CAT Scanned Fish
Image showing the otoloith stones in the 3-D scans of the juvenile cobia. (Image credit: Sean Bignami)
Scientists at NOAA’s Atlantic Oceanographic and Meteorological Laboratory and the University of Miami (UM) collaborated to use innovative 3-D technology to determine how changing ocean chemistry could impact cobia, an economically important, pan-tropical fish species. This represents the first time this technology has been applied to fish species, and the protocols developed have opened the doors to similarly study almost any juvenile fish species.
AOML’s new three-dimensional micro-computed tomography technology allowed researchers to peer inside the skeletons of juvenile fish to measure minute changes in the growth and structure. The approach allowed researchers at the University of Miami to document changes in the size and density of small ear stones called otoliths, a structure that traditionally needed to be physically removed to be studied. The extraction process exposes the tiny structure to physical damage and eliminates the possibility of precise observations.
To conduct the experiment, scientists adapted protocols typically used to study changes in coral specimens.Thousands of x-ray images are digitally reconstructed into a three-dimensional image stack. Scientists can then manipulate the 3-D scans to view the specimen from any angle and even zoom in on a particular structure. (Click here to see an example of how scientists view the resulting imagery) This also allows researchers to collect very detailed measurements to document how the specimen is affected by certain environmental changes.
This study considered the impact of ocean acidification on cobia, which shares many life history traits with a diversity of high-value tropical open ocean fishes. Ocean acidification increased the size, density, and mass of otoliths, which could lead to a 50 % increase in hearing range. This may improve detection of some sounds, but could also lead to increased sensitivity to disruptive background noise. Scientists predict that altered hearing may affect larval navigation, dispersal, and population distribution, depending on the species.
This study was led by Sean Bignami, Su Sponaugle, and Robert Cowen at UM's Rosenstiel School of Marine and Atmospheric Science, and Ian Enochs and Derek Manzello with UM's Cooperative Institute for Marine and Atmospheric Studies at NOAA's Atlantic Oceanographic and Meteorological Laboratory. This study is published in the Proceedings of the National Acadmy of Sciences.