Agreement on the Conservation of Albatrosses and Petrels

Modelling seabird bycatch vulnerability in pelagic longline fisheries

A Wandering Albatross lands behind a fishing vessel; artwork by Maureen Bennetts, after a photograph by Dimas Gianuca

Can Zhou (Texas A&M University, College Station, USA) and Nigel Brothers have published in the journal Bird Conservation International on assessing bycatch in pelagic longline fisheries by recording seabird interactions.

The paper’s abstract follows:

“The incidental mortality of seabirds in fisheries remains a serious global concern. Obtaining unbiased and accurate estimates of bycatch rates is a priority for seabird bycatch mitigation and demographic research. For measuring the capture risk of seabird interactions in fisheries, the rate of carcass retrieval from hauled gear is commonly used. However, reliability can be limited by a lack of direct capture observations and the substantial pre-haul bycatch losses known to occur, meaning incidence of seabird bycatch is underestimated. To solve this problem, a new measure (bycatch vulnerability) that links an observed interaction directly to the underlying capture event is proposed to represent the capture risk of fishery interactions by seabirds. The new measure is not affected by subsequent bycatch loss. To illustrate how to estimate and analyse bycatch vulnerability, a case study based on a long-term dataset of seabird interactions and capture confirmation is provided. Bayesian modelling and hypothesis testing were conducted to identify important bycatch risk factors. Competition was found to play a central role in determining seabird bycatch vulnerability. More competitive environments were riskier for seabirds, and larger and thus more competitive species were more at risk than smaller sized and less competitive species. Species foraging behaviour also played a role. On the other hand, no additional effect of physical oceanic condition and spatio-temporal factors on bycatch vulnerability was detected. Bycatch vulnerability is recommended as a replacement for the commonly used bycatch rate or carcass retrieval rate to measure the capture risk of an interaction. Combined with a normalized contact rate, bycatch vulnerability offers an unbiased estimate of seabird bycatch rate in pelagic longline fisheries.”

Read a related paper by the same authors.

With thanks to Nigel Brothers.


Zhou, C. & Brothers, N. 2021.  Seabird bycatch vulnerability in pelagic longline fisheries based on modelling of a long-term dataset.  Bird Conservation International Cooper, ACAP Information Officer, 13 March 2021