Symposium on Integrating New Advances in Mediterranean
Oceanography and Marine Biology
Session 5: Fisheries, Marine protected areas, population outbrusts,
biodiversity shifts
An ExtendSim platform to simulate the
effects of trawling on benthic communities
Alba Muntadas1*, Johanna Ballé-Béganton2, Michel Lample2, Silvia de Juan1, Denis Bailly2,
Dolors Blasco1, Montserrat Demestre1
1Institut
de Ciències del Mar, ICM-CSIC- Barcelona; 2Université de Bretagne Occidentale, UBO- Brest
* amuntadas@icm.csic.es
An ExtendSim platform to simulate the effects of trawling on benthic
communities
PLATFORM: SIMULATION OF TRAWLING EFFECTS ON BENTHIC COMMUNITIES AND EXPLOITED
RESOURCES
BLOCKS
● SYSTEM
PRESENTATION
● METHODOLOGY
● STUDY AREAS
● SIMULATION
THE SYSTEM
BLOCK : SYSTEM PRESENTATION
This platform is
meant to be a tool
to estimate the
status of a
community
subjected to a
provided fishing
effort
[ Find out more ...]
Commercial
species
Management
● Trawling affects benthic
communities modifying
Essential Fish Habitats 
Effects on the resources.
● Platform goal  link
Fishing effort
fishing – benthos –
commercial species
● This platform is meant to
Benthos
be a useful tool for
stakeholders: managers,
fishermen, scientists,
politicians…
Dayton et al. 1995. Aquatic Conservation. 5:205-232
METHOD
BLOCK : METHODOLOGY
[ Find out more ...]
FISHING EFFORT ESTIMATION
-There are many ways to estimate fishing
effort: CPUE, swept area, total length of trawl
tracks..
Chosen unit:
GT x days at sea/month
- This information can be obtained in any area
were the simulations wants to be applied
Demestre et al. CIESM 2010
METHOD
BLOCK : METHODOLOGY
[ Find out more ...]
BENTHIC COMMUNITY REPRESENTATION : THE TRAITS APPROACH
● Species composition is highly influenced
by local characteristics  it can mask
fishing impact consequences
● SPECIES  TRAITS :
- Reduces the number of variables :
 Overcome regional differences
 Highlights fishing effects
● For the simulation we used simple traits
easily assigned to species and directly
related to trawling resistance/vulnerability
de Juan, S. and Demestre, M. 2012. Ecological Indicators. 18: 183–190.
METHOD
BLOCK : METHODOLOGY
[ Find out more ...]
BENTHIC COMMUNITY REPRESENTATION : THE TRAITS APPROACH
Traits used in the simulation
Position
Feeding
Motility
Size
Other attributes
Legend
Emergent
Filter
feeding
Sessile
(attached)
Large
>10 cm
Fragile
Very resistant*
Surface
Deposit
feeding
Sedentary
Medium
5-10 cm
No protection
Surface
burrowing
Predators
Motile
(crawlers)
Small
<5cm
Flexible
Deep
burrowing
Scavengers
Highly motile
(swimmers)
Resistant*
Vulnerable*
Strong
Regeneration
Vermiform
Hard shell
Very vulnerable*
* Vulnerability regarding to
trawling
STUDY AREAS
BLOCK : STUDY SITES
[ Find out more ...]
STUDY SITES
-Presentation of the data
available in each study
site.
Community structure is
presented by:
● Trait structure
● Species composition
SIMULATION
BLOCK : SIMULATION
[ Find out more ...]
● INPUTS
PRESENT FISHING EFFORT
25000
GT * days at sea/month
DESIRED FISHING EFFORT
20000
GT * days at sea/month
HABITAT TYPE
Mud
Sandy-mud
Gravelly-mud
Sand
Sandy-gravel
Maërl
> 80% Mud
60-70% Mud
40-30% Sand
SIMULATION
BLOCK : SIMULATION
[ Find out more ...]
SIMULATION OUTPUT : PRESENT VS DESIRED EFFORT STRUCTURE
-Total abundance PLOT
-Percentage of trait categories within trait type
PLOT
RESET
Actual status
Structure at
desired effort
Uncertainity of
the simulation
SIMULATION
BLOCK : SIMULATION
[ Find out more ...]
SIMULATION OUTPUT : PRESENT VS DESIRED EFFORT STRUCTURE
Relationship between traits:
- Possibility to show one selected trait against another trait
PRESENT STRUCTURE
STRUCTURE AT DESIRED EFFORT
Size
Size
Scavenging
Predator
Feeding
Deposit
feeding
Scavenging
Small
Predator
Small
Deposit
feeding
Medium
Filter
feeding
Medium
Filter
feeding
Large
Large
Feeding
An ExtendSim platform to simulate the effects of trawling on benthic
communities
WORK STATUS
● DONE:
-Epifauna and physical data collection
-Platform structure
● IN PROGRESS:
-Statistical basis to run the simulation
-Building the graphical interface
FUTURE CHALLENGES :
- Include information on infaunal community
- Include the link benthos – comercial species