Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea
Cod (Gadus morhua) and capelin (Mallotus villosus) are commercially important species with key roles in the Barents Sea ecosystem. Cod is a major predator on capelin, and fluctuations in the capelin stock has influenced growth and reproduction of cod. Cod-capelin population dynamics are central to t...
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Format: | Doctoral or Postdoctoral Thesis |
Language: | English |
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The University of Bergen
2019
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ftunivbergen:oai:bora.uib.no:1956/20890 2023-05-15T14:28:07+02:00 Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea Fall, Johanna 2019-05-27 application/pdf http://hdl.handle.net/1956/20890 eng eng The University of Bergen Paper I: Fall, J., Fiksen, Ø (2020). No room for dessert: a mechanistic model of prey selection in gut-limited predatory fish. Fish and Fisheries 21(1): 63-79. The article is available at: https://hdl.handle.net/1956/23598 Paper II: Fall, J., Ciannelli, L., Skaret, G. & Johannesen, E (2018). Seasonal dynamics of spatial distributions and overlap between Northeast Arctic cod (Gadus morhua) and capelin (Mallotus villosus) in the Barents Sea. PLOS ONE 13(10): e0205921. The article is available in the main thesis. The article is also available at: https://doi.org/10.1371/journal.pone.0205921 Paper III: Fall, J., Johansen GO., Fiksen Ø., Englund G. & Johannesen, E. (In prep). The vertical distribution of pelagic prey affects individual feeding success in a demersal fish predator. The article is not available in BORA. http://hdl.handle.net/1956/20890 Copyright the author. All rights reserved Doctoral thesis 2019 ftunivbergen 2023-03-14T17:42:31Z Cod (Gadus morhua) and capelin (Mallotus villosus) are commercially important species with key roles in the Barents Sea ecosystem. Cod is a major predator on capelin, and fluctuations in the capelin stock has influenced growth and reproduction of cod. Cod-capelin population dynamics are central to the fisheries management of capelin and play an important role in ecosystem models and assessments. The codcapelin interaction has mainly been studied at population level, but variation at smaller scales can have a large influence on population-level processes. In this thesis, I aimed to quantify and explain spatial and temporal variation in the cod-capelin interaction at different scales, with a focus on spatial overlap and consumption. The work combines theoretical modelling with statistical analyses of survey data collected over 12 years in late summer and winter. In Paper 1, we develop optimal foraging models to study individual-level mechanisms of cod prey selection and show that capelin is the most profitable of cod’s many prey species. Under assumptions of active prey search and homogeneous prey distributions, the models predict selective feeding on capelin at a rate that is limited by cod’s digestion rather than prey encounter. However, a comparison with field data revealed that cod’s feeding on capelin varies considerably between individuals. In Paper 2, we analyse cod-capelin spatial distributions with spatially explicit statistical models and identify the main overlap areas in late summer and winter. We find that cod has a weak aggregative response to capelin in both seasons, and that increasing population sizes and water temperatures have influenced a northward shift in the late summer overlap area. In Paper 3, we use statistical models to analyse cod stomach data from the overlap area in late summer. We find that a large proportion of the population-level diet is capelin, but individual consumption is highly variable. Variation in capelin density alone cannot explain variation in cod feeding since cod’s ... Doctoral or Postdoctoral Thesis Arctic Barents Sea Gadus morhua University of Bergen: Bergen Open Research Archive (BORA-UiB) Barents Sea Fish and Fisheries 21 1 63 79 |
institution |
Open Polar |
collection |
University of Bergen: Bergen Open Research Archive (BORA-UiB) |
op_collection_id |
ftunivbergen |
language |
English |
description |
Cod (Gadus morhua) and capelin (Mallotus villosus) are commercially important species with key roles in the Barents Sea ecosystem. Cod is a major predator on capelin, and fluctuations in the capelin stock has influenced growth and reproduction of cod. Cod-capelin population dynamics are central to the fisheries management of capelin and play an important role in ecosystem models and assessments. The codcapelin interaction has mainly been studied at population level, but variation at smaller scales can have a large influence on population-level processes. In this thesis, I aimed to quantify and explain spatial and temporal variation in the cod-capelin interaction at different scales, with a focus on spatial overlap and consumption. The work combines theoretical modelling with statistical analyses of survey data collected over 12 years in late summer and winter. In Paper 1, we develop optimal foraging models to study individual-level mechanisms of cod prey selection and show that capelin is the most profitable of cod’s many prey species. Under assumptions of active prey search and homogeneous prey distributions, the models predict selective feeding on capelin at a rate that is limited by cod’s digestion rather than prey encounter. However, a comparison with field data revealed that cod’s feeding on capelin varies considerably between individuals. In Paper 2, we analyse cod-capelin spatial distributions with spatially explicit statistical models and identify the main overlap areas in late summer and winter. We find that cod has a weak aggregative response to capelin in both seasons, and that increasing population sizes and water temperatures have influenced a northward shift in the late summer overlap area. In Paper 3, we use statistical models to analyse cod stomach data from the overlap area in late summer. We find that a large proportion of the population-level diet is capelin, but individual consumption is highly variable. Variation in capelin density alone cannot explain variation in cod feeding since cod’s ... |
format |
Doctoral or Postdoctoral Thesis |
author |
Fall, Johanna |
spellingShingle |
Fall, Johanna Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
author_facet |
Fall, Johanna |
author_sort |
Fall, Johanna |
title |
Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
title_short |
Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
title_full |
Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
title_fullStr |
Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
title_full_unstemmed |
Drivers of variation in the predator-prey interaction between cod and capelin in the Barents Sea |
title_sort |
drivers of variation in the predator-prey interaction between cod and capelin in the barents sea |
publisher |
The University of Bergen |
publishDate |
2019 |
url |
http://hdl.handle.net/1956/20890 |
geographic |
Barents Sea |
geographic_facet |
Barents Sea |
genre |
Arctic Barents Sea Gadus morhua |
genre_facet |
Arctic Barents Sea Gadus morhua |
op_relation |
Paper I: Fall, J., Fiksen, Ø (2020). No room for dessert: a mechanistic model of prey selection in gut-limited predatory fish. Fish and Fisheries 21(1): 63-79. The article is available at: https://hdl.handle.net/1956/23598 Paper II: Fall, J., Ciannelli, L., Skaret, G. & Johannesen, E (2018). Seasonal dynamics of spatial distributions and overlap between Northeast Arctic cod (Gadus morhua) and capelin (Mallotus villosus) in the Barents Sea. PLOS ONE 13(10): e0205921. The article is available in the main thesis. The article is also available at: https://doi.org/10.1371/journal.pone.0205921 Paper III: Fall, J., Johansen GO., Fiksen Ø., Englund G. & Johannesen, E. (In prep). The vertical distribution of pelagic prey affects individual feeding success in a demersal fish predator. The article is not available in BORA. http://hdl.handle.net/1956/20890 |
op_rights |
Copyright the author. All rights reserved |
container_title |
Fish and Fisheries |
container_volume |
21 |
container_issue |
1 |
container_start_page |
63 |
op_container_end_page |
79 |
_version_ |
1766302250763812864 |