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Identifier

000454369

Title

Spatial analysis of cetacean strandings in Greek seas in relation to fishing grounds, potential feeding grounds and surface circulation

Alternative Title

Χωρική ανάλυση των εκβρασμών ειδών κητωδών σε σχέση με αλιευτικά και πιθανά διατροφικά πεδία καθώς και με τη θαλάσσια κυκλοφορία στις ελληνικές θάλασσες

Author

Ανδριώτης, Εμμανουήλ Σ.

Thesis advisor

Τσερπές, Γεώργιος

Reviewer

Γιαννουλάκη, Μαριάννα
Σωμαράκης, Στυλιανός

Abstract

Cetacean strandings are a phenomenon that is observed on the coasts and serves as an indicator of cetacean mortality in the sea. Reasons for direct human-induced cetacean mortality include entanglement in fishing gear (by-catch), intentional killing (shooting, wounding), collision with boats/vessels, ingestion of macroplastics, noise pollution from military sonars/seismic surveys. A small percentage of dead cetaceans wash up on beaches and are recorded, which depends on many factors (distance from the coast, marine traffic, morphology and accessibility of the coast) that are often difficult to estimate. The purpose of this study is to investigate the distribution of cetacean strandings in Greek waters and their relationship with coastal fishing and marine traffic. A total of 1378 strandings of 9 cetacean species were studied, during the period 2010-2021, using the stranding database of the Hellenic Center for Marine Research (HCMR). Kernel density estimate maps were created to identify spatial hotspots of strandings by species and cause of death. Generalized additive models (GAMs) were developed to explore the relationship between strandings and coastal fishing and potential feeding areas. In a stranding hotspot area of particular interest, the possible origin of the dead animal was estimated using the stochastic ensemble trajectory model, Leeway, which estimates the movement of objects on the water surface under the effect of wind and current. The study showed significantly clustered spatial distributions for both total cetacean strandings and when 4 species of cetaceans were examined separately, revealing the existence of hotspot areas in the study region. Generalized additive models demonstrated a possible positive relationship between stranding events and the extent of fishing grounds, as well as the significant role of the coastline in the recording of stranding events. Finally, possible estimates were made for the potential origin of strandings in the Pagasitikos gulf and surrounding areas using the Leeway model.

Language

English

Subject

GAMs

Hotspot analysis

Trajectory models

Εκβρασμοί

Κητώδη

Μοντέλα

Issue date

2023-03-24

Collection