Thousands Of Voracious, Fast-Growing Fish Escape And Are Migrating Up The Coast

It sounds like science fiction: tens of thousands of voracious, fast-growing fish escape from ocean pens in a foreign environment and begin migrating up the coast, wreaking havoc on native fisheries.

But this is really happening, as thousands of cobia, which are found in the Atlantic but unknown to the Eastern Pacific, were accidentally released from an Ecuadorian aquaculture facility during late summer.

They’ve since been detected off Colombia and Panama, and at least one scientist believes the “rogue” fish are headed to California, with potentially “horrifying” consequences.


Cobia prey on crabs, fish and squid, and are considered voracious. Photo: Courtesy of Milton Love

The cobia have been migrating north at a rate of about 200 miles per month, according to UC Santa Barbara research biologist, Milton Love.

Love stated recently that there’s a 50-50 chance that the cobia will reproduce along the way, and he added that water conditions will be prime for their arrival in Southern California this summer.

“The idea is intellectually interesting and vaguely horrifying at the same time,” Love said. “This is the first time that Southern California waters potentially could have a large and voracious non-native species invade.”

“What effect that will have on the native fishes, no one knows. It might not have any observable effects or it might have considerable ones. A possible scenario is for these fish to become well-established and start chomping down on native fishes.”


Cobia are an important aquaculture species because of their firm, white flesh. Photo: Courtesy of Wikipedia

Cobia, which can measure 6 feet and weigh about 100 pounds, prey on crabs, fish and squid. They’re also known to follow sharks and other large predators to scavenge on what they kill.

Cobia don’t travel in schools except during spring to early fall spawning seasons, and prefer offshore (pelagic) waters.

Their flesh is white and firm, making the fish ideal aquaculture specimens. The cobia being reared off Ecuador were in netted pens that somehow broke open. Those fish are now considered invasive, and their potential impact remains unknown.

Ross Robertson, a Smithsonian scientist, noted that the lionfish, an Indo-Pacific species now abundant as an invasive and harmful species in the Caribbean, “provides a compelling lesson about the strong adverse effects that alien marine fish can have on native ecosystems.”

Robertson added, “As cobia is the only species in its family, which is most closely related to remoras or shark-suckers, it too represents an unusual type of predator for the tropical East Pacific, which only increases both the degree of uncertainty about its effects and the potential for major disruption of the area’s ecosystems.”

Love, author of Certainly More Than You Wanted to Know About the Fishes of the Pacific Coast, noted that California’s crab fishery might be impacted, since crabs are a chief prey item for cobia.

The researcher said anglers might be the first to encounter cobia, which are an important angling species in the Atlantic and Caribbean (they’re sometimes referred to as black salmon).

“You might expect to see cobia as summer migrants like yellowtail,” Love said. “They seem to be able to compete well with other fish in the vicinity and are generalists as far as what they feed on. Here, they would be in competition with yellowtail, bonito or even with reef fishes like kelp bass.”

To be sure, Southern California anglers will be delighted to catch cobia. But from a fisheries standpoint, their arrival will signal cause for concern.
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