Dead Fish on the lake?

During March every year you see lots of fishes pupping up dead around the lake.. Lots of people wonders why? Once I have collected 7 kilos of dead fishes but them in ice and took them to AMSCLAE for them to take them to the laboratory.. After some analysis they determine that they died of stress...
Following the best explanation I got for years ... It is a problem of population numbers, food and space.  The fishes dying are not able to find their place in the lake environment.
When it is rainy season the temperature of the water is too high. Therefore the crappies don't stay in the shallow areas and go deep.. When the temperatures hits 20 degrees in the dry season their number explode,  and they are every where above 8 meters. It is usually before the Easter Week and when everybody is out from the village fishing on the piers all along the shore.
Two species, the sunfish or mojarra and the bass (both introduced species) only breed in the shallows and also very territorial. There is literally no space for these fish to continue to breed as a majority of the shallows are taken up by dense vegetation and other fish there nesting. The stress levels increase in these fish as the population numbers grow out of control. And then they start to die raising to the surface, drifting to the shore making food for the Grey Heron and other big birds.

But right now the water is absolutely gorgeous...