Characterising seabird vessel interactions associated with demersal ocean trawling: vessel attendance by birds depends on intrinsic and extrinsic predictors

Abstract

Seabirds are declining on a global scale, and this trend is concerning as they play an important role in the marine ecosystem. The decline is due to multiple reasons, but harvest fisheries are a major contributor. The impact of fisheries, however, appears to vary; demersal trawlers cause mortality of many birds in some areas and very few in others. Fishery-dependent monitoring is required to understand this impact on seabirds, and particularly to better understand the variable impact of demersal trawling. We employed a targeted observer program to gather data on seabird assemblages, catastrophic interactions with trawl vessels and predictors of vessel attendance by the seabirds. The latter is a useful proxy for catastrophic interactions and provides information on potential mitigation. Throughout the program period, 1040942 seabirds from ~21 species attended New South Wales (NSW) ocean demersal trawlers. These species included 7 species of petrel and albatross listed by the IUCN, including the flesh footed shearwater Ardenna carneipes and wandering albatross Diomedea exulans. Two catastrophic interactions were recorded, and intrinsic and extrinsic predictors of vessel attendance (e.g. offal discharge and wind, respectively) were characterised. The results of the study will provide information to managers, with the goal of ensuring the sustainability of NSW ocean trawling—in particular its coexistence with threatened seabirds. The NSW Ocean Trawl fishery appears to directly harm very few seabirds which is not always the case when considering worldwide trawl fisheries. Predictors of attendance such as space, time and offal discharge can potentially be used to mitigate the attractiveness of trawlers to seabirds.