Linkages between larvae and recruitment of coral reef fishes along the Florida Keys Shelf: an integrated field and modeling analysis of population connectivity in a complex system (2006-2011)

green razorfishThe degree to which populations of marine organisms are connected via the dispersal of larval propagules is a central unanswered ecological and oceanographic question. The complex oceanography of marine systems, and high mortality and diffuse concentrations of larvae make direct measurement of larval sources generally not feasible, particularly for marine populations distributed along open coastlines. Furthermore, ecological population connectivity is not only a function of the physical transport of the larvae, but also the interaction of factors influencing larval growth, survival, and condition at settlement (Pineda et al. 2007; Cowen & Sponaugle 2009).

Our recent research into connectivity of reef fishes in the Florida Keys entailed a collaborative, interdisciplinary NSF-sponsored project that integrated intensive field sampling with biophysical modeling to define dispersal kernels for reef fish populations in an oceanographically dynamic regions. We linked high-resolution shipboard ichthyoplankton and physical oceanographic sampling along and upstream of the Florida Keys to simultaneous reef-based sampling of larval supply and juvenile recruitment. For her dissertation, Kathryn Shulzitski examined the distributions of fish larvae along the Florida Keys and found significant differences in the growth of larvae collected from within vs. outside of mesoscale eddies (Shulzitski et al. 2015) as well as their preferential success during settlement (Shulzitski et al. in prep). Evan D’Alessandro also “tracked” larval cohorts of commercially important fish from the pelagic realm to nearshore reefs through the analysis of their otolith growth trajectories (D’Alessandro et al. 2013). Martha Hauff further compared larval growth and condition indices of fish larvae with distance from shore, finding that nearshore larvae grow faster and are of higher condition than those collected offshore (Hauff et al. in prep.). Several undergraduates also used otolith analysis to examine spatial and temporal patterns in growth (and selective mortality) of larval reef fish and clupeids (Lisa Havel, Jennifer Boulay, Kayelyn Simmons, Jared Robbins). Empirical data were incorporated into a coupled biophysical model (a comprehensive three-dimensional hydrodynamic model that acquires high resolution current dadta from a nested ocean circulation model, which was run iteratively to quantify the probabilities that larvae settling to the Florida Keys were sourced from local versus upstream sources (Sponaugle et al. 2012a).

fish trackingOther lab research supported by this project include a blue-water field study of the orientation and navigation abilities of a coral reef fish (Huebert & Sponaugle 2009), and an experimental analysis of nighttime predation on settling fish larvae (D’Alessandro & Sponaugle 2011). Continuation of our monthly reef fish recruitment survey through 2010 comprised a 7-yr baseline time series on recruitment magnitude and timing and enabled us to compare recruitment to reserves and non-reserves for a suite of reef fish species (Sponaugle et al. 2012b). Additional publications from this project are forthcoming.

PIs on this project were Robert Cowen, Su Sponaugle, Claire Paris, and Villy Kourafalou. Field, laboratory, and shipboard efforts were coordinated by Senior Research Associates Cedric Guigand and Kristen Delano Walter, and Morgan Witman, a high school science teacher, was selected by the National Science Foundation ARMADA program to participate in our second 2007 cruise. Her experience is fully documented in her online journal at http://www.armadaproject.org/journals/2007-2008/hardwick-witman/7-29-30.htm.

Physical oceanographic data are available at http://data.nodc.noaa.gov/cgi-bin/iso?id=gov.noaa.nodc:0066847. Biological data are archived at http://www.bco-dmo.org/dataset/529658