Burkhead, N. 2012. Extinction Rates in North American Freshwater Fishes, 1900–2010. BioScience 62: 798-808.

"Widespread evidence shows that the modern rates of extinction in many plants and animals exceed background rates in the fossil record. In the present article, I investigate this issue with regard to North American freshwater fishes. From 1898 to 2006, 57 taxa became extinct, and three distinct populations were extirpated from the continent. Since 1989, the numbers of extinct North American fishes have increased by 25%. From the end of the nineteenth century to the present, modern extinctions varied by decade but significantly increased after 1950 (post-1950s mean = 7.5 extinct taxa per decade). The modern extinction rate for North American freshwater fishes is conservatively estimated to be 877 times greater than the background extinction rate for freshwater fishes (one extinction every 3 million years). Reasonable estimates project that future increases in extinctions will range from 53 to 86 species by 2050."

I agree with the general message, but believe the extinction rates in the Western Gulf Slope, especially central to far west Texas, exceed the "background extinction rate... one every 3 million years). The natural fluctuations in climate due to glacial cycles are extreme, and we have been experiencing increased extirpations in the region for the past 11,000 years. Also, our evidence of past fish distributions is very poor, but what is available from arid regions is eye opening. Fishes found in West TX 11,000 years ago haven't been found there since that time, but persist to the north and east. There are also disjunct taxa that most likely have been isolated only since the Pleistocene, which shows there have been a number of extirpations within river basins. Also, any fish under 3" or so are rarely identified to species level at paleontological sites in the studies I'v looked into, so we are missing a lot to decomposed bones, and bones sitting in boxes at universities that nobody has examined.

I'm not arguing that human caused fragmentation, dewatering, etc isn't a huge problem, but I think we are confounding it by being in a time that is naturally (as in since the last glacial maximum) experiencing increasingly elevated rates of extinctions in many areas.