Northwest Fisheries Science Center

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Document Type: Journal Article
Center: NWFSC
Document ID: 8594
Title: Risky business for a juvenile marine predator? Testing the influence of foraging strategies on size and growth rate under natural conditions
Author: Nigel Hussey, Joey DiBattista, Jonathan W. Moore, E. J. Ward, Aaron Fisk, Steven Kessel, Tristan Guttridge, Kevin Feldheim, Brian Franks, Samuel Gruber, Ornelia Weideli, Demian Chapman
Publication Year: 2017
Journal: Proceedings of the Royal Society of London. Series B
Keywords: stable isotopes,Carbon,maladaptive genes,juvenile growth,lemon shark,local adaptation,
Abstract:

Mechanisms driving selection of body size and growth rate in wild marine vertebrates are poorly understood limiting our knowledge of their fitness costs at ecological, physiological and genetic scales. Here, we indirectly test selection for size related traits of juvenile sharks that inhabit a nursery hosting two dichotomous habitats, protected mangroves and exposed seagrass beds, each with low and high inherent predation risk. Juvenile sharks displayed a continuum of foraging strategies between mangrove and seagrass areas, with individuals preferentially feeding in one habitat over another. Foraging habitat was correlated with growth rate, whereby slower growing, smaller individuals fed predominantly in sheltered mangroves, whereas larger, faster growing animals fed over exposed seagrass. These data provide evidence for variable body size trait trajectories amongst juveniles within the nursery that do not satisfy the phenotypic optimum, which means selection can favour smaller size and slower growth rate. The direction of body size trait selection under natural conditions is likely more plastic than currently assumed and may be a critical to adaptation within predator driven ecosystems.

Theme: Recovery and rebuilding of marine and coastal species
Foci: Characterize the population biology of species, and develop and improve methods for predicting the status of populations.
Develop methods to use physiological, biological and behavioral information to predict population-level processes.