Clarias not batrachus

Post by **Silurus** » 24 Jun 2003, 20:42

You know how they're always saying that C. batrachus has been introduced into Florida. well, I had the opportunity to look at one such specimen from Florida in our collection today and it is definitely not C. batrachus (it's C. gariepinus). I also seemed to recall a photo from an old issue of National Geographic that had a pic of a Florida Clarias and it seemed that the color pattern wasn't right (the fish had a mottled pattern characteristic of C. gariepinus).
Anyone from Florida collected/seen any "native" Clarias recently to back up my claim ?

FatCat · Post by **FatCat** » 24 Jun 2003, 20:57

I had read of this before myself. But the information that i had obtained pointed out that the highly visible color vareity of C. batrachus that was itroduced was suffering greatly due to predation. Read that aligators love them. Is it possible that both were introduced and that C. gariepinus proved to be more sucessful because it might have been more fit for the environment?

Post by **Silurus** » 25 Jun 2003, 00:40

Hmm maybe. I'm surprised no one has picked up on C. gariepinus, especially since they reach about 4 times the size of C. batrachus.
Since Clarias gariepinus have to contend with Nile crocs in their native Africa, maybe they're better at dodging reptilian predators.

jscoggs27 · Post by **jscoggs27** » 25 Jun 2003, 08:08

I would be very surprised that no one has picked this one up before! I did here somewhere that maximum sizes attained by clarias species in florida was 24" which points to c Gariepinus. If both species are present that makes more sense, since floridas waters must be teeming with predators. But since the Us government makes no distinction between species to the point where only ictalurids are regarded as catfish then it shouldnt surprise me that this has been overlooked.
jason
HH care to put your theory on my site?

Post by **Silurus** » 25 Jun 2003, 08:10

Jason,

I'm in the process of trying to get more confirmation as to the actual identity of the fish. I'll put it up on your site until then.

FatCat · Post by **FatCat** » 25 Jun 2003, 17:21

The department of fish and game refers to the fish specifically as C. batrachus from the research i have done recently. However being as similar as they are to the average observer or even fish and game personell the thought probibally never crossed anobodys mind that there might be two seperate species. Also i found that C. batrachus and C. gariepinus have been hybridized. Maby some of those swimming around as well. No telling what litterally walked away from fish farms in florida before they started fencing them in. From what i found out last night these guys like to stick together and will go onto peoples prize ponds and lakes and devouer everything then leave for the next one. This is causing people to fence in their own ponds to keep these guys out. Very interesting if it is all factual.

jscoggs27 · Post by **jscoggs27** » 25 Jun 2003, 18:02

According to 'Florida Sportsman Online' florida's record for walking catfish(C batracus) is 1lb 8 oz. This doesnt sound like C gariepinus. I didnt know that they had been hybridizing C batrachus and C gariepinus I think C gariepinus and C macrocephalus hybrids are more common in Asian fish farms. Slightly off topic.... I was told recently that C gariepinus was unavailable in britain because not enough are caught (BAS) in Africa. But I thought that nowdays C gariepinus was comercially bred in Asia as a food source. So maybe we'll see some of those here sold as C batrachus in the future?
jason

Post by **Silurus** » 25 Jun 2003, 18:19

Well, I looked at the single specimen from Florida here and here's what I observed:
The fish does not look like C. batrachus on the account of its head shape. When viewed from the top, C. batrachus has a characteristic egg-shaped head...the Florida Clarias here had a more squared-off snout. Also, the top of the head is much flatter than in C. batrachus, and the skin covering the skull roof is very thin...so much so that the roughened surface of the bones of the skull roof are easily discernible. These are all characteristics consistent with C. gariepinus.
Clarias may have been introduced into Florida more than once, and the possibility that both C. gariepinus and C. batrachus are now found there. The only info I could find to datee stated that broodstock brought over from Asia were the initial cadre introduced. Given that C. gariepinus is cultured extensively in Asia, it may not be surprising that this species should also occur in Florida.

beng · Post by **beng** » 05 Dec 2004, 15:02

See
http://floridafisheries.com/Fishes/non- ... ml#walking

which states that it was first reported in 1967 in Broward County and later in Hillsborough County, now these two populations have joined; abundance has decreased since 1970, and it has not had the great adverse ecological impact that was feared.

I wonder if the two populations also represent different species?

see also
http://nis.gsmfc.org/nis_factsheet.php?toc_id=181

"Walking catfish were originally introduced to Florida by means of an accidental release from Penagra Aquariums, west of Deerfield Beach in Broward county, during the mid 1960's (Courtenay et al., 1974). The escaped specimens were from a brood which originated in Thailand (Courtenay et al., 1984). The first specimen reported from open waters, was caught by an angler the 15th of March of 1967 (Shafland, 1994). The population established in Hillsborough county represents an independent introduction (Courtenay et al., 1974; Courtenay, 1978)."

and
http://aquat1.ifas.ufl.edu/mcfish5d.html

The first time that i heard of C. gariepinus in Asia was in the 1990's. Was it there by the 1960's?

In Singapore C. gariepinus is now found in some canals and ponds (Pandan canal, NTU pond, possibly Bt Timah / Rochor canal lower tidal part, and possibly Jln Toa Payoh canal though it too is tidal and brackish), but it (so far) is not found in the small shallow streams where C. batrachus lives, preferring deeper waters.

C. gariepinus may thus become the most common Clariid in Singapore as the small shallow stream and drain habitats (both rural and urban) that C. batrachus favoured have been almost all eradicated, being turned into new straight-sided underground concrete drains unsuitable for fish life. All other small stream fish (gouramies, swamp eels, snakeheads, etc) are also likewise threatened by development.

Post by **Silurus** » 05 Dec 2004, 15:57

I think I may have found the solution. Apparently, C. macrocephalus-C. gariepinus hybrids have been around for some time in Thailand and a even back-crossing with wild C. macrocephlaus.
Maybe these things are hybrids, or the back-cross of the hybrids.

The reference is:

Na-Nakorn U, W Kamonrat W & T Ngamsiri, 2004. Genetic diversity of walking catfish, Clarias macrocephalus, in Thailand and evidence of genetic introgression from introduced farmed C. gariepinus. Aquaculture, 240: 145-163.

And the abstract:

The Thai walking catfish, Clarias macrocephalus Gunther, 1864, is economically important to Thailand. It occupies marshes and swamps that are severely endangered due to population expansion and natural populations are thought to be suffering from massive back-crossing with the C. macrocephalus x C. gariepinus hybrids. Therefore, a study on genetic diversity of this species is required to enable efficient conservation and management plans. In this study, 25 natural populations were collected throughout the country, 12 populations from provinces locate in the Chaophraya river basin in the center of the country, 5 from the Mekong river basin, 1 from the east and 7 from the south. One population of hatchery origin was obtained from the Department of Aquaculture, Kasetsart University in Bangkok.

Twelve isozymes and one protein system were analyzed. Among 18 loci resolved, 8 were polymorphic. The number of alleles per locus, average polymorphism and individual polymorphic were significantly higher in collections from the Chaophraya river basin than from the Mekong, east and south. The hatchery population also had relative high genetic variation. Six out of twenty-six populations differed significantly from Hardy-Weinberg equilibrium after Bonferroni correction. None of loci pairs showed significant linkage disequilibrium after Bonferroni correction. The F-st value across loci was highly significant from zero. A neighbor-joining tree reveals that populations from the south were genetically distinct from the remaining populations.

Alleles peculiar to the African catfish [C. gariepinus (Burchell, 1822)] genome were observed in 12 of the natural populations and the hatchery, population. This is evidence of genetic introgression which has probably persisted for several generations, since there was no significant genotype disequilibrium between the macrocephalus and gariepinus alleles at three diagnostic loci.

beng · Post by **beng** » 05 Dec 2004, 18:10

Some other notes on the Thai C. macrocephalus hybrids:
<http://www.fao.org/DOCREP/003/W3595E/w3 ... ridization>
They even hybridized it with non-clariids like Pangasius sutshi!

However the garipinus seems a more recent introduction to Asia, according to Fishbase introductions list, this is how it may have happened:

1974, Central African Republic to Vietnam

1980, Vietnam to Laos

1981, Central African Republic to China (perhaps the one i saw in Jinan came from that)

1982, Viet Nam to Cambodia

1985, Thailand & Taiwan to Philippines

1987, Laos to Thailand (but it was alreaDy in Thailand?)

At any rate it doesn't look like it could have been in Thailand at the time of the introduction from Thailand to Florida of "C. batrachus". The C. gariepinus x C. macrocephalus crossing took place in Thailand in 1988.

I don't know when large clariids (gariepinus or hybrids thereof) appeared in Singapore but the first i heard of them was in anglers' reports of fishing in NTU pond in 2000, that pond is artificially stocked with imported fish. Thereafter, quite large specimens turned up in the Pandan canal which must have been 5 or more years old.

beng · Post by **beng** » 05 Dec 2004, 18:14

Also, from the abstract you quoted, it seems they identified the fishes as being C. macrocephalus and then only after DNA analysis, concluded that they had introgressed with the gariepinus hybrids. Does this suggest that phenotypically, the hybrids look more like macrocephalus than gariepinus?

Also, fishbase puts macrocephalus max TL at 120cm and mentions it has been introduced to China and the Philippines, which if true, gives another candidate for the large Clariid i saw in Jinan in China.

Post by **Silurus** » 05 Dec 2004, 18:30

Also, fishbase puts macrocephalus max TL at 120cm and mentions it has been introduced to China and the Philippines, which if true, gives another candidate for the large Clariid i saw in Jinan in China.

FB took that size data from: Frimodt, C., 1995. Multilingual illustrated guide to the world's commercial warmwater fish.. Fishing News Books, Osney Mead, Oxford, England. 215 p.

I would not consider a book written by fishermen for fishermen would be accurate with regards to species identification.

beng · Post by **beng** » 05 Dec 2004, 18:58

Silurus wrote:I would not consider a book written by fishermen for fishermen would be accurate with regards to species identification.

True, this Philippines pdf file says that in size it is similar to batrachus:
http://www.seafdec.org.ph/downloads/catfish.pdf

Fishbase also mentions that the pectoral spine of gariepinus is serrated only on the outer edge whereas for batrachus it rough on its outer edge and serrated on its inner edge, which may be another thing to look out for if you get to see that Florida specimen again.

In case anyone is interested there's a photo of a C. gariepinus i caught from the Pandan canal in Singapore at:
http://www.fishingkaki.com/forum/viewtopic.php?t=649
It was a male, 49cm TL, caught on hook and line at night using a dead juvenile Parachromis managuensis (jaguar guapote) as bait.

I put it in my 4 foot tank put it jumped out through the cover and i found it the next day dried up on the floor. I thought it was dead at first because its skin was dry, but when i put it back in the water it came back to life and seemed none the worse for wear!

Someone also caught a big one in a reservoir:
http://www.fishingkaki.com/forum/viewtopic.php?t=1382

beng · Post by **beng** » 06 Dec 2004, 10:14

According to this article now available only in google cache, gariepinus was introduced to Florida:

http://66.102.9.104/search?q=cache:NvSR ... .htm&hl=en

beng · Post by **beng** » 06 Dec 2004, 13:25

Here's another archived/cached page mentioning the possible ecological impacts of introducing gariepinus in places where it is not native:

http://web.archive.org/web/200311021911 ... at229a.htm

And another copy (with pictures) of the google cached link is here:
http://web.archive.org/web/200210090348 ... /cat4a.htm

beng · Post by **beng** » 10 Dec 2004, 14:40

Silurus wrote:The Thai walking catfish, Clarias macrocephalus Gunther, 1864, is economically important to Thailand. It occupies marshes and swamps that are severely endangered due to population expansion and natural populations are thought to be suffering from massive back-crossing with the C. macrocephalus x C. gariepinus hybrids.

Hybrids are also used extensively in the tilapia farming industry, mainly to produce all male stocks, as males grow faster and also a pond of all male fish won't reproduce out of control and over-crowd themselves.

In Singapore hybrid tilapia (mostly of a red variety, crosses of O. niloticus with some other species) were released into the wild in the late 1980s and since then the feral tilapia stocks (formerly consisting exclusively of O. mossambicus, intorduced to singapore from Java by the Japs during WWII and introduced from Singapore to Hawii) have crash. I suspect that this is mainly due to the hybrid tilapia breeding with the wild stocks and producing a sex-skewed population which has more males than females. Wild-caight tilapis showing phenotypic characteristics of O. niloticus and O. aureus and O. honorum are now quite common, and the proportion of males in my catch is much higher than in the early 1980s.

Whilst tilapia is a non-native fish in Singapore and its decline is no great loss to local biodiversity, it does show how introgression can threaten wild fish stocks. I wonder if the Clarias hybrids that are now common may have a similar effect on wild Clarias stocks in Asia. Does anyone know if the hybrids have skewed sex ratios for example?

Also, why do they hybridise them? Does one Clarias species taste different from another? Why not just farm un-hybridised fish? Surely the taste has more to do with what the fish is fed with and the water quality it is grown in?

MatsP · Post by **MatsP** » 10 Dec 2004, 15:01

beng wrote: Also, why do they hybridise them? Does one Clarias species taste different from another? Why not just farm un-hybridised fish? Surely the taste has more to do with what the fish is fed with and the water quality it is grown in?

My guess on the subject would be that the cross-breed is easier to raise in one way or another. Most likely that it grows quicker or tolerates bigger numbers for the same water-volume.

It could also be that the cross is sterile and thus doesn't spawn to increase the population in a growout pond. Having lots of small spawn isn't good when you want food-fish.

That's of course just a guess.

--
Mats

beng · Post by **beng** » 12 May 2005, 16:55

Silurus wrote:Jason,

I'm in the process of trying to get more confirmation as to the actual identity of the fish. I'll put it up on your site until then.

Any news on the Florida gariepinus? In Singapore the feral gariepinus grow to quite obviously large sizes so i wouldn't be surprised if florida anglers start catching unusually big walking cats.

See:
http://www.outdoorpages.co.za/Gallery/P ... gariepinus
(scroll down to around record 44 for a pic of a singapore gariepinus)

The USGS factsheet for C batrachus list some surprisingly northern US states as places where it has been found:
http://nas.er.usgs.gov/queries/factshee ... ciesID=486
Is it possible for Clariids to survive winter temperatures in Massachusetts?

beng · Post by **beng** » 17 Aug 2005, 11:57

According to an article in:
http://pdacrsp.oregonstate.edu/pubs/aqu ... mmer98.pdf
gariepinus was introduced in Asia first in Vietnam, by the French colonials during the 1950's before uncle Ho kicked them out. It survived the Vietnam war and from there it reached Thailand in the early 80's, and reached Bangladesh in 1991.

Another source says 1989 was the year it reached Bangladesh from Thailand:
http://banglapedia.search.com.bd/HT/E_0081.htm

And the Bangladeshi's have a manual for farming it:
http://www.fao.org/docrep/field/003/AC379E/AC379E00.htm

An African culture manual is here:
http://cdserver2.ru.ac.za/cd/catfish/catfish/

As for Florida Clarias, the IGFA record (International Game Fish Association records, quite stringent criteria) there is only 1 pound, which suggests that gariepinus hasn't been cauht there yet (it grows to well over a metre long and would weigh more than 1 lb).
http://floridafisheries.com/offices/cityfish/vol3b.html

Has anyone in florida seen the African walking catfish? Whats the biggest walking cat you've seen there?

beng · Post by **beng** » 17 Aug 2005, 12:09

Silurus wrote:I also seemed to recall a photo from an old issue of National Geographic that had a pic of a Florida Clarias and it seemed that the color pattern wasn't right (the fish had a mottled pattern characteristic of C. gariepinus).

is it:
Idyll, Clarence P. â??New Florida Resident, the Walking Catfish,â?

Clarias not batrachus

Clarias not batrachus

Re: Clarias not batrachus

Re: Clarias not batrachus

Re: Clarias not batrachus