Tuesday, August 21, 2007

Yet Another Mesoplodont Whale?

Dear Constant Readers,

Ziphiids are among my favorite group of animals, so you can expect me to elaborate on them quite a bit in the future. Beaked whales are the second largest family of cetaceans but also happen to be the most poorly known. Some species are so rarely encountered that they have yet to be ID'd alive (Dalebout et al 2002). Males in the genus Mesoplodon (the largest genus) posses large, distinctive teeth - but as Christ Taylor noted in a comment, identification of females is exceedingly difficult. Future posts will touch on how this even occurs post-mortem in females from time to time.

Lots of interesting things have been happening with this group as of late. Mysterious ziphiids only known from sightings have been classified as have some overlooked old remains. I was wondering if there was some mystery that I haven't heard about that has yet to be solved. Lo and behold...

An unpublished paper by ubiquitous Dalebout (et al) used an approach to uncover hidden biodiversity called "DNA taxonomy". This has been used by other teams to increase the species of Right whales (Eubalaena) to three in recent years, for example. The variability of mtDNA within a species has been found to be very low (less than 1%) with relatively high divergence outside species (over 8%), indicating that the markers are adequate for species identification. The study used large samples sizes (up to six) vs. a previous study done by them (two) to demonstrate that diversity wasn't drastically overestimated - it wasn't. So with an increased database from a "historic" approach (not using morphological characters) an updated phylogenetic tree was created for the group. And lo and behold, some interesting things turned up:

In a subject apparently to be covered in a future paper, it turns out that Mesoplodon mirus (True's beaked whale) may be split into sub-species or even species occupying the Northern and Southern hemispheres. In this paper at least, it is used as a further example that this new phylogenetic tree makes logical groupings.

The focus of this paper is on two skulls recently discovered near Palmyra (Syria) identified as M. ginkgodens (Ginkgo-toothed whale) and a tissue sample from Kiribati (Central Pacific). The Ginkgo-toothed whale itself was first described in 1958 and as of 2002 was known from less than 30 specimens. Despite the skulls being identified by morphology as M. ginkgodens, they formed a distinctive clade with the tissue samples. The Kiribati-Palmyra samples differ by a single diagnostic site and from M. ginkgodens by 26, and posses characters distinct from all other mesoplodonts. Unlike M. mirus, these genetically distinct groups overlap in range. The authors suggest that this should be a distinct species or sub-species, but more work will have to be done to classify it properly. The samples from Kiribati come from either one or two individuals and it is not known if skeletal remains are present.

Since female and juvenile remains have been misclassified in the past, it wouldn't be too much of a surprise for there to be a new species out there. I still haven't heard if scientists are seeing more unclassifiable mesoplodonts at sea though....



Dalebout, Merel L. et al. 2002. A New Species of Beaked Whale Mesoplodon perrini sp.n. (Cetacean: Ziphiidae) Discovered Through Phylogenetic Analyses of Mitochondrial DNA Sequences. Marine Mammal Science. 18, 3: 577-608. Available: Here

Dalebout, Merel L. et al. Published online. A Divergent mtDNA Lineage among Mesoplodon Beaked Whales: Molecular Evidence for a New Species in the Tropical Pacific? Available: Here

Thursday, August 16, 2007

The Future is Irregular

Dear Constant Readers,

I certainly have developed a great deal deal of respect for people that can write on scientific topics on a regular basis. When I wasn't working, it seems like all my time was eaten away by blog-related activities. And yet...looking back it doesn't seem like my output was that astounding. Perhaps I just write (or rather, re-re-re-write) in a rather time consume way. Now my summer is coming to a close and there are still some things that I'd like to do. A vacation away from blogging if you will.

When I get back to school, I know that my modest current pace and content are going to be impossible to keep up. You can probably expect a return to my occasionally scientific and much shorter posting. This by no means is the end of my semi-quasi-whatever-technical posting, but it will certainly become a rarity. The future is irregular and unpredictable, so I can't really say anything for certain. That is, except for my interest in Zoological matters. I tend to enjoy sharing what I learn with people and blogging is currently the best output for this tendency. Instead of rushing to do topics, I'll let them come more naturally and at a slower pace. Of course I'll never be able to write about or even learn about everything I want to, but at least I have the satisfaction of constantly learning.

What's next? I have no idea...


Ambiguous Washed-Up Carcasses

Dear Constant Readers,

My acronym for this subject is a bit unwieldy (AWUCs?) and I should note that Cryptozoologists typically use the term "globsters" for this particular subject. The team of Pierce et al seems to prefer "blob" and I have even seen "blobster" used. My designation is broader, something I'll get into later. As the names indicate, these blobs all lack a recognizable morphology outside of being a large mass of decomposing tissue. As such, laymen are often prone to pareidolian observations which are unfortunately taken at face-value. For those of you that dare, you can take this link to read some of the startlingly strange AWUC descriptions. As we'll see, description and actually appearance are often drastically dissimilar. There's a lot of things to see later really.

I should point out the sentimental attachment that I have to these particular blobs. While I had dabbled in Cryptozoology before things really didn't take off until I looked at the back cover of Richard Ellis' Monsters of the Sea and saw the St. Augustine carcass. I think I was 12-ish then, and I don't think I've fully recovered since. Looking back on these old subjects I realize how uncritically and unconditionally I accepted them as monsters. It's a bit embarrassing really. So I suppose now is the time to revisit this old subject and clear up what I can.

Globsters: No Longer a Mystery

While many AWUCs are shrouded in their characteristic ambiguity, many globsters have actually received recent scientific analysis. There still are some, uh, interesting individuals who reject these studies apparently on the basis that they really really want these carcasses to be "monsters". Heck, I'll admit that I'd really want them to be monsters, but unfortunately reality dictates otherwise.

Previously mentioned here, the St. Augustine carcass is the most famous of globsters despite being overlooked by early Cryptozoologists. There is an interesting story behind it told many times and I truly do salute the Wikipedian that wrote this comprehensive article. Saves me a heck of a lot of trouble. In short: this was a carcass initially thought to be a cephalopod until it was rejected by a prominent Zoologist, re-"confirmed" as a giant octopus in the 70's and 80's, and then determined to be whale blubber by Pierce et al 1995. That paper (which is...free) determined the St. Augustine carcass to be wholly composed of collagen arranged in a banded pattern, wholly unlike the complex network present in the octopus (since they change shape). High levels of imino acids (not a typo) also pointed to the carcass coming from a warm-blooded animal. Despite this, some individuals (Ellis for one) were not convinced that such a huge mass of collagen could come off of a whale. The molecular tests were also doubted due to the age of the carcass (~100 years!). Oh, if only there was a fresher version of the St. Augustine monster...

A carcass that washed up in Chile in 2003 proved to be the defining point for my take on globsters. My faith was faltering by then, but at first this truly did seem to be a cephalopod-like mass with apparently identical features to the St. Augustine carcass. Pareidolia makes it seem as if there is a large mantle, at least one arm-like appendage, and what appears to be some webbing. Pierce et al 2004 were able to manage to extract DNA from the carcass and incontrovertibly showed it to come from a Sperm whale. The decomposition of a sperm whale into a "globster" has not been observed, but if I may speculate, I think it is a question of time more than getting the skin off in one piece. While the carcass is floating at the top, the cellular material slowly decomposes and the skeleton disarticulates and eventually detaches. Perhaps the more pronounced "mantle" was composed of the floating portion and the "tentacles" were portions hanging down from it. Pierce et al 2004 note that one globster was observed by a scientific team two years after it first beached, indicating that this may be a very long process. Presumably the reason we don't have more is that some may sink or be scavenged before only the collagen remains. The three Bermuda blobs* (see here for the 1995 and '97 examples) are all examples of this decomposition form as well.

* Pierce et al 1995 demonstrate it to be a vertebrate and speculate that the first may be from a large teleost or elasmobranch. The follow-up demonstrates the '88 and '95 examples to be cetacean. The '97 Bermuda carcass wasn't mentioned, but could indicate that these carcasses are actually fairly common.

In addition to the "octopus-like" decompositional form, a paper by Carr et al 2002 uses DNA testing on another carcass from Newfoundland in 2001 to demonstrate that it is also a sperm whale.

As you can see from this picture, the carcass isn't octopus-like but has strange "lobes" on the side. The authors speculate that this may be the remnants of tissue from in between the ribs, apparently not actually making it that amorphous. Interestingly, this feature has shown up in numerous carcasses which haven't been tested, but could very well have come from cetaceans. Yes, I know this is speculation, but it has a very solid case. There is proof that sperm whales can take the form of blobs with lobes, what are the odds that there is some bizarre giant unknown species with a very similar morphology? Close to none I'd say. While it may seem like a bold statement, I think it is reasonable to state that globsters are simply no longer a mystery. So let us give a farewell to the globsters. You can consult the Wikipedia category for some surprisingly complete information.

The famous Tasmanian globster from 1960, the example that the term was coined after. Pierce et al 2004 note that a 1962 expedition determined it to be a whale. The "gill arches" may be comparable to lobes.

A globster that washed up in the Hebrides in 1990. It has not been subjected to analysis (no samples taken). The species is unknown but it could very well be cetaceous.

Another Tasmanian carcass from 1997. Its identity is also unknown, but there is no reason to think it is an unknown species. Just because a carcass cannot be easily identified does not make it a new species.

Pseudoplesiosaurs and Pseudo-Sea-Serpents

While the cetacean/pseudo-cephalopod connection has only been confirmed fairly recently, the basking shark-as-pseudoplesiosaur identification is much older. Heuvelmans documented 12 as of 1964 (probably over-conservative) and Wood identified that 90% of "sea serpent" carcasses identified in the press as of 1982 were basking sharks. So why does the basking shark make a pseudoplesiosaur? The gill rakers are loosely attached and during decomposition they fall off, taking the lower jaw with it. This forms the appearance of a plesiosaur-like carcass, although conspicuously lacking a lower jaw. Further decomposition leaves nothing more than a long spinal column with a small attached head, leading to the impression of a "sea-serpent". The famous Zuiyo Maru carcass of 1977 was analyzed and found to quite clearly be a basking shark; this excellent page saves me a great deal of time in discussing why this is a reasonable explanation. Carr et al 2002 are the most recent published reference to this phenomenon, but unlike globsters recent molecular testing has not been done. This is no reason to doubt the explanation, but there are some odd cases that need looking into.

Wood notes that while there have been reports of basking sharks up to 50'/15.2 m, the largest accurately caught specimen was 40'3"/12.27 m in length. This is pretty amazing in light of the average being 26'/7.9 m according to Wood. But the problem is, some carcasses reportedly exceed the maximum substantially. The famous Stronsa beast of 1808 was a reported 55'/16.8 m and had six "limbs". It also had no lower jaw, "grisly" bones, and skin that was rough one way and smooth the other. According to Heuvelmans the carcass was measured a few times (varying 54-55 feet), but Wood notes that the vertebrae were identical to (but slightly smaller than) a shark of 25'/7.6 m. Was the size an exaggeration of the already fairly fantastic description? Like other carcasses this does have a modern counterpart of sorts:

The Effingham (British Columbia) carcass of 1947 did not possess "limbs" like the Stronsa/Stronsay carcass, but was incredibly long ("at least" 40 feet!). The largest vertebrae were the same size as Stronsa (6" diameter) and thus the 25' shark as well. Interestingly, Heuvelmans claimed that the vertebrae count (145) was conspicuously larger than the average basking shark figure of 105-115. I can't find figures to back this claim up, but if true it is quite perplexing. I've never heard any reports or indications of unusually long-bodied basking sharks or any sort of disorder that increased length by ~ 140%. There is no indication of scale, so can this too simply be an exaggeration?

While basking sharks-as-"plesiosaurs" certainly deserved to get mentioned, what isn't as known is that there is another group of animal that can form pseudoplesiosaurs: beaked whales.

Heuvelmans notes that despite appearances, the skull of the 1925 Santa Cruz carcass was found to be that of Baird's beaked whale Berardius bairdi. Though I can't find a picture of the same angle this somewhat gory picture demonstrates that yes, the resemblance is indeed quite strong. There are some Internet arguments of it having a "square bill", although the "squaring" is curiously not perpendicular to the angle of the head...it is obviously a fragmented lower mandible (the gory picture also seemed to have one). Claims of small numerous teeth in the head also probably stem from damage to the mandible. So then that begs the question of exactly what the heck the head of a known creature is on what appears to be a long "neck". Heuvelmans thought that the skin detached and rolled up on itself like a Swiss roll...but honestly I am not quite certain exactly what he means by that. The possibility of pranksters was also raised. But, as usual, unusual carcasses are never normally singularities...

Tim Dinsdale in "Monster Hunt" documented this carcass from Barra in the Outer Hebrides in 1961. A biologist identified it as a beaked whale (no species was mentioned --- unsurprisingly) as well. This carcass appears to have nearly the same form as the Santa Cruz example less decomposed and ambiguous looking. I am still quite baffled at what mechanism could be responsible for this, although given the improbable forms seen it should by no means be dismissed.

This was of course not meant to be a comprehensive overview of AWUCs, but more of a conceptual introduction to two of the best defined decompositional forms. There are many other strange carcasses out there, but they as well have plausible mundane explanations. What I do find encouraging is that scientists are not hesitating to resolve these mysteries, and do seem to genuinely want for them to be something unusual and unknown. For those of you that scream "bias" at the idea of your favorite monster being a hunk of blubber; it should be noted that one of the authors from the first paper, Eugene Clark, was on the board of directors for the International Society of Cryptozoology (see here). Many of the other carcasses are described vaguely and/or in a fantastic manner, which doesn't give much credibility to their cases. It seems exceedingly strange to me how ambiguous washed up carcasses are always assumed to be a new and strange species instead of the more plausible option of having a known one that decomposed irregularly. However, I think it would be in the best interest of all involved (and interested) for every available carcass to be analyzed in the future. The notion of large unknown animals in the ocean cannot be discounted, but there is no hard evidence to support their existence.

If there is another AWUC that washes up, you'd better believe that I'll cover it here. A new species or not, this is a fascinating subject that deserves discussion.



Carr, S. M. et al. 2002. How To Tell a Sea Monster: Molecular Discrimination of Large Marine Animals of the North Atlantic. Biol. Bull. 202: 1-5. Available (for free): Here

Heuvelmans, Bernard. In the Wake of the Sea-Serpents. Hill and Wang, New York, 1965.

Pierce, S. K., et al. 1995. On the Giant Octopus (Octopus giganteus) and the Bermuda Blob: homage to A.E. Verrill. Biol. Bull. 188: 219–230. Available (for free): Here

Pierce, S. K. et al. 2004. Microscopic, Biochemical, and Molecular Characteristics of the Chilean Blob and a Comparison With the Remains of Other Sea Monsters: Nothing but Whales. Biol. Bull. 206: 125-133. Available (for free): Here

Wood, Gerald. Guinness book of Animal Facts and Feats. Guinness Superlatives, Middlesex, 1982.

Tuesday, August 7, 2007

Megafishes: Catfishes

Dear Constant Readers,

Fortunately this is not a very obscure group of animals, so there is plenty of popular literature to go on. Well, for the basic information at least. The Wikipedia page on catfishes actually makes a decent primer (for once), but I'd recommend the Tree of Life page even more. This is a huge group of fish with over 3000 species and 36 families, one of which was described as recently as 2005. Apparently 1 in 4 freshwater fishes, 1 in 10 fishes, and one in 20 vertebrate species is a catfish. On the Palaeos catfishes are closely grouped with knifefish and electric eels* in the clade "Siluriphysi" which is defined partially by the re-evolution of electroreception. Click here to see their relative position in the colossal Teleost radiation. Aside from electroreception, catfishes often have a benthic habitat, scaleless skin, small eyes (reliant on tactile barbels, chemosensitivity, oflaction), an adipose fin, and so forth. Some however are covered in armor plates, have sucker mouths, breathe air, have spinous fins, drink blood, and even digest wood. The Tree of Life suggest modification of the upper jaw for barbels and locking fin spines are good synapomorphies, although Fishbase "remarks" on more technical characters. Phew.

*This species apparently can get over 2 meters in length, however it is not considered a "Megafish", perhaps due to its eel-like shape? At the Shedd Aquarium in Chicago, they did have a specimen there that did seem to be around 2 meters, so I don't think 2.5m is a "fish story".

Now there is no ambiguity as to what a "catfish" entails, I should discuss the more impressive members of the group, their contributions to the "Megafishes". Out of the 20 species of Megafishes, 6 of them were Siluriformes. Even more remarkably, 3 of these species live in the Mekong River of Southeast Asia. I should also mention that most catfishes are small to moderately sized (5-20 cm or 2-8") with some species reaching maturity at below 1 cm. This gives a roughly 300-fold length difference between the smallest and largest species, and perhaps a weight difference a million-fold or over. I'll leave ridiculous size differences for later, here are the Megafishes:

Family: Silururidae

This family is defined by a lack of an adipose fin and occasionally pelvic and dorsal fins, a very long anal fin, no nasal barbels, et cetera. As you can tell from the name, these are very archetypal catfish in appearance. While most of you familiar will be correct in assuming the wels (Silurus glanis) will be discussed, according to the Megafishes article in Science, there is another giant catfish in the genus.

Silurus soldatovi, Nikolskii & Soin, 1948
Northern Sheatfish
Soldatov's Catfish

Not even graced with a Wikipedia article, information is hard to come by for this species. There were journal articles on the genetics, reproduction, and eggs of this fish, but I could find nothing on morphology. This fish lives in the Amur river basin, so like the Chinese paddlefish, there is the problem of most information being in languages I can't begin to understand (Russian and Chinese). What is astounding is that the Science article gives it an incredible length of 4 m (13'), yet the Fishbase page gives a weight (from the same source) at an astoundingly low 40 kg (88 lbs) at the same length. Perhaps the source itself was composed of two different specimens...or it was just another "big fish" story. It is odd how warning bells didn't go off for the author for such jarring figures. This Chinese page has a picture of what does indeed seem to be a wels-sized silurid catfish, although exact size is difficult to determine...or if it actually is this species (see below...it also bears a resemblance to the Megamouth, oddly). Pages seemed pretty adamant about the size, but it will have to be regarded as large but unknown for now. Unsurprisingly the Science article mentions it was not evaluated by the IUCN, but is probably being threatened by harvest, habitat, and pollution. Given how people seem obsessed by large fish, I find it exceedingly odd how this species apparently slipped under the radar.

Silurus glanis, Linneaus 1758

At the exact opposite of the popularity spectrum (imaginary) is this large Eurasian species. Mercifully, I don't have to go digging through technical literature to find the basic information. I should note that uniquely among Megafishes, this species is not threatened and is in fact regarded as least concern by the IUCN. Fishbase even regards this as potentially being a pest species. So it looks like this is one Megafish we shouldn't be overly worried about. It is also worth mentioning that this species was capable of entering the saltwater Aral Sea (note...was); making it all the more mysterious why sturgeons weren't considered "Megafish". By looking at Fishbase, you probably would have noticed something very strange as far the reported size. It, the Tree of Life and Science all report an astounding 5 m maximum size with variously given weights (306 and 300 kg --- 327 in Wood, 1982). This is a rather widely cited figure, a fact which I find unfortunate. For once thing, the Science article reported a stingray of the same length at 600 kg...shouldn't that set off warning bells for both figures there? A wels that size should weight 7-800 kg or even more, but I don't think they ever got that big.

So, how big does the wels get?

Gerald Wood mentioned several claims of excessive size (200 kg is "normal"?!), but I trust Markus Bühler/Sordes much more on this subject. The Wels grows larger in Southern Europe (Wood has no claims from there) due to warmer temperatures and a lack of parasites; the world record is an Italian specimen that measured 2.78 m (9'1.5") and weighed 144 kg (317 lbs). Compare this to the record German specimen which was 2.47 m and 89 kg (8'1" and ~200 lbs)

You can even see a Youtube video (what isn't on there?) of a catfish of nearly the same size (I'm not sure from where).

I haven't found any specific average size figure for this species, but Wikipedia (translated from European articles) suggests 1.3 to 1.6 m, which would make a 2.7-something meter fish a genuine monster...and make larger sizes quite unbelievable. Perhaps before exploitation I could imagine some 3-meter leviathans roaming around, but 5 meters is stretching things far beyond credibility. Perhaps they were confused with sturgeons (like Chinese Paddlefish), or maybe like many of these claims they were exaggerations or fabrications. But as you can tell by the video, the wels is a monster that doesn't need exaggerating.

Wallago attu, Bloch & Schneider 1801
Great White Sheatfish
Ikan Tapah

That's right, the Sheatfish family has a third member of allegedly gigantic size and a representative from the Mekong river basin. Fishbase describes this sheatfish as being a large, predatory species capable of delivering traumatic bites to humans. This species dwells mostly in rivers and lakes (streams in flood season), but apparently can tolerate brackish water as well. They also aren't limited to Southeast Asia, and can be found in Pakistan and possibly Afghanistan as well. Giri et al (2002) describe this sheatfish as being a fairly good candidate for captive rearing since it grows fast and has palatable flesh. The wels, in comparison, tastes bad at large sizes and apparently has poisonous eggs. The size reported for this fish is somewhat confusing. Giri et al give a maximum length of 2 m and a weight of "more than" 45 kg (6'6" and 100 lbs), which is around 10 kg less than the non-Megafish Blue and Flathead catfish of America, for instance. This badly translated abstract gives a weight of 25 kg for a 2 meter catfish and this page shows a rather large looking catfish that weighs only 9 kg. It also reported a 2.4 m specimen weighing 18.6 kg, a length (not weight) repeated in Fishbase and Science. If a fish that long weighed 18.6 kg, then a 9 kg fish would have to be 1.9 m long (6'3"), and I don't think the fellow in the picture is pushing 8 feet tall. The Science article lists this fish as being "not evaluated", but Fishbase reports it being "near-threatened" in Western Ghats, India and "lower risk" elsewhere. I do not see why length should be a more important measure than weight when it comes to fish, so either the definition of a "Megafish" should be broadened or this low-risk fish should be excluded.

Family: Pimelodidae
Brachyplatystoma filamentosum, Lichtenstein 1819

Yet another surprisingly poorly known species (to the public) of very large catfish. Petrere et al 2004 note that catfish over 1.6 m and 50 kg (5'3" 110 lbs) and are given the name "Piraiba" and there have been suggestion that smaller fish are in fact a different species. This species is a top predator of the Amazon River channel, mostly inhabits whitewater areas, and is migratory. Petrere et al note that this species used to make up a huge proportion of the catch in the Amazon (94% !) in 1977, but now makes up only5% of the total catch. This was apparently the most important fishery of any catfish, and the authors draw parallels to the over-exploitation of sharks in marine waters. In addition to over-exploitation, the breeding waters of this fish are being disrupted by mining and land degradation, although the location of breeding grounds (headwaters of the Amazon) are apparently not known with certainty. Oh yes, and this species is also capable of living in brackish water, specifically river mouths.

So obviously this can be a rather large fish, reported at being 3.6 m and 200 kg (11'10" and 440 lbs) in Science, although Fishbase once again demonstrates that the length and weight are from different sources. Gerald Wood, who normally simplifies these matters, instead confuses them greatly. He insists that B. filamentosum (lau-lau) is indeed the longest catfish in the Amazon, but there is a heavier species called the..."pirahyba" (Piratinga piraiba), hmm. This turned up a negative result on Fishbase, although there is a synonym (Piratinga piraaiba) that is awfully close. Wood reported that the latter "species" weighed 159 kg at 1.85 m (6'1" and 350 lbs) and was estimated at a maximum size of 2.1 m and 181 kg (7' and 400 lbs). The conversions are Wood's and not mine. It should also be noted that the figures are much heavier than what would be expected from Petrere's figure; it is normally the opposite of that and it is possible that these fish to get bulkier as they increase length. None other than Teddy Roosevelt related a tale of a 3 m catfish getting killed after attacking a canoe, but this is of course rather dubious. As for the actual species, none other than William Beebe caught specimens, the largest of which was 2.11 m without the tail measured and presumably about 2.4 m (8') with. Judging by the weights reported by the "pirahyba", it is possible that this or a similar sized specimen is responsible for the 200 kg figure. A 3.7 meter+ claim (Wood's figure differs) is probably not realistic for a pre-exploitation animal...and would dwarf every other Megafish at a presumed weight of over 1 ton/tonne. But don't worry, the largest species has yet to be covered...

Family: Pangasiidae

Now here's a problem: 2 different fish species in the same family are reported to reach the same size (3m and 300kg)! Now that the wels and the paraiba have been downsized, what is the largest species of catfish? Well, I never fully discounted the reported 4 m size of the Soldatov's Catfish, but let's assume it's an exaggeration. Considering that every single reported size by the Science article appears to be wrong, I don't think that would be unjust.

Pangasius sanitwongsei, Smith 1931
Giant Pangasius
Dog-eating Catfish

Like a few other species, this one seems seldom mentioned despite its apparently gigantic size. This one is "Data Deficient", but the Science article mentions that many locals are surprised that this fish even still exists. 2 meter specimens were no longer caught in Thailand by World War II, and it may very well be extinct there and going extinct in the Mekong River valley. This could be another "so long we hardly knew thee" situation as with the Chinese paddlefish. Fishbase oddly claims that this species is often referred to in popular material and textbooks, but this has to be confusion with the upcoming species. There are people who claim to be keeping this species in captivity under the name "Paroon shark", but I can't help but wonder if it is a different species in the same genus; perhaps P. hypothalamus. Selling one of the world's biggest species of freshwater fish sounds a bit improbable to me, and from experience I know that pet stores and dealers often don't go by orthodox taxonomy. So how big does this fish get? Zeb Hogan in a previous paper describes this species as getting "slightly less gigantic" than the next species, and gives a length of 2.75 m maximum (9 feet). It is not known to what size 300 kg is supposed to go with, or even if the fish can actually get this big at all. Due to a huge gap in information, it looks like this fish too will have to remain a mystery.

Pangasianodon gigas, Chevey 1931
Mekong Giant Catfish
Pa beuk

In the Guinness Book of World Records this is the biggest species of freshwater fish. There is quite unambiguous of a 2.7 m female that weighed 293 kg (~9' and 646 lbs) caught in 2005, although record keeping for the species has only been going on since 1981. Gerald Wood comments upon a source in the 20's claiming a size of 3 m (~10 feet) for this species, and this has been a generally accepted figure despite the dubious corresponding weight of 240 kg. The weight has normally been reported at 300 kg for this size, but---do I even need to say this?---it Fishbase shows it came from a different source. Fishbase also states that this fish can grow 150-200 kg in 6 years, apparently making it one of the fastest growing known fish as well. Wood also remarked that only 14 specimens were caught in 1974, and the population has been estimated to have fallen 80% in the last 13 years according to the IUCN! It is no surprise that this fish is regarded as "Critically Endangered".

So let's see what happens here. Once again we have a species that is critically endangered, so can we save it this time? Hopefully Zeb Hogan can draw even more publicity to this species and save it from the apparent fate of the Chinese paddlefish. But, what about the more obscure species. I never heard about Soldatov's Catfish until a few days ago and I only heard vague mentions of the giant pangasius, and after looking for information the situation was hardly better! I somewhat doubt the public is more aware of these species and their plight than I do, and it may already be too late. The giant pangasius appears to be in an even worse situation than the Mekong giant catfish, which is quite alarming. But then, according to Hogan, we really don't know anything about this species. While discovering new species is one thing, I think that knowing so little about described species is nearly as surprising.

There's still a lot I'm curious about regarding these catfish. How are they capable of getting so large anyways? The Pangasiids are certainly not typical looking or behaving catfish (e.g. predatory giant pangasius and herbivorous Mekong giant catfish), so is it something other than niche occupation? Do the old records actually indicate that these species "shrunk" with exploitation. Were there even large Pleistocene cousins? I always seem to have a lot of questions here.

I'm not certain if I'll do more Megafish or not. My summer and blogging-spree is coming to an alarming stop here. Dang.


Addendum 8-7-07:

Top: Mekong giant catfish (Pangasianodon gigas) portrayed at hypothetical 3 m length. Source image

Giant pangasius (Pangasius sanitwongsei) at hypothetical 2.75 m length. Source image
Piraiba (Brachyplatystoma filamentosum) at record 2.37 m length. Source image

Right: Wels (
Silurus glanis) at record 2.78 m length. Source image
Soldatov's catfish
(Silurus soldatovi) length unknown, portrayed at 2.5 m. Source image
Wallago (
Wallago attu) portrayed at 2 m. Source image

Center: And of course, a puny human at 1.74 m tall.


Girri, S. S. et al. 2002. Larval survival and growth in Wallago attu (Bloch and Schneider): Effects of light, photoperiod and feeding regimes. Aquaculture. 213, 151-161. Available: Here

Hogan, Zeb, et al. 2004. Imperiled Giants of the Mekong. American Scientist. Available for free: Here

Petrere, Miguel et al. 2004. Review of the large catfish fisheries in the upper Amazon and the stock depletion of piraı´ba (Brachyplatystoma filamentosum Lichtenstein). Reviews in Fish Biology and Fisheries. 14: 403-414. Available: Here

Stone, Richard. 2007. The Last of the Leviathans. Science. 316, 1684-1688. Available: Here

Wood, Gerald. Guinness book of Animal Facts and Feats. Guinness Superlatives, Middlesex, 1982.