title: Travelling light: white sharks (Carcharodon carcharias) rely on body lipid stores to power ocean-basin scale migration.
abstract: Many species undertake long-distance annual migrations between foraging and reproductive areas. Such migrants depend on the efficient packaging, storage and utilization of energy to succeed. A diverse assemblage of organisms accomplishes this through the use of lipid reserves; yet, it remains unclear whether the migrations of elasmobranchs, which include the largest gill breathers on Earth, depend on such a mechanism. We examine depth records from pop-up satellite archival tags to discern changes in buoyancy as a proxy for energy storage in Eastern Pacific white sharks, and assess whether lipid depletion fuels long-distance (approx. 4000 km) migrations. We develop new algorithms to assess body condition, buoyancy and drift rate during drift dives and validate the techniques using a captive white shark. In the wild, we document a consistent increase in drift rate over the course of all migrations, indicating a decrease in buoyancy caused by the depletion of lipid reserves. These results comprise, to our knowledge, the first assessment of energy storage and budgeting in migrating sharks. The methods provide a basis for further insights into using electronic tags to reveal the energetic strategies of a wide range of elasmobranchs.
authors.affiliation: Hopkins Marine Station, Department of Biology, Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA. gdelraye@hawaii.edu
authors.forename: Gen
authors.initials: G
authors.lastname: Del Raye
authors.forename: Salvador J
authors.initials: SJ
authors.lastname: Jorgensen
authors.forename: Kira
authors.initials: K
authors.lastname: Krumhansl
authors.forename: Juan M
authors.initials: JM
authors.lastname: Ezcurra
authors.forename: Barbara A
authors.initials: BA
authors.lastname: Block
mesh_terms: D000465:Algorithms; D025041:Animal Migration; D000818:Animals; D004734:Energy Metabolism; D050356:Lipid Metabolism; D008962:Models, Theoretical; D009792:Oceans and Seas; D017215:Satellite Communications; D012754:Sharks / Q000378:metabolism / Q000502:physiology*; D014872:Water Movements
keywords: bioenergetics; buoyancy; migration; white shark