Entanglement is a costly life-history stage in large whales
Author(s)
van der Hoop, Julie; Corkeron, Peter; Moore, Michael
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Individuals store energy to balance deficits in natural cycles; however, unnatural events can also lead to unbalanced energy budgets. Entanglement in fishing gear is one example of an unnatural but relatively common circumstance that imposes energetic demands of a similar order of magnitude and duration of life-history events such as migration and pregnancy in large whales. We present two complementary bioenergetic approaches to estimate the energy associated with entanglement in North Atlantic right whales, and compare these estimates to the natural energetic life history of individual whales. Differences in measured blubber thicknesses and estimated blubber volumes between normal and entangled, emaciated whales indicate between 7.4 × 10¹⁰ J and 1.2 × 10¹¹ J of energy are consumed during the course to death of a lethal entanglement. Increased thrust power requirements to overcome drag forces suggest that when entangled, whales require 3.95 × 10⁹ to 4.08 × 10¹⁰ J more energy to swim. Individuals who died from their entanglements performed significantly more work (energy expenditure × time) than those that survived; entanglement duration is therefore critical in determining whales’ survival. Significant sublethal energetic impacts also occur, especially in reproductive females. Drag from fishing gear contributes up to 8% of the 4-year female reproductive energy budget, delaying time of energetic equilibrium (to restore energy lost by a particular entanglement) for reproduction by months to years. In certain populations, chronic entanglement in fishing gear can be viewed as a costly unnatural life-history stage, rather than a rare or short-term incident.
Date issued
2017-01Department
Massachusetts Institute of Technology. Department of Biology; Woods Hole Oceanographic InstitutionJournal
Ecology and Evolution
Publisher
Wiley Blackwell
Citation
van der Hoop, Julie; Corkeron, Peter and Moore, Michael. “Entanglement Is a Costly Life-History Stage in Large Whales.” Ecology and Evolution 7, no. 1 (December 2016): 92–106 © 2016 The Authors
Version: Final published version
ISSN
2045-7758