Near our residence at Panchwati in Udaipur there is a nullah (water overflow channel). The excess water of two lakes of Udaipur is discharged through this nullah. During the rainy season of 1989, the lakes had overflowed and hence the nullah had small pools of water here and there with small fish in it.

On 15^th March 1990, I was standing near the nullah watching some waders. One of the pools was completely chocked with floating aquatic vegetation, mostly angiospermic plants (Lema minor) and pteridophyte Azolla species, except a patch of about 3m to 4m that was exposed.

When I went near the nullah on 16^th March at 9 am, I observed extraordinary activity of the fish in the exposed part of the pool. They were darting out of the water, sometimes high in the air or rushing to the surface with speed. This activity was observed throughout the day. Next day the same thing was observed but this time the open space was broadened.

For four consecutive days the fish were in the same mood. On the sixth day the water of the pool became calm with a few fish breaking the surface here and there but neither vigorously nor constantly.

From this activity of the fish I inferred that as gradually the pool’s surface was covered with floating plants because of the shallowness and the small span of water, the dissolved oxygen in the pool depleted. The fish created ripples and pushed the floating plants to corners of the pool to expose a greater part of the pool to air and by creating ripples dissolved more oxygen so that they could survive.

I caught some of the fishes of the pool with a landing net and identified them as under:

1. Chela bacaila
2. Chela gora
3. Pantius sarana
4. Channa puntatus
5. Mystus cavasious