Spatiotemporal Overlap of Baleen Whales and Krill Fisheries in the Western Antarctic Peninsula Region

Summary

This study examined when and where humpback and minke whales encounter krill fishing operations in the Western Antarctic Peninsula. Researchers tracked 58 humpback whales and 19 minke whales between 2012-2018 using satellite tags, then compared their movements with fishing boat activity and catch records from 2015-2020.Using spatial random forest models, the team mapped where whales forage each month and found substantial overlap with fishing areas, particularly in the Bransfield Strait. Both whales and fishing vessels followed similar seasonal patterns, moving toward coastal waters as the season progressed. The highest overlap occurred in April-May when fishing effort peaked. Throughout the season, humpback whales increasingly concentrated in the Bransfield Strait, while minke whales stayed closer to shore in more limited areas.The findings reveal a critical management problem: current fishing regulations operate across massive areas (658,730 km² Subareas), but whales and fishing boats actually interact in much smaller zones spanning just tens of kilometers. This mismatch means existing protections may be inadequate.The research emphasizes the urgent need for smaller-scale, seasonally adjusted management strategies that respond to the changing patterns of both whale foraging and fishing activities. This becomes increasingly important as whale populations continue recovering and fishing operations expand in Antarctic waters.

For humpback whales (A) and minke whales (B), this shows how whale behavior changed throughout the season. Green areas indicate where whales became less likely to stay in one place for feeding as the season progressed, while other colors show where whales became more likely to concentrate their feeding activities.

Key Findings

Peak whale-fishery overlap occurs in April-May in the Bransfield Strait, where fishing effort and catches reach their highest intensity.

Humpback whales increasingly concentrate in the Bransfield Strait throughout the season, mirroring the spatial patterns of fishing vessels.

Minke whales prefer nearshore bays and sea ice areas, displaying different habitat preferences than humpback whales.

Current CCAMLR management covers massive areas (658,730 km²) while actual whale-fishery interactions occur at much smaller scales of tens of kilometers.

Both whales and fisheries move southwest toward inshore waters as summer progresses.

Voluntary Buffer Zones around penguin colonies protect ~74,160 km² of area that also benefits baleen whales.

Sea surface temperature drives humpback distribution while sea ice presence determines minke whale locations.

Abstract

In Antarctica, abundant consumers rely on Antarctic krill for food, but krill are also the subject of a commercial fishery. The fishery overlaps in time and space with the foraging areas of these consumers, thus potential competition between krill fisheries and krill consumers is a major management concern. The fishery is managed by the Commission for the Conservation of Antarctic Marine Living Resources with an ecosystem approach, according to which fishing should not interfere with either the population growth of krill, or krill-dependent consumers. Krill catches have become increasingly spatially concentrated in a small number of hotspots, raising concerns about how local depletion of krill impacts consumers. Such concentrated fishing demonstrates that there is a mismatch between the spatial and temporal scale at which krill fisheries are currently managed, and that at which fisheries operate and consumers forage. Information on the seasonal dynamics of predator abundance and their foraging behaviour is fundamental to future precautionary management of the krill fishery. We analysed the spatiotemporal distribution of two major krill consumers -- humpback and minke whales -- and that of krill fishing, off the Western Antarctic Peninsula. We used whale tracking data (58 humpback whale tracks and 19 minke whale tracks) to develop spatial random forest models predicting the monthly distribution of whale foraging areas from January-July. Using these predictions, we calculated spatiotemporally-explicit geographic overlap between whales and fisheries, the latter represented by krill fishing effort and catch data. Over the krill fishing season, fishing effort and catch hotspots shifted to the southwest, into the Bransfield Strait where effort and catch was highest. Predicted humpback whale foraging areas increased in the Bransfield Strait over the same period, while predicted minke whale foraging areas showed an opposite trend. For both we predicted a whale-fishing interaction hotspot in the Bransfield Strait, strongest in April and May. Our results illustrate the fine spatial scale of likely interactions between baleen whales and the krill fishery, and their concentration over the season, underlining the need for fishery management more closely aligned to the spatiotemporal scale of likely predator-fishery interactions.

Published in

Frontiers in Marine Science

2022

Authors

Reisinger, R. R., Trathan, P. N., Johnson, C. M., Joyce, T. W., Durban, J. W., Pitman, R. L., Friedlaender, A. S.

Institutions

Ocean and Earth Science, University of Southampton, National Oceanography Centre SouthamptonBritish Antarctic Survey, CambridgeWorld Wide Fund for Nature, AustraliaCurtin University, Centre for Marine Science & TechnologyMarine Mammal Institute, Oregon State UniversityOcean Sciences & Institute for Marine Sciences, University of California Santa Cruz

Methods

DataField

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