The Burdekin Basin has 21 obligate freshwater fishes (meaning they are restricted to freshwater environments), 18 are recorded from below Burdekin Falls and 18 from above, with three species only recorded from below Burdekin Falls (Mouth Almighty, Southern Purple Spotted Gudgeon and Sleepy Cod) and three only recorded from above Burdekin Falls (Western Carp Gudgeon, Flinders Mogurnda and Burdekin Mogurnda). Thus, 15 obligate freshwater fish species are known to occur both upstream and downstream of Burdekin Falls. The only non-obligate freshwater species naturally occurring above the falls were the eels. Burdekin Falls is a major barrier to fishes, and has been present for millions of years. To understand the evolutionary origin of Burdekin River fishes, and correctly interpret phylogeographic patterns in fishes sampled from upstream and downstream of Burdekin Falls, it is critical to sample across the entire Burdekin Basin, and throughout surrounding river basins that may exchange fishes with the Burdekin Basin over evolutionary time scales. The key question being addressed is whether fish populations above and below Burdekin Falls are substantially genetically different. The short answer is yes, most were except for Spangled Perch. Come along to find out more details as the Burdekin system is one of the most complex biogeographic stories in Australian freshwater fishes.
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