Mating game by goldfish

I HAVE a pond on the patio with half a dozen goldfish in it.

Most of the time they’re quite boring, skulking around under bits of vegetation and only becoming active when I sprinkle flakes of goldfish food on the surface. But over the past few evenings this has changed.

At a certain stage in the evening they start chasing each other round the pond at ferocious speed and, if the chasing is successful, butting the other fish in the flank. It’s easy to ascribe this sort of behaviour to ‘play’ but I suspected it was more significant.

I don’t know very much about goldfish, apart from the fact that they are an East Asian member of the carp family that was domesticated by the Chinese a very long time ago, first as a food fish and then as an ornamental species with many colours and shapes. So I went to the Internet to educate myself.

As I half suspected, the ‘play’ was mating behaviour. The male chases the female and nudges her to induce her to lay eggs, which he then fertilises. The eggs are sticky and attach themselves to vegetation before hatching into little fry 48 to 72 hours later.

There are several factors that induce this behaviour but one is a drop in water temperature from around 24 or 25 degrees down to about 20. So I got a thermometer. The water temperature was 19 degrees, but it was now evening. It had been a sunny day and I’m sure that in the middle of the afternoon, when the little pond gets the full sun, it had been about 5 degrees higher.

My mystery was solved but my research into goldfish threw up a few more interesting facts. I have three kinds —- yellow ones, orange ones and those multi-coloured ones called shubunkins. The shubunkins were bred by the Japanese, who learned the art from the Chinese at a fairly early date. Yellow goldfish are genetically easier to produce than orange ones but they are less common. The reason for this goes back to 1162 when a Chinese empress of the Song Dynasty ordered an ornamental fish-pond to be built and stocked. But because yellow was the imperial colour only the imperial family were allowed to keep them - everyone else had to make do with orange.

Nature Table

STINGING NETTLE (Urtica dioica)

Stinging nettles are a plant that everyone recognises — the tingling sting is a great teacher and it’s worse at this time of year when the nettles are tall and green.

Both the stalks and leaves have hollow hairs which act like hypodermic needles, injecting a cocktail of irritant chemicals. But nettles have their uses.

They are the food plant of the larvae of many butterflies and moths — the stings protect the caterpillars from predators. They can be eaten, made into beer and used for medicines, dyes, fabrics and twines. Cooking them completely eliminates the stinging chemicals and they are nutritious and delicious.

Only young nettles should be eaten. Nettles need a rich soil, particularly one rich in potassium. Because of this, they are often associated with human habitation. Archaeologists have used this fact to locate habitation sites long after the buildings themselves have disappeared.


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