There is increasing concern about local krill depletion in the Western Antarctic Peninsula, as fisheries expand and operate in increasingly spatially concentrated hotspots. Simultaneously, populations of several krill consumers are increasing, as they recover from historical overexploitation. The Commission for the Conservation of Antarctic Marine Living Resources (CCAMLR) recognises the need to rely on a small-scale management approach to ensure sustainable exploitation of krill. However, precautionary krill catch limits have been set at a wide spatial scale (658,738.58 km2) for one of the most heavily fished areas, Subarea 48.1 (the Western Antarctic Peninsula).
Using tracking data from 52 humpback whales and 19 minke whales, and AIS from krill trawlers, we assess the spatial scale of their search for krill and quantify their spatiotemporal overlap, from 2012-2018, within the area fished within Subarea 48.1.
First Passage Time analyses revealed similar krill search scales for humpback (20.1 ± 21.2 km) and minke whales (16.7 ± 25.6 km). Search scale was significantly larger for fishing vessels (35.2 ± 46.8 km) than for whales; no significant differences were observed for search scales between traditional and continuous trawlers. Humpback whales had a higher spatial overlap with fishing vessels, suggesting they may be more vulnerable to competition for krill than minke whales.
Our results highlight the extent of interactions between krill, predators and trawlers in Subarea 48.1, and confirm the urgent need to now include baleen whales in precautionary ecosystem-based management and monitoring. We provide information that will help CCAMLR to spatially and temporally sub-divide the precautionary catch limit, within the new candidate Krill Fisheries Management Units, and inform the design of the D1MPA proposal, including seasonal protection zones.