Table of Contents

• Coverage
• Dataset Description
  • Methods & Sampling
  • Data Processing Description
• Data Files
• Related Publications
• Parameters
• Instruments
• Deployments
• Project Information
• Funding

Otolith increment data from five species of coral reef fish collected in the Straits of Florida as 1) larvae in the plankton inside and outside of mesoscales eddies, 2) late-stage larvae over reefs, and 3) juveniles in reef and rubble habitats.

Related publications and references:
Guigand CM, Cowen RK, Llopiz JK, Richardson DE (2005) A coupled asymmetrical multiple opening closing net with environmental sampling system. Mar. Tech. Soc. J 39, 22-24. doi:10.4031/002533205787444042

Shulzitski K, Sponaugle S, Hauff M, Walter K, D’Alessandro EK, Cowen RK (2015) Close encounters with eddies: oceanographic features increase growth of larval reef fishes during their journey to the reef. Biol Lett 20140746. doi:10.1098/rsbl.2014.0746

Shulzitski K, Sponaugle S, Hauff M, Walter K, Cowen RK (2016) Encounter with mesoscale eddies enhances survival to settlement in larval coral reef fishes. PNAS. doi:10.1073/pnas.1601606113

Ichthyoplankton samples were collected during three cruises aboard the R/V Walton Smith: WS-07-14 (May 29 - June 13, 2007), WS-07-20 (July 30 - August 13, 2007), and WS-08-09 (June 17 - July 1, 2008). During each cruise, samples were collected at seven stations along each of six cross-shelf transects spanning the western Straits of Florida. Ichthyoplankton was collected using a modified Multiple Opening Closing Net and Environmental Sensing System (MOCNESS, Guigand et al. 2005). The MOCNESS sampled discrete 20-m depth bins down to 80 m using paired nets (4 m2 and 1 m2) fitted with 1-mm and 150-μm mesh, respectively. All tows were conducted during daylight hours; samples were preserved immediately in 95% ethanol, and transferred to 70% ethanol upon returning to the laboratory. Specimens used in this study were all collected with the large-mesh nets (i.e., 1-mm). During and after the cruises (i.e., June – September 2007; July – September 2008), late-stage larvae and juveniles were sampled from American Shoal (AS) and Looe Key (LK) reefs in the lower Florida Keys. Four replicate light-traps were deployed at each reef 1 m below the surface and 50 m apart. Traps fished from sunset to sunrise during 15-d periods encompassing both the new and third-quarter lunar phases, when most coral reef fishes settle. One week into light-trap sampling, juvenile collections were initiated by SCUBA divers using quinaldine and hand nets.

The investigators followed standard procedures for analyzing otolith microstructure of a subset of fish from five species (Xyrichtys novacula, Thalassoma bifasciatum, Cryptotomus roseus, Sphyraena barracuda, and Stegastes partitus) to obtain individual growth rates and ages. Standard length (SL) or notochord length (NL) was measured to the nearest 0.01 mm for each fish using a Leica MZ12 dissecting microscope, a Cool Snap-Pro monochrome digital camera, and Image-Pro Plus 4.5 image analysis software (Media Cybernetics). Sagittal (X. novacula, T. bifasciatum, and C. roseus) or lapillar (S. partitus) otoliths were dissected from each sample and stored in immersion oil ~7-14 days while lapillar otoliths of S. barracuda were dissected and sectioned to facilitate reading. All otoliths from a given species were analyzed by a single reader. Otoliths were read along the longest axis at 400X magnification (with the exception of S. barracuda lapilli which were read at 1000X magnification) through a Leica DMLB microscope and with the aid of the digital camera and Image-Pro Plus software. All otoliths were read at least twice, and if the reads differed by ≤ 5%, one read was randomly chosen for analysis. If reads differed by > 5%, a third read was conducted. This third read was then compared to the first two reads. If either comparison differed by ≤ 5%, one read from that comparison was randomly chosen for analysis; otoliths where all reads differed by > 5% were removed from any further analysis.

For individuals used in a study to address selective mortality, the investigators provide complete otolith data including increment number, increment width, and otolith radius. For individuals that were only used in a study comparing recent otolith growth between larvae collected inside and outside of mesoscale eddies, the investigators provide a subset of otolith data including larval age, average recent growth, and last otolith radius.

BCO-DMO Processing Notes:
- Modified parameter names to conform with BCO-DMO naming conventions;
- Added the official cruise identifier in the cruise_id column;
- Replaced blanks (missing values) with 'nd' to indicate 'no data';
- Replaced spaces with underscores;
- Replaced "no eddy" with "NE" and "eddy" with "ED" for consistency;
- Formatted dates to mm/dd/yyyy.

Description from NSF award abstract:
This project deals with the important and timely theme of marine population connectivity. The degree to which populations of benthic 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 unfeasible, particularly for marine populations distributed along open coastlines. In addition, ecological population connectivity is not only a function of the physical transport of larvae, but also the interaction of factors influencing larval growth, survival, and condition at settlement. For example, oligotrophic open-ocean environments may lead to slower larval growth, longer pelagic larval durations, and lower survivorship of larvae compared to larvae from nutrient-rich nearshore waters. Data indicate that the relative condition of larvae influences their survival on the reef and the degree to which they contribute to the population. Ultimately, as ocean currents, spawning patterns, larval survivorship, settlement, and their interactions are highly variable, the only method for examining ecological population connectivity over multiple time and space scales in oceanographically complex environments will be data-validated three dimensional biophysical models capable of assessing dispersal outcomes over a wide range of temporal and spatial variation. 

The overall goal of this study is to quantify the relative contributions of upstream (far-field) versus local (near-field) sources of reef fish larvae to the Florida Keys. The proposed study will integrate a comprehensive, three dimensional hydrodynamic model with a Lagrangian particle tracking model to connect the pathways between observed ichthyoplankton distributions and larval settlement.