We are actively investigating the physical processes contributing to the recruitment of fishes to the Florida Keys . Although the Florida Keys is the only coral reef system in the contiguous U.S. , very little is known about how populations of reef organisms are replenished and sustained over time. We have conducted a series of near-reef plankton tows and light trap sampling along the Florida Keys which have shown that (1) near-reef larval fish assemblages differ markedly from offshore assemblages and their abundance is strongly event-related ( Sponaugle et al. 2003 ), and (2) very large multi-taxa pulses of settlement stage fish occur in association with the nearshore passage of mesoscale Florida Current eddies (Sponaugle et al. in revision). We have continued these efforts with expanded biophysical sampling in 2002 and 2003 (see MS research of Evan D'Alessandro), and new sampling programs are being developed for the future.
Without fundamental data on patterns of recruitment, it is difficult to examine the underlying processes creating such pattern. My lab began a year-round monthly reef fish recruitment survey in 2003, which I hope will form the start of a long-term data set. Monthly surveys are conducted across the upper Florida Keys shelf encompassing replicate fringing reef, patch reef, seagrass, and mangrove sites. Students are incorporating the recruitment dynamics of particular species into their research (see PhD research of Michelle Paddack) and comparing recruitment among protected and non-protected sites in the Florida Keys National Marine Sanctuary (see PhD research of Kirsten Grorud Colvert).
A recent collaborative National Sea Grant project with Simon Thorrold (WHOI), Jon Hare (NOAA Beaufort Lab), Luiz Barbieri (FMRI) and Bob Cowen is designed to determine the larval sources and essential fish habitat of the gray snapper along the southeast US coast. Using a combination of otolith increment analysis and microchemistry (elemental profiles), we are tracking larval dispersal pathways from spawning aggregations to settlement in nursery areas. Results of this project will shed light on population connectivity, which is a major area of interest in the field of marine ecology. The otolith aging work was part of the MS research of Kelly Denit ( Denit & Sponaugle 2004 );
A collaborative Sea Grant funded project with Jiangang Luo (RSMAS) and Joe Serafy (NOAA/NMFS Miami Lab) is focused on the older stages of snapper and involves tracking the diel, seasonal, and ontogenetic movement of gray snapper among nearshore habitats of the Florida Keys . We are using conventional, acoustic, and archival tagging techniques to track snapper within and among mangroves, seagrasses, and coral reefs near Biscayne Bay .
Larval growth and survivorship
Successful settlement of reef fishes is more than successful larval transport between spawning sites and juvenile habitat. My lab is actively involved in quantifying aspects of larval growth and survivorship for several model reef fishes. The analysis of fish otoliths is a central tool in this research as a method for comparing relative growth rates and condition among individuals. Building upon previous work on the relationship between variation in early life history traits and survival of fishes in Barbados ( Searcy & Sponaugle 2000, 2001 ), and the effect of distinct physical oceanographic features on larval growth and transport ( Sponaugle & Pinkard 2004a, b ), we have been investigating natural variability in early life history traits and the consequences of that variability to recruitment, early juvenile growth and survival of fishes in the Florida Keys.
A relatively new avenue of research is my collaboration in a NSF-sponsored interdisciplinary study of the transport, growth, and fate of billfish larvae in the highly dynamic Florida Straits (see Cowen webpage for more detail). My component of the project involves larval otolith aging to determine larval pathways as well as measurement of habitat-specific growth rates to examine the relative contributions of pelagic habitats to the growth and survival of these important oceanic predators. Our initial aging work of larval blue marlin demonstrates that larvae in Exuma Sound , Bahamas , grow significantly faster than larvae in the Straits of Florida (Sponaugle et al. in revision).
One component of the NSF-sponsored reef fish project is the investigation of how recruitment and early survival are influenced by variation in the local abundance of predators, as occurs in predator-rich marine protected areas. In addition to field sampling, my PhD student, Kirsten Grorud Colvert, is conducting a series of mesocosm and laboratory experiments to quantify the influence of predation on trait selection in young reef fishes (see research of Kirsten Grorud Colvert).
An essential component of larval reef fish transport and survival is their capacity for active behavior. My PhD student, Klaus Huebert, has begun a series of experiments to examine the behavioral capabilities of larvae as they near settlement. Initial experiments with larvae caught at sea have generated interesting results and additional work is planned using hatchery-reared larvae (see research of Klaus Huebert)