Characteristics of the grey seal (Halichoerus grypus) diet in the Vistula River mouth (Mewia Łacha Nature Reserve, southern Baltic Sea), based on the osteological and molecular studies of scat samples

Keszka, Sławomir; Panicz, Remigiusz; Stepanowska, Katarzyna; Biernaczyk, Marcin; Wrzecionkowski, Konrad; Zybala, Mikołaj

doi:10.1016/j.oceano.2020.04.005

Cited by 4 publications

(4 citation statements)

References 14 publications

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“…A study conducted upstream of the tidal area of the Gironde estuary showed that 80% of tagged lampreys were eaten by European catfish ( Silurus glanis Linnaeus 1758) within a month and 50% within 8 days (Boulêtreau et al, 2020). Such large predator fish are lacking at our study site, but harbour seals (Phoca vitulina , Linnaeus 1758 ) and grey seals ( Halichoerus grypus Linnaeus 1758) do occur (Brasseur et al, 2015) and are known to feed on river lampreys (Keszka et al, 2020). Whether Great cormorant ( Phalacrocorax carbo , Linnaeus 1758), abundantly present in the area, also predate on sea lamprey or whether they are too vigorous for cormorants to predate them is unknown though some consider them as potential predators (Braga et al, 2020).…”

Section: Discussionmentioning

confidence: 98%

Passage efficiency and behaviour of sea lampreys (Petromyzon marinus, Linnaeus 1758) at a large marine–freshwater barrier

Griffioen

Keeken

Hamer

et al. 2022

River Research & Apps

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Passage success of sea lampreys Petromyzon marinus and behaviour in the vicinity of man‐made structures such as marine–freshwater barriers are poorly understood. To mitigate these migratory problems, a better understanding of passage behaviour is needed. To investigate this, 25 sea lampreys were tagged with V7 VEMCO acoustic transmitters at a large marine‐freshwater barrier, consisting of ten sluice gates and a ship lock complex in the Netherlands. Overall passage success was assessed to be 16%, with four sea lampreys passing the sluice gates, while none passed the ship locks. Successful passage through the barrier occurred either at the beginning or at the end of a discharge period, when water level differences between sea and lake and thus water velocities were relatively low. Most sea lamprey showed exploratory searching behaviour but only for a short duration, before leaving the area again when unsuccessful. Low passage success and search duration were likely related to the unnatural infrequent occurrence of flow and only short lasting windows with suitable conditions for passage at the sluice gates. To mitigate the poor migration success of sea lampreys at the marine‐freshwater barrier with the current adapted sluice management, a fish passage facility with lower water velocities and longer or continuous passage opportunities is needed.

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Section: Discussionmentioning

confidence: 98%

Passage efficiency and behaviour of sea lampreys (Petromyzon marinus, Linnaeus 1758) at a large marine–freshwater barrier

Griffioen

Keeken

Hamer

et al. 2022

River Research & Apps

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“…Grey seals in this study fed mainly on Agonidae , Leuciscidae and Ammodytidae . Grey seals from the neighbouring Baltic Sea, in contrast, fed on C. harengus , S. sprattus or C. clupeaformis (Keszka et al, 2020; Lundström et al, 2010; Suuronen & Lehtonen, 2012), highlighting the differences between the North and Baltic Sea ecosystem. Contrary to this study, grey seals from Scotland showed a higher frequency of Ammodytes spp., Saithe ( Pollachius virens ) and Atlantic cod ( Gadus morhua ) (Wilson & Hammond, 2016), while in the English Channel they had a similar diet as those in this study but did not prey on L. limanda (Planque et al, 2021).…”

Section: Discussionmentioning

confidence: 99%

Deciphering Eurasian otter (Lutra lutra L.) and seal (Phoca vitulina L.; Halichoerus grypus F.) diet: Metabarcoding tailored for fresh and saltwater fish species

et al. 2022

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Long‐lived top predators shape biodiversity structure in their ecosystems and predator–prey interactions are critical in decoding how communities function. Studies on the foraging ecology of seals and Eurasian otters in Western Europe are outdated and most studies solely performed traditional hard part analysis. Molecular metabarcoding can be used as an innovative noninvasive diet analysis tool, which has proven efficient and complementary to hard part analysis, however, lacking application in the wider North Sea area. In this study, DNA from digesta, collected between 2014–2020, were used to identify fish species in the diet of 47 Eurasian otters, 54 harbour seals and 21 grey seals by applying a next‐generation metabarcoding approach. A newly designed 16S rRNA primer, providing the best coverage of >130 local marine and freshwater fish species, was used to amplify prey DNA from seal scats and otter gut content sampled from the North Sea and regional freshwater bodies. Frequent fish species included tench, ninespine stickleback and white bream in otters; hooknose and common roach in grey seals and Pleuronectidae and sand gobies in harbour seals. Bipartite network analysis showed a strong overlap of harbour and grey seal diets. Otter diet intersected with both seal species in terms of freshwater species. This study provides new knowledge about dietary composition and community assemblage of fish prey in otters and seals in the North Sea and regional freshwaters, and a new molecular tool to elucidate predator–prey interactions and interspecies competition in complex and changing ecosystems under pressure from anthropogenic activities.

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“…In the analysis of injury type, salmon with seal‐induced injuries had scars, lacerations, and lamprey wounds more often than these injury types were found in the general population. Lampreys have been detected in the grey seal diet in Europe (Gosch et al, 2014; Keszka et al, 2020), so one possibility for the higher prevalence of lamprey wounds in conjunction with a seal‐induced injury is that seals specifically target these fish. Based on these findings, it is also possible that salmon weakened by lamprey parasitism or by more serious injuries like lacerations, compared with an abrasion, bruise, or scale loss, may be more easily targeted by seals.…”

Section: Discussionmentioning

confidence: 99%

Examining the impacts of pinnipeds on Atlantic salmon: The effects of river restoration on predator–prey interactions

Leach

Simpson

Stevens

et al. 2022

Aquatic Conservation

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1. Seal populations in the Gulf of Maine have been recovering from historical bounty-driven declines since they received federal protection in 1972. In the past few decades, their population growth has sparked renewed concerns over conflict between pinniped and fish conservation.2. In the Penobscot River in Maine, USA, where restoration efforts over the past decade have aimed at restoring diadromous fish runs, seal predation on the endangered Atlantic salmon (Salmo salar) has become a growing concern.3. Quantitative and qualitative data for individual salmon, as well as the presence of putative seal-induced injury, have been collected from salmon passing upriver at dams in the Penobscot River since 2012.4. An analysis of seal-induced injury rate with demographic data, river herring returns, estuary fish biomass estimates, and timing of peak estuary fish biomass revealed that the seal-induced injury rate declined in the Penobscot River from 2012 to 2019, coincident with increasing river herring returns and estuary fish biomass. Despite a potentially increasing seal population, these results suggest that predator swamping from increasing forage fish may provide protection to salmon against seal predation. 5. The presence of multiple injuries on an individual salmon was also significantly associated with the probability of a salmon having a seal-induced injury. Lamprey wounds and lacerations on salmon were commonly associated with seal-induced injury, suggesting a confounding effect of multiple stressors.6. This assessment illustrates how multi-species diadromous restoration activities may alter predator-prey interactions in ways that support salmon conservation efforts. As demonstrated in the Penobscot River, a focus on overall ecosystem health and restoration can benefit multiple species that use the river. Insights from this study may help inform future management decisions in other humanimpacted systems where protected predators come into conflict with endangered prey.

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Characteristics of the grey seal (Halichoerus grypus) diet in the Vistula River mouth (Mewia Łacha Nature Reserve, southern Baltic Sea), based on the osteological and molecular studies of scat samples

Cited by 4 publications

References 14 publications

Passage efficiency and behaviour of sea lampreys (Petromyzon marinus, Linnaeus 1758) at a large marine–freshwater barrier

Passage efficiency and behaviour of sea lampreys (Petromyzon marinus, Linnaeus 1758) at a large marine–freshwater barrier

Deciphering Eurasian otter (Lutra lutra L.) and seal (Phoca vitulina L.; Halichoerus grypus F.) diet: Metabarcoding tailored for fresh and saltwater fish species

Examining the impacts of pinnipeds on Atlantic salmon: The effects of river restoration on predator–prey interactions

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