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. 2025 Sep 17;20(9):e0330441.
doi: 10.1371/journal.pone.0330441. eCollection 2025.

Assessing fishery interaction on cetaceans stranded along the Italian coastline between 1986 and 2023

Guido Pietroluongo  1   2 , Michela Podestà  3 , Donatella Belluscio  4 , Enrica Berio  5 , Cristina Canonico  6 , Cristina Casalone  7   8 , Federica Cavaliere  6 , Cinzia Centelleghe  1   9 , Luca Ceolotto  1 , Cristiano Cocumelli  10 , Bruno Cozzi  1 , Daniele Denurra  11 , Alessandra Di Donato  12 , Gabriella Di Francesco  13 , Giovanni Di Guardo  14 , Fabio Di Nocera  15 , Ludovica Di Renzo  13   16 , Stefano Gavaudan  6 , Federica Giorda  7   8 , Giuseppe Lucifora  15 , Leonardo Marino  4 , Letizia Marsili  17 , Sergio Migliore  18 , Ilaria Pascucci  6 , Gianni Pavan  19 , Antonio Petrella  4 , Antonio Pintore  11 , Roberto Puleio  18 , Silva Rubini  12 , Giuliana Terracciano  20 , Anna Toffan  21 , Carla Grattarola  7   8 , Sandro Mazzariol  1   9
Affiliations

Assessing fishery interaction on cetaceans stranded along the Italian coastline between 1986 and 2023

Guido Pietroluongo et al. PLoS One. .

Abstract

Monitoring stranded cetaceans represents a strategic method to assess their health, conservation status, and ecological role in the marine ecosystem. Efficient stranding networks and standardized protocols are essential to monitor this phenomenon and investigate its causes. This study assesses the evidence of fishery interaction on stranded cetacean carcasses found along the Italian coastline from 1986 to 2023. Evidence assessment and post-mortem investigation methods evolved over three macro-periods, from non-standardized reporting (1986-2014) to an integrated national stranding network (2015-2019), and finally to the creation of a new standardized, evidence-based diagnostic framework under the EU-funded LIFE DELFI project (LIFE18 NAT/IT/000942) (2020-2023). A total of 5355 cases were selected for this analysis. A literature review and evidence of interaction on stranded carcasses supported the categorization of findings, ranging from case history to pathological observations, allowing the assessment of temporal variation, demographic parameters, geographical distribution, and fishing gear identification. Evidence of fishery interaction was found in 12.89% of the cases (690/5355), with an annual average of 18.15 affected animals, and fishery interaction was identified as the likely cause of death in 10.32% of the cases. The most frequently reported species were Stenella coeruleoalba and Tursiops truncatus, showing significant differences in fishery interactions, particularly in relation to sex, age class, and geographical distribution. Adult male Tursiops truncatus exhibited a higher susceptibility to gillnet interaction in the Adriatic Sea. The results of this study emphasize the importance of standardized post-mortem investigations and long-term monitoring to identify risk hotspots, implement species- and region-specific mitigation strategies, and establish threshold values for cetacean conservation.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Temporal trends of cetacean strandings with evidence of fishery interaction from 1986 to 2023.
(A) Total strandings; (B) Stenella coeruleoalba (Sc); (C) Tursiops truncatus (Tt); (D) Physeter macrocephalus (Pm).
Fig 2
Fig 2. Age class (A) and sex (B) prevalence in Stenella coeruleoalba (Sc) and Tursiops truncatus (Tt) with evidence of fishery interaction between 1986 and 2023.
Fig 3
Fig 3. Evidence of fishery interaction in cetaceans stranded along the Italian coastline: A. By-catch in animal history; B. Presence of fishing gears; C. Larynx entanglement; D. Ingestion; E. Net marks; F. Amputation; G. Penetrating wounds: G1.
External view of the penetrating wound; G2. Focus on the penetrating wound; G3. Internal focus of the penetrating wound.
Fig 4
Fig 4. Distribution of anthropogenic interaction categories for Stenella coeruleoalba (Sc) and Tursiops truncatus (Tt).
Bars represent the number of specimens per category, asterisks (*) indicate cases where multiple interaction signs were observed in the same specimen (not represented in the graph).
Fig 5
Fig 5. Stranding distribution of Stenella coeruleoalba (Sc), Tursiops truncatus (Tt), and Physeter macrocephalus (Pm) across the GSAs.
Fig 6
Fig 6. Cetacean-fishery interactions across different GSAs.
The maps show the locations of the analyzed areas, while the bar charts display the number of interactions categorized as “Unintentional interaction”, “Net-foraging behavior”, and “Intentional interaction” for the two most represented species: Tursiops truncatus (Tt, in gray) and Stenella coeruleoalba (Sc, in black).
Fig 7
Fig 7. Illustration of the fishery interaction categories associated with the COD.
The innermost ring represents the main categories, including gillnet (GILLNET), undetermined gears (UND. GEARS), and driftnet or fishing line (DRIFTNET). The middle ring provides a more detailed classification of specific causes, such as entanglement in fishing gear (Enta), larynx Entanglement (LE), chronic entanglement in fishing gear (Chronic Enta.), ingestion (Ingestion), peracute underwater entrapment (PUE), and non-accidental. The outermost ring represents the species involved, identified by their abbreviations: Stenella coeruleoalba (Sc), Tursiops truncatus (Tt), Grampus griseus (Gg), Delphinus delphis (Dd), Globicephala melas (Gm), Physeter macrocephalus (Pm).
See this image and copyright information in PMC

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