06 April 2018

Predicting dolphin distribution within an Important Marine Mammal Area in Greece



Silvia is attending the 32nd Annual Conference of the European Cetacean Society in La Spezia, Italy (6-10 April 2018).

On Sunday she is going to make a verbal presentation, summarising our work on dolphins in the Gulf of Corinth. The abstract is copied below.

Predicting dolphin distribution within an Important Marine Mammal Area (IMMA) in Greece to support spatial management planning

Bonizzoni S (1,2), Furey NB (1,3), Valavanis VD (4), Bearzi G (1,2)

1) Dolphin Biology and Conservation, Cordenons, Italy
2) OceanCare, W├Ądenswil, Switzerland
3) University of British Columbia, Vancouver, Canada
4) Marine Geographic Information Systems Lab, Hellenic Centre for Marine Research, Iraklion, Greece

The success of a marine protected area depends on knowledge of distribution and habitat use by the species it aims to protect. The Gulf of Corinth, a 2400 km2 semi-enclosed embayment in Greece, has been identified as an Important Marine Mammal Area (IMMA) based on the satisfaction of all four selection criteria for IMMA status. In this area, three odontocete species can be predictably encountered within 11 km of the nearest coast: striped dolphins Stenella coeruleoalba, common dolphins Delphinus delphis and common bottlenose dolphins Tursiops truncatus. Striped dolphins occur in single-species groups or in mixed groups with common dolphins, whereas bottlenose dolphins only occur in single-species groups. We used a seven-year (2011–2017) dataset comprising 29907 km of boat-based visual surveys and 3448 km (590 h) of dolphin follows to predict striped and bottlenose dolphin distribution in the entire Gulf. Multiple geographic, bathymetric, oceanographic and anthropogenic variables were incorporated in a combined generalized additive model and generalized estimation equation framework (GAM-GEE) to describe dolphin occurrence and construct maps of predictive distributions. Modelling indicated that striped dolphins prefer deep (>300 m) oligotrophic waters in the central and southern part of the Gulf; bottlenose dolphins prefer shallow (<300 m) waters and areas close to fish farms along the northern-central shores. Spatial distribution of dolphin suitable habitats was predicted by using the retained variables identified in species-specific models. Prediction maps of dolphin distribution identified 1) a core dolphin habitat of approximately 1600 km2 (encompassing two thirds of the entire Gulf surface), and 2) a clear partitioning of striped and bottlenose dolphin distribution, calling for separate management measures within each species' core habitat, threatened by different anthropogenic impacts of concern. The results of this study can inform spatial management and ensure meaningful conservation action, consistent with IMMA designation.


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Bonizzoni S., Furey N.B., Valavanis V.D., Bearzi G. 2018. Predicting dolphin distribution within an Important Marine Mammal Area (IMMA) in Greece to support spatial management planning. Proceedings of the 32nd Annual Conference of the European Cetacean Society. La Spezia, Italy, 6-10 April 2018.

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