An investigation of factors related to the bycatch of small cetaceans in fishing gear
The bycatch of cetaceans in fishing gear is considered to be one of the biggest conservation threats to these species. Gear modifications have the potential to reduce these bycatches in global fisheries but there is little available information on how such modifications may change the fishing perfor...
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2011
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ftstandrewserep:oai:research-repository.st-andrews.ac.uk:10023/1888 2023-07-02T03:32:29+02:00 An investigation of factors related to the bycatch of small cetaceans in fishing gear Mackay, Alice I. Northridge, Simon P. Hammond, Philip S. Natural Environment Research Council (NERC) Great Britain. Department for Environment, Food & Rural Affairs (DEFRA) v, 317 p. 2011-06-22T11:57:34Z application/pdf http://hdl.handle.net/10023/1888 en eng University of St Andrews The University of St Andrews Sea Mammal Research Unit, Scottish Oceans Institute uk.bl.ethos.552589 http://hdl.handle.net/10023/1888 Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ Incidental capture Bycatch Cetacean Harbour porpoise PAM Gillnet Fisheries Trawl SH344.6G5M5 Gillnetting--Bycatches Fisheries--Equipment and supplies Cetacea--Conservation Thesis Doctoral PhD Doctor of Philosophy 2011 ftstandrewserep 2023-06-13T18:29:16Z The bycatch of cetaceans in fishing gear is considered to be one of the biggest conservation threats to these species. Gear modifications have the potential to reduce these bycatches in global fisheries but there is little available information on how such modifications may change the fishing performance of gear, or indeed the behavior of cetaceans interacting with fishing gear. Generalized linear models (GLMs) were used to identify factors related to cetacean bycatches in UK bottom set gillnets. Rigged net height had a significant positive relationship with harbour porpoise (Phocoena phocoena) bycatch in ICES Area VII suggesting that lowering the profile of gillnets may have the potential to reduce bycatch rates. Modifications to gillnets, such as changing the amount of floatation or increasing the density of the meshes, were found to have significant effects on the active fishing heights of these nets. However, results from a bycatch mitigation trial in Argentina showed that the reduced fishing profile of one experimental net did not result in a concurrent reduction in the bycatch rate of Franciscana dolphins (Pontoporia blainvillei). While there was no significant difference in the rate, length or intensity of harbour porpoise encounters in the presence or absence of gillnets, the proportion of fast echolocation click trains were significantly higher when a net was present, indicating that porpoises either increased acoustic inspection of the net or foraging in the vicinity of the net. An analysis of underwater video footage collected inside trawl nets in an Australia fishery showed that bottlenose dolphins (Tursiops sp.) were present inside nets more frequently than they were caught and were actively foraging inside these nets. The orientation of dolphins inside these nets indicates that the current design of excluder devices used in this fishery could be improved to further reduce bycatch rates. Doctoral or Postdoctoral Thesis Harbour porpoise Phocoena phocoena University of St Andrews: Digital Research Repository Argentina |
institution |
Open Polar |
collection |
University of St Andrews: Digital Research Repository |
op_collection_id |
ftstandrewserep |
language |
English |
topic |
Incidental capture Bycatch Cetacean Harbour porpoise PAM Gillnet Fisheries Trawl SH344.6G5M5 Gillnetting--Bycatches Fisheries--Equipment and supplies Cetacea--Conservation |
spellingShingle |
Incidental capture Bycatch Cetacean Harbour porpoise PAM Gillnet Fisheries Trawl SH344.6G5M5 Gillnetting--Bycatches Fisheries--Equipment and supplies Cetacea--Conservation Mackay, Alice I. An investigation of factors related to the bycatch of small cetaceans in fishing gear |
topic_facet |
Incidental capture Bycatch Cetacean Harbour porpoise PAM Gillnet Fisheries Trawl SH344.6G5M5 Gillnetting--Bycatches Fisheries--Equipment and supplies Cetacea--Conservation |
description |
The bycatch of cetaceans in fishing gear is considered to be one of the biggest conservation threats to these species. Gear modifications have the potential to reduce these bycatches in global fisheries but there is little available information on how such modifications may change the fishing performance of gear, or indeed the behavior of cetaceans interacting with fishing gear. Generalized linear models (GLMs) were used to identify factors related to cetacean bycatches in UK bottom set gillnets. Rigged net height had a significant positive relationship with harbour porpoise (Phocoena phocoena) bycatch in ICES Area VII suggesting that lowering the profile of gillnets may have the potential to reduce bycatch rates. Modifications to gillnets, such as changing the amount of floatation or increasing the density of the meshes, were found to have significant effects on the active fishing heights of these nets. However, results from a bycatch mitigation trial in Argentina showed that the reduced fishing profile of one experimental net did not result in a concurrent reduction in the bycatch rate of Franciscana dolphins (Pontoporia blainvillei). While there was no significant difference in the rate, length or intensity of harbour porpoise encounters in the presence or absence of gillnets, the proportion of fast echolocation click trains were significantly higher when a net was present, indicating that porpoises either increased acoustic inspection of the net or foraging in the vicinity of the net. An analysis of underwater video footage collected inside trawl nets in an Australia fishery showed that bottlenose dolphins (Tursiops sp.) were present inside nets more frequently than they were caught and were actively foraging inside these nets. The orientation of dolphins inside these nets indicates that the current design of excluder devices used in this fishery could be improved to further reduce bycatch rates. |
author2 |
Northridge, Simon P. Hammond, Philip S. Natural Environment Research Council (NERC) Great Britain. Department for Environment, Food & Rural Affairs (DEFRA) |
format |
Doctoral or Postdoctoral Thesis |
author |
Mackay, Alice I. |
author_facet |
Mackay, Alice I. |
author_sort |
Mackay, Alice I. |
title |
An investigation of factors related to the bycatch of small cetaceans in fishing gear |
title_short |
An investigation of factors related to the bycatch of small cetaceans in fishing gear |
title_full |
An investigation of factors related to the bycatch of small cetaceans in fishing gear |
title_fullStr |
An investigation of factors related to the bycatch of small cetaceans in fishing gear |
title_full_unstemmed |
An investigation of factors related to the bycatch of small cetaceans in fishing gear |
title_sort |
investigation of factors related to the bycatch of small cetaceans in fishing gear |
publisher |
University of St Andrews |
publishDate |
2011 |
url |
http://hdl.handle.net/10023/1888 |
op_coverage |
v, 317 p. |
geographic |
Argentina |
geographic_facet |
Argentina |
genre |
Harbour porpoise Phocoena phocoena |
genre_facet |
Harbour porpoise Phocoena phocoena |
op_relation |
uk.bl.ethos.552589 http://hdl.handle.net/10023/1888 |
op_rights |
Creative Commons Attribution-NonCommercial-NoDerivs 3.0 Unported http://creativecommons.org/licenses/by-nc-nd/3.0/ |
_version_ |
1770272080146726912 |