A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland

The Swedish population of great cormorant (Phalacrocorax carbo sinensis) has rapidly increased to over 40 000 breeding couples since the EU-protection 1980. Since the cormorant are high efficient predators living in large colonies, they are accused for reducing fish populations and competing with fi...

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Main Author: Larsson, Anton
Format: Other/Unknown Material
Language:English
Published: SLU/Dept. of Wildlife, Fish and Environmental Studies 2017
Subjects:
Online Access:https://stud.epsilon.slu.se/11054/
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record_format openpolar
spelling ftsluppsalast:oai:stud.epsilon.slu.se:11054 2023-05-15T16:19:19+02:00 A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland Dieten hos storskarv (Phalacrocorax carbo sinensis) på Gotland efter reproduktionssäsongen Larsson, Anton 2017 https://stud.epsilon.slu.se/11054/ eng eng SLU/Dept. of Wildlife, Fish and Environmental Studies https://stud.epsilon.slu.se/11054/ Baltic sea regurgitated pellets otoliths prey species composition sea birds H2 2017 ftsluppsalast 2022-09-10T18:11:15Z The Swedish population of great cormorant (Phalacrocorax carbo sinensis) has rapidly increased to over 40 000 breeding couples since the EU-protection 1980. Since the cormorant are high efficient predators living in large colonies, they are accused for reducing fish populations and competing with fishery. An intense conflict between cormorants, fishery and conservationist has arisen. Cormorants are top predators in the food web. It is therefore essential to attain knowledge regarding their ecological role and fish consumption, to be able to evaluate the effects on the ecosystem, but also to evaluate the competition between cormorants and fishery. This study aims to assess the prey species composition of cormorants on Gotland based on otoliths from regurgitated pellets. 397 pellets were collected and analysed from four different localities, divided into north and south. The pellets together contained 4363 otoliths which were identified to the lowest possible taxon. To correct for biases caused by eroded otoliths, and complete loss of otoliths, size correction factors (SCF) and numerical correction factors (NCF) were applied. Results shows that cod (Gadus morhua), European flounder (Platichthys flesus) and sticklebacks (Gasterosteidae) dominated the diet in the north area, while shorthorned sculpin (Myoxocephalus scorpius), cod and European flounder dominated in the south. The results contribute with valuable information regarding cormorant diet in the Baltic sea. This information increases the understanding how cormorants can affect fish populations and identify possible management measures. To fully evaluate the effects of cormorants on fish populations, ecosystem and fishery, additional studies are necessary. Keywords: Baltic sea, regurgitated pellets, otoliths, prey species composition, sea birds Other/Unknown Material Gadus morhua Swedish University of Agricultural Sciences: Epsilon Archive for Student Projects
institution Open Polar
collection Swedish University of Agricultural Sciences: Epsilon Archive for Student Projects
op_collection_id ftsluppsalast
language English
topic Baltic sea
regurgitated pellets
otoliths
prey species composition
sea birds
spellingShingle Baltic sea
regurgitated pellets
otoliths
prey species composition
sea birds
Larsson, Anton
A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
topic_facet Baltic sea
regurgitated pellets
otoliths
prey species composition
sea birds
description The Swedish population of great cormorant (Phalacrocorax carbo sinensis) has rapidly increased to over 40 000 breeding couples since the EU-protection 1980. Since the cormorant are high efficient predators living in large colonies, they are accused for reducing fish populations and competing with fishery. An intense conflict between cormorants, fishery and conservationist has arisen. Cormorants are top predators in the food web. It is therefore essential to attain knowledge regarding their ecological role and fish consumption, to be able to evaluate the effects on the ecosystem, but also to evaluate the competition between cormorants and fishery. This study aims to assess the prey species composition of cormorants on Gotland based on otoliths from regurgitated pellets. 397 pellets were collected and analysed from four different localities, divided into north and south. The pellets together contained 4363 otoliths which were identified to the lowest possible taxon. To correct for biases caused by eroded otoliths, and complete loss of otoliths, size correction factors (SCF) and numerical correction factors (NCF) were applied. Results shows that cod (Gadus morhua), European flounder (Platichthys flesus) and sticklebacks (Gasterosteidae) dominated the diet in the north area, while shorthorned sculpin (Myoxocephalus scorpius), cod and European flounder dominated in the south. The results contribute with valuable information regarding cormorant diet in the Baltic sea. This information increases the understanding how cormorants can affect fish populations and identify possible management measures. To fully evaluate the effects of cormorants on fish populations, ecosystem and fishery, additional studies are necessary. Keywords: Baltic sea, regurgitated pellets, otoliths, prey species composition, sea birds
format Other/Unknown Material
author Larsson, Anton
author_facet Larsson, Anton
author_sort Larsson, Anton
title A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
title_short A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
title_full A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
title_fullStr A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
title_full_unstemmed A diet study of post-breeding Great cormorants (Phalacrocorax carbo sinensis) on Gotland
title_sort diet study of post-breeding great cormorants (phalacrocorax carbo sinensis) on gotland
publisher SLU/Dept. of Wildlife, Fish and Environmental Studies
publishDate 2017
url https://stud.epsilon.slu.se/11054/
genre Gadus morhua
genre_facet Gadus morhua
op_relation https://stud.epsilon.slu.se/11054/
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