Grey seal <i>Halichoerus grypus</i> recolonisation of the southern Baltic Sea, Danish Straits and Kattegat

Galatius, Anders; Teilmann, Jonas; Dähne, Michael; Ahola, Markus; Westphal, Linda; Kyhn, Line A.; Pawliczka, Iwona; Olsen, Morten Tange; Dietz, Runé

doi:10.2981/wlb.00711

Cited by 24 publications

(19 citation statements)

References 27 publications

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“…3). We argue that such settings of carrying capacity are not an issue as the grey seal population has been relatively stable after 2014, though it has a slight increase in 2019 (Anders et al 2020). Setting the carrying capacity as 37,000 individuals represents the assumption that the seal population has reached its maximum and, if nothing changes, remains at recent levels in the future as it is close to the counted seal numbers in 2014 (32,019 individuals reported by HELCOM SEAL Expert Group ( 2015)) multiplied by the hidden parameter 1.15 (Holma et al 2014).…”

Section: Carrying Capacity Of the Grey Seal Populationmentioning

confidence: 84%

“…To examine the effects of the levels of prey and predator change on salmon fisheries and population, we designed three scenarios with the assumption that (1) seal population increases in the future ( K = 50,000) (scenario I-S); (2) herring fishing mortality increases to F h t = 0.25 (scenario I-H); and (3) both of the previous two cases occur simultaneously (scenario I-HS). The reasons for these scenarios are the increasing trend of herring harvest and fishing mortality in the Gulf of Bothnia (ICES 2017a) and the rising grey seal population in the Baltic Sea (Anders et al 2020;HEL-COM SEAL Expert Group 2015).…”

Section: Scenarios For Single Species Management Contextmentioning

confidence: 99%

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The Role of Food Web Interactions in Multispecies Fisheries Management: Bio-economic Analysis of Salmon, Herring and Grey Seal in the Northern Baltic Sea

Lai

Lindroos

Kronbak

et al. 2021

Environ Resource Econ

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Multispecies bio-economic models are useful tools to give insights into ecosystem thinking and ecosystem-based management. This paper developed an age-structured multispecies bio-economic model that includes the food web relations of the grey seal, salmon, and herring, along with salmon and herring fisheries in the Baltic Sea. The results show that the increasing seal population influences salmon fisheries and stock, but the impacts on the harvest are stronger than on the stock if the targeted management policies are obeyed. If seal population growth and a low herring stock occur simultaneously, the salmon harvest could face a serious threat. In addition, scenarios of the multispecies management approach in this paper reveal a benefit that our model can evaluate the performance of different fisheries with identical or different management strategies simultaneously. The results show the most profitable scenario is that both fisheries pursuit aggregated profits and reveal a trade-off between herring fisheries and salmon fisheries. Our model indicates that the herring harvest level and the approaches to managing herring fisheries can influence the performance of salmon fisheries. The study also demonstrates a way to develop a multispecies bio-economic model that includes both migratory fish and mammalian predators.

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Section: Carrying Capacity Of the Grey Seal Populationmentioning

confidence: 84%

Section: Scenarios For Single Species Management Contextmentioning

confidence: 99%

The Role of Food Web Interactions in Multispecies Fisheries Management: Bio-economic Analysis of Salmon, Herring and Grey Seal in the Northern Baltic Sea

Lai

Lindroos

Kronbak

et al. 2021

Environ Resource Econ

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“…Underlying this pattern was a negative effect of sea surface salinity on habitat suitability. The effect of sea surface salinity should, however, be interpreted with care as Baltic gray seals are currently recolonizing areas with relatively high salinity levels, such as the Kattegat in the northern part of our study area (Galatius et al, 2020).…”

Section: Discussionmentioning

confidence: 99%

Forecasting shifts in habitat suitability of three marine predators suggests a rapid decline in inter‐specific overlap under future climate change

Beest

Dietz

Galatius

et al. 2022

Ecology and Evolution

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Understanding how environmental and climate change can alter habitat overlap of marine predators has great value for the management and conservation of marine ecosystems. Here, we estimated spatiotemporal changes in habitat suitability and inter-specific overlap among three marine predators: Baltic gray seals (Halichoerus grypus), harbor seals (Phoca vitulina), and harbor porpoises (Phocoena phocoena) under contemporary and future conditions. Location data (>200 tagged individuals) were collected in the southwestern region of the Baltic Sea; one of the fastest-warming semi-enclosed seas in the world. We used the maximum entropy (MaxEnt) algorithm to estimate changes in total area size and overlap of species-specific habitat suitability between 1997-2020 and 2091-2100. Predictor variables included environmental and climate-sensitive oceanographic conditions in the area. Sea-level rise, sea surface temperature, and salinity data were taken from representative concentration pathways [RCPs] scenarios 6.0 and 8.5 to forecast potential climate change effects. Model output suggested that habitat suitability of Baltic gray seals will decline over space and time, driven by changes in sea surface salinity and a loss of currently available haulout sites following sea-level rise in the future. A similar, although weaker, effect was observed for harbor seals, while suitability of habitat for harbor porpoises was predicted to increase slightly over space and time. Inter-specific overlap in highly suitable habitats was also predicted to increase slightly under RCP scenario 6.0 when compared to contemporary conditions, but to disappear under RCP scenario 8.5. Our study suggests that marine predators in the southwestern Baltic Sea may respond differently to future climatic conditions, leading to divergent shifts in habitat suitability that are likely to decrease inter-specific overlap over time and space. We conclude that climate change can lead to a marked redistribution of area use by marine predators in the region, which may influence local food-web dynamics and ecosystem functioning.

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“…In species of pinniped that form breeding colonies on land, pups may be counted during the pupping season from a boat (e.g., Boyd, 1993), from land (e.g., Guinet et al, 1994;Wege et al, 2016), or often most efficiently via aerial surveys (e.g., Russell et al, 2019). Collating data from diverse counting methods may be required (e.g., Galatius et al, 2020). Pup counts or estimates of total pup production are frequently used as indices of relative abundance, especially when considering population trends over time (e.g., Guinet et al, 1994;Shaughnessy et al, 2000;Wege et al, 2016).…”

Section: Pup Countsmentioning

confidence: 99%

Estimating the Abundance of Marine Mammal Populations

et al. 2021

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Motivated by the need to estimate the abundance of marine mammal populations to inform conservation assessments, especially relating to fishery bycatch, this paper provides background on abundance estimation and reviews the various methods available for pinnipeds, cetaceans and sirenians. We first give an “entry-level” introduction to abundance estimation, including fundamental concepts and the importance of recognizing sources of bias and obtaining a measure of precision. Each of the primary methods available to estimate abundance of marine mammals is then described, including data collection and analysis, common challenges in implementation, and the assumptions made, violation of which can lead to bias. The main method for estimating pinniped abundance is extrapolation of counts of animals (pups or all-ages) on land or ice to the whole population. Cetacean and sirenian abundance is primarily estimated from transect surveys conducted from ships, small boats or aircraft. If individuals of a species can be recognized from natural markings, mark-recapture analysis of photo-identification data can be used to estimate the number of animals using the study area. Throughout, we cite example studies that illustrate the methods described. To estimate the abundance of a marine mammal population, key issues include: defining the population to be estimated, considering candidate methods based on strengths and weaknesses in relation to a range of logistical and practical issues, being aware of the resources required to collect and analyze the data, and understanding the assumptions made. We conclude with a discussion of some practical issues, given the various challenges that arise during implementation.

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Grey seal Halichoerus grypus recolonisation of the southern Baltic Sea, Danish Straits and Kattegat

Abstract: BioOne Complete (complete.BioOne.org) is a full-text database of 200 subscribed and open-access titles in the biological, ecological, and environmental sciences published by nonprofit societies, associations, museums, institutions, and presses.

Cited by 24 publications

References 27 publications

The Role of Food Web Interactions in Multispecies Fisheries Management: Bio-economic Analysis of Salmon, Herring and Grey Seal in the Northern Baltic Sea

The Role of Food Web Interactions in Multispecies Fisheries Management: Bio-economic Analysis of Salmon, Herring and Grey Seal in the Northern Baltic Sea

Forecasting shifts in habitat suitability of three marine predators suggests a rapid decline in inter‐specific overlap under future climate change

Estimating the Abundance of Marine Mammal Populations

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