Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea
Incidental catch, or bycatch, of harbour porpoise (Phocoena phocoena) in fishing operations is an international conservation issue. The main objective of this thesis was to develop methods for determining the impact of bycatch on the state and dynamics of porpoise populations and for calculating byc...
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University of St Andrews
2009
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/715 2023-07-02T03:32:29+02:00 Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea Winship, Arliss Hammond, Philip S. xxvi + 243 2009-06-18T16:18:58Z 15880357 bytes application/pdf http://hdl.handle.net/10023/715 en eng University of St Andrews The University of St Andrews uk.bl.ethos.552235 http://hdl.handle.net/10023/715 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ Bycatch Conservation Harbour porpoise Management Modelling Phocoena phocoena QL737.C434W5 Bycatches (Fisheries)--North Sea Phocoena--Conservation--North Sea Animal populations--Mathematical models Fishery management Thesis Doctoral PhD Doctor of Philosophy 2009 ftstandrewserep 2023-06-13T18:26:58Z Incidental catch, or bycatch, of harbour porpoise (Phocoena phocoena) in fishing operations is an international conservation issue. The main objective of this thesis was to develop methods for determining the impact of bycatch on the state and dynamics of porpoise populations and for calculating bycatch limits that will achieve conservation objectives in the future. I applied these methods to the North Sea as a case study. First, I analysed sighting rates of harbour porpoise on seabird surveys in the North Sea during 1980-2003 to determine whether these data could provide informative time-series of relative abundance. Some general patterns and trends in sighting rates were consistent with previous studies. However, the standardised indices of abundance were relatively imprecise and thus have limited value for a monitoring framework that relies on statistical detection of trends. Second, I used a population model to integrate available data on harbour porpoise in the North Sea and to assess the dynamics of the population during 1987-2005. There was a high probability that bycatch resulted in a decrease in abundance. The estimated life history parameters suggested a limited scope for population growth even in the absence of bycatch. The model and data were not informative about maximum population growth rate or carrying capacity. The model suggested that dispersal was the most plausible explanation for observed changes in distribution within the North Sea. Third, I considered management procedures for calculating bycatch limits. I performed simulations to compare the behaviour of the procedures, to tune the procedures to specific conservation objectives and to test the robustness of the procedures to a range of uncertainties regarding population dynamics and structure, the environment, observation and implementation. Preliminary annual bycatch limits for harbour porpoise in the North Sea ranged from 187-1685 depending on the procedure, tuning and management areas used. Doctoral or Postdoctoral Thesis Harbour porpoise Phocoena phocoena University of St Andrews: Digital Research Repository |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
Bycatch Conservation Harbour porpoise Management Modelling Phocoena phocoena QL737.C434W5 Bycatches (Fisheries)--North Sea Phocoena--Conservation--North Sea Animal populations--Mathematical models Fishery management |
spellingShingle |
Bycatch Conservation Harbour porpoise Management Modelling Phocoena phocoena QL737.C434W5 Bycatches (Fisheries)--North Sea Phocoena--Conservation--North Sea Animal populations--Mathematical models Fishery management Winship, Arliss Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
topic_facet |
Bycatch Conservation Harbour porpoise Management Modelling Phocoena phocoena QL737.C434W5 Bycatches (Fisheries)--North Sea Phocoena--Conservation--North Sea Animal populations--Mathematical models Fishery management |
description |
Incidental catch, or bycatch, of harbour porpoise (Phocoena phocoena) in fishing operations is an international conservation issue. The main objective of this thesis was to develop methods for determining the impact of bycatch on the state and dynamics of porpoise populations and for calculating bycatch limits that will achieve conservation objectives in the future. I applied these methods to the North Sea as a case study. First, I analysed sighting rates of harbour porpoise on seabird surveys in the North Sea during 1980-2003 to determine whether these data could provide informative time-series of relative abundance. Some general patterns and trends in sighting rates were consistent with previous studies. However, the standardised indices of abundance were relatively imprecise and thus have limited value for a monitoring framework that relies on statistical detection of trends. Second, I used a population model to integrate available data on harbour porpoise in the North Sea and to assess the dynamics of the population during 1987-2005. There was a high probability that bycatch resulted in a decrease in abundance. The estimated life history parameters suggested a limited scope for population growth even in the absence of bycatch. The model and data were not informative about maximum population growth rate or carrying capacity. The model suggested that dispersal was the most plausible explanation for observed changes in distribution within the North Sea. Third, I considered management procedures for calculating bycatch limits. I performed simulations to compare the behaviour of the procedures, to tune the procedures to specific conservation objectives and to test the robustness of the procedures to a range of uncertainties regarding population dynamics and structure, the environment, observation and implementation. Preliminary annual bycatch limits for harbour porpoise in the North Sea ranged from 187-1685 depending on the procedure, tuning and management areas used. |
author2 |
Hammond, Philip S. |
format |
Doctoral or Postdoctoral Thesis |
author |
Winship, Arliss |
author_facet |
Winship, Arliss |
author_sort |
Winship, Arliss |
title |
Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
title_short |
Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
title_full |
Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
title_fullStr |
Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
title_full_unstemmed |
Estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the North Sea |
title_sort |
estimating the impact of bycatch and calculating bycatch limits to achieve conservation objectives as applied to harbour porpoise in the north sea |
publisher |
University of St Andrews |
publishDate |
2009 |
url |
http://hdl.handle.net/10023/715 |
op_coverage |
xxvi + 243 |
genre |
Harbour porpoise Phocoena phocoena |
genre_facet |
Harbour porpoise Phocoena phocoena |
op_relation |
uk.bl.ethos.552235 http://hdl.handle.net/10023/715 |
op_rights |
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ |
_version_ |
1770272077098516480 |