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Marine Ecology Progress Series

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MEPS 525:217-228 (2015)  -  DOI:

Reconstructing habitat use by juvenile salmon sharks links upwelling to strandings in the California Current

Aaron B. Carlisle1,*, Steven Y. Litvin1, Elliott L. Hazen2, Daniel J. Madigan3, Kenneth J. Goldman4, Robert N. Lea5, Barbara A. Block1

1Hopkins Marine Station of Stanford University, 120 Oceanview Boulevard, Pacific Grove, CA 93950, USA
2Environmental Research Division, NOAA Southwest Fisheries Science Center, 1352 Lighthouse Avenue, Pacific Grove, CA 93950, USA
3School of Marine and Atmospheric Sciences, Stony Brook University, Stony Brook, NY 11794, USA
4Alaska Department of Fish and Game, 3298 Douglas Place, Homer, AK 99603, USA
5Marine Region, California Department of Fish and Wildlife, 20 Lower Ragsdale Drive, Suite 100, Monterey, CA 93940, USA
*Corresponding author:

ABSTRACT: The use of nursery areas by elasmobranchs is an important life history strategy that is thought to reduce juvenile mortality and increase population growth rates. The endothermic salmon shark Lamna ditropis uses the California Current System (CCS) as a nursery area, though little is known about how juveniles use this ecosystem. Juvenile salmon sharks consistently strand along the west coast of North America. Strandings in the southern CCS occurred throughout the year, while those in the northern CCS were limited to summer and autumn, when mean sea surface temperatures were warmest. Strandings primarily occurred when water temperature was between 12 and 16°C, suggesting that juveniles occupy a relatively narrow thermal niche. Stable isotope analysis (SIA) indicated that juveniles primarily feed on offshore meso- and epipelagic prey from the outer shelf, slope, and oceanic habitats as opposed to inshore and coastal habitats, although sharks appeared to move closer to shore prior to stranding. Generalized additive models indicate that the probability of stranding was greatest when mean water temperatures were relatively high (~14°C) and sharks were exposed to acute cold-water events (~9°C) during coastal upwelling. This suggests that juveniles are thermally limited and stressed by upwelling events, resulting in bacterial infections that are the proximate cause of the strandings.

KEY WORDS: Trophic ecology · Oceanography · Thermal niche · Elasmobranch · Nursery · Stable isotope analysis · Lamna ditropis

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Cite this article as: Carlisle AB, Litvin SY, Hazen EL, Madigan DJ, Goldman KJ, Lea RN, Block BA (2015) Reconstructing habitat use by juvenile salmon sharks links upwelling to strandings in the California Current. Mar Ecol Prog Ser 525:217-228.

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