This document summarizes a study that developed habitat suitability models for four cephalopod species (Todaropsis eblanae, Illex coindetii, Eledone moschata, and Eledone cirrhosa) in the Strait of Sicily using data on species densities and environmental variables collected from 1998-2011. Generalized additive models were used to relate species presence/absence and abundance to depth, slope, rugosity, salinity, temperature, chlorophyll-a, and light levels. The models showed different habitat preferences between species that relate to environmental conditions. Predictive maps highlighted key habitat areas that can inform conservation efforts in the region. Further analysis of long-term trends is planned.

1. Environmental effects on the habitat
selection of four cephalopods
in the Strait of Sicily
V. Lauria, G. Garofalo, M. Gristina & F. Fiorentino
Scientific basis and tools to support the fisheries management plans in the framework of the Common Fisheries
Policy and of the environmental and economic policies (Fishnet III) – MIPAAF project

2. Background
Cephalopods are a significant component of marine assemblages and play an
essential role in marine food webs
Cephalopods are highly sensitive to changes in environmental conditions
Cephalopods represent an important fishery worldwide that has been increasing
during the last decades
Cephalopod stocks in Europe are still not quota-regulated
In the Mediterranean Sea they are exploited from local fisheries such as bottom
trawl and artisanal fleets

3. Objectives
Aims
To develop habitat suitability models of four cephalopod species:
Todaropsis eblanae, Illex coindetii, Eledone moschata and Eledone
cirrhosa as a function of oceanographic and physical environmental
variables
 to better understand the habitat utilisation of cephalopods in the
Strait of Sicily (central Mediterranean Sea)
 to provide information for effective management

4. Materials & Methods: study area
• wide range of depths and habitats
• high biodiversity (e.g. fish, crustaceans, cephalopods and
elasmobranchs)
• very complex topography and circulation

5. Materials & Methods: time series data (1998-2011)
• Density data (N/km2) of four cephalopod species:
Todaropsis eblanae, Illex coindetii, Eledone moschata and Eledone
cirrhosa were collected from the Mediterranean International Trawl
Survey program (MEDITS)
Biotic data
Environmental predictors
• Depth (m)
• Slope (expressed in degrees with values from 0° to 90°)
• Rugosity
• Surface Salinity (Practical Salinity Unit)
• Sea Surface temperature (SST in °C)
• Chlorophyll-a (in mg/m3)
• Photosynthetic Active Radiation P(AR in einstein/m2/day)
• Year

6. Materials & Methods: habitat suitability models
Generalised
Additive Models
(GAMs) were used
to construct habitat
suitability models
binomial
(presence/absence) model
positive (truncated)
abundance model
Delta model
Species
distribution
prediction
Model building:
Model evaluation: model predictions were compared with survey
values
Model selection: best models were selected using the wAICc
Model mapping: maps of species predictions and model error were
constructed by interpolation in ArcGIS

7. Results: species-environmental variables relationship
• Depth was the main environmental predictor in all four species
habitat models
• All species preferred areas with low slope and rugosity values
• All species were positively associated to productive areas (higher
Chlorophyll-a) with exception of Eledone moschata
• SST influenced the habitat suitability of squids while no effect was
shown for the octopus
• The effect of salinity on the habitat selection varied amongst
cephalopod species
• Both squids and Eledone cirrhosa favoured habitats with higher
water trasparency, Eledone moschata preferred waters with lower
values
• No overall temporal trend was evident amongst species between
1998-2011

8. Results: Model behaviour – Todaropsis eblanae

9. Results: Model behaviour – Illex coindetti

10. Results: Model behaviour – Eledone moschata

11. Results: Model behaviour – Eledone cirrhosa

12. Results: prediction maps
Todaropsis eblanae Illex coindetti Eledone moschata Eledone cirrhosa

13. Conclusions and further development
• Our results and predictive maps revealed different habitat
preference among species, probably related to different
environmental conditions (e.g. depth, light, nutrients and
currents)
• The majority of species were associated with areas with minimum
or gentle terrain variation which tend to be associated with fine
sediment
• Predictive maps of habitat suitability highlighted hot-spots for the
conservation of cephalopods in the central Mediterranean Sea
• Manuscript to be submitted for peer-review
• Further work on the analysis of temporal trend will be conducted
in the next few months

14. Acknowledgments
This work was carried out within the Data Collection Regulation and
Framework-module trawl surveys (MEDITS) (Mediterranean International
Trawl Surveys) funded by the European Union and the Italian Ministry of
Agricultural, Food and Forestry Policies.
We thank all the technical staff of CNR-IAMC UOS, Mazara del Vallo (Italy)
involved in data collection and processing.
Thank you
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