Night fell as the two scientists got to work, unfurling long nets off the end of their boat. The jungle struck up its evening symphony: the sweet chittering of insects, the distant bellowing of monkeys, the occasional screech of a kite. Crocodiles lounged in the shallows, their eyes glinting when headlamps were shined their way.
Across the water, cargo ships made dark shapes as they slid between the seas.
The Panama Canal has for more than a century connected far-flung peoples and economies, making it an essential artery for global trade — and, in recent weeks, a target of President-elect Donald J. Trump’s expansionist designs.
But of late the canal has been linking something else, too: the immense ecosystems of the Atlantic and the Pacific.
The two oceans have been separated for some three million years, ever since the isthmus of Panama rose out of the water and split them. The canal cut a path through the continent, yet for decades only a handful of marine fish species managed to migrate through the waterway and the freshwater reservoir, Lake Gatún, that feeds its locks.
Then, in 2016, Panama expanded the canal to allow supersize ships, and all that started to change.
In less than a decade, fish from both oceans — snooks, jacks, snappers and more — have almost entirely displaced the freshwater species that were in the canal system before, scientists with the Smithsonian Tropical Research Institute in Panama have found. Fishermen around Lake Gatún who rely on those species, chiefly peacock bass and tilapia, say their catches are growing scarce.
Researchers now worry that more fish could start making their way through from one ocean to the other. And no potential invader causes more concern than the venomous, candy-striped lionfish. They are known to inhabit Panama’s Caribbean coast, but not the eastern Pacific. If they made it there through the canal, they could ravage the defenseless local fish, just as they’ve done in the Gulf of Mexico and the Caribbean.
Already, marine species are more than occasional visitors in Lake Gatún, said Phillip Sanchez, a fisheries ecologist with the Smithsonian. They’re “becoming the dominant community,” he said. They’re “pushing everything else out.”
