I think that the “mini Crocodile” is better known as a caiman, a close cousin (but not kissing). At least the authorities have, I presume, removed some of the other natural impediments; piranhas, electric fish, anacondas and then there is that little fish that has been know to swim upstream for those who are taking a ‘natural break’, the Candirú.
Oh, the caiman has its uses, and could score quite well with the critters you name. Y’see, the albumen of its eggs, iirc, is an infallibly deadly toxin. Great murder mystery poison, btw. I hadn’t known that they ranged as far South as Brazilian golf courses near Rio.