Thursday, 28 April 2016

Are all aquarium fishes equal?

There is a branch of a nationwide pet store in town that sells aquarium fish. Well, sell is not quite the word. It will only sell to those who have bought and set up what the store considers to be a suitable aquarium—one that includes mechanical filtration and aeration. That seems to be ticking all the right boxes for concern over the welfare of the animals they sell. The cynic might also notice that selling relatively expensive filtration equipment is also good for profits. On seeing the store’s policy, I did query it with the assistant tending the fish. I pointed out that some of the fish for sale were those from still waters and were not subjected had they ever seen the wild, rather than a Singapore fish farm, to the constant noise from motors thrashing water and strong water currents hitting them from all directions. Might they not be better housed in the good old fashioned way, with no water circulation and, where appropriate, lots of growing plants? But, no, the  company’s policy had to be adhered to with all their fish. I withdrew, bemused but annoyed at the same time by such stupidity.

Last week this episode at the eppier end of epizoology was brought to mind while searching some newly acquired magazines from the 1950s for my other blog site. Water Life (December 1951-January 1952) contained a report on fish keeping in Holland by W.J. van der Kolk. Most aquarium fish were then wild caught and I dare say that modern aquarium fish are  better adapted to environmental insult. However, the results he reported were dramatic in comparing what happened to Dwarf Gouramis (then Colisa lalia, now Trichogaster lalius) kept in noisy or quiet aquaria. Dwarf gouramis live in still or slowly moving water in the Indian subcontinent:

     Two identical aquaria were set up, and in each was placed 50 dwarf gouramis. One tank was left undisturbed apart from the movements necessary at feeding and cleaning times. The other tanks was deliberately disturbed (the glass sides were tapped several times a day). After two and a half years the population in the “quiet tank” was 47 fishes; in the disturbed aquarium only five fishes remained of the original 50*.

Need I say more?


Colisa lalia-Male and Female
Male and Female Dwarf Gouramis. Photograph by Felix Gertz

*for the statistically minded 𝛸2=70.7 with p<0.01, a result many a PhD student would be delighted to obtain.