AB 13:263-273 (2011)  -  DOI: https://doi.org/10.3354/ab00370

Growth- and size-selective mortality in pelagic ­larvae of a common reef fish

S. Sponaugle1,*, J. N. Boulay2, T. L. Rankin3

1Marine Biology and Fisheries, Rosenstiel School of Marine and Atmospheric Science, University of Miami, 4600 Rickenbacker Cswy., Miami, Florida 33149, USA
2Present address: Department of Biology, The Pennsylvania State University, 213 Mueller Laboratory, University Park, Pennsylvania 16802, USA
3Present address: Office of Habitat Conservation, Habitat Protection Division, 1315 East-West Highway, SSMC3, 14th Floor F/HC2, Silver Spring, Maryland 20910, USA

ABSTRACT: Larvae of most aquatic species experience high mortality in the plankton and where traits are naturally variable, mortality can be selective. We tested the hypothesis that reef fish larvae with faster growth rates and larger size-at-age will be more likely to survive the pelagic larval period. We examined the otolith microstructure of larval bluehead wrasse Thalassoma bifasciatum collected across the Straits of Florida to obtain daily growth rates and relative size-at-age. Using a cross-sectional approach, we compared these traits between 2 larval age groups (young larvae: 18 to 26 d old, survivors: 27 to 36 d old) to determine whether mean traits varied with age. In contrast to expectations, survivors had slower early growth and were smaller-at-age than the young larvae, suggesting that faster growing, larger individuals were selectively removed from the population over time. To examine the role of water masses, we estimated maximum upstream larval positions. Differential current speeds across the Straits of Florida resulted in substantial overlap in back-estimated upstream locations of larvae at younger ages, suggesting that differences in early growth environments were unlikely the cause of the observed patterns. Instead, the most parsimonious explanation is the selective loss of fast-growing, large-at-age larvae in the plankton. Shifts in the direction of selective pressures across stages may contribute to the maintenance of high plasticity in the early life history traits of this species. 

KEY WORDS: Larval growth · Straits of Florida · Growth−mortality hypothesis

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Cite this article as: Sponaugle S, Boulay JN, Rankin TL (2011) Growth- and size-selective mortality in pelagic ­larvae of a common reef fish. Aquat Biol 13:263-273. https://doi.org/10.3354/ab00370

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