he Ariidae family is wide spread, ranging throughout the continents of Asia, Africa, Australasia, South and Central America and there are about 80 species with the vast amount of them occurring along sea coastlines, estuaries and coastal lagoons hence one of the common name of this genus, ‘Sea Catfishes’. Until 2007 this species was known as Arius graeffei but there has been a name change for the members of the Ariidae family who reside from Southern New Guinea and Northern Australia, Arius to Neoarius.

The species we are concentrating on this month is one of only 5 represented in the freshwater rivers of Australia and Papua New Guinea, the 'Lesser Salmon Catfish', Neoarius graeffei.

Make sure that you don't let the p.H. drop too low as they like it more on the alkaline side. They have appeared periodically in the tanks of retailers and I would be interested if someone out there is still keeping this species.One cause for concern is the poisonous spines of the dorsal and pectoral fins as they will need to be treated with respect as it can take quite a while for a wound of this nature to heal up if you are unlucky enough to be punctured.

Colouration is not terrifiic in this species as they have a dark brown to blue upper body fading to a white/creamy underbelly. They are also treated as a food fish in its native habitats, they are renowned for their good taste if prepared properly but some fisherman treat them as pests as they can get caught in their nets and can take a considerable amount of time to disentangle them, and of course as well as avoiding the sharp spines they can ruin a net for future use.

One very interesting subject that was thrown up by my enquires was the  ‘homeing device’ or electrical fields that this species possesses and below I have reproduced a published paper from the Australian Defence Science site from Alan Theobald DSTO Defence and Darryl Whitehead of the University of Queensland Australia called, Using Fish Sense for Mine sensing.

“The superior sensory capabilities of fish may one day replace conventional sonar as a means of detecting marine threats such as sea mines. New research sponsored by DSTO's Maritime Operations Division at the University of Queensland's Zoology Department is exploring the electro-reception used by various fish species for possible military applications.

For example, catfish (Siluriformes) and sharks and rays (elasmobranches) can detect electrical fields as weak as 0.07 and 0.001 microvolts per centimetre, respectively. Researchers at the University of Queensland have shown that the Australian salmon-tailed catfish (Neoarius graeffei) has a sensitivity equal to or better than any other bony fish. In fact many indigenous animals, such as platypus and echidna, can detect the very low electric fields from their prey. 
 
The new research program will target species that inhabit estuarine waters and, indeed, migrate between fresh and salt water which have vastly different electrical conductivities. It is hoped that a good understanding of the physical and biological processes will result from observing differentpopulations of the same species.

“The illustration (above), for example, shows the changes in heart rate (top) and blood pressure (bottom) when a voltage of 70 nanovolts is introduced along the sides of the fish.” 
 
“This research has a long way to go before military applications can be realised. However, if it is possible to replicate the type of natural mechanism plus the signal processing chain, then an alternative to sonar could be produced. In the first instance, noting that the ranges at which fish themselves detect electric fields is of the order of metres, this work is targeted at the possibility of detecting mines, which might be buried in the sea bed and therefore difficult to detect using acoustics.”
 
“The basic electro-receptive unit in fishes is the ampullary organ (shown) which is the ampulla enlarged portion of the canal containing receptor cells and supportive cells. Receptor cells are electro-receptive sensory cells and the cup-like cells that encase them are the supportive cells.” 

“The length and structure of the ampullary canals varies greatly between species and habitats. They can be six centimetres long on the marine catfish (Plotosus anguillaris), whilst on freshwater catfish they can be just 0.1 to 0.2 millimetres long. The ampullae themselves may contain hundreds of sensory cells and species may have thousands of ampullae over the skin.” 

“In nature only the toothed whales, such as dolphins and porpoises, have been shown to have evolved active sonar as a detection mechanism in water. Left : Darryl Whitehead, University of Queensland with Neoarius graeffei. Many fish species do, however, detect water-borne acoustic energy up to a few kilohertz from sources other than themselves.”

“Typically marine animals have evolved other sensory systems such as olfactory, magnetic, electric and tactile, as well as optical. These systems are used for both detection of prey and navigation. By contrast, human technology has developed sonar systems, either passive or active, primarily to detect underwater objects. Since World War Two, vast military funding has been directed at the development of complex sonar systems. This research represents one step in the search for complementary approaches to sonar for underwater detection.”

Acknowledgments:  Darrryl Whitehead of the University of Queensland for his permission to use his paper, Using Fish Sense for Mine sensing.

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