Lionfish: Controlling the predator
As many Bermuda residents are now aware, lionfish that are native to the Indo-Pacific region have invaded the western Atlantic.
First spotted off Florida in the 1980s, lionfish have been in Bermuda since at least 1999 and have now spread throughout the Caribbean and Gulf of Mexico.
Marine creatures here do not recognise them as predators, so the lionfish feed voraciously on juvenile and other small fishes.
Lionfish therefore have the potential to seriously impact both commercial and recreational fishing, as well as the overall health of our coral reefs.
While the extent of the lionfish invasion across the region means that it will not be possible to get rid of them completely, control of the lionfish population in Bermuda is vital to both our environment and our economy.
The Bermuda Lionfish Taskforce, along with a wide range of partners, has been working towards this goal.
Although sightings in shallow water are becoming more common as the population is expanding, lionfish in Bermuda are concentrated in deeper waters (100-200 feet) that are inaccessible to the volunteers participating in the culling programme.
However, lionfish have been caught incidentally in commercial lobster traps since at least 2003 and regularly since 2008. They are caught predominantly in the deeper ‘offshore’ traps which are set outside the reef line during the first half of the season.
The Department of Environmental Protection’s Marine Resources Section is working with commercial fishermen to develop a lionfish trap that will enable large-scale, long-term removal of this invasive species from deeper waters.
The goal is to modify the traps and fishing practices used by commercial lobster fishermen in order to increase the catch of lionfish while reducing the catch of spiny lobster, and keep the incidental catch of other fish low, as these traps were designed to do.
Monitoring commercial lobster traps with underwater cameras has helped assess lionfish numbers in the deeper areas where the offshore lobster fishery operates, and has provided insights into the way lionfish interact with the standard traps.
Initial observations agree with those of technical divers, and show that lionfish appear to be present at low levels in most areas between 120 and 240 feet, but that some areas appear to be ‘hot spots’ with much higher numbers.
In most cases, two or three lionfish were observed near the trap over four to six days. However, in one instance, three lionfish were caught on camera when the trap was first set, and a photograph at dawn the next day showed 26 lionfish.
Behaviours observed included ‘circling’ the trap, ‘investigating’ the funnel, and ‘perching’ on top of the trap. One lionfish was observed ‘sheltering’ in the mouth of the funnel from early morning through late afternoon, but leaving as dusk approached.
Experimental trapping began in January, and modifications include shading the traps and varying the funnel opening. The ‘sheltering’ behaviour suggests that shading the traps may enhance the feeling of protection they provide and entice more lionfish inside.
The ‘investigating’ behaviour suggests that lionfish may be deterred from entering the traps when they see the white PVC ring that is used to hold the funnel open, so alternatives include replacing this ring with wire, removing it altogether, or bending the opening downwards.
Different baiting strategies are also being tested.
To start with, the various traditional methods for baiting traps are being used. However, artificial baits resembling small fish may serve to attract lionfish but not lobsters or other fish and, if shelter is more important than bait as an attractant for lionfish, then not baiting the traps at all may achieve this as well.
It is anticipated that lionfish trapping would take place alongside the offshore lobster fishery from September through December. If incidental lobster catch can be sufficiently reduced then lionfish trapping could also take place during the summer months, but the need to protect female lobsters with eggs must take priority over expanding the lionfish trapping season.
This work is part of the Bermuda Lionfish Control Initiative that is being supported by a Darwin Plus grant from the UK’s Department of Environment, Food and Rural Affairs.
Other work associated with this grant aims to map the distribution of the local lionfish population in order to aid the trapping and culling programmes, and to figure out why they seem to prefer certain areas. Partners in this research include the Bermuda Zoological Society, Bermuda Institute of Ocean Sciences, Bermuda Aquarium, Museum and Zoo, Ocean Support Foundation, Bermuda Government Department of Conservation Services and the University of Massachusetts at Dartmouth.
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