Estimating common dolphin bycatch in the pole-and-line tuna fishery in the Azores

PeerJ

article

Maria João Cruz¹  Miguel Machete²  Gui Menezes¹  Emer Rogan³  Mónica A. Silva² 

[1] Departamento de Oceanografia e Pescas, Universidade dos Açores;MARE—Marine and Environmental Sciences Centre and IMAR—Instituto do Mar, Universidade dos Açores;School of Biological, Earth and Environmental Sciences, University College Cork, Enterprise Centre;Department of Biology, Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution

关键词: Bycatch;    Cetacean conservation;    Fishery interaction;    Statistical modelling;    Delphinus delphis;    Azores;   

DOI  :  10.7717/peerj.4285

学科分类：社会科学、人文和艺术（综合）

来源: Inra

【 摘 要 】

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.

【 授权许可】

CC BY