Stable isotope analysis of vertebrae reveals ontogenetic changes in habitat in an endothermic pelagic shark

Abstract

Ontogenetic changes in habitat are driven by shifting life-history requirements and play an important role in population dynamics. However, large portions of the life history of many pelagic species are still poorly understood or unknown. We used a novel combination of stable isotope analysis of vertebral annuli, Bayesian mixing models, isoscapes and electronic tag data to reconstruct ontogenetic patterns of habitat and resource use in a pelagic apex predator, the salmon shark (Lamna ditropis). Results identified the North Pacific Transition Zone as the major nursery area for salmon sharks and revealed an ontogenetic shift around the age of maturity from oceanic to increased use of neritic habitats. The nursery habitat may reflect trade-offs between prey availability, predation pressure and thermal constraints on juvenile endothermic sharks. The ontogenetic shift in habitat coincided with a reduction of isotopic niche, possibly reflecting specialization upon particular prey or habitats. Using tagging data to inform Bayesian isotopic mixing models revealed that adult sharks primarily use neritic habitats of Alaska yet receive a trophic subsidy from oceanic habitats. Integrating the multiple methods used here provides a powerful approach to retrospectively study the ecology and life history of migratory species throughout their ontogeny.

Trophic structure of a coastal fish community determined with diet and stable isotope analyses

“…This limited size range may contribute to the classification of S . acanthias as a strict piscivore (Munroe et al , ; Carlisle et al , ). Nonetheless, stomach and isotope samples were collected from the same individuals; thus, diet results would be expected to reflect the trophic position derived from nitrogen stable‐isotope analysis.…”

Incorporating stable isotopes into a multidisciplinary framework to improve data inference and their conservation and management application

“…Recently, there has been increased use of stable isotopes in conjunction with other established ecological tools, for example, compound-specific isotope analysis of amino acids (CSIA-AA) (Seminoff et al 2012;Vander Zanden et al 2013;Hussey et al 2015a), fatty acids (Kharlamenko et al 2001;Couturier et al 2013), trace elements (Werry et al 2011;Honda et al 2012), genetics (Clegg et al 2003; Introduction § This article is based on a paper presented at the 'Sharks International 2014' conference, held 2-6 June 2014, Durban, South Africa, and is part of a special issue 'Advances in Shark Research' edited by DA Ebert, C Huveneers and SFJ Dudley Christiansen, Fisk and Hussey 190 Valenzuela et al 2009), telemetry (Cunjak et al 2005;Ceriani et al 2012;Matich and Heithaus 2013;Carlisle et al 2014), and measures of organism condition Gannes et al 1998), to name but a few. This is leading to a multidisciplinary approach that inherently will yield more precise conclusions compared to the use of stable isotopes as a stand-alone tool.…”

Intrapopulation variability in the timing of ontogenetic habitat shifts in sea turtles revealed using δ15N values from bone growth rings

“…; Carlisle et al . ). When the periodicity of an inert tissue's deposition and growth is known (i.e., annual growth layers for bones and teeth), then isotopic patterns from those periods can be used to identify timing of ontogenetic shifts between isotopically distinct regions, providing a useful method by which access life‐history patterns from difficult‐to‐track animals such as marine turtles (Snover et al .…”