Putting it to Work: New Publication from the Grouper Moon Project

Diver-based fish length surveys conducted by REEF volunteers and Grouper Moon scientists were used in the study published earlier this year. Photo by Phil Bush.

We are proud to share the latest publication to result from REEF's programs - the paper, titled "Hydroacoustics for the discovery and quantification of Nassau Grouper (Epinephelus striatus) spawning aggregations" was published in the scientific journal Coral Reefs earlier this year. The Grouper Moon Project is always looking for new and/or better ways of accurately estimating the number of spawning Nassau Grouper at the aggregation sites being monitored. In 2014, we tested the use of a split-beam echosounder as a tool for surveying the abundance and size of fish at the aggregation site; the results of the study are detailed in this peer-reviewed paper. We found that the echosounder performs fairly well at providing an index of abundance, although the absolute accuracy of the method was not sufficient to replace other survey methods (e.g. mark and recapture monitoring). After calibrating the method with diver-based fish length surveys, the tool was able to accurately capture estimates of aggregating fish sizes. Surveys on all 3 islands (Little Cayman, Cayman Brac, and Grand Cayman) showed that the average size of Nassau Grouper on Little Cayman was significantly larger than on both Brac and Grand. Furthermore, the sizes of Nassau Grouper on Brac and Grand were not significantly different. Based on this study, the echosounder is a potentially useful tool for surveying aggregations, but is likely best used to complement more intensive diver-based survey methods.

Grouper Moon researchers, Dr. Brice Semmens and Dr. Scott Heppell, along with our colleague from Cayman Islands Department of Environment, Croy McCoy, were co-authors on the paper. You can find a link to this paper, along with information on all publications that have resulted from REEF's programs can be found at www.REEF.org/db/publications.

Design by Joanne Kidd, development by Ben Weintraub