Lionfish wreak havoc on marine ecosystems

By Roisin McDonough

Look at me. I’m the top predator now. | Image: Jens Petersen

The lionfish, beautiful in appearance and un-problematic in their native regions of the Indo-Pacific have wreaked havoc as an invasive species in the Atlantic; having become well established  in the Southeast coast of the US, the Gulf of Mexico and the Caribbean.

The Lionfish invasion was likely caused by humans releasing this popular ornamental fish from home aquariums when they were no longer wanted (over the course of 25 years). Their journey to the Atlantic was then possibly aided by the warm Gulf Stream  current which dispersed buoyant lionfish eggs and larvae further afield.

Warm currents like the Gulf Stream could be letting lionfish blag a cheeky ride to where they aren’t welcome | Image: Sommerstoffel

At first, their arrival into new areas was not considered to be much of a problem, as it was thought that that they would not survive very long. However, over the years, the lionfish have not just survived, they have thrived. Their success has led to the unfortunate and worrying decline of many native fish species and an alteration in the very delicate reef ecosystem.

Lionfish out-compete, out-live and out-breed native fish. But why?  For starters, they are highly tolerant to a range of temperatures, salinities and depths and biologically resistant to most diseases and parasites that affect native fish. Further, they have very few, if any, natural predators in the Atlantic. They become sexually mature at 1 year of age and can live in excess of 15, so have a long, rich reproductive life. In optimal conditions, females can release a staggering 2,000,000 eggs per year!

“Do you think that new guy looks dangerous?” “Who, the grumpy looking stripy one who’s at least 1000 times bigger than the rest of us?” “Yeah” “Nah, there’s something about his vast, leafy appendages I find sort of… comforting” | Image: Alexander Vasenin

Lionfish are un-selective carnivores with voracious feeding habits, encompassing a huge range of small fish and crustaceans. Included in their diets are popular commercial fish like grouper and snapper and commercially important crustaceans such as lobster, crab and squid. In their non-native environments they have easy pickings when it comes to food, as generally, native species do not recognise the lion fish as a threat. In fact, some small fish will assemble around these invasive creatures in the hope that their fin rays/feathery pectoral fins will provide them with shelter and protection.

So far, lionfish hunting  seems to be the only feasible method of controlling their numbers. Certain areas which are regularly hunted see an increase in the number of native fish over time. However, the areas that can be reached by lionfish hunters is very small in relation to the vast marine environment lionfish now cover.

Invasive lionfish populations are an ever-growing problem – native marine life has suffered dramatic reductions as a result of their predation. Commercial fisheries, recreational activities and food security have also all been negatively affected as a consequence. We do not know the extent of the devastation to marine habitats in the near future, but it is likely to be bleak if their populations are not controlled.

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