DO POSTLARVAL FISHES ASSOCIATED WITH SARGASSUM HABITAT GROW FASTER THAN POSTLARVAE COLLECTED IN OPEN

WATER ?

Jason TilleyBruce ComynsChet RakocinskiHarriet PerryEric Hoffmayer

What is Sargassum?Genus of brown algae with benthic and pelagic formsSargassum natans and S. fluitans are the dominant

pelagic forms in the Atlantic OceanAchieve buoyancy with pneumatocysts, small gas-

filled bladders

Sargassum Distribution

Why is Sargassum important?Important spawning substrateProvides nursery area for pelagic speciesSargassum associated species provide important

prey for tuna, billfish, dolphinfish, wahoo, and amberjack

Species Examined Caranx crysos – blue runner, “hardtail”

4 station pairs (total n=114, 2.89mm-18.75mm) Prognichthys occidentalis – bluntnose flyingfish

5 station pairs (total n=132, 3.04mm-18.72mm) Randomly stratified into 2mm size classes

Caranx crysos Prognichthys occidentalis

Materials and Methods Field Sampling

Surface tows were made using a 1 X 2 m neuston net along Sargassum windrows and at sites approximately 1 nautical mile away

Samples were preserved in 95% ethanol

Materials and Methods Otolith Processing

Sagittal otoliths were removed and sectioned in the transverse plane

Measurements were made along the longest axis from the primordium to each increment

Data Analysis Analysis of covariance (ANCOVA) Important assumptions

Linearity Normal Homoscedastic Parallel slopes

Variables used Fixed factor: Habitat Dependent variables: Distance across one or the three

outermost growth rings Covariate: Otolith radius to the outermost increment

ResultsCaranx crysos

• No significant difference in growth was found between habitats for the station pairs or the pooled data; however, a significant difference in the slopes of the regressions was found for the last three days of growth for one station pair

Sig. = 0.084Sig. = 0.494

ResultsCaranx crysos

• No significant difference in growth was found between habitats for the station pairs or the pooled data; however, a significant difference in the slopes of the regressions was found for the last three days of growth for one station pair

Int. Sig. = 0.016

ResultsPrognichthys occidentalis

• No significant difference in growth was found between habitats for the station pairs or the pooled data; however, a significant difference in the slopes of the regressions was found for the last day of growth for two station pairs and the pooled data

Sig. = 0.20 Int. Sig = 0.018

ResultsPrognichthys occidentalis

• No significant difference in growth was found between habitats for the station pairs or the pooled data; however, a significant difference in the slopes of the regressions was found for the last day of growth for two station pairs and the pooled data

Int. Sig. = 0.027 Int. Sig. = 0.019

Conclusion ANCOVA yielded no significant difference in

growth Very low observed power (max power = 0.636) in

the analysis

Future Directions Currently examining stomach contents for further

comparisons Further sampling to increase sample sizes Alternate data methods (e.g. orthogonal design)

ThanksJim Franks, Read Hendon, William Dempster, Gary Gray, Chris Butler, Richard Waller, Buck Buchanan, William “Corky” Perret, Vernon Asper, Jim Gower, Stephanie King, Gary Borstad, Leslie Brown, Doug Perrine

University of Southern Mississippi - Gulf Coast Research Laboratory

Center for Fisheries Research and DevelopmentUnited States Fish and Wildlife ServiceMississippi Department of Marine ResourcesCaptain and crew of the R.V. Tommy MonroeFishman Forecasting ServiceSouth Atlantic Fishery Management Council Advancing the Science of Limnology and Oceanography National Oceanic and Atmospheric Administration

- Ocean Explorer