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Ashley

Ashley Frisch

Year of Award: 2013 Award State: Queensland Science > General
The Dr Dorothea Sandars and Irene Lee Churchill Fellowship to develop advanced methods for measuring and monitoring the condition of imperiled reef shark populations - USA
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Sharks, like other large predators, are critically important because they help to maintain the ecological balance among numerous marine organisms. The ability to accurately measure and monitor shark populations is paramount for their effective conservation and management, but robust methods for rapid census of shark populations are lacking in Australia. The aim of my project was to investigate the limitations of existing methods and, where possible, develop new methods that improve accuracy and efficiency of shark monitoring projects. Ultimately, this research will lead to improved management and sustainable use of sharks, which are currently being captured at unprecedented rates.

The Dr Dorothea Sandars and Irene Lee Churchill Fellowship enabled me to travel to the U.S.A. where I was based at the Pacific Islands Fisheries Science Centre (Hawaii) and the Rosenstiel School of Marine and Atmospheric Science (Florida). I worked closely with eminent scientists such as Dr. Ivor Williams, Dr. Marc Nadon, Dr. Carl Meyer and Dr. Neil Hammerschlag, who routinely perform shark counts across vast archipelagos of coral reefs and are widely regarded as world experts in measuring and monitoring shark populations. During my six week visit, I attended numerous workshops, seminars and fieldtrips, as well as compiled a robust dataset to rigorously evaluate the effectiveness of several underwater census methods. I learned about the design, accuracy, and limitations of advanced census methods such as baited remote underwater video (BRUV), diver-based GPS belt transect (DBT) and stereo-video transects (SVT), and I assisted in the development of a new census method known as audible stationary count (ASC). I also learned about the characteristics of shark behavior that may lead to biased estimates of shark populations and how to overcome these problems.

Due to the heterogeneous spatial distribution of sharks and their tendency to respond variably to divers, noise, boats and bait, it was concluded that large variation exists in the outputs of different survey methods, and that each method has a range of advantages and disadvantages with respect to cost, convenience, detection capacity and opportunities for bias. In most situations, diver-based surveys were found to produce reliable results, but only when (1) transect length was relatively long, to minimize upward bias associated with initial shark attraction to divers, (2) water depth was shallow enough to enable SCUBA diving but deep enough to encompass the depth distribution of coastal sharks, and (3) water visibility was sufficient to enable wide transects and a clear view of sharks, thereby ensuring that sharks were properly identified and not incorrectly double-counted. Results from this study form the basis of a scientific publication which has been submitted to the internationally recognised Journal of Animal Ecology. Research funding is also being sought to expand this research to the Great Barrier Reef and provide necessary training for marine park managers and university students in this field.

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