Why are Blue-eyed plecs so uncommon?

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In the mid- to late-1990s you used to be able to buy Blue-eyed plecs for around a tenner each. Now you're looking at four figures to get one. Why are they so uncommon and expensive now?

I’ve overheard fishkeepers talk about over-fishing, environmental disasters, hydroelectric plants and export restrictions as reasons behind this fish’s scarcity in the aquarium trade, but I’ve not heard anything from the academic community concerning their status in the wild.

I remember when tankloads of Blue-eyed plecs were sold for £10-15 each in the late 1990s. Given their 200-300% increase in price over the past decade, investors would have done well to buy and look after them all. They didn’t — and nor did we. Now just as kids, we only want something when we can’t have it.

I don t know why these fish have become so rare, but their abundance and low price during the last decade suggest that Venezuela and Colombia had effective programmes to collect and export them.

Blue-eyed plecs come from streams feeding into Lake Maracaibo in north-western Venezuela and the adjacent Rio Magdalena. Most were collected by baiting traps with a particular kind of tree bark; the preferred diet of large Panaque.

When I was in Maracaibo in 1999-2000, the grey-hairs in the team lamented how much forest had been replaced by pasture. In these areas, where cattle were ranched and allowed access to streams, we found no fishes.

A stream without any is extremely rare and sad in South America, so we suspected environmental damage. It is unlikely that cows with their hooves and manure affect fish so badly, so we feared that chemical fertilisers and pesticides had been to blame.

No hydroelectric plants have been built recently, so if there is a real drop in their numbers in the wild it is likely due to a combination of over-fishing and environmental degradation.