Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores
Small-scale artisanal fisheries can have a significant negative impact in cetacean populations. Cetacean bycatch has been documented in the pole-and-line tuna fishery in the Azores with common dolphins being the species more frequently taken. Based on data collected by observers on ∼50% of vessels o...
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doaj-f7c296bb9aa547d7bb412c090b1eabe02020-11-24T21:54:21ZengPeerJ Inc.PeerJ2167-83592018-02-016e428510.7717/peerj.4285Estimating common dolphin bycatch in the pole-and-line tuna fishery in the AzoresMaria João Cruz0Miguel Machete1Gui Menezes2Emer Rogan3Mónica A. Silva4Departamento de Oceanografia e Pescas, Universidade dos Açores, Horta, Açores, PortugalMARE—Marine and Environmental Sciences Centre and IMAR—Instituto do Mar, Universidade dos Açores, Horta, Açores, PortugalDepartamento de Oceanografia e Pescas, Universidade dos Açores, Horta, Açores, PortugalSchool of Biological, Earth and Environmental Sciences, University College Cork, Enterprise Centre, Distillery Fields, North Mall, Cork, IrelandMARE—Marine and Environmental Sciences Centre and IMAR—Instituto do Mar, Universidade dos Açores, Horta, Açores, PortugalSmall-scale artisanal fisheries can have a significant negative impact in cetacean populations. Cetacean bycatch has been documented in the pole-and-line tuna fishery in the Azores with common dolphins being the species more frequently taken. Based on data collected by observers on ∼50% of vessels operating from 1998 to 2012, we investigate the influence of various environmental and fisheries-related factors in common dolphin bycatch and calculate fleet-wide estimates of total bycatch using design-based and model-based methods. Over the 15-year study dolphin bycatch occurred in less than 0.4% of the observed fishing events. Generalized additive modelling results suggest a significant relationship between common dolphin bycatch and duration of fishing events, sea surface temperature and location. Total bycatch calculated from the traditional stratified ratio estimation approach was 196 (95% CI: 186–205), while the negative binomial GAM estimated 262 (95% CI: 249–274) dolphins. Bycatch estimates of common dolphin were similar using statistical approaches suggesting that either of these methods may be used in future bycatch assessments for this fishery. Our work shows that rates of common dolphin bycatch in the pole-and-line tuna fishery in the Azores are low, despite considerable variations between years. Dolphins caught were released alive although the fate of these individuals is unknown. Continued monitoring will provide a better understanding of dolphin bycatch and more accurate estimates essential in the development of potential mitigation measures.https://peerj.com/articles/4285.pdfBycatchCetacean conservationFishery interactionStatistical modellingDelphinus delphisAzores |
collection |
DOAJ |
language |
English |
format |
Article |
sources |
DOAJ |
author |
Maria João Cruz Miguel Machete Gui Menezes Emer Rogan Mónica A. Silva |
spellingShingle |
Maria João Cruz Miguel Machete Gui Menezes Emer Rogan Mónica A. Silva Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores PeerJ Bycatch Cetacean conservation Fishery interaction Statistical modelling Delphinus delphis Azores |
author_facet |
Maria João Cruz Miguel Machete Gui Menezes Emer Rogan Mónica A. Silva |
author_sort |
Maria João Cruz |
title |
Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores |
title_short |
Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores |
title_full |
Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores |
title_fullStr |
Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores |
title_full_unstemmed |
Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores |
title_sort |
estimating common dolphin bycatch in the pole-and-line tuna fishery in the azores |
publisher |
PeerJ Inc. |
series |
PeerJ |
issn |
2167-8359 |
publishDate |
2018-02-01 |
description |
Small-scale artisanal fisheries can have a significant negative impact in cetacean populations. Cetacean bycatch has been documented in the pole-and-line tuna fishery in the Azores with common dolphins being the species more frequently taken. Based on data collected by observers on ∼50% of vessels operating from 1998 to 2012, we investigate the influence of various environmental and fisheries-related factors in common dolphin bycatch and calculate fleet-wide estimates of total bycatch using design-based and model-based methods. Over the 15-year study dolphin bycatch occurred in less than 0.4% of the observed fishing events. Generalized additive modelling results suggest a significant relationship between common dolphin bycatch and duration of fishing events, sea surface temperature and location. Total bycatch calculated from the traditional stratified ratio estimation approach was 196 (95% CI: 186–205), while the negative binomial GAM estimated 262 (95% CI: 249–274) dolphins. Bycatch estimates of common dolphin were similar using statistical approaches suggesting that either of these methods may be used in future bycatch assessments for this fishery. Our work shows that rates of common dolphin bycatch in the pole-and-line tuna fishery in the Azores are low, despite considerable variations between years. Dolphins caught were released alive although the fate of these individuals is unknown. Continued monitoring will provide a better understanding of dolphin bycatch and more accurate estimates essential in the development of potential mitigation measures. |
topic |
Bycatch Cetacean conservation Fishery interaction Statistical modelling Delphinus delphis Azores |
url |
https://peerj.com/articles/4285.pdf |
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