Dataset: FL Multispecies Otolith Data
Deployment: WS0720

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.