Nothing to Stop Cobia Becoming Invasive in East Pacific, says Scientist

Lucy Towers
16 March 2016, at 12:00am

PANAMA - Scientists from the Smithsonian Tropical Research Institute have responded to claims that their recent comments over the invasive potential of cobia are absolute nonsense".

Following a mass escape of juveniles from a seacage on the coast of Ecuador, where Cobia mariculture recently began, a press release from the Smithsonian Tropical Research Institute, Panama, noted the potential for it to become an invasive species with adverse ecological consequences in the East Pacific.

The native range of the Cobia (Rachycentron canadum) includes the Atlantic and Indo-west Pacific oceans, but not the eastern two thirds of the Pacific ocean.

Following the release, Intrafish spoke to an aquaculture expert at the University of Miami who said that the idea that Cobia might become invasive is “absolute nonsense”, as it is cannibalistic, uncommon and innocuous in its natural range and that to compare cobia with Indo-Pacific lionfish, an invasive species in the Caribbean, is nonsense.

In response to the comments, Ross Robertson, a Staff Scientist at the Smithsonian Tropical Research Institute, said: "When biologists talk about invasive species they are referring to alien species introduced to areas outside their native geographic ranges, where they often become abundant and damaging. The fact that Cobia is alien to the East Pacific is a crucial point. No biologist who actually studies invasive species can accurately predict what will happen when you dump an alien into an area outside its native range for the first time, or would ever claim that a particular organism “cannot become invasive, period”.

"The notion that Cobia will not become invasive in the East Pacific because it is uncommon in parts of its native range and unproblematic there is absurd, and the lionfish invasion of the Caribbean shows why. In its natural range lionfish is uncommon and causes no problems; but, in the Caribbean, it has become superabundant and highly disruptive.

"Lionfish succeeded in the Caribbean for two reasons: First, as there are no native lionfish in the Atlantic, Caribbean prey have little idea of the threat such an unusual predator poses (for example, lionfish eat lots of Caribbean cleaner-shrimp, which approach predatory native fish when proffering their services). Second, lionfish originated in a high-diversity area (the Indo-west Pacific) and lower-diversity ecosystems (here the Caribbean) have lower “biotic resistance” to invasion, i.e. reduced ability to thwart invaders from higher-diversity areas.

Cobia has the same two cards stacking the deck in its favor in the East Pacific. The East Pacific has distinctly lower diversity than areas in Cobia’s natural range, and, as the only member of its taxonomic family, Cobia is unique, and has no native equivalent in the East Pacific, explained Dr Robertson.

The idea that because Cobia are cannibals in mariculture, cannibalism will control an East Pacific Cobia population is wishful thinking: lionfish cannibalism hasn’t prevented its population explosion in the Caribbean.

All in all, nobody can predict the exact consequences of Cobia establishing a population there. It took the lionfish invasion 2-3 decades to reach its full scope in the Caribbean, so any effects of a Cobia population in the East Pacific likely will take many years to become fully evident.