Lionfish, an invasive species: How did they get into the Gulf of Mexico?

Pterois volitans, the red lionfish, is an incredibly invasive species in the Gulf of Mexico, Caribbean and is travelling up the Atlantic Coast of the United States. The fish is originally from the Indo-Pacific part of the world, but mysteriously made its way very west all the way to North America in the 90s. There are many theories as to how lionfish invaded the Caribbean and Gulf of Mexico, in this blog post we’ll discuss these different theories and tell you what the most likely explanation is based on the scientific literature. 

Lionfish are, by most standards, the perfect invasive species. They multiply very quickly (females can lay 2 million eggs per year), can survive without food for extended periods of time (up to 3 months) and have no natural predators in the Caribbean/Gulf of Mexico region. Due to these factors, they spread like wildfire when they arrived in their new North American home.

You’d think a cool new fish from across the world would be a fun addition to a natural reef environment, right? Well guess again – lionfish destroy juvenile fish populations because they’ll basically eat anything smaller than them (and lionfish can grow to over 1 foot long so that’s a lot of food options). 

So how did they arrive? There are a few different theories, here’s a brief list before we go into detail for each one:

  • Accidental aquarium release during Hurricane Andrew (1992)
  • Release from ballast water
  • Release from personal fish tanks

Release from ballast water – most unlikely 

Cruise ships and other big boats have to take on water in dedicated tanks and cargo holds to balance out the overall weight distribution of the boats to keep them safe and upright. When boats pick up this water, they don’t necessarily do so in places that have aquatic environments matching those of the boat’s destination. This is how other invasive species have invaded new parts of the world, and is even the leading theory on how the common lionfish invaded the Mediterannean Sea.

If this were the case, then this would mean that a boat, either cruise ship or of another kind, hailing from the Indo-Pacific filled its ballast tanks with water that happened to include one or a few lionfish. Then, it travelled to the Gulf of Mexico where it dumped its ballast water as it got to port.

You may be asking yourself, how is this practice allowed? It is clearly a very easy way for any aquatic species to be improperly introduced into a foreign environment and become invasive. Thankfully, a Ballast Water Management Convention was put into place in 2004 go help prevent the wrongful transfer of aquatic organisms from one region to another. 

While this method of invasion certainly is possible, it’s far less likely than the alternatives. Keep reading to find out why

Accidental aquarium release during Hurricane Andrew – likely 

Lionfish, as you may know, are beautiful fish that are often kept in public aquariums or even in private fish tanks. Due to their beauty, they were kept in these places far before the fish became invasive in North America. Hurricane Andrew in 1992 destroyed many of these aquaria – public and private, and may have been the source of the escaped lionfish. 

However, the first ever recorded sighting of a lionfish was in 1985 in Dania, FL just north of Miami, so how could Hurricane Andrew be responsible in 1992? It’s possible that aquarium release in 1992 intensified the problem that had been taking place since 1985, but the original cause may not have been Hurricane Andrew.

Release from personal fish tanks – most likely

The most likely way that lionfish were released into the Gulf of Mexico was through release by individuals who had lionfish in their tanks at home. Lionfish can grow to be extremely big, and can live for many years (up to 15 years in the wild), so when an unknowing lionfish owner finds themself with a lionfish who outgrew their tank, they might think it’d be a good idea to release it into the wild. Of course, by now you know this is a terrible idea. All it would take is one or a few people to follow this chain of logic, release their lionfish into the Atlantic, and the invasion could begin. 

Since lionfish had been spotted in Florida 7 years before Hurricane Andrew ever hit, this release of lionfish was most likely due to release from tanks by individuals. However, it is possible there was some sort of other un-reported accident that resulted in release of lionfish from captivity into the Atlantic Ocean.

In conclusion, it seems that lionfish were released into the Gulf of Mexico by accident by people releasing their domestic fish into the wild. There is still no definitive proof of what route the lionfish took to get to the Atlantic but however they came here, they’re here to stay unless we control their numbers! Get involved by going out and spearing lionfish at your local reef if they are a problem there, and make sure you have StingMaster with you in case you get poked!

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