A Sting in the Name

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The fish that live in the realm between fresh and seawater rarely get a look in. Chris Sergeant spotlights a brackish species worth setting up for.

When it comes to their common names, fish can be particularly confusing. Take the Bombay duck Harpadon nehereus, or Montagu’s sea snail, Liparis montagui, prime examples of fish masquerading under the guise of another animal. Meanwhile, working out what creatures like the Sarcastic fringehead, Neoclinus blanchardi, or Monkeyface prickleback, Cebidichthys violaceus, are based on their name alone is nigh on impossible. Then you have Zebra sharks, Stegostoma fasciatum, which are spotted, whilst Electric eels, Electrophorus sp., are actually species of knifefish. I would continue, but you get the picture.

Most naming confusion causes relatively few issues within the aquarium trade. If there’s any ambiguity, we revert back to the scientific titles. But there’s a small assortment of fish where misleading names can lead to their detriment. 

For many aquarists, the thought of a lionfish, toadfish or waspfish will likely conjure up images of fishes dwelling over coral reefs, hunting prey with impunity, or buried under sand, spiky and venomous. But scour the stock tanks at any of the more specialised aquarium stores and you’ll often yourself face-to-face with a ‘freshwater’ alternative. 

Admittedly, the Grunting toadfish, Allenbatrachus grunniens, and Three-spined lionfish, Batrachomoeus trispinosus, (confusingly also a species of toadfish) can be rare finds. Probably the most commonplace, at least from my own personal experience, is the Freshwater waspfish, Neovespicula depressifrons.

Salty little wasps

These little fish have a multitude of other colloquial hobby names: Leaf goblinfish, Butterfly goby, Dusky panther goby or the Butterfly grouper to name just a few. Despite the insinuations, they are neither goby nor grouper, but instead hail from the order Scorpaeniformes and the family Tetrarogidae, a group known collectively as the waspfish. 

Reaching a maximum size of approximately 10cm, from a morphological perspective N. depressifrons ticks the majority of waspfish boxes; a small, bottom-dwelling fish that possesses venom sacs at the base of the dorsal and pectoral fins (hence the name), and a lachrymal saber, a switch-blade like protrusion on the bone under each eye. Another distinguishing feature is the split dorsal fin, with the first fin raised considerably higher than the second, giving rise to yet another tag; the Mohican waspfish.

Before freshwater tank owners start rubbing their hands together in delight however, all it not quite as it seems. N. depressifrons is not actually a true freshwater species. In fact, neither are the A. grunniens or
B. trispinosus species I’ve mentioned either — they all live under that fuzzy banner of the ‘brackish fishes’, species which may at different times been found in rivers, estuaries, or full blown seawater. 

So, if N. depressifrons and the rest aren’t actually freshwater fish, why attribute the freshwater tag?

The likeliest answer is that being euryhaline they can tolerate a variety of salinities, with juveniles in particular being found frequently in freshwater. The key thing here is tolerance, though. They tolerate a variety of salinities, but that’s not the same as saying that they thrive in them all. These little waspfish will often be offered on sale from freshwater tanks, but remember that very few retailers have brackish water facilities, and keep any brackish fish in freshwater only as a temporary measure. 

Read the rest of the feature in the January 2022 issue. Buy the latest digital edition and read instantly on your computer, mobile or tablet device.


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