An Invasive Species: The Lionfish

An Invasive Species: The Lionfish

Posted by Michael Starbuck on 12th Sep 2022

What are invasive species?

Invasive species in their many forms are now a widespread issue and add to the ever-growing list of global environmental concerns. Many introduced animals and plants adapt to and reproduce too quickly in areas in which they are not native, often causing harm both environmentally and economically, thus branding them as invasive.

Not all introduced species are invasive; food crops, for example, were purposely introduced worldwide and now feed many people and animals. The organism must harm native plants and/or animals, the economy, or property to fall into the invasive category.

Introduction of Invasive Species

In many cases, invasive species introduction was accidental; marine species would often arrive in new regions, either from physical attachment to boats or from ballast water taken onboard and dispersed by ships in multiple locations. The European green crab is one such example; having been introduced via ballast water to the US in the 1950s, this species has cost the American fishing industry millions as they prey on native commercially important shellfish and scallops. The North Pacific seastar introduced to south-eastern Australia and Tasmania was also likely transported by ballast water which contained the species larvae. In Australia, the North Pacific seastar has become an enormous threat to the already endangered handfish as they eat their eggs.

Invasive Northern Pacific Seastar

Species introduced on purpose, commonly for pest control, often made matters worse. The cane toad released by farmers in 1935 in Queensland, Australia, was done so in an effort to control cane beetle populations that were destroying sugar cane fields. Soon after, 102 imported toads from Puerto Rico multiplied into more than 1.5 billion toads across Australia, becoming pests themselves due to their secretion of deadly toxins and eating native plants. The case of the Marion Island cats in South Africa resulted in a similar fate. After 5 unneutered cats were bought to the island in 1949 to control rodent populations, their numbers grew to around 3,400 cats in 1977, which, in turn, began to endanger native bird populations.

Invasive Cane Toad

A form of invasive species introduction not mentioned previously has come from the release of unwanted or escaped exotic pets. Burmese pythons, goldfish, green iguanas, and even macaques are just a few species that have grown to problematic numbers in non-native ranges due to the exotic pet trade. Florida has had a particularly hard time with exotic pet invasions. In the 1930s, 6 rhesus macaques were bought via the pet trade and released in Silver Spring State Park to create a Tarzan-themed attraction; today, there are approximately 300-400 macaques, and around 30% of these monkeys carry the herpes B virus posing a significant threat to humans. The Burmese python’s invasion of the everglades started in the 1980s, released due to their size, they would become too large and too expensive to care for. Another species with a population growing at an alarming rate, starting first along the coastlines of Florida and spreading throughout the Southeast and Caribbean coastal waters, is the lionfish.

Invasive Burmese Python

The Lionfish Invasion

Lionfish are a predatory species native to the Indo-Pacific Ocean and are known for their bold red and white striped appearance, long fin rays and venomous spines.

Invasive Lionfish Appearance

First detected along the Florida coasts in the mid-1980s, the populations of two lionfish species rapidly increased to uncontrollable and problematic levels. They are now an established and significant invasive species around the Caribbean and the Eastern coast of the United States. The most probable and likely source of the invasion is the release of unwanted lionfish from the aquarium trade.

Map of Lionfish Invasion
(Credit: Matthew Neilson, PhD - https://www.usgs.gov/media/images/1985-2018-lionfish-invasion)

Lionfish are reported to live longer than 15 years, have no real predators outside of their native range, and the females release egg clusters around every 3-4 days, having the potential to produce 2 million eggs per year. This, alongside ocean currents, ballast water, potentially hurricanes etc. have contributed to their wide distribution.  

As lionfish are carnivorous and will eat almost anything they come into contact with, they are detrimentally affecting coral reefs. Researchers have found that a single lionfish has the potential to reduce native juvenile fish populations by 79%. As they outcompete native predators at a higher consumption rate and deplete their prey and young, they may significantly reduce native species causing unbalanced marine ecosystems, which also affects local fisheries and the economy. Lionfish are also eating herbivore species that help control the growth of algae, the removal of these herbivores means that algal growth will likely increase and damage the survival rates of corals which are already affected by climate change, pollution, and physical destruction.

Lionfish Graphic
(Credit: Katie Free - https://superscience.scholastic.com/issues/2019-20/100119/lionfish-invasion)

Due to the extent of the invasion and the enormous geographic range they now cover, eradication is deemed impossible. Response management plans now strive to remove lionfish and suppress population densities to stop further ecological and economic damage. Localised and frequent removal has been shown to be effective at keeping lionfish numbers low in protected areas, diving sites and moorings.

In their native range, lionfish are considered a delicacy, so in an effort to reduce lionfish numbers across the US, the National Oceanic and Atmospheric Administration (NOAA) and Reef Environmental Education Foundation (REEF) launched the ‘Eat Lionfish’ campaign. The campaign was designed to increase the consumption of lionfish, encourage their removal, and promote the species as a sustainable seafood choice in an effort to keep native fish populations intact.

Belize Marine Education & Conservation Project

The Belize Barrier Reef is a significant reef reserve system and UNESCO World Heritage Site severely affected by the lionfish invasion. As the largest reef complex in the Atlantic-Caribbean region, and the second-largest in the world, its ecological importance is colossal; over half a billion people rely on coral reefs for food, income and protection. Belize reported their first lionfish sightings in 2008, and in less than a year, reported sightings were across the entire length of the Belizean barrier reef. In some regions, densities as high as 1,000 individuals per acre were recorded, and in some instances, have surpassed native fish species populations. For this reason, conservation volunteer projects like the Belize Marine Education and Conservation Project are extremely important. 

Volunteer on the Belize Marine Education & Conservation Project

For a chance to help protect the Belize Barrier Reef through conservation activities and gain an in-depth marine education, join the Belize Marine Education and Conservation Project today.

More information on the issues caused by lionfish and the efforts being undertaken to combat them can be found below:

NOAA (National Oceanic and Atmospheric Administration)
REEF (Reef Environmental Education Foundation)
NCEI (Nation Centre for Environmental Information)
GCFI (Gulf and Caribbean Fisheries Institute)
CORE (Caribbean Oceanic Restoration & Education Foundation)
Belize Fisheries Department


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