![]() All elasmobranchs possess highly developed liver lipid stores that may help to fuel migration behaviours. Although these movements have been well documented using the current generation of electronic tags as well as isotopic data, the physiology and energetics of these migrations remain challenging to resolve with current technologies.Īs in other long-distance migrants, stored energy rather than locally obtained resources could be a major factor in white shark migration strategy. In the California Current ecosystem, white sharks have been shown to migrate seasonally between highly productive inshore waters, where pinnipeds are a principal food item, and oligotrophic offshore waters, where prey is thought to be scarce. Satellite tagging has revealed extensive movement patterns that involve large-scale trans-oceanic movements coupled with fidelity to coastal foraging sites. Recent studies indicate that white sharks, Carcharadon carcharias, are prodigious migrants. Lipids are usually the preferred energy storage molecules in migrants because of their high-energy density and because they can be synthesized from any type of ingested food. Similarly, European eels ( Anguilla anguilla) require a minimum threshold of body fat content before they embark on their prolonged spawning migrations to the Sargasso Sea. In avian long-distance migrants, for example, the accumulation of stored energy can cause pre-migration body mass to easily surpass twice the normal body weight. Thus, migrants commonly cease to seek resources during their journey, supplanting localized foraging activity with directed movement and relying instead upon stored energy and nutrients to supply the cost of travel. Such behaviours often necessitate long sojourns through suboptimal habitat. ![]() Migration optimizes resource availability by allowing migrants to take advantage of seasonal changes in distant environments. The methods provide a basis for further insights into using electronic tags to reveal the energetic strategies of a wide range of elasmobranchs. These results comprise, to our knowledge, the first assessment of energy storage and budgeting in migrating sharks. ![]() 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. We develop new algorithms to assess body condition, buoyancy and drift rate during drift dives and validate the techniques using a captive white shark. 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. 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. ![]() Such migrants depend on the efficient packaging, storage and utilization of energy to succeed. Many species undertake long-distance annual migrations between foraging and reproductive areas. ![]()
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