# Opportunistic records of entangled seals in
Ísafjarðardjúp (2021–2023)

David Pierre Milesi Gaches, Alexandre Lhériau-Nice

► To cite this version:

David Pierre Milesi Gaches, Alexandre Lhériau-Nice. Opportunistic records of entangled seals in Ísafjarðardjúp (2021–2023). 2025, pp.4. hal-05142419

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Submitted on 15 Jul 2025

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Distributed under a Creative Commons Attribution 4.0 International License
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**David Pierre Milesi-Gaches**<fnref n="1" /> | Department of zoology, University of South Bohemia in České Budějovice

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https://orcid.org/0000-0002-0605-7038

**Alexandre Lhériau-Nice** | Oceanly Science Ltd, Wellington, New Zealand

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https://orcid.org/0000-0002-7221-1232

# Opportunistic records of entangled seals in Ísafjarðardjúp (2021–2023)

## Context

The harbour seal (Phoca vitulina) population in Iceland has declined over recent decades, with human activities such as fisheries and tourism identified among the main pressures (Granquist 2022). Entanglement in fishing-related debris—including nets, ropes, and straps—is a well-known threat to pinnipeds elsewhere (Pemberton et al. 1992; Waluda & Staniland 2013), but remains poorly documented in Iceland, especially in the Westfjords. Despite local aquaculture expansion and growing tourism in the Ísafjarðardjúp fjord, there is currently no dedicated seal rescue centre in the country. This note reports several observations of entangled seals in this fjord between 2021 and 2023.

## Methods

Observations were collected opportunistically during ongoing fieldwork on seal behaviour, with increased attention to entanglement cases after a second sighting in 2022. Monitoring focused on regular surveys during low tide in Ísafjörður, Súðavík, Hvítanes and Vigur Island, mainly in spring and summer (Figure 1). Whenever seals were spotted—even incidentally—data collection was prioritised and entangled individuals were

systematically observed for at least one hour. A Focus Hawk 20-60×60 spotting scope and a Canon EOS 60D with a MC Granit-11 80-200 mm zoom lens were used, or photos were taken directly through the scope for distant individuals.

## Results & conclusion

Since 2021, 11 observations of entangled harbour seals have been recorded in the Westfjords: in Hvítanes, Ísafjörður, Súðavík, and Skutulsfjörður (Figure 1, 2). No entangled individual was noted in Vigur Island or other regular haul-out sites. Due to limitations in individual identification, it remains uncertain whether these observations concern 10 or 11 distinct individuals, as some seals may have been sighted multiple times. For instance, Seal E and Seal F are confidently identified as the same individual based on consistent fur patterns. Only the seal observed in Hvítanes in 2021 (Figure 2A) could be reliably recognised across five separate sessions, forming part of a behavioural study.

Seal A was a subadult with two visible constriction wounds, likely caused by a monofilament line. The seal exhibited reduced mobility, especially in head movement, and signs of discomfort. Despite frequent tourist disturbance at the site, including people crossing the fence and entering the hauling area, Seal

<footnote n="1">¹ milesi.david@gmail.com</footnote>
A showed less vigilance than nearby conspecifics and remained lethargic, suggesting compromised health and low survival prospects.

Seal B, a mature adult, was observed in 2022 and possibly again in 2023 as Seal C, in Ísafjörður, also part of a behavioural study. It bore a neck entanglement but showed no behavioural abnormalities. During one session, a group of kayakers caused a flush response; Seal B reacted similarly to non-entangled seals and resumed hauling shortly after. The absence of visible impairment suggests the entanglement occurred in adulthood or was superficial.

Seal E, observed nine times between August and October 2023 near Súðavík, was a young adult. Distinct marks on its fur confirm that Seal F is the same individual. Like Seal B, Seal E displayed normal

behaviour and did not appear to be hindered by the entanglement.

For all observations, the entangling materials could not be collected, but visual inspection suggests they were consistent with monofilament fishing line or similar synthetic debris, such as plastic thread or fine rope. These types of materials have been widely reported in pinniped entanglement cases globally (Pemberton et al. 1992; Arnould & Croxall 1995; Waluda & Staniland 2013). The constriction marks observed on Seal A strongly resemble injuries caused by thin synthetic filament, as described by Allen et al. (2012).

No entangled grey seals (*Halichoerus grypus*) were observed during the study period, despite regular sightings of the species at several monitored sites.

<figure><img src="image_5.png" /><figcaption>**Figure 1.** Map showing the locations where entangled seals were spotted. (Basemap: U.S. Geological Survey).</figcaption></figure>
<figure><img src="image_6.png" /><figcaption>**Figure 2.** Photographs of entangled Phoca vitulina individuals observed in the Westfjords of Iceland between 2021 and 2023.</figcaption></figure>

(A) Subadult seal in Hvítanes (2021) with visible constriction wounds on the neck and head.

(B) Adult seal in Ísafjörður (2022), entanglement visible around the neck.

(C) Possibly the same individual as B, observed in 2023.

(D) Seal in Skutulsfjörður (2023).

(E–F) Young adult seal observed nine times near Súðavík (2023), identified as the same individual.

(G-H-I-J-K) Other entangled individuals spotted once between 2022 and 2023, photographed at distance with signs of constriction or debris around the neck. Identification and condition could not be reliably assessed.

**Acknowledgements**

We thank the owners of Æðey for their permission and hospitality. We are also grateful to the Arctic Lab

expedition for logistical support aboard the Peter Pan, and to Vincent Grison, Jean Guérin, Guillaume
Roissard, Clément Pichard and Gérard Lambert for
their warm welcome.

References

Allen, R., Jarvis, D., Sayer, S., Mills, C., 2012.

Entanglement of grey seals Halichoerus grypus at
a haul out site in Cornwall, UK. Marine Pollution
Bulletin 64, 2815-2819.

https://doi.org/10.1016/j.marpolbul.2012.09.005

Arnould, J.P.Y., Croxall, J.P., 1995. Trends in
entanglement of Antarctic fur seals

(Arctocephalus gazella) in man-made debris at
South Georgia. Marine Pollution Bulletin 30,
707-712.

https://doi.org/10.1016/0025-326X(95)00054-0

Granquist, S., 2022. The Icelandic harbour seal (Phoca vitulina) population: trends over 40 years (1980-2020) and current threats to the population. NAMMCO Scientific Publications 12.

https://doi.org/10.7557/3.6328

Pemberton, D., Brothers, N.P., Kirkwood, R., 1992.

Entanglement of Australian fur seals in man-made
debris in Tasmanian waters. Wildl. Res. 19,
151-159. https://doi.org/10.1071/wr9920151

Waluda, C.M., Staniland, I.J., 2013. Entanglement of
Antarctic fur seals at Bird Island, South Georgia.

Marine Pollution Bulletin 74, 244-252.

https://doi.org/10.1016/j.marpolbul.2013.06.050

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This field note is part of the *Commentarii de Natura series*, a collection of descriptive field observations, shared in support of open and reproducible naturalist documentation.

© 2025 David Pierre Milesi-Gaches

This field note is licensed under a [Creative Commons Attribution 4.0 International License (CC BY 4.0)](https://creativecommons.org/licenses/by/4.0/).

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