Mitigating the impact of longline fisheries on seabirds - learning from the South Georgia case

Lately, in the most varied areas and fields, the impact of human activities on natural ecosystems has been widely discussed. One of these main activities is fisheries. Fisheries are crucial worldwide both economically and socially. Fisheries can be of different types of methods, different gear, more coastal or offshore, and each has distinct impacts. Within this context, we focus on longline fishing, which in addition to the clear impacts associated with the targeted species (target fish species), has been linked to the mortality of a great number of seabirds globally.

In the Southern Ocean, more specifically in South Georgia, longline fishing is well consolidated, having started in the 90's. The target species is the Patagonian toothfish (Dissostichus eleginoides), and squid is commonly used as bait in this fishery. South Georgia is also home to numerous species of seabirds ranging from albatrosses (eg.: black-browed albatross (Thalassarche melanophris), grey-headed albatross (Thalassarche chrysostoma)) to petrels (eg.: Southern giant petrel (Macronectes giganteus), white chinned petrel (Procellaria aequinoctialis)) that breed and feed in the waters around this island. Since the 90s, there has been a decrease in these seabird populations in the region, which was later associated with the fishery. Seabirds were being attracted by the bait, and accidentally getting got caught on the hook and drowning. Nowadays, the seabird mortality by longline fishing in South Georgia is almost zero.

A study performed by British researchers of British Antarctic Survey, addresses what measures have been implemented over the years to mitigate the impacts of longline fishery on these species. To understand the impact of such measures on seabird conservation, the researchers analysed data from 1996, from all vessels operating in the area. These data were collected by fishing observers working for the Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR). Within the measures that contributed to the reduction in seabird mortality, was for example reducing the fishing season to winter months only, as most seabirds reproduce in the summer, thus reducing interaction with fisheries; the placement of the lines at night, as more than 80% of mortality events took place in daylight; and the introduction of suspended objects or streamer lines to prevent seabirds from reaching the bait. Together these and other measures considering the ecology of the seabird species, helped reducing the impact of longline fishery on these seabird populations.

Number of seabirds accidentally killed in the longline Patagonian toothfish fishery at South Georgia (1996 – 2019). Different colours represent different species. Red – White-chinned Petrel; Orange – Black-browed albatross; Light Blue – Grey-headed albatross; Green – Petrels; Dark-Blue – Others. Note: the small graphic is a zoom in of recent years with an adjusted scale.

In 1996 it was estimated that nearly 6,000 seabirds of these species died as a result of the longline fishery. However, in the past few years, that number decreased to less than 50 per year.

Hence, this work carried in the South Georgia longline fishery, show that scientific knowledge together with the knowledge of fisheries and associated gear, make it possible to minimize one of the impacts of longline fishery. Thus, we can continue to learn and evolve, applying the knowledge gained in other marine areas of the world.

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Source: Collins, M. A., et al. Mitigating the impact of longline fisheries on seabirds: Lessons learned from the South Georgia Patagonian toothfish fishery (CCAMLR Subarea 48.3). Marine Policy 131 (2021): 104618. https://doi.org/10.1016/j.marpol.2021.104618

Author: José Abreu