A number of Burmese pythons have been found on Key Largo, and a few in the Lower Keys.  However, there is as yet no evidence of a breeding population anywhere in the Keys.  Because pythons regularly escape or are released from captivity, it can be diff
In some places, yes, but under several constraints. Specifically, importation of live snakeheads and their interstate transport is prohibited. Many states prohibit possession of snakeheads, and several of those states have done so for decades.
Most snakeheads will avoid contact with humans. In captivity, many will actually act shy around people. However, when guarding their eggs or young, they can become aggressive if approached.
Dead snakeheads--on ice or frozen--can be imported for food purposes to any state except those where importation or possession of dead snakeheads is illegal.
Although claims of their mobility have been greatly exaggerated, several species of snakeheads are able to wriggle overland from one body of water to another, particularly if the ground is wet.
Zebra mussels do not have many natural predators in North America. But, it has been documented that several species of fish and diving ducks have been known to eat them. 
Northern snakeheads were purposefully introduced and established into Japan in the early 1900s.
Generally zebra mussels are small averaging about a half to one inch long. Two inches is approximately the maximum size. Their life span is four to five years. 
The USGS focus is to document the zebra mussel's geographic distribution and to learn as much as possible about its behavior and biology.
Prior to being added to the list of injurious wildlife under the Lacey Act in October 2002, which banned import and interstate transport without a permit from the U.S.