Researchers have found lionfish grow faster and larger in Bermuda than elsewhere, but have greater challenges breeding.

A newly published scientific paper, The life history characteristics of invasive lionfish in Bermuda, suggests the island’s cooler waters have helped to slow the invasion of the invasive species.

Lionfish, first recorded in Bermuda in 2000, are considered a serious threat to reef fish in the Atlantic where they have no natural predators.

Corey Eddy, a Bermuda-based researcher and one of the paper’s authors, said: “It appears the waters get just cold enough in the winter so that lionfish are not reproducing year-round as in other places.

“Even though Bermuda was the first country outside of the US that lionfish invaded, it seems we have not yet experienced the population explosion typical of invasive species. While they’re certainly common, they’re not yet superabundant like people find in Florida and the Bahamas.

“We have been curious to learn why this might be and this short reproduction season may help explain things.”

Lionfish are native to the Pacific and Indian Oceans, but it is believed the species was accidentally introduced to the waters off the coast of Florida in the 1980s.

The species have since spread to reefs around the US Southeast, the Caribbean and the Gulf of Mexico.

Dr Eddy said that as part of their research into Bermuda’s invasive lionfish, scientists studied more than 1,500 lionfish caught in Bermuda’s waters between 2012 and 2016.

He added that the fish were measured and by examining their otoliths — small “ear bones” — researchers were able to determine the ages of the fish caught.

Dr Eddy explained: “These otoliths have growth rings just like a tree, which you can count to figure out the age of a fish, which is the general science we relied upon for much of the work.

“Although it is generally assumed that one growth ring is laid down each year, its really a good idea to verify that and we did.

“In fact, we are the first to do this for lionfish.”

He said the study found that lionfish in Bermuda’s waters live about nine years and males can reach 18.5 inches — although even larger fish have been reported around the island.

Dr Eddy said: “Compared to lionfish from other locations in both the invaded and native ranges, lionfish in Bermuda appear on average to reach larger sizes — in both total length and weight.

“I’m not saying we’re setting world records, but just that the population in Bermuda has a whole lot of monster-big lionfish.”

He added the researchers also compared the lionfish found in both deep and shallow water, and found them to be similar in both size, age and reproductive behaviour.