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Exploring the world of invasive lionfish

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New light has been shed on the threats that lionfish could pose to Bermuda's waters thanks to the publication of a PhD thesis that has been three years in the making.

The University of Massachusetts paper by Corey Eddy has drawn on many sources including samples and stomach contents from more than 1,500 lionfish, multiple ocean surveys at varying depths, and research conducted based on 2,300 reported captures and sightings.

As a result new information has been found which is broken into four separate chapters of the thesis: abundance and distribution; age, growth and reproduction; feeding ecology using stomach contents; and feeding ecology based on stable isotopes — which could all help to inform future environmental policy and legislation.

According to the findings lionfish appear to be more abundant in Bermuda's shallow waters during the winter months challenging the belief that the Indo-Pacific invaders are a deep-sea problem only, and fish found in the shallow waters were found to be marginally larger than fish found in deep waters.

The remains of 46 fish species and 19 crustacean species were found in the stomachs of those fish tested and the results show that they eat twice as many red night shrimp as they do any other marine species.

Research conducted using stable isotopes, a popular method for understanding aquatic ecosystems, also suggests that most of the lionfish's food web is anchored in other animals that primarily eat plankton rather than seaweed.

Mr Eddy, who organised a Lionfish Winter Derby to help collect information and samples for his study, told The Royal Gazette: “I have been in Bermuda long enough to recognise how healthy and gorgeous the marine reef environment is and I recognised that lionfish could become a big problem. I wanted to contribute to understanding the fish, to understanding what they might do and to help inform management.

“We are still not seeing any major negative impact but we still think the invasion could be at an early stage — we are certainly not in the same position as the Bahamas are but we are still very concerned there could be some big impacts coming.”

Mr Eddy said that the Bermuda Government will now be able to use his research to help to inform management decisions as they relate to the issue of lionfish while others will also benefit from the information. He explained: “Our research on abundance and distribution could help Government to target lionfish not just with traps but when we recognise that they are moving shallow through the off season — this helps us to target them more efficiently.

“The information on seasonal movement into shallow water in the winter is very important because it suggests recreational lionfish hunters can make a big impact with little effort. Either way, lionfish are most abundant between Watch Hill Park and Clearwater, year round, and that information is vital to targeting them.

“With regards to stomach contents they eat everything, especially red night shrimp. They eat whatever is available to them, which only varies by season and depth. We found a lot of juvenile barbers at deep sites which could in time affect the fishermen because that is a targeted species. We also found a lot of bluehead wrasse which are cleaning wrasse. We did see parrotfish but not as much as other things.

“This is the first study to describe Bermuda's reef ecosystem using stable isotopes. My work suggests a lot of resource overlap (competition) with cony, red hinds, and yellowtail snapper. It is obvious when you see stomach contents that certain things are getting hit hard but with the stable isotopes it informs us more about competition. With all the information on feeding ecology we will get an idea of which species could be impacted the most.”

Stomach contents paper will be published in Marine Ecology Progress Theories and the chapter on abundance and distribution should go to Biological Invasions. The other chapters in the thesis are also expected to be published in scientific journals.

“The Lionfish Research Team, the Lionfish Taskforce, Bermuda Ocean Explorers and the active recreational lionfish cullers have all been integral to providing samples, support and feedback. I am grateful for having this opportunity and appreciate everything everybody has done to support me.”

• This article was amended to correct the number of reported captures and sightings of lionfish Mr Eddy used for his research. The correct figure was 2,300, not 22,300 as initially reported.

Object of fascination: Corey Eddy holds up a lionfish. Below right, two captive lionfish (Photograph by Jennifer Burland Adams)
Ocean threat: two captive lionfish
Unfussy eaters: some of the local fish species found in the stomachs of lionfish in Bermuda

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Published June 02, 2016 at 9:00 am (Updated June 02, 2016 at 1:07 pm)

Exploring the world of invasive lionfish

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