Dear Constant Readers,
I really avoid re-hashing news articles as much as possible; but occasionally something comes along that I feel strongly prompted to write about. After seeing a recent online article in National Geographic and the Science article it was based on, I knew I had to comment on the subject. The subject in question are freshwater "Megafishes": 20 unrelated species over 2 meters in length and/or 100 kilograms in weight. The Nat. Geo. article colorfully refers to them as the "real-life Loch Ness monsters and Bigfoots of the aquatic world", which isn't too much of a hyperbole. Not being charismatic megafauna like pandas; many of these species are poorly known and could possibly be nearing extinction. For those that didn't click the link, it focuses on the 3-year multi-continental research project by Zeb Hogan which hopes to address this dire situation. I laud the articles and the research bringing attention to and trying to remedy this mess.
I do have a gripe with these articles (preliminary though they are) and it is that even they fall prey to the traditional "big fish" exaggerations. No matter how big or interesting a species is, there are always poorly supported and widely reproduced claims of far larger sizes. Though I am probably just a stickler for this sort of thing; I think factual accuracy is of vital importance in order for this to be taken quite seriously. If something as basic as size is wrong, then what do we know about Megafishes?
I was originally planning to do a review of some of the more interesting species of Megafishes, but it was beginning to get rather cluttered. So, I will split the Megafishes up into installments. I will not be able to cover all of them, but I hope to get the most interesting a vital information put up. Who knows, perhaps in the Honkin' Big Animals grand finale you'll see them all together...
What do we know about Chinese Paddlefish?
Psephurus is a large fish placed in the order Acipenseriformes along with a related American species of paddlefish and 21 species of sturgeon. Although they have cartilaginous skeletons, as you can see from this cladogram they are actually fairly basal "bony fishes". Palaeos.com's entry on this group gives a great deal of information on their strange anatomy and evolutionary development. But perhaps the most important thing to know about this group is that most members are threatened and this has been called an "endangered order" (Artyukhin, 2006).
Information on this species appears to be mostly found in China, making research rather difficult. A paper (more like a note) by Chenchan & Zeng provides a decent amount of information. Unlike the planktivorous American paddlefish, Psephurus is a strong-swimming predator of small to medium size fish as well as shrimp and crabs. This fish is commonly said to be known from the Yangtze river and tributaries, but is also known from the unconnected Qiantang and Yangjian rivers. It apparently has been known to live in the Yellow river as well (Fan, 2006). Despite being called a freshwater fish (e.g. by Science), this species was apparently capable of living in the East China and Yellow seas. I can't help but wonder if the American paddlefish is also capable of being anadromous, as sturgeons are as well.
A controversial matter is exactly how big this fish can get. There have been no length/weight before Chenchan & Zeng in 1988. They measured 46 yearlings (12 - 46 cm) from '74 to '75 and strongly correlated them with larger individuals (1 - 1.54 m). I'll be using their measurement of a 1 m fish weighting 3.3 kg as a benchmark for future estimations. To test this: a recent powerpoint gives a figure of a 3.3 m/117 kg specimen, which I predict will weigh (3.3/1)^3 x 3.3 kg = 118.6 kg, a very close approximation. Why do this? Well, Nat. Geo./Science state the maximum size is 7 m and 500 kg, whereas I predict ~1.1 tonnes. Hmm. Chenchan & Zeng mention a size of over 7 m in papers from the 30's and 40's. Curious. Fishbase reveals that these measurements came from different sources and one "Paxton" (none other than Charles Paxton?) regards these sizes as dubious. However, their measurement of 3 m and 300 kg is considerably heavier than predicted (~90 kg) and thus suspect. The powerpoint by Qiwei Wei unambiguously demonstrates that the fish can reach over 3.5 meters and presumably 140+ kg (they estimated 220 kg). So while not strictly a freshwater fish and maybe not a 7-meter leviathan, this is still a very big and interesting species. But also in a lot of trouble.
Chenchan & Zeng note that specimens over 100 kg were quite rare in the 70's, making the Yibin specimen rather impressive. A 1995 conference found the situation grim for Acipenseriformes in Eurasia, noting that now only a few adult paddlefish were seen annually. So how could it go from 25 tonnes caught a year to just a few individuals seen? Despite it being listed as a protected animal since 1989, the creation of hydroelectric dams has cut off access to spawning grounds and the species has thus lost many valuable resources (Fan, 2006). Even effects such as cooler water in deep places negatively affects spawning and individual growth (Fan again). This is not to mention poaching (this species carries caviar), boat traffic, and pollution and their negative effects. What makes the aforementioned Yibin specimen all the more remarkable is that as of 2003, it has been the last captured paddlefish (Fan, 2006 & Science). While Science speculates that there probably are other specimens swimming around, the species could very well be beyond saving. There was a recent report of a captured paddlefish, but it was in fact a sturgeon, see here for info (and rare pictures).
I hope that Zeb Hogan and affiliated researchers turn up some sort of pocket population, but it looks like we'll have to say goodbye to old Psephurus. And what a shame that is, before we could ever really learn anything about this fish. Hopefully this could be an example of what to avoid in the future with other Megafish.
Artyukhin, Evgenii. 2006. Morphological Phylogeny of the Order Acipenseriformes. Journal of Applied Ichthyology. 22 (Suppl. 1) 66-69. Available: Here
Chenchan, Liu & Yongjun, Zeng. 1988. Notes on the Chinese Paddlefish, Psephurus gladius (Martens). Copeia. Volume 1988, 482-484. Available: Here
Fan, Xiang-guo. 2006. A review of the concervation issues in the upper Yangtze River - a last big challenge: Can Chinese paddlefish, Dabry's sturgeon, and other fish be saved? Journal of Applied Ichthyology. 22 (Suppl. 1) 32-39.
Stone, Richard. 2007. The Last of the Leviathans. Science. 316, 1684-1688. Available: Here