Selective mortality in juvenile coral reef fish: The role of larval performance and dispersal histories
by Hamilton, Scott L., Ph.D., UNIVERSITY OF CALIFORNIA, SANTA BARBARA, 2007, 150 pages; 3272826

Abstract:

For organisms with complex life cycles, population regulation may occur in a number of different life stages or more importantly at the transition between stages. It has been well established for many terrestrial and aquatic species that early life experiences can carryover to have important ramifications for performance and survival in later life stages. In many coral reef fish, metamorphosis is an energetically costly process and mortality immediately following settlement (i.e., transition from pelagic larvae to demersal juvenile) is intense and potentially selective for individuals with particular traits and/or histories. Given this backdrop, I set out to investigate the role of larval performance on quality at settlement, the effects of spatial variation in density-dependent processes on selective mortality in juveniles, and how larval dispersal history differentially affects larval traits and survival potential in a common coral reef fish, the bluehead wrasse (Thalassoma bifasciatum), on the Caribbean island of St. Croix. By analyzing the lipid content of early post-metamorphic bluehead wrasse, I ascertained that larval growth histories, recorded in otoliths (i.e., ear stone), influenced levels of energy reserves, and I established a long-sought positive relationship between the width of the otolith metamorphic band (i.e., permanent record) and a measure of condition (Chapter 1). Because individuals varied substantially in larval traits at settlement, I set out to investigate the role of predation in influencing selective morality. The probability of survival was well predicted by condition and size at settlement, however, the intensity of phenotypic selection, as densities increased, was mediated by predator abundance and the form of per-capita density-dependent mortality, which differed in consistent ways between two sites on opposite shores of St. Croix (Chapter 2). Lastly, I used techniques in otolith chemistry to identify the effects of nearshore (i.e., high otolith lead content) or offshore (i.e., low otolith lead content) larval residence on larval performance and survival. Surprisingly, offshore developers settled in better condition and survived in greater numbers compared to nearshore self-recruiting fish (Chapter 3). Intense selection for growth and condition occurred primarily in nearshore developers because offshore fish only survived to settlement if they performed well as larvae.

 
AdviserRobert R. Warner
SchoolUNIVERSITY OF CALIFORNIA, SANTA BARBARA
SourceDAI/B 68-07, p. , Nov 2007
Source TypeDissertation
SubjectsEcology; Biological oceanography
Publication Number3272826
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