First evidence of grey seal predation on marine mammals in the German Baltic Sea

Westphal, Linda; Klemens, Lisa; Reif, Farina; Neer, Abbo van; Dähne, Michael

doi:10.1016/j.seares.2023.102350

Cited by 3 publications

(1 citation statement)

References 38 publications

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“…As grey seal and harbour seal diets may overlap in areas where both species occur (Wilson and Hammond, 2016;Scharff-Olsen et al, 2019), it is likely that there will be direct competition between the species. Furthermore, grey seal predation on harbour seals has been documented since 10 years ago in the North Sea (van Neer et al, 2015) and recently in the Baltic Sea (Westphal et al, 2023). Increasing overlap and contact between the two subspecies may facilitate the transmission of this phenomenon.…”

Section: Moulting Seasonmentioning

confidence: 99%

Evidence of distribution overlap between Atlantic and Baltic grey seals

Galatius,

Olsen,

Allentoft-Larsen

et al. 2024

J. Mar. Biol. Ass.

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Grey seals from both the Atlantic and Baltic Sea subspecies are recovering from dramatic declines and recolonising former ranges, potentially leading to overlapping distributions and an emerging subspecies transition zone in Kattegat between Denmark and Sweden. The two subspecies have asynchronous moulting and pupping seasons. We present aerial survey data from 2011 to 2023 in Danish Kattegat during the Atlantic subspecies' moulting (March–April) and pupping (December–January) seasons, as well as the Baltic subspecies' moulting season (May–June). During the Atlantic subspecies' peak moulting season, 82% of the grey seals were recorded north of the island of Læsø (N57°18′, E11°00′). In contrast, during the Baltic moulting season in those years, only 9% of the grey seals were recorded here. This indicates a predominance of Atlantic grey seals in the north and Baltic grey seals in central and southern Kattegat. In 2022 and 2023, three pups were recorded around Læsø during early January, which coincides with the pupping season of northern Wadden Sea grey seals. Previously, pups have been recorded in the same locations during the Baltic pupping season, which demonstrates overlapping breeding ranges. Grey seals are known to have plasticity in the timing of pupping indicated by a west to east cline of progressively later pupping in the eastern North Atlantic. Historical sources document that the Baltic pupping season in Kattegat was earlier than it has been in recent years. Thus, the expanding ranges may be associated with convergence of Atlantic and Baltic subspecies' pupping seasons and potential hybridisation in this emerging transition zone.

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Section: Moulting Seasonmentioning

confidence: 99%

Evidence of distribution overlap between Atlantic and Baltic grey seals

Galatius,

Olsen,

Allentoft-Larsen

et al. 2024

J. Mar. Biol. Ass.

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Biomonitoring of persistent pollutants in grey seal (Halichoerus seagrypus) pups from the Gulf of Riga, Baltic Sea

Salcedo,

Di Marzio,

Martínez-López

2024

Marine Pollution Bulletin

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Pinniped response to diadromous fish restoration in the Penobscot River Estuary

Leach,

Stevens,

Cammen

2024

Front. Conserv. Sci.

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Successful conservation of pinnipeds in the northwest Atlantic has led to increasing populations of harbor seals (Phoca vitulina) and gray seals (Halichoerus grypus) in the Gulf of Maine. Within this region, habitat restoration and diadromous fish conservation in the Penobscot River have also been top priorities for the past decade. To understand the overlap between the regional recovery of pinnipeds and the aggregative response of pinnipeds to increasing forage fish, we assessed how counts, distribution, and behavior of seals in the Penobscot River Estuary have changed over time from 2012 to 2020 and determined whether those changes were related to changes in fish biomass that are occurring as the result of diadromous fish restoration. We did not see increased counts of hauled-out seals, but consistent with regional harbor seal phenology, hauled out seal counts were highest in late spring and declined throughout the summer and into the fall. The number of swimming harbor and gray seals, analyzed as a proxy for changes in behavior, showed a stronger annual trend with an increase throughout the study period. Fish biomass was negatively associated with total number of hauled out seals and swimming gray seals but positively associated with swimming harbor seals. We also documented the potential displacement of harbor seals when gray seals are present. Together, these results begin to provide insights into how regional conservation and local restoration efforts interact to affect multiple trophic levels in an ecosystem. Continued monitoring of predator-prey interactions, along with diet and movement studies, will further elucidate seal aggregative response to increasing prey species in this system and the potential impact of recovering predator populations on restored prey populations. Knowledge gained regarding pinniped response to increasing fish biomass has important implications for other systems with ongoing conservation measures that aim to improve habitat, decrease exploitation, or recover protected species. Studies like these can be critical for finding paths forward to reconcile the potentially competing objectives of marine mammal protection and fish restoration.

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First evidence of grey seal predation on marine mammals in the German Baltic Sea

Cited by 3 publications

References 38 publications

Evidence of distribution overlap between Atlantic and Baltic grey seals

Evidence of distribution overlap between Atlantic and Baltic grey seals

Biomonitoring of persistent pollutants in grey seal (Halichoerus seagrypus) pups from the Gulf of Riga, Baltic Sea

Pinniped response to diadromous fish restoration in the Penobscot River Estuary

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