Last year farmer Luc’s lake was not looking healthy enough for his liking. Most of the fish in it had died and much of the lake’s surface was covered with weed. Mind you, it did support a large population of damselflies and an utterly enormous population of frogs, despite Marcel (Luc’s father) trying to trap them for the plate, which sang more or less constantly all night long. We find the frogs’ singing acts like a lullaby and sends us to sleep though other campers have disagreed rather strongly.
Luc made an arrangement with a local pisciculture man who has a fish farm near Bram just a few kilometres away. He has stocked the lake with some enormous Grass Carp that cruise around resembling nuclear submarines eating the weed. The fish man, in exchange for this service, breeds Koi Carp in Luc’s lake. There are thousands of the tiny beggars which, when a little bigger, he will take out, grow on and sell, Koi being quite valuable fish.
I am a little concerned than the natural balance of the lake has been somewhat overcorrected. There are so many voracious, large grass Carp that there is now very little weed. Whilst the water may, indeed, look very clear, damselflies need some floating weed on which to perch and oviposit [lay eggs]. One result is that any small remaining patch of weed tends to attract a dense collection of damsels in tandem all trying simultaneously to lay eggs. Today, I even saw one pair land on another pair, using the first female’s wings as a perch, and start trying to oviposit, seemingly in her face. “Get your damned eggs out of my face!”
A related concern is the effect of fish predation on the damsel and dragonfly populations. Both eggs and larvae are eaten by fish and, given the numbers of fish in the lake at the height of the dragonfly breeding season, I’m wondering how many will successfully mature for the coming years.
I’ll just have to return to monitor the situation. 😉