The clinging catfish

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Glyptothorax aren’t the kind of catfish you see in stores often, which could be as much our loss as it is their salvation. Given the propensity of many new hobbyists to jam any old fish into a mixed community tank, at scorching temperatures and lacking in waterchanges, the glyptos are dodging a bullet. These are delicate fish, and high maintenance, but not without their charm. In fact, scrub that — they are packed with charm. 

Most of us have looked at a Goonch catfish, Bagarius yarrelli, at some point and thought it would be really cool to keep one. The problem, of course, is that we don’t have room to house a 200cm, 100kg fish at home. In step their comparatively tiny cousins of Glyptothorax — assuming you can find them, and assuming you’re up to the challenge. They look ‘goonchy’, they sort of behave ‘goonchy’, and they have surprisingly similar requirements, minus the one for an absurdly sized tank. Stick with me…

Who are they? 

Glyptothorax are Asian catfish from the Sisoridae family, and have a distribution that stretches from Turkey, eastwards to China, and down southwards to Java. Currently fishbase.org lists 101 known species, with the last couple of decades being something of a taxonomic tidal wave, seeing dozens described. It’s certain that more will be described in coming years, too, with importers reporting new arrivals that don’t conform to any of the known species. 

The size range within the genus is quite extreme (the smallest species, Glyptothorax panda has a standard length of 3.1cm, while the giant of the genus, G. saisii, can reach 90cm), with the majority of them sitting somewhere at the shorter end, from around 8cm to 15cm. 

Although widely distributed, many are captives of their immediate firmly on the stenotopic spectrum (unable to adapt to changes in their habitat). That’s because their choice of real estate is pretty niche: these fish love a river. More specifically, they love torrential flows, and the high speed rough and tumble associated with hillstreams, mountain streams and rocky whitewaters that they call home. 

Sticky business

To call Glyptothorax rheophilic (river loving) is an understatement. They insist upon rivers and the associated conditions: high oxygen, often cool waters, and a lack of pollutants. When your water is coming straight down the side of a mountain having just defrosted from snow, it tends not to be packed with nitrates. 

To help them cope with the flows that they’re exposed to, Glyptothorax have evolved unique undersides. We’re used to fish ‘sucking’ on to rocks (think of Sewellia loaches, or the many gobies that have adapted their paired fins into suction cups), but these catfish are a bit more ‘grippy’ than that. 

The genus name literally translates to ‘carved breastplate’ in reference to the corrugated flesh that’s present just down behind the throat. Under a microscope, a look at these skin folds will reveal that they are covered in tiny spiky projections, keratinized (hardened, like scales or fingernails) and rough. Rather than create a little ‘sucky patch’ of negative pressure on their undersides, like other bottom dwelling rheophiles do, Glyptothorax use this toughened skin to grip directly to rocks and their associated biofilms, clinging on for dear life. 

Delicate flowers

Being tied as they are to their rivers comes with some problems — chiefly, threats of extinction. For millions of years, Glyptothorax have been doing their thing happily out of sight in their pristine streams, and then mankind suddenly appeared and started tearing up the landscape. Damming of rivers can wreak havoc on populations (they typically migrate to spawn), while local deforestation can lead to siltation. That’s a problem as many species like to spawn in gravel beds — once those are buried under soft mud, the cats have nowhere to lay their eggs. 

Add to that burden the presence of introduced invasive species, and things get worse. Mosquito fish, guppies and tilapia might not eat the catfish outright, but they do chisel away at their food supply, depleting resources. Then you have bigger, openly hostile invasives like Clarias that do eat the Glyptothorax.

Read the rest of the feature in the June issue, available to read instantly on our digital edition HERE  or purchase the print edition HERE.

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