Pielanesberg Fix pics id please!!

Went to the Pielanesberg last weekend. And i saw these fish in the big dam there. But i have no clue what they are. I think that the second photo might be a different type. Can anyone identify them?
They were all gulping air, behaving strange in large groups, if you have any explanation for this behavior it would be appreciated aswel.

 

Tilapia (Mombasica) in the top pic & could be large mouth bass in 2nd pic..... looks like they're in poor quality water gulping for air??....

 

All are Oreochromis mossambicus. Second pic is a male of the species.

The behaviour may be one of two things - either they were gulping for air, or they have accustomed to people feeding them. Koi also show such behaviour, and rise to the surface 'gulping' in anticipation of food... 'begging', if you want to think of it that way.

 

the water did not look poor at all. this was a few days after we had huge torrential rains in the area, maybe this behavior is connected to it. The dam they are in is huge, lack of oxygen could be a problem but as it had rained heavily in the previous 3 days not sure if this is the problem. the fish eagles were having a party though!!

another question of interest, are Oreochromis mossambicus native to south african waters or an invasive species?

 

Yes and no.

It is native to some water systems in South Africa, but otherwise has been introduced to other systems for fishing or other purposes.