Final answer:
The claim regarding the infestation of Frankenfish in a lake in Travis County as a factual certainty is not verifiable without further context. However, such an infestation typically leads to the decline of native fish populations due to competition and rapid reproduction of this invasive species.
Step-by-step explanation:
The assertion that a lake has experienced an infestation of Frankenfish if but only if it's in Travis County cannot be deemed universally true or false without additional context. However, we can discuss the broader implications and characteristics of such an infestation. Frankenfish, or snakehead fish, are known invasive species that disrupt native ecosystems. Their presence in a body of water, such as a lake, often leads to the decline of native fish populations because they compete for food and resources.
These invasive species can reproduce rapidly, further compounding their impact on the local habitat. If a new predator was established in a stream's ecosystem between 1998 and 2008, it could potentially affect the population of invasive species like Frankenfish by preying on them or competing for resources. If this predator is present only downstream or in both upstream and downstream sections, it can have varying impacts on the ecosystem.