Flying fish from Asia are invading America's waterways and turning innocent boating trips into boxing matches as fish "knock out" anglers. National Geographic Explorer Zeb Hogan heads to the Illinois River, one of the areas where their population is thickest, to see what can be done to stop them ... and the answer could be as simple as your dinner plate.

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Dr Zeb Hogan searches the southern United States for the rapidly disappearing alligator gar.

Zeb travels Thailand in search of giant fish; freshwater protected areas.

Zeb Hogan is on a mission to find the giants of the sea.

Zeb travels to Spain for the wels catfish, a vicious predator that destroys local ecosystems.

Zeb Hogan attempts to fathom the uncontrolled spread of flying Asian carp in America's waterways.

Amazonian expedition to assess the impact of humanity on the area's fish population.

Zeb faces the crocodiles and goes in search of Africa's biggest freshwater fish: the Nile perch.

Aquatic ecologist Dr Zeb Hogan goes in search of the paddlefish.

Aquatic ecologist Zeb Hogan and fellow scientists search for Nile perch.