Male Antarctic fur seals: neglected food competitors of bioindicator species in the context of an increasing Antarctic krill fishery

Summary

This study examined how male Antarctic fur seals, krill fishing boats, and breeding chinstrap penguins use the same ocean areas and resources in Antarctic waters. Researchers found significant overlap between where male fur seals forage for food, where two different types of fishing vessels catch krill, and where penguins hunt during their breeding season when they must stay close to their chicks.Male fur seals are abundant krill-eating predators, but they are not included in the CCAMLR Ecosystem Monitoring Program that tracks other species like female seals and penguins. The study discovered that different fishing methods operate in distinct patterns across space and time, and that both seals and fishing vessels hunt at similar depths that change with the seasons. This creates a complex, overlapping competition for krill resources.The overlap is especially important during the penguin chick-rearing period, when adult penguins can only make short trips from their nests to find food for their young. The findings suggest that current fisheries management needs a more comprehensive approach that considers how multiple krill consumers—seals, fishing operations, and penguins—interact and potentially compete with each other in the Antarctic ecosystem.

This figure shows how male Antarctic fur seals (panel A, heatmap showing time spent in different areas) overlap with two types of krill fishing gear: continuous pumping trawlers (panel B) and traditional trawlers (panel C) in the western Antarctic Peninsula and Scotia Sea. Panel D reveals the temporal complexity, showing how continuous pumping vessels (red line) move between fishing areas throughout the season, while traditional trawlers (blue line) operate in a more concentrated pattern. The vertical dashed line marks when chinstrap penguin chicks typically leave their nests—a critical period when adult penguins are restricted to short foraging trips near breeding colonies. This overlap creates a complex competitive environment where seals, fishing vessels, and breeding penguins all depend on the same krill resources in overlapping areas and timeframes, highlighting the need for ecosystem-based fisheries management that considers multiple krill consumers.

Key Findings

Male Antarctic fur seals show significant geographic and temporal overlap with the krill fishery

Male fur seals represent an abundant but unmonitored krill predator

Current monitoring programs focus only on breeding female fur seals and penguins

Different fishing gear types (continuous pumping vs. traditional trawls) showed different spatiotemporal patterns

The complex interaction between these predators requires a more holistic approach to fishery management

Abstract

The fishery for Antarctic krill is currently managed using a precautionary, ecosystem-based approach to limiting catch, with performance indices from a long-term monitoring program focused on several krill-dependent predators that are used to track ecosystem health. Concerns over increased fishing in concentrated areas and ongoing efforts to establish a Marine Protected Area along the Peninsula, a key fishing region, is driving the development of an adaptive management system for the fishery. The cumulative effects of fishing effort and interactions among krill-dependent predators and their performance is at present neglected in the CCAMLR Ecosystem Monitoring Program. However, we show considerable overlap between male Antarctic fur seals and the krill fishery in a complex mosaic, suggesting potential for cumulative impacts on other krill dependent predators. A holistic view is required as part of future efforts to manage the krill fishery that incorporates various sources of potential impacts on the performance of bioindicator species, including the fishery and its interactions with various krill dependent predators.

Published in

Scientific Reports

2020

Authors

Lowther, A. D., Staniland, I., Lydersen, C., & Kovacs, K. M.

Institutions

Norwegian Polar InstituteBritish Antarctic Survey

Methods

Biological sampling DataField

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