources and estimation methods.
Bi=Initial biomass (t km�2 ); P/B=Production/biomass ratio (years�1); Q/B=Consumption/biomass ratio (years�1 ); U/Q=Unassimilated food;
Landings and discards (t km �2 years�1 ).
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 69
2000s, sardine has been more abundant than anchovy
in previous assessments from the 1980s. A total of 135
different theoretical scenarios were applied to fishing
effort, environmental forcing and flow control situa-
tions based on previous work from the Southern Ben-
guela of dynamics of small and medium-sized pelagic
fishes and their preys related to overfishing situations
and large scale environmental changes (Shannon et al.,
2004). The scenarios defined were: a) four fishing
effort scenarios: no increase of fishing effort and
increases of 10%, 20% and 30% from 1994 to 2004
for trawling and purse seine fleets; b) Nine environ-
mental forcing functions: no forcing function and for-
cing function of 10%, 20% and 30% affecting the
interaction between small and medium-sized pelagic
fishes and their preys in 10, 5 and 1 years of the
simulation; c) three flow control situations: mixed
control, bottom-up and wasp-waist control to describe
interactions between functional groups (Cury et al.,
2000; Shannon et al., 2000).
Default values of vulnerabilities v =2 were used to
represent mixed flow control, whilst values of v =1
were set to describe vulnerability of phytoplankton and
zooplankton groups to their predators to represent bot-
Fig. 5. Results from the Factorial Correspondence Analysis of trophic data of 44 fish species with first and second axes represented (species codes
are listed in Table A2).
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9670
tom-up flow control. Values of vN1 of the prey to small
and medium-sized pelagic fish (top-down control of
small and medium-sized pelagic fish on their prey) and
v =1 of small and medium-sized pelagic fish to their
predators (bottom-up control of small and medium-
sized pelagic fish on their predators) were set to represent
wasp-waist flow control in the ecosystem. The generic
Fig. 6. Results from the Factorial Correspondence Analysis of trophic data of
listed in Table A2).
environmental forcing function applied to affect the
interaction of small and medium-sized pelagic fishes
and their preys, phytoplankton and zooplankton, had
the aim to reproduce a generic environmental anomaly
that would have negatively affected the availability of
prey by these fish groups. This function could be related
to direct or indirect anthropogenic or climatic factors,
44 fish species with first and third axes represented (species codes are
Fig. 7. Cluster analysis representing similitude between 44 fish spe
cies analyzed with the Factorial Correspondence Analysis (species
codes are listed in Table A2).
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 71
e.g., a decrease of the Ebro river runoff through time
(Lloret et al., 2004), an increase of water surface tem-
perature (Salat and Pascual, 2002) or an increase of
gelatinous plankton (Buecher, 1999).
3. Results and discussion
3.1. Factorial Correspondence Analysis
Three factors accumulated 45.56%of the total variance
in the Factorial Correspondence Analysis (FCA) of the 44
fish species that needed to be grouped. Factors 1 and 2
(representing the first and second axes) explained 18.45%
and 15.24%of variance, respectively (Fig. 5), and factor 3
explained 11.86% of variance (Fig. 6) (Species codes for
Figs. 5, 6 and 7 are listed in Table A2). Zooplankton had
positive values along the first axis, while cephalopods,
fish species, benthic invertebrate, detritus and jellyfish
had negative values. Along the second axis, benthic
invertebrates had a highly positive value, followed by
jellyfish, detritus, polychaetes and zooplankton, while
cephalopods, fish species, suprabenthos and decapod
crustaceans showed negative values. Finally, a total of
4 new groups were defined from the FCA and are
illustrated in the cluster analysis (Fig. 7):
– Class 1 was composed of demersal fish species with
mixed trophic habits (main prey being benthic inver-
tebrates, detritus, suprabenthos, crustaceans, cephalo-
pods and small demersal fishes) and was named
bdemersal fishes (1)Q;– Class 2 was composed of demersal fishes with trophic
habits based on non-crustacean benthic invertebrates
mainly (main prey being brittlestars, starfish, gastro-
pods, etc.) and was named bdemersal fishes (2)Q;– Class 3 was composed of demersal fishes with trophic
habits based on small demersal and pelagic fishes as
main prey species andwas named bdemersal fishes (3)Q;– Class 4 and Class 5 were composed of benthopelagic
fish species with trophic habits based on zooplankton.
These latter two classes were joined together in a single
functional group named bbenthopelagic fishesQ.
3.2. Modified input parameters and data quality
Modified input parameters and resulting output para-
meters of the model are shown in Table 2 and the diet
matrix for the final run of the model is shown in Table 3.
Ecotrophic efficiencies (EE) were high for most func-
tional groups, whilst respiration/assimilation ratios (R/
A), production/respiration ratios (P/R) and net food
conversion efficiencies were within the expected range
-
(Christensen et al., 2004). Minimum biomass required
for the balanced model was larger than surveys for most
of the demersal and benthopelagic functional groups, of
which initial biomasses were assessed by the swept area
method, and suggested some undersampling in surveys.
Initial biomasses of some medium and large pelagic
Table 2
Modified input parameters and output parameters form the South Catalan Sea model
Functional group TL Bf P/Q EE F M2 M0 F/Z OI NE R/A P/R FD Q
1 Phytoplankton 1.00 10.20 – 0.83 0.00 31.56 6.35 – 0.00 – – – 64.72 –
2 Micro and Mesozooplankton 2.05 9.86 0.43 0.66 0.00 13.75 7.12 – 0.05 0.53 0.47 1.15 166.59 481.71
3 Macrozooplankton 2.77 0.54 0.40 0.91 0.00 18.48 1.92 – 0.28 0.48 0.52 0.91 5.44 27.51
4 Jellyfish 2.83 0.39 0.27 0.22 0.00 3.00 10.87 – 0.26 0.31 0.69 0.44 6.19 19.64
5 Suprabenthos 2.11 0.05 0.15 0.93 0.00 7.46 0.59 – 0.10 0.21 0.79 0.27 0.74 2.62
6 Polychaetes 2.00 15.54 0.16 0.32 0.00 0.59 1.24 – 0.00 0.38 0.62 0.60 123.13 179.18
7 Shrimps 2.98 0.05 0.43 0.97 1.03 1.95 0.10 0.34 0.39 0.54 0.46 1.15 0.07 0.33
8 Crabs 2.89 0.15 0.44 0.97 0.96 1.09 0.06 0.45 0.43 0.56 0.44 1.25 0.15 0.72
9 Norway lobster 2.82 0.04 0.26 0.98 0.25 0.92 0.03 0.21 0.72 0.33 0.67 0.49 0.04 0.20
10 Benthic invertebrates 2.02 8.87 0.33 0.43 0.00 0.43 0.59 0.001 0.02 0.57 0.43 1.34 17.17 27.77
11 Benthic cephalopods 3.10 0.21 0.44 0.97 1.10 1.16 0.08 0.47 0.11 0.51 0.49 1.03 0.16 1.11
12 Benthopelagic cephalopods 3.67 0.20 0.08 1.00 0.20 1.85 0.01 0.10 0.29 0.12 0.88 0.14 1.86 5.30
13 Mullets 3.16 0.06 0.33 0.97 1.83 0.40 0.06 0.80 0.10 0.42 0.58 0.71 0.09 0.42
14 Conger eel 4.22 0.06 0.40 0.97 0.75 0.61 0.04 0.54 0.05 0.50 0.50 1.00 0.04 0.20
15 Anglerfish 4.39 0.05 0.40 0.98 1.33 0.04 0.02 0.95 0.22 0.50 0.50 1.00 0.04 0.19
16 Flatfishes 3.20 0.04 0.28 0.98 1.56 0.50 0.04 0.74 0.16 0.35 0.65 0.54 0.06 0.31
17 Poor cod 3.31 0.03 0.22 0.95 0.55 0.89 0.08 0.36 0.30 0.27 0.73 0.37 0.05 0.23
18 Juvenile hake 3.45 0.04 0.18 0.98 0.49 0.78 0.02 0.38 0.40 0.22 0.78 0.28 0.06 0.32
19 Adult hake 4.10 0.35 0.24 0.98 0.59 0.00 0.01 0.98 0.04 0.30 0.70 0.42 0.18 0.89
20 Blue whiting 3.40 1.17 0.11 0.98 0.15 0.50 0.01 0.22 0.17 0.14 0.86 0.16 1.40 6.93
21 Demersal fishes (1) 3.08 0.52 0.17 0.99 0.33 0.82 0.02 0.28 0.09 0.21 0.79 0.27 0.72 3.55
22 Demersal fishes (2) 3.01 0.03 0.14 0.83 0.25 0.58 0.17 0.25 0.01 0.17 0.83 0.21 0.04 0.18
23 Demersal fishes (3) 3.96 0.14 0.07 0.97 0.01 0.41 0.01 0.02 0.12 0.09 0.91 0.09 0.18 0.87
24 Demersal small sharks 3.68 0.06 0.08 0.90 0.10 0.28 0.04 0.25 0.34 0.10 0.90 0.11 0.07 0.32
25 Bentopelagic fishes 3.49 0.22 0.15 0.97 0.30 1.04 0.03 0.22 0.13 0.22 0.78 0.28 0.61 1.99
26 European anchovy 3.05 2.64 0.10 0.96 0.36 0.93 0.05 0.27 0.00 0.14 0.86 0.16 11.14 36.71
27 European pilchard 2.97 3.58 0.17 0.97 0.79 0.67 0.04 0.53 0.08 0.24 0.76 0.32 9.66 31.73
28 Small pelagic fishes 3.00 0.92 0.07 1.00 0.02 0.50 0.00 0.03 0.05 0.10 0.90 0.11 2.03 6.77
29 Horse mackerel 3.19 1.55 0.08 0.30 0.01 0.10 0.27 0.04 0.10 0.09 0.91 0.10 2.00 7.93
30 Mackerel 3.55 0.61 0.09 0.51 0.09 0.14 0.22 0.19 0.13 0.12 0.88 0.13 0.74 2.99
31 Atlantic bonito 4.06 0.27 0.08 0.13 0.04 0.00 0.30 0.13 0.92 0.10 0.90 0.11 0.32 1.19
32 Large pelagic fishes 4.19 0.12 0.26 0.72 0.31 0.00 0.12 0.72 1.02 0.33 0.67 0.49 0.05 0.20
33 Loggerhead turtle 2.54 0.03 0.06 0.07 0.01 0.00 0.14 0.07 0.41 0.08 0.92 0.08 0.02 0.08
34 Audouins gull 3.22 0.001 0.07 0.00 0.02 0.00 4.62 0.00 0.92 0.08 0.92 0.09 0.02 0.07
35 Other sea birds 2.19 0.001 0.06 0.33 0.02 1.47 3.07 0.00 0.35 0.08 0.92 0.08 0.02 0.07
36 Dolphins 4.33 0.03 0.01 0.28 0.02 0.00 0.05 0.28 0.09 0.01 0.99 0.01 0.08 0.39
37 Fin whale 3.81 0.36 0.01 0.00 0.00 0.00 0.04 0.00 1.00 0.01 0.99 0.01 0.46 1.50
38 Detritus 1.00 70.00 – 0.866 – – – – – – – – 0.18 –
39 Discards 1.00 0.38 – 0.508 – – – – – – – – 0.002 –
40 By-catch 1.00 0.002 – 0.000 – – – – – – – – – –
TL=Trophic level; Bf=final biomass (t km�2); P/Q=production/consumption ratio or Gross efficiency; EE=Ecotrophic efficiency; F=Fishing
mortality (years� 1); M2=Predation mortality (years� 1); M0=Other natural mortality (years� 1); F/Z=Exploitation rate; OI=Omnivory index;
NE=Net efficiency; R/A=respiration/assimilation ratio; P/R=production/respiration ratio; FD=Flow to detritus (t km�2 years� 1); Q=Con-
sumption (t km�2 years� 1).
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9672
fishes, which were estimated from neighbouring areas or
referred to the entire Mediterranean basin, were slightly
lower in the balanced model (Table A1).
The pedigree index of the model (0.670, Table 4), a
measure of the model quality, ranked within the highest
values when compared with other 50 previously con-
structed models for which pedigree values ranged be-
tween 0.164 and 0.676 (Lyne Morisette, Fisheries
Centre, UBC, personal communication). The sensitivity
analysis routine showed that by altering the input para-
meters of a functional group, the largest impact was on
the output parameters of the same functional group.
3.3. Trophic levels and flows
Results of the model showed that functional groups
were organized within four integer trophic levels (TL)
with the highest TLs corresponding to anglerfish, dol-
phins, conger eel, large pelagic fishes and adult hake
(Table 2). The remaining functional groups were classi-
Table 3
Diet composition matrix for the functional groups in the South Catalan Sea model
Prey Predator
2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 19 18 17 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37
1. Phytoplankton 0.65 0.15 0.10 0.08 0.05
2. Micro and
Mesozooplankton
0.05 0.65 0.70 0.10 0.15 0.02 0.31 1.00 0.92 0.94 0.70 0.28
3. Macrozooplankton 0.05 0.14 0.13 0.31 0.01 0.01 0.01 0.47 0.01 0.14 0.61 0.17 0.62 0.01 0.46
4. Jellyfish 0.05 0.05 0.01
5. Suprabenthos 0.15 0.03 0.03 0.22 0.14 0.02 0.04 0.03 0.01
6. Polychaetes 0.25 0.34 0.01 0.32 0.48 0.19 0.66 0.10 0.50 0.73 0.08 0.07 0.01 0.03 0.04
7. Shrimps 0.05 0.03 0.04 0.02 0.02 0.05 0.02 0.01 0.00 0.03 0.01 0.01
8. Crabs 0.01 0.01 0.04 0.10 0.17 0.06 0.01 0.04 0.07 0.01
9. Norway lobster 0.04 0.01
10. Benthic invertebrates 0.18 0.17 0.09 0.02 0.89 0.06 0.01 0.52 0.53 0.01 0.12 0.99 0.05 0.32 0.08 0.01 0.29
11. Benthic cephalopods 0.00 0.01 0.03 0.02 0.01 0.07 0.01 0.14 0.03
12. Benthopelagic
cephalopods
0.01 0.02 0.03 0.02 0.00 0.14 0.31 0.01
13. Mullets 0.02 0.01
14. Conger eel 0.17 0.01
15. Anglerfish
16. Flatfishes 0.07
17. Poor cod 0.01 0.01
18. Juvenile hake 0.10 0.01 0.01
19. Adult hake
20. Blue whiting 0.03 0.27 0.05 0.12 0.02 0.03 0.08 0.16
21. Demersal fishes (1) 0.01 0.12 0.43 0.08 0.06 0.03 0.13 0.01 0.07 0.02 0.02
22. Demersal fishes (2) 0.02 0.03
23. Demersal fishes (3) 0.01 0.09 0.01 0.01 0.04 0.01 0.01
24. Demersal small sharks
25. Bentopelagic fishes 0.23 0.02 0.01 0.14 0.05 0.06 0.01 0.05
26. European anchovy 0.32 0.22 0.02 0.35 0.10 0.02 0.06 0.27 0.15 0.19
27. European pilchard 0.21 0.57 0.35 0.05 0.23 0.02 0.31 0.01 0.01
28. Small pelagic fishes 0.03 0.24 0.09 0.12 0.02 0.19 0.03
29. Horse mackerel 0.07 0.10 0.06 0.01
30. Mackerel 0.07
31. Atlantic bonito
32. Large pelagic fishes
33. Loggerhead turtle
34. Audouins gull
35. Other sea birds 0.02
36. Dolphins
37. Fin whale
38. Detritus 0.30 0.15 0.15 0.89 1.00 0.20 0.27 0.48 0.98
39. Discards 0.01 0.02 0.01 0.01 0.01 0.02 0.01 0.01 0.01 0.29 0.38 0.37
40. By Catch
41. Import 0.40 0.40 0.40 0.02 0.60 0.50
Total 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00 1.00
M.Collet
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73
Table 4
Ecological indicators of the South Catalan Sea model related with community energetics, community structure, cycling of nutrients and information
theory
Statistics and flows
Sum of all consumptions 852.11 t km� 2 years� 1
Sum of all exports 61.27 t km� 2 years� 1
Sum of all respiratory flows 327.16 t km� 2 years� 1
Sum of all flows into detritus 416.91 t km� 2 years� 1
Total system throughput 1657.0 t km� 2 years� 1
Sum of all production 658.0 t km� 2 years� 1
Calculated total net primary production 386.68 t km� 2 years� 1
Total primary production/total respiration 1.18
Net system production 59.52 t km� 2 years� 1
Total primary production/total biomass 6.55
Total biomass/total throughput 0.04
Total biomass (excluding detritus) 58.99 t km� 21
Total transfer efficiency 12.60 %
Total catches 5.36 t km� 2 years� 1
Mean trophic level of the catch 3.12
Primary production required to sustain the fishery (from pp) 36.70 %
Primary production required to sustain the fishery (from pp+det) 41.99 %
Gross efficiency (catch/net p.p.) 0.014
Ecopath Pedigree index 0.67
Network flow indices
Throughput cycled (excluding detritus) 27.39 t km� 2 years� 1
Predatory cycling index (of throughput w/o detritus) 3.33 %
Throughput cycled (including detritus) 6.56 t km� 2 years� 1
Finn’s cycling index (of total throughput) 25.19 %
Finn’s mean path length 4.27
Finn’s straight-through path length (without detritus) 2.40
Finn’s straight-through path length (with detritus) 3.19
Connectance index 0.20
System omnivory index 0.19
Information indices
Ascendency 25.50 %
Overhead (Total) 5300.80 Flowbits
Overhead 74.50 %
Capacity (Total) 7119.30 Flowbits
Ai/Ci 26.30 %
Ai=Internal ascendency; Ci=Internal capacity.
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9674
fied between 3.96 and 3.0 for fish species, and between
3.0 and 2.0 for invertebrates, with cephalopods showing
TLs of 3.1–3.67; the lowest, by definition, were the
primary producers and detritus groups (TL=1). Europe-
an sardine showed TLb3.0 because it feeds partially on
phytoplankton.
TLs of fish species (see Tables A1 and A2 for a list of
scientific names) were in line with the lower range of
previous results for the Mediterranean (Stergiou and
Karpouzi, 2002) and lower than those from the Cantab-
rian Sea (Sanchez and Olaso, 2004). Trophic levels
obtained for dolphins, fin whales and demersal sharks
were similar to those previously recorded (Pauly et al.,
1998b; Cortes, 1999). However, the trophic levels of
seabirds and turtles were low because discards are as-
sumed to be a detritus group with TL=1, which under-
estimate the trophic level of these groups. Discards are
consumed by gulls, terns, shearwaters and storm-petrels
and are mainly composed of small pelagics and benthic-
demersal small fishes (Arcos, 2001). Various studies
focusing on seabird feeding ecology and trophic levels
have described the average TL of similar seabird species
to be between 3.5 and 4 (Hobson et al., 1994), while
marine turtles can reach TL between 3.3 and 3.6 (Mack-
inson et al., 2000; Guenette et al., 2001).
Fig. 8 schematically represents the Catalan Sea eco-
system flow diagram organized by its integer trophic
levels (TL) in the form of the Lindeman spine (Lindeman,
1942; Ulanowicz, 1986; Wulff et al., 1989; Libralato et
al., 2002), where primary producers and detritus are
Fig. 8. The South Catalan Sea ecosystem flow diagram organized by its integer trophic levels (TL) in the form of the Lindeman spine. Primary
producers (P) and detritus (D) are separated to clarify the representation (both with TL=I).
Fig. 9. The fate of total system throughput in percentage per integer
trophic level.
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 75
separated to clarify the representation (both with TL=I)
(t km�2 years�1). Most flows are within TL I, II and III,
while flows from TLN III are practically insignificant.
TL I (primary production and detritus) generated 49.4%
of the total system throughput (t km�2 years�1), the sum
of all flows within the ecosystem, followed by the TL II
(41.9%). The average transfer efficiency (TE=12.6%),
the fraction of total flows at each trophic level that are
either exported or transferred to other trophic levels
through consumption, was within the range of values
reported in the literature (Odum, 1971; Pauly and Chris-
tensen, 1995), i.e., on average lower for detritus (12.1%)
than for the primary producers (13.2%). Values of TE for
flows through TL II and TL III were high, both high-
lighting good coupling between zooplanktivorous and
detritivorous and their predators (Baird et al., 1991). This
could indicate that the ecosystem may be food limited
(Shannon et al., 2003). Fig. 9 represents the fate, in
percentage, of total system throughput per discrete tro-
phic level. High proportions of the throughput were
consumed by predators at TL I, followed by TL II and
TL III, aligned with results from TE values.
More than 80% of the total system throughput was
related to the pelagic domain, but important flows were
also related to benthic invertebrates.Moreover, in terms of
biomass (t km�2) (Table 2), the detritus, phytoplankton,
zooplankton and non-crustacean benthic invertebrate
groups were the dominant groups, followed by sardine,
anchovy and the remaining small and medium-sized
pelagic fish species. Much lower biomasses of demersal
target and non-target fish species were sustained. Ninety-
nine percent of the total production (t km�2 years�1) of
the system was by phytoplankton, zooplankton, non-
crustacean benthic invertebrates and small pelagic fish
groups; while 95% of the consumption (t km�2 years�1)
was concentrated within the detritus, phytoplankton,
zooplankton, non-crustacean benthic invertebrates and
small and medium-sized pelagic fish groups.
3.4. Summary statistics
The total system throughput, also an index of the
ecosystem size (Christensen and Pauly, 1993b) and the
ig. 10. Main partitioning of a) total consumption of production,
xcluding plankton and benthic invertebrates, by predators; and b)
tal consumption of fished organisms production by predators (in-
luding the fishery) (higher than 2%).
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9676
total system biomass (td km�2) (Table 4) were small
compared with other modelled ecosystems from up-
welling and temperate regions (e.g., Christensen and
Pauly, 1993a; Jarre-Teichman, 1998; Guenette et al.,
2001; Sanchez and Olaso, 2004). The ecological indi-
cators related to community energetics, community
structure, cycling of nutrients and information theory,
and the comparison of these with other previously
modelled ecosystems (e.g., Christensen and Pauly,
1993a; Christensen, 1995b; Jarre-Teichman, 1998;
Guenette et al., 2001; Sanchez and Olaso, 2004),
suggest that the South Catalan Sea ecosystem is at
an intermediate–low developmental stage sensu
Odum’s theory (Odum, 1969, 1971). For example,
the primary production/respiration ratio (Pp/R) indicat-
ed that there was more energy produced than respired
within the system; the primary production/biomass
ratio (Pp/B) was also high indicating a low level of
biomass accumulation within the system compared
with primary production. Moreover, the total system
biomass/system production ratio (B/P), described as an
indirect estimate of the average size of organisms
within the system (and assumed to increase with in-
creasing average size) (Christensen and Pauly, 1993b;
Christensen, 1995a), was medium in the ecosystem.
The system showed moderate-low rates of cycling and
a low connectance and system omnivory index.
3.5. Consumption
The analysis of the consumption (higher than 2%)
of production of the system, excluding plankton,
macrobenthos and detritus groups, highlighted the
importance of sardine and anchovy within the system,
followed by jellyfish and horse mackerel (Fig. 10a).
The relevance of gelatinous plankton in the consump-
tion of production in the NW Mediterranean Sea was
also an important feature of the Namibia ecosystem
(Heymans et al., 2004; Roux and Shannon, 2004),
where the proliferation of jellyfish appeared after the
collapse of sardine fisheries in the 1960–1970s. The
proliferation of some jellyfish species in the NW
Mediterranean since the 1980s has been also described
(e.g., Buecher, 1999).
The analysis of the consumption (higher than 2%)
of fished organisms (from functional groups 7 to 32)
by main predators within the ecosystem highlighted
the high impact of the fishery, followed by cephalo-
pods and some demersal and pelagic fish species (Fig.
10b). Seabirds consumed 14.2% of discards generated
in the area and marine turtles consumed the 5.9%
(Table 2).
F
e
to
c
3.6. Mortality
Concerning mortalities, the general results are in
accordance with the range of values from stock assess-
ment in the region (Lleonart, 1990; AAVV, 2002b),
where most of the groups showed high predation mor-
tality (Table 2). Juvenile hake and small pelagic fish
showed high levels of fishing and predation mortality,
while fishing mortality was very high for some demersal
target species such as conger eel, anglerfish, red mullet,
flatfishes or adult hake. Some invertebrate groups such
as benthic cephalopods and crabs also showed high
fishing mortality. The exploitation rates (F/Z), where
F is the fishing mortality and Z is the total mortality
(Table 2), showed particularly high values for some
target species, like the small pelagics, some demersal
fishes and hake. The exploitation rate of sardine was
higher than the recommended rate of 0.50 for sustainable
fisheries management (Patterson, 1992; Mertz and
Myers, 1998; Rochet and Trenkel, 2003). In addition,
the exploitation rates for demersal fishes were high, and
in the case of anglerfish, mullets and adult hake the rate
Fig. 11. The Mixed Trophic Impact analysis from the model. Impacted groups are placed along the horizontal axis and impacting groups are down the vertical axis. The bars indicate relative impact
(between 0–1) where positive impacts are above zero line and negative impacts are below.
M.Collet
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M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9678
was higher than the recommended exploitation rate of
0.8 for groundfish stocks (Mertz and Myers, 1998;
Rochet and Trenkel, 2003).
3.7. Mixed trophic impacts
Direct and indirect interactions within the ecosystem
were analyzed by means of the mixed trophic impact
routine (MTI) (Fig. 11). The analysis showed that all
groups had a negative impact on themselves due to
within-group competition. Indirect impacts of predators
on the system could also be detected, as, for example, the
negative effect of sardine or anchovy on other small
pelagic fishes due to some extent of niche overlapping.
An increase of adult hake had a negative impact on
juvenile hake, probably due to cannibalism and compe-
tition for prey. Other indirect impacts in the form of
trophic cascades (Menge, 1995) could also be identified,
e.g., an increase of dolphins would have an indirect
positive impact on anchovy due to the decrease of
other anchovy predators.
Moreover, numerous functional groups in the model
were impacted by the groups at the base of the food web
such as phytoplankton, micro-, meso- and macro-zoo-
plankton, suprabenthos and benthic invertebrates. This
could be related to possible bottom-up predator–prey
interactions occurring in the ecosystem (Hunter and
Price, 1992). Small pelagic fishes also had a wide impact
on numerous functional groups of higher and lower
trophic levels, highlighting the importance of these
groups in the ecosystem and possible wasp-waist pred-
ator–prey interactions (Cury et al., 2000).
Competition interactions between functional groups
of similar trophic levels were revealed by the analysis of
the MTI routine. In addition, important demersal-pelag-
ic relationships were identifying within the system be-
tween demersal predators (e.g., adult hake or conger eel)
and forage fishes or between medium-sized pelagic
fishes (mackerel and horse mackerel) and benthic inver-
tebrates, indicating coupled pelagic-demersal interac-
Table 5
Ecological information characterizing the main fleets of the South Catalan
Fishing fleet Landings Discards
Trawling 2.17 0.23
Purse seine 2.61 0.14
Longline 0.17 0.01
Troll bait 0.03 0.00
Total 4.98 0.37
Landings and discards (t km�2 years�1); TLc=mean trophic level of the ca
sustain the fishery from primary producers (pp) and primary producers and
tions. This was also found to be an important feature
of the Namibian upwelling ecosystem after depletion of
its stocks due to industrial fishing and environmental
events, an important trend that appears to set this system
apart from other upwelling ecosystems (Moloney et al.,
2005), and one that is also characteristic of highly fished
temperate regions (Sanchez and Olaso, 2004).
The trawling fleet had the widest-ranging impact on
all ecosystem compartments and the largest impacts on
some demersal groups (Fig. 11). An increase of trawling
activity would negatively impact various benthic and
demersal groups, as well as dolphins and marine turtles,
mainly due to the decrease of their main prey and the
direct mortality associated with by-catch. However, it
would positively impact the suprabenthos, juvenile hake
and demersal fish (3), possibly due to top-down effects
or trophic cascades caused by removal of predators
(Christensen et al., 2004). The longline fishery had
large negative impacts on its main target species and
on its by-catch (marine turtles, dolphins and seabirds),
whilst it had positive impacts on anchovy, and other
small and medium-sized pelagic fishes mainly due to
predator removal. The purse seine and troll bait fisheries
also showed important impacts on their target species;
the former impacted dolphins and large pelagic fishes
due to removal of prey, whilst the latter had positive
impacts on prey species of removed predators. Fishing
activity also impacted seabird groups by increasing or
decreasing discard availability and through direct mor-
tality. On the contrary, cetaceans, seabirds and marine
turtles did not significantly impact fishing activity, in
contrast with recent published results (AAVV, 2002a).
3.8. Primary production required to sustain fisheries
and trophic level of the catch
Primary production required to sustain the fishing
activity at the 1994 level relative to the primary pro-
duction of the system (%PPR) was very high (Pauly
and Christensen, 1995), when taking into account both
Sea
TLc OI %PPR
(pp)
%PPR
(pp+det)
3.16 0.13 15.95 23.21
3.01 0.01 13.78 10.43
4.04 0.06 5.47 6.98
4.16 0.06 1.50 1.36
3.12 0.10 36.70 41.99
tch; OI=fleet omnivory index; %PPR=primary production required to
detritus (pp+det).
Table 6
Final catch/initial catch ratio (Cf/Ci) from Ecosim dynamic simulations a) under 10–20–30% increases in fishing effort (A); b) with environmental
forcing reducing prey availability of small and medium-sized pelagic fishes (B) by 10–20–30% over 10 years; c) both combined (under mixed flow
control, bottom-up control and wasp-waist control)
a) Fishing effort (A) 10% 20% 30%
Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist
European anchovy 1.1 1.09 1.05 1.2 1.18 1.08 1.3 1.27 1.08
European pilchard 0.98 1.07 0.8 0.93 1.14 0.62 0.87 1.2 0.46
Little pelagic fishes 1.14 1.1 1.17 1.3 1.21 1.34 1.46 1.31 1.53
Horse mackerel 1.09 1.09 1.09 1.18 1.19 1.17 1.28 1.29 1.25
Mackerel 1.07 1.09 1.04 1.14 1.17 1.08 1.2 1.26 1.11
Demersal catch 1.02 1.03 0.98 1.02 1.05 0.95 1.13 1.07 0.93
Total system catch 1.01 1.07 0.9 1.01 1.13 0.81 1 1.18 0.73
b) Environm. anomaly (B) 10% 20% 30%
Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist
European anchovy 0.97 1 0.8 0.93 1 0.54 0.88 1 0.27
European pilchard 0.96 1 0.83 0.92 1 0.62 0.85 1 0.39
Little pelagic fishes 0.96 1 0.87 0.92 1 0.7 0.85 1 0.51
Horse mackerel 0.98 1 0.93 0.96 1 0.86 0.93 1 0.79
Mackerel 0.97 1 0.91 0.93 1 0.82 0.89 1 0.73
Demersal catch 0.99 1 0.94 1 1 0.88 1 1 0.82
Total system catch 0.97 1 0.86 0.93 1 0.69 0.89 1 0.51
c) A combined with B 10%A / 10%B 20%A / 10%B 30%A / 10%B
Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist
European anchovy 1.07 1.09 0.8 1.16 1.18 0.79 1.26 1.27 0.76
European pilchard 0.93 1.07 0.63 0.87 1.14 0.47 0.79 1.2 0.33
Little pelagic fishes 1.11 1.1 1.01 1.26 1.21 1.14 1.41 1.31 1.28
Horse mackerel 1.07 1.09 1.02 1.16 1.19 1.1 1.25 1.29 1.17
Mackerel 1.04 1.09 0.95 1.1 1.17 0.98 1.16 1.26 1.02
Demersal catch 0.99 1.03 0.92 1 1.06 0.91 0.99 1.07 0.89
Total system catch 0.98 1.07 0.76 0.97 1.13 0.67 0.94 1.18 0.6
10%A / 20%B 20%A/20%B 30%A/20%B
Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist
European anchovy 1.03 1.09 0.51 1.12 1.18 0.48 1.22 1.27 0.44
European pilchard 0.86 1.07 0.44 0.78 1.14 0.31 0.69 1.2 0.21
Little pelagic fishes 1.06 1.1 0.8 1.2 1.21 0.89 1.35 1.31 0.98
Horse mackerel 1.04 1.09 0.94 1.13 1.19 1.02 1.22 1.29 1.08
Mackerel 1 1.09 0.86 1.12 1.17 1 1.11 1.26 0.93
Demersal catch 0.98 1.03 0.88 0.98 1.05 0.87 0.98 1.07 0.85
Total system catch 0.93 1.07 0.6 0.91 1.13 0.53 0.88 1.18 0.47
10%A / 30%B 20%A / 30%B 30%A / 30%B
Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist Mixed Bottom-up Wasp-waist
European anchovy 0.98 1.09 0.25 1.07 1.18 0.22 1.16 1.27 0.19
European pilchard 0.78 1.07 0.26 0.69 1.14 0.17 0.58 1.2 0.11
Little pelagic fishes 0.99 1.1 0.57 1.13 1.21 0.62 1.27 1.31 0.67
Horse mackerel 1.01 1.09 0.86 1.1 1.19 0.93 1.18 1.29 1
Mackerel 0.95 1.09 0.77 1 1.17 0.81 1.05 1.26 0.85
Demersal catch 0.95 1.03 0.83 0.95 1.05 0.84 0.95 1.07 0.83
Total system catch 0.87 1.07 0.45 0.84 1.13 0.41 0.81 1.18 0.38
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 79
the primary producers (36.7%) and the primary produ-
cers and detritus together (41.9%) (Table 5). The trawl-
ing fleet was the most impacting fleet in terms of its
contribution to the total %PPR, followed by the purse
seine fleet. The importance of trawling increased con-
siderably when taking into account flows from detritus
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9680
due to the high proportion of detritivorous species
caught by this fleet.
Small pelagic fish (anchovy and sardine) dominated in
terms of catches (70.1%), with benthic cephalopods
(4.3%), adult hake (3.9%), blue whiting (3.2%), demersal
fishes (1) (3.2%), crabs (2.7%) and other demersal fishes
and invertebrates atmuch lower catch levels (Table 1). The
recorded mean trophic level of the catch was 3.12 (Table
5). This was similar to that obtained from direct calcula-
tions from fishing data from the Central Catalan coast in
1996 (TL=3.04, Tudela, 2000); slightly lower than that
computed for the Western Mediterranean in 1998
(TL=3.25, Pinnegar et al., 2003); and slightly higher
than that obtained for the whole Mediterranean basin in
1994 (TL=3.0, Pauly et al., 1998a). The trawling fleet
was catching organisms with lower but wider ranges of
TLs (with higher omnivory index), while the purse seine
was catching organisms with lower and narrow TLs
ranges, and longline and troll bait were focusing on
organisms with high and narrow TLs range (Table 5).
3.9. Temporal dynamic simulations
Results from simulations with the temporal dynamic
Ecosimmodule showed that fishing effects were larger and
major perturbations were propagated throughout the sys-
tem under a wasp-waist control situation, while the mixed
control situation showed intermediate results and under
bottom-up control fishing impacts and environmental forc-
ing were more limited and had shorter propagated effects.
Similar results had previously been achieved when explor-
ing fishing effects for the Southern Benguela (Shannon et
al., 2000). Table 6 includes the final catch/initial catch
ratios (Cf/Ci) resulting from 45 Ecosim simulations with
increases of both trawling and purse seine fishing effort
from 1994 to 2003, with a persistent environmental
forcing for 10 years and with both factors combined.
Results assuming a shorter environmental forcing (1 and
Fig. 12. Ecosim dynamic simulation. Final biomass/initial biomass ratio (B
under wasp-waist flow control for small pelagic fishes, 20% increase of fish
sized pelagic fishes trough a sustained environmental forcing. 1—Benthopel
small pelagic fishes; 6—European anchovy; 7—European pilchard.
5 years) (related with the other 90 simulations) are not
included because they were not reproducing observed
recent dramatic trends in both landings and pelagic
biomass in the area between 1994 and 2003. In general,
a 55% decrease in total landings (Cf/Ci=0.45), 70%
reduction in anchovy landings (Cf/Ci=0.30) and 72%
reduction in sardine landings (Cf/Ci=0.28) can be seen,
while demersal landings showed small fluctuations with
a decrease of the 18% (Cf/Ci=0.82) (Fig. 3).
It was not possible to fully reproduce the observed
trends in catch and biomasses by simulating either
increases in fishing mortality (assumed to represent in-
creased fishing effort) in the area from 10% to 30% for
different periods of time or an environmental forcing for
different periods of time under any of the flow control
scenarios (Table 6). However, dynamic simulations com-
bining both factors, an increase of 10% to 30% of fishing
effort and 20% of forcing function, under wasp-waist
control, allowed the reproduction of recent dramatic
trends in both landings (Table 6) and pelagic biomass
(Fig. 12) in the area between 1994 and 2003. For in-
stance, a 20% increase in fishing for 10 years in combi-
nation with a 20% forcing function negatively affecting
the interaction between small and medium-sized pelagic
fish and their prey groups would lead to a 47% reduction
in overall landings (Cf/Ci=0.53), a 69% reduction in
sardine catches (Cf/Ci=0.31) and a 52% reduction in
anchovy catches (Cf/Ci=0.48), while demersal catches
would have decreased by 13% (Cf/Ci =0.87). A 10%
increase in fishing mortality for 10 years in combination
with a 30% decrease in prey availability would lead to a
55% reduction in overall landings (Cf/Ci =0.45), a 75%
reduction in anchovy landings (Cf/Ci=0.25) and a 74%
reduction in sardine landings (Cf/Ci=0.26), while the
demersal fraction would have decreased by 17% (Cf/
Ci=0.83). Moreover, these simulations yielded biomass
levels of sardine lower than those for anchovy (Fig. 12);
this situation has been recorded, for the first time in the
f/Bi) through 1994–2003 for small and medium-sized pelagic fishes
ing effort and 20% decrease of prey availability of small and medium-
agic fishes; 2—Jellyfish; 3—Horse mackerel; 4—Mackerel; 5—Other
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 81
area, by the stock assessments carried out in 2003 (Quin-
tanilla et al., 2004; Torres et al., 2004).
These results are supporting the general perception
that there has been an increase of the real fishing effort in
the area due to the increase of fishing capacity of vessels
(Bas et al., 2003). It is also important to underline that
results from dynamic simulation showed that an increase
of fishing effort would not translate into increased
catches (Table 6) under mixed nor wasp-waist flow
control situations; on the contrary, a decrease in catches
is predicted as fishing effort increases. Only small
increases in catches are predicted under bottom-up
flow control, even when the forcing function is not
included in the simulation. This would be in line with
the highlighted intense exploited status of the ecosystem
described and its resulting fragility.
4. Conclusions
The present model constitutes the first mass-balance
model constructed to characterise shelf and upper slope
exploited ecosystems from the western Mediterranean
Sea and it represents an important effort to integrate the
available biological data from the area in a coherent
format. Deficiencies in available biological data have
been identified. Further efforts to better characterise key
elements of the ecosystem, such as the trophic niche of
sardine and medium-sized pelagic fishes within the west-
ern basin, could be an important step forward towards the
characterisation of the ecosystem. Data is also scarce for
cephalopods and benthopelagic fishes, macrozooplank-
ton, suprabenthos and gelatinous zooplankton. More-
over, the incorporation of ontogenetic studies in
assessments would also be appropriate to increase the
quality of the model, as Mediterranean catches are par-
tially supported by recruits of target species (Lleonart and
Maynou, 2003; Sarda et al., 2005). Thus, although the
pedigree index of the model was high and the sensitivity
analysis proved the robustness of the model, the contin-
uous incorporation of new empirical data from the region
into the model would improve its results.
The ecosystemwas dominated by the pelagic domain,
which accounted for the main biomass and catches and
where flows mainly occurred. This ecosystem feature,
with the dominance in terms of biomass and catches of
small pelagic fishes (sardine and anchovy) and the pos-
sible wasp-waist predator-prey interactions, along with
the importance of hake and horse mackerel, are features
that usually characterise upwelling ecosystems (Jarre-
Teichman, 1998; Cury et al., 2000; Shannon et al., 2003;
Heymans et al., 2004; Moloney et al., 2005). However,
the studied ecosystem was limited by production (high
TE and EE values) and both primary production and
detritus were intensively used within the system. On
the other hand, benthic invertebrates had a higher im-
portance within this ecosystem than within typical up-
welling systems (Shannon et al., 2003; Heymans et al.,
2004; Moloney et al., 2005) or Atlantic ecosystems
(Sanchez and Olaso, 2004). Important pelagic–demersal
interactions were identified, and are a common feature of
highly fished areas (Moloney et al., 2005; Sanchez and
Olaso, 2004). The important role of gelatinous jellyfish
in the ecosystem was also highlighted.
Zooplankton and benthic invertebrates were identi-
fied as playing key roles in the ecosystem functioning
related to bottom-up control, while small pelagic fishes
would be involved in wasp-waist control situations, as
reinforced by the outcomes of the dynamic simulations.
A marginal top–down control of forage fish by predator
populations (e.g., dolphins and adult hake) within the
system was identified. This is in agreement with the long
history of fishing activity in the region that would have
strongly reduced the biomass of top predators to low
levels (Bas et al., 1985), resulting in the fishing fleets
acting as top predators in the ecosystem.
The ecotrophic efficiencies and mortality rates sug-
gested that the ecosystem is highly constrained by predators
(natural predators and the fishery). Although the predation
mortality was high for most of the groups of the model as
has been proved to occur in marine ecosystems even under
heavy fishing (Jarre-Teichman, 1998; Christensen and
Pauly, 1995), fishing mortality was very high for some
modelled groups, in agreement with results on growth
and recruitment overfishing of some demersal and pe-
lagic resources (Farrugio et al., 1993; Papaconstantinou
and Farrugio, 2000; Lleonart and Maynou, 2003; Bas et
al., 2003). At the same time, the intermediate-low devel-
opment of the ecosystem in terms of Odum’s theory of
ecosystem development (Odum, 1969, 1971; Christen-
sen, 1995a) was, at least partially, related to high fishing
intensity and further supported by a high gross efficiency
ratio, high primary production required to sustain the
fishery and the low trophic level of the catch (Pauly and
Christensen, 1995; Pauly et al., 1998a).
In addition, fishing impact per fleet indicated large
impacts on the principal components. Trawling was not
only the most non-selective gear and had the widest-
ranging impact on the different functional groups of the
ecosystem (important in terms of demersal biodiversity)
but it had the largest impacts on some demersal target
and non-target groups. The ecosystem impacts of the
longline fleet were especially important due to by-catch
of long-lived, slow-growing protected species; while
purse seines targeted high proportions of low trophic
M. Coll et al. / Journal of Marine Systems 59 (2006) 63–9682
level fishes that are main prey for top predators. On the
contrary, neither the consumption of fished production
nor the mixed trophic impact analysis suggests signif-
icant competition between vulnerable species (ceta-
ceans, seabirds and turtles) and fishing activity.
The assessment of non-reported landings was impor-
tant for many species, showing how the correction of
official statistics to include discards and IUU landings is
essential when placing fishing within the ecosystem and
assessing ecosystem status in theMediterranean Sea. For
instance, seabird dynamics were clearly influenced by
discard because it modifies their food supply, competi-
tion and predation interactions between species. The
model correctly captured positive and negative impacts
of discarding on seabird populations due to the direct
increase of food availability and to direct mortality,
respectively (Oro and Ruız, 1997; Oro et al., 1997;
Belda and Sanchez, 2001). Moreover, it could be seen
that discarding causes important changes in seabird
populations (Furness, 2003), where an increase or a
decrease in discards can be linked with both changes in
interactions between seabird species and with negative
effects on seabird biodiversity, as the larger species affect
the smaller ones, indirectly by competing for discards, or
directly through predation (e.g.,. Gonzalez-Solis et al.,
1997; Martınez-Abraın et al., 2003).
The low trophic level of the catch, characterising
Mediterranean ecosystems (Pauly et al., 1998a; Pinne-
gar et al., 2003) and ratified in the present study, is also
in line with the long history of exploitation in the
Mediterranean (Bas et al., 1985). However, the steady
decline in landings in the area from 1994 to 2003,
coupled with an important decline of pelagic biomass
within the system (Quintanilla et al., 2004; Torres et al.,
2004), is of special relevance and indicates the high
fragility of the ecosystem with respect to perturbations.
In fact, the application of a new index of ecosystem
impact of fishing based on the loss in secondary pro-
duction at higher trophic levels (Tudela et al., 2005;
Libralato et al., submitted for publication) suggested
that the fishing situation in 1994 signalled a high risk to
ecosystem overfishing sensu Murawski (2000), with
high probabilities of stock declines or collapses.
Moreover, dynamic simulations showed that a mod-
erate increase in fishing pressure from 1994 to 2003
synergistically coupled with a moderate forcing function
could reproduce the observed patterns of decreasing land-
ings and biomasses within the system when assuming
wasp-waist control. It was also shown that an increase in
fishing would not have been translated into an increase in
landings. These results highlighted the highly exploited
state of the present ecosystem and its low resistance, and
support the idea that the state of the resources in the
western Mediterranean Sea can dramatically change as
a consequence of fishing activities, in conjunction with
environmental forcing, and can lead to important changes
of the whole ecosystem (Farrugio et al., 1993; Lleonart
and Maynou, 2003), in contrast with the presumed
boverfishing steady stateQ of Mediterranean resources
(Caddy, 1997). Due to the key role that small pelagic
fish play within the system, decreases in pelagic biomass
would likely have important consequences on the whole
ecosystem structure and functioning (Cury et al., 2000;
Libralato et al., submitted for publication).
Although the Mediterranean basin is characterised by
marked heterogeneity in terms of ecological, geograph-
ical and also social and economical factors (Farrugio et
al., 1993), current results from the South Catalan Sea
model could be regarded as representative of other shelf
and upper slope regions of the western Mediterranean
and would imply the low resistance of these exploited
ecosystems and their inability to cope with synergistic
perturbations. In this context, ecological modelling can
be an important tool allowing the inclusion of trophic
interaction dynamics in the assessment and management
of marine resources within the context of the precaution-
ary approach and an adaptive management process. The
present model settles the basis to further develop dynam-
ic simulations in order to understand the extent to which
fishing activities, the environment and other anthropogen-
ic factors are driving marine resources in the area and to
describe the configuration of trophic interactions (Walters
et al., 1997; Christensen and Walters, 2004). The output
of different management strategies can then be studied.
Acknowledgements
This research was funded by the Spanish research
project CICYT.REN 2000-0878/MAR. During the
work M.C. was supported financially by a FPI follow-
ship from the MYCT of the Spanish Government. The
authors wish to acknowledge all those colleagues from
the Institute of Marine Science (ICM), the Centre for
Advanced Studies of Blanes (CEAB), the Mediterra-
nean Institute for Advanced Studies (IMEDEA) and the
Spanish Institute of Oceanography (IEO) that provided
essential data and technical advice for the development
of this work, with special mention to M. Carrasson with
her assistance on the analysis of trophic data and F.
Maynou for his continuous contributions and com-
ments. Moreover, they thank those scientific research-
ers from the Fisheries Centre (University of British
Columbia) that kindly supported the work and advised
on ecological modelling procedures with special men-
Appendix A
T le A1
In ut data and references by functional group for the South Catalan Sea Model
F tional group Original value Reference Observations
1. hytoplankton
B mass 0.4 mg Cl-a m�3
(10.2 t km�2)
Maso, 1989 Conversion factor used to transform units of
Cl-a m�3 to carbon units/m3 and organic matter
units/km2 from Jorgensen et al. (1991) and
Dalsgaard and Pauly (1997)
P 232 g C m�2 years�1
(37.91 years�1)
Tudela, 2000 Conversion factor used to transform carbon
units/m2 year to organic matter (Sorokin, 1990)
2. icro- and mesozooplankton
B mass 0.049 mgC dm�3
(9.86 t km�2)
Alcaraz et al., 2003;
Calbet et al., 2001
Dimensions of organisms between 53 Am to
5 mm. Data from 1996 and 2000
P 20.87 years�1 Pinnegar, 2000 Data modified to consider area’s temperature
(Opitz, 1996)
Q 48.85 years�1 Pinnegar, 2000 Data modified to consider area’s temperature
(Opitz, 1996)
T phic data Calbet et al., 2002 Indirect consideration of the microbial loop
taking into account the food intake of micro-and
mesozooplankton from the microbial food web
3. acrozooplankton
B mass 0.54 t km�2 Maynou et al., 2003 Dimensions of organisms N5 mm. Data
from 1998 to1999
P 20.41 years�1 Labat and Couzin-Roudy, 1996
Q 50.94 years�1 Baamstedt and Karlson, 1998
T phic data Baamstedt and Karlson, 1998;
Casanova, 1974
4. ellyfish
B mass 0.389 t km�2 Alcaraz et al., 2003 Dimensions of organisms N5 mm. Used
conversion factor to transform units of mgC/l
to g mo/m2 of 1.1 (M. Alcaraz. Pers. com).
P 13.87 years�1 Malej, 1989 Data from the Adriatic Sea corrected to consider
differences of temperature between areas
(Opitz, 1996)
Q 50.48 years�1 Malej, 1989 Data from the Adriatic Sea corrected to consider
differences of temperature between areas
(Opitz, 1996)
T phic data Orek, 2000
(continued on next page)
M.Collet
al./JournalofMarin
eSystem
s59(2005)63–96
83
ab
p
un
P
io
/B
M
io
/B
/B
ro
M
io
/B
/B
ro
J
io
/B
/B
ro
Table A1 (continued)
Funtional group Original value Reference Observations
5. Suprabenthos
Biomass 0.028 t km�2 Maynou et al., 2003 Maximum value weighted by bathimetric ranges
from 60 m, 150m and 200m depths. Data from
1998-1999
P/B 8.05 years�1 Cartes and Maynou, 1998
Q/B 52.12 years�1 Cartes and Maynou, 2001
Trophic data Cartes et al., 2001
6. Polychaetes
Biomass 15.54 t km�2 Sarda et al., 2000; Desbruyeres et al., 1973 Used conversion factor from dry weight to wet
weight of 15% (Rumohr et al., 1987)
P/B 1.83 years�1 Moodley et al., 1998 Data from the Adriatic Sea corrected to
consider differences of temperature between
areas (Opitz, 1996)
Q/B 11.53 years�1 Mackinson et al., 2000 Data from the Florida shelf corrected to
consider differences of temperature between
areas (Opitz, 1996)
Trophic data Fauchald and Jumars, 1979
7. Shrimps
Biomass 0.025 t km�2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994-2000) in the Catalan Sea
P/B 3.08 years�1 Marano et al., 1998 Data from the Adriatic Sea corrected to
consider differences of temperature
between areas (Opitz, 1996)
Q/B 7.20 years�1 Maynou and Cartes, 1998
Trophic data Cartes, 1991, 1993; Cartes et al., 2001
8. Crabs
Biomass 0.085 t km�2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 2.10 years� 1 M=Mackinson et al., 2000
Q/B 4.73 years� 1 Maynou and Cartes, 1998
Trophic data Cartes, 1991; Guerao, 1993
9. Norway lobster
Biomass 0.034 t km�2 Sarda, 1994, 2001 Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 1.20 years� 1 Froglia and Gramitto, 1988
Q/B 4.56 years� 1 Sarda and Valladares, 1990
Trophic data Cristo, 2000
M.Collet
al./JournalofMarin
eSystem
s59(2006)63–96
84
10. Benthic invertebrates
Biomass 8.873 t km�2 Desbruyeres et al., 1973; Sarda, 1994,
2001; Lleonart, 2001; Sarda et al., 2000
Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea. Complemented
from literature to include benthic macroinfauna
P/B 1.02 years� 1 Moodley et al., 1998 Data from the Adriatic Sea corrected to
consider differences of temperature between
areas (Opitz, 1996)
Q/B 3.13 years� 1 Pauly et al., 1993; Opitz, 1996
Trophic data Riedl, 1986.
11. Octopuses
Biomass 0.129 t km�2 Sarda, 1994; Lleonart, 2001; Sarda, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 2.338 years� 1 Mackinson et al., 2000 Data from the Florida shelf model corrected to
consider differences of temperature between
areas (Opitz, 1996)
Q/B 5.3 years� 1 Amaratunga, 1983
Trophic data Sanchez, 1981; Quetglas et al., 1998
12. Squids
Biomass 0.139 t km�2 Sarda, 1994, 2001 Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 2.015 years� 1 Mackinson et al., 2000 Data from the Florida shelf model corrected to
consider differences of temperature between
areas with the equation of Opitz, 1996
Q/B 26.47 years� 1 Amaratunga, 1983
Trophic data Sanchez, 1982; Quetglas et al., 1999
13. Mullets
Biomass 0.061 t km�2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 2.294 years� 1 Z=F+M; M=empirical equation from
Pauly, 1980
Q/B 6.90 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Aguirre, 2000
14. Conger eel
Biomass 0.031 t km�2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 1.56 years� 1 Z=F+M; M=empirical equation from
Pauly, 1980
Q/B 2.88 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981
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Table A1 (continued)
Funtional group Original value Reference Observations
15. Anglerfish
Biomass 0.052 t km�2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 1.58 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 2.70 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981
16. Flatfishes
Biomass 0.044 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 2.10 years� 1 Z=F+M; M=empirical equation from
Pauly, 1980
Q/B 7.53 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981; Tito de Morais, 1986;
Morte et al., 1999a
17. Poor cod
Biomass 0.022 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 1.52 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 6.97 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Morte et al., 2001
18. Juvenile hake
Biomass 0.023 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 1.32 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 8.74 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Bozzano et al., 1997, in press
19. Adult hake
Biomass
P/B 0.594 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B
Trophic data Bozzano et al., 1997, in press
20. Blue whiting
Biomass 0.658 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
(1994–2000) in the Catalan Sea
P/B 0.656 years� 1 Z=F+M; M=empirical equation from
Pauly, 1980
Q/B 5.93 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981
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21. Demersal fishes (1)
Biomass 0.318 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 Biomass estimates from trawling surveys
994–2000) in the Catalan Sea
P/B 1.159 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 6.85 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Matallanas, 1980; Macpherson, 1981;
Rosecchi, 1983; Moreno and Matallanas, 1983;
Moreno-Amich, 1992, 1994, 1996;
Casadevall et al., 1994; Morte et al., 1999b
22. Demersal fishes (2)
Biomass 0.013 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 iomass estimates from trawling surveys
994–2000) in the Catalan Sea
P/B 0.99 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 7.17 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981
23. Demersal fishes (3)
Biomass 0.09 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 iomass estimates from trawling surveys
994–2000) in the Catalan Sea
P/B 0.43 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 6.25 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981; Matallanas, 1982; Scotto di Carlo
et al., 1982; Zander, 1982; Stergiou and Fourtouni, 1991
24. Demersal small sharks
Biomass 0.055 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 iomass estimates from trawling surveys
994–2000) in the Catalan Sea
P/B 0.42 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 5.43 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1980, 1981
25. Benthopelagic fishes
Biomass 0.116 t km� 2 Sarda, 1994, 2001; Lleonart, 2001 iomass estimates from trawling surveys
994–2000) in the Catalan Sea
P/B 1.37 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 9.03 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Macpherson, 1981; Scotto di Carlo et al., 1982
26. European anchovy
Biomass 2.44 t km� 2 Palomera, 1995 iomass estimated from acoustic surveys
994) in the South Catalan Sea
P/B 1.33 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 13.91 years� 1 Tudela and Palomera, 1995
Trophic data Tudela and Palomera, 1997
(continued on next page)
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(1
B
(1
B
(1
B
(1
B
(1
B
(1
Table A1 (continued)
Funtional group Original value Reference Observations
27. European pilchard
Biomass 3.37 t km� 2 Palomera, 1995 Biomass estimated from acoustic surveys
(1994) in the South Catalan Sea
P/B 1.50 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 8.86 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Demirhindi, 1961
28. Small pelagic fishes
Biomass 0.69 t km� 2 Palomera, 1995 Biomass estimated from acoustic surveys
(1994 and 1996) in the South Catalan Sea
P/B 0.52 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 7.39 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Andreu and Rodriguez-Roda, 1951
29. Horse mackerel
Biomass 1.75 t km� 2 IFREMER. Non published data Biomass estimated from acoustic surveys
(1997) in the Catalan Sea
P/B 0.39 years� 1 Z=F+ M; M=empirical equation from Pauly, 1980
Q/B 5.13 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Ben Salem, 1988; Kyrtatos, 1998a,b
30. Mackerel
Biomass 0.68 t km� 2 IFREMER. Non published data Biomass estimated from acoustic surveys
(1997 and 1999) in the Golf of Lion
P/B 0.46 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 4.88 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Moreno and Castro, 1995
31. Atlantic bonito
Biomass 0.3 t km� 2 Lleonart, 1990 VPA assessment from the Catalan Sea
P/B 0.35 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 4.36 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Moreno and Castro, 1995
Migration movements Sabates and Recasens, 2001
32. Large Pelagic Fishes
Biomass 0.14 t km� 2 ICCAT, 2003, in press
P/B 0.43 years� 1 Z=F+M; M=empirical equation from Pauly, 1980
Q/B 1.63 years� 1 Empirical equation from Pauly et al., 1990
Trophic data Orsi Relini et al., 1995
Migration movements De La Serna and A lot, 1990; Block et al., 2001
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33. Loggerhead turtle
Biomass 0.32 t km� 2 Gomez de Segura et al., 2003 Data from visual surveys around the area.
Units of individuals/km2 has been transform
to T/km2 with the mean body weight per
specie (Merchan and Martınez, 1999)
P/B 0.15 years� 1 Mackinson et al., 2000 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Q/B 2.54 years� 1 Polovina, 1984 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Trophic data Tomas et al., 2001
Bycatch Caminas, 1988; Aguilar et al., 1995;
Caminas and De la Serna, 1995
34. Audouins gull
Biomass 0.0011 t km� 2 Oro and Ruız, 1997; Oro, 1999 Data from visual surveys around the area.
Units of individuals/km2 has been transform
to T/km2 with the mean body weight per
specie (Del Hoyo et al., 1992)
P/B 4.64 years� 1 Pinnegar, 2000 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Q/B 70.0 years� 1 Nilsson and Nilsson, 1976
Trophic data Oro et al., 1997
Bycatch Belda and Sanchez, 2001; Tudela, 2004
35. Other sea birds
Biomass 0.0011 t km� 2 Aguilar, 1991; Oro and Ruız, 1997; Oro, 1999 Data from visual surveys around the area.
Units of individuals/km2 has been transformed
to T/km2 with the mean body weight per
specie (Del Hoyo et al., 1992)
P/B 4.56 years� 1 Pinnegar, 2000 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Q/B 73.20 years� 1 Nilsson and Nilsson, 1976
Trophic data Bosch et al., 1994; Oro, 1996; Granadeiro
et al., 1998; Arcos, 2001
Bycatch Belda and Sanchez, 2001; Tudela, 2004
36. Dolphins
Biomass 0.03 t km� 2 Forcada et al., 1994; GRUMM. 2002.
Non-published data.
Data from visual surveys around the area.
Units of individuals/km2 has been transformed
to T/km2 with the mean body weight per
specie (Carwardine and Camm, 1998)
P/B 0.07 years� 1 Mackinson et al., 2000 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Q/B 13.49 years� 1 Innes et al., 1987; Trites et al., 1997
Trophic data Wurtz and Marrale, 1993; Blanco et al., 2001
Bycatch Tudela, 2004
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Table A1 (continued)
Funtional group Original value Reference Observations
37. Fin whale
Biomass 0.39 t km� 2 Forcada et al., 1993 Data from visual surveys around the area.
Units of individuals/km2 has been transform
to T/km2 with the mean body weight per
specie (Carwardine and Camm, 1998)
P/B 0.04 years� 1 Mackinson et al., 2000 Data modified to consider area’s temperature
with an empirical equation (Opitz, 1996)
Q/B 4.11 years� 1 Innes et al., 1987; Trites et al., 1997
Trophic data Pauly et al., 1998b
Migration movements Grannier, 1998
38. Detritus
Biomass 70. 0 t km� 2 Puig and Palanques, 1998 Used conversion factor to transform units
of carbon units to organic matter
(Parsons et al., 1977)
IFREMER=Institut Francais de Recherche pour l’Exploitation de la Mer.
GRUMM=Marine Mammal Research and Conservation Group (University of Barcelona, Spain).
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Table A2
Code Scientific name
Antomeg Antonogadus megalokynodon (Kolombatovic, 1894)
Aspicuc Aspitrigla cuculus (Linnaeus, 1758)
Aspiobs Aspitrigla obscura (Linnaeus, 1764)
Callmac Callionymus maculatus (Rafinesque-Schmaltz, 1810)
Caprape Capros aper (Linnaeus, 1758)
Ceporub Cepola rubescens (Linnaeus, 1766)
Chimmon Chimaera monstrosa (Linnaeus, 1750)
Chloaga Chlorophthalmus agassizii (Bonaparte, 1840)
Coelcoe Coelorhynchus coelorhynchus (Risso, 1810)
Deltqua Deltentosteus quadrimaculatus (Valenciennes, 1837)
Diplann Diplodus annularis (Linnaeus, 1758)
Eutrgur Eutrigla gurnardus (Linnaeus, 1758)
Gadiarg Gadiculus argenteus (Guichenot, 1850)
Gnatmys Gnathophis mystax (Delaroche, 1809)
Gobibuc Gobius bucchichi (Steindachner, 1870)
Gobinig Gobius nige (Linnaeus, 1758)
Helidac Helicolenus dactylopterus (Delaroche, 1809)
Hymeita Hymenocephalus italicus (Giglioli, 1884)
Lepicau Lepidopus caudatus (Euphrasen, 1788)
Lepicav Lepidotrigla cavillone (Lacepede, 1810)
Lepilep Lepidion lepidion (Risso, 1810)
Lesufri Lesueurigobius friesii (Malm, 1874)
Macrsco Macroramphosus scolopax (Linnaeus, 1758)
Maurmue Maurolicus muelleri (Cocco, 1838)
Molvdip Molva dipterygia (Rafinesque, 1810)
Myctpun Myctophum punctatum (Rafinesque, 1810)
Notabon Notacanthus bonapartei (Risso, 1840)
Ophibar Ophidion barbatum (Linnaeus, 1758)
Ophiruf Ophichthus rufus (Rafinesque, 1810)
Pageaca Pagellus acarne (Risso, 1829)
Pagebog Pagellus bogaraveo (Brunnich, 1768)
Pageery Pagellus erythrinus (Linnaeus, 1758)
Phycble Phycis blennoides (Brunnich, 1768)
Pomaspp Pomatoschistus spp. (Canestrini, 1861)
Scornot Scorpaena notata (Rafinesque, 1810)
Serrcab Serranus cabrilla (Linnaeus, 1758)
Serrhep Serranus hepatus (Linnaeus, 1758)
Spicspp Spicara spp. (Linnaeus, 1758)
Tracdra Trachinus draco (Linnaeus, 1758)
Tracsca Trachyrincus scabrus (Risso, 1810)
Triglas Trigloporus lastoviza ( Brunnich, 1768)
Triglyr Trigla lyra (Linnaeus, 1758)
Zeusfab Zeus faber (Linnaeus, 1758)
Epigden Epigonus denticulatus (Dieuzeide, 1950)
M. Coll et al. / Journal of Marine Systems 59 (2005) 63–96 91
tion to S. Heymans. They also thank E. Morello and
L.J. Shannon for constructive comments on the draft
manuscript.
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