Tuesday, July 31, 2007

Megafishes: The Chinese Paddlefish

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 gladius
Chinese Paddlefish
Chinese Swordfish
Elephant fish

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.

-Cameron



References:

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

10 comments:

Caitling said...

Fine, you made me click the link, you're far too clever. I would have found it a bit more interesting had you focused on the three gorges dam and less on fish, but it's your blog.

I feel terrible that I cannot be considered a megafish. I'm far too small, and human-y.

I assume that chinese paddle fish are used as paddles, perhaps in canoes. The pointer ones (chinese swordfish) are also used as paddles.

Yeah, well I caught a fish this big

(-------------- 0< ------------)

Sordes said...

Well, those site about alleged megafish is full of big-fish-stories. I can´t understand how somebody who tries to examines a topic for NG, can work so unrespectable. I work also alot with length-site-relation-calculations to examine the credibility of fish (and also other animals), and it came out that really most of the alleged records (not the official fishing records, but all those old ones) can´t be real. This paddlefish is a godd example for this. BTW, did you know that also normal paddlefish are not only planctivorous? I read on a site from a guy who breeds different fish in ponds, that his small paddlefish ate other fish more than half of their own size.
But to come back to the megafish. In the case of the Taimen I am also sceptic. Some time ago I read an article about the taimen in a fishing magazine (the "Blinker", Europes biggest fishing-magazine). They wrote they made some research and couldn´t find any autheticated records about taimens of 2m. Even in the archives of the Museum in Ulan Bator, they found nothing. Interestingly, even the record-fishes from around 1900 and before were not larger than the modern record-speciemens, only about 1,30m. I have really problems to believe in a 2m long taimen.
The Arapaima is a similar case, you can read nearly everywhere that it can reach 4,5m and 200kg. Well, this is actually nothing but bullshit. Even the relatiion of length and weight is completely unrealistic, it would have the proportions of an eel. An actual 4,5m arapaima would weigh around 900kg. The reason why you can hear and read so often this claims, are because a 19th century explorer named Schomburgk (not identical to the other famous naturalist Hans Schomburgk), which was probably the first European who wrote about this species, brought back stories from indios, which had told him, that the arapaima would grow that big. Since this time, thousands of authors used this dates from Schomburgk, which actually has never seen an arapaima of this size, without any critical thinking. In fact the largest south american arapaima was only 2,32 and weighed 133kg. That´s really big, but there is still a huge gap between this one and the alleged 4,5m ones. Some years ago an even larger arapaima was caught in Thailand in a fishing-pond. Due to best conditions, it reached an immense size of 2,65 and weighed 185kg. That´s really monstrous for a pure freshwater fish, and even this one is not even close to 4,5m.
BTW, I made a longer post about this here: http://bestiarium.kryptozoologie.net/?p=6
I made also a lot of research about the european catfish Silurus glanis. As I life in middle-europe, and this species is common here, I have also a special interest about them. You will find very often claims of 4,5 or even 5m and weights of 300kg. Again this are nothing more then tell-taled fishing stories. The largest actually authenticated wels catfish was a monstrous leviathan of 2,78m and 144kg. Such a size is really enormous and far away from even those sizes, which are already seen a gigantic. Tbis fish came from the italian Po-delta, where this fish was introduced nearly a century ago. Perhaps it was even one of the first ones, which lived there. Because the water there is much warmer and they have plenty of food and lack of specific parasites and diseases, Silurus glanis grows in the warm waters of Italy, spain and Greece much faster and larger than its original habitat. But again, even this one is still far away from the alleged record sizes. I could wrote still much more about this topic, if you want, I can give you also further imformation about this species.
Another of the megafishes is surely also just a big-fish-story. Those giant freshwater-rays are indeed very big, but if you look at their flat bodies, they will never weigh 500kg (much more than a 3m Pangasius gigas) at a diameter of 240. I suppose there are also other cases in this list, which are not actually records, but only big-fish-stories.

Darren Naish said...

Thanks to sordes for that clarification: I did a double-take on seeing wels catfish being given a maximum length of 500 cm. A 5-m-long wels would bring credence to those stories of child-, swan- and dog-eating :)

Cameron McCormick said...

Interesting, I've never heard about paddlefish eating whole fish before. I thought the non-protrusile jaw would make things difficult...although not impossible. I also find it exceedingly odd how a vulnerable species has been introduced into Europe. Ooh, if only I had more blogging time.

Anyhoo, thanks for the epic post though Sordes! It's good to know that somebody out there cares about accuracy. I've often wondered why publications and Fishbase all put the maximum size (often of outsized or non-existent freaks) of the fish at all. Even though its less impressive, wouldn't the average be a whole lot more useful? Well, I'll cover this too, and certainly use the information you've uncovered.

Darren, I've looked and looked at the wels and I certainly don't see any limbs...I've always assumed you've had some sort of vendetta against those non-tetrapods.

Sordes said...

Well, paddlefish are not really introduced in Europe, but as well as many species of sturgeons, they can be bought for commercial fish-breeding ponds (or just for fun if you have a pond laaaarge enough) besides typical fish like carps for example. They are produced in special ponds, and not catched from nature. Although they don´t grow as big as in the warmer USA, they can still reach respectable sizes.
But to keep about the original topic. I also really hate it, that many books gives often only record-and allgeded record-sizes for animals. Only some days ago, I read for the eustarine crocodile: Length: 7-9m. I think I don´t have to write more about this (or have you ever seen a 7m saltie?). It really makes no sense to give such sizes, not only because they are often not true, but also because you get no idea about the normal size. If you catch a wels catfish in central Europe, you can be lucky if it is around 1,5m, in GB this would even be extraordinairy.
Wels catfish have the potential to grow really large, but not as large as many people think.
They make also very good candidates for monster-stories about man-eating or pet-eating behavior. In the case of dogs, it could be really true. The dog which was said to be eaten was only a dachshund puppy. If such a dog swims in the water, it is for a wels which regularly eats ducks and swimming rats, really no problem. The german record wels catfish, which was caught some years ago about 2km away from where I live, ate large amounts of waterbirds like ducks, but a swan would be really not possbile. The 2,78m record catfish from Italy had a mouth which was 35cm wide. This could be probably enough for a swan, but a wels would never grow in the cold waters of britain to such a size.
Man-eating is also nearly impossible. Only a very large wels of more than 2,5m could perhaps eat a very small child, but never an older child or even a human. I suppose those stories about man-eating wels catfish come from their sheer size and noctural behavior, and not from actual facts. But althouh a wels could never eat a complete human, it would have no problems to eat pieces of a chopped body. If a murderer chopped a victim to pieces and threw it in the water, it could actually be, that a wels would eat it, and fisherman could find it in its stomach. But that´s just an idea. Wels catfish are knwon that they can be catched with innards of birds and mammals, so it wouldn´t be improbable, that they would also eat human flesh or limbs.

Cameron McCormick said...

They were introduced to Russia (I'm not sure which part) and they actually are established. They were recently seen in the lower Danube, but they are escapees and it is unknown if they'll establish. Free pdf:

http://www.aquaticinvasions.ru/2006/AI_2006_1_3_Simonovic_etal.pdf

And fishbase:

http://fishbase.org/Introductions/IntroductionsList.cfm?ID=174&GenusName=Polyodon&SpeciesName=spathula&fc=33&StockCode=188


As for the wels eating human remains, I wonder how many other "maneaters" actually just scavenge people.

I think I'll do catfish next.

Sordes said...

If you want I can give you some further information and self-made photos of the inofficial german record specimen.

Cameron McCormick said...

Sure, it's always pretty difficult coming across free-use photos. Thanks in advance.

Anonymous said...

Hi,
I am just new to this site and want to fully agree with Sordes. Coming from Bavaria, Germany and being interessted in fishing and fish I can only agree to record size of taimen, wels etc. The largest taimen a photo exists is around 160-170 cm (it was not measured) but looking at the picture could be true. The angling record (IGFA) is 156 cm and about 42 kg. So much to it, but sometime I have the feeling that people also anglers like to exaggerate. But why are some of these unreliable sizes of fish published in literature (books or media) of well established scientist remains for me a myth as the fish itself.
Here are some max sizes of freshwater fish established:
pike (esox lucius): 151 cm, Günzstausee dead found 1975 picture exists, 152 cm Austria 1975 dead found, 160 cm dead found river Lech 1989)
huchen (hucho hucho): 150 cm
taimen (hucho taimen): 160-170 cm (photo length estimated)
muskellunge (esox masquinongy): 173 cm (caught by commercial fisherman, photo exists), 168 cm angler caught mount exists
wels (silurus glanis): 278 cm river Po (picture and mount exists)
karpfen (cyprinus carpio): 126 cm
zander (stizostedion lucioperca): 120 cm Starnberger See 1958; 115 cm 1990 Germany angler caught
Now don't get me wrong I think the max size of any species is interessting to know, but that's about it. There are now 8 foot child-eating pike or 15 foot man-eating wels. It is confirmed though that pike sometimes or lets say in the rarest occassions bite a human swimming in the foot or hand. If it happens the tabloids often bring the "culprid" to trial as a monster pike of 1.5 + metres trying to harass the poor peolpe intruding its element.
anywasy have a good one.
Andreas

Anonymous said...

hi, just want to say thanks for writing this, its helped a lot with my highschool project.