16 September 2005

Caribbean: Lionfish on the increase warn scientists

Poisonous lionfish which were swept into Bermuda in the wake of Hurricane Andrew 13 years ago could be breeding and multiplying in the island's waters, scientists have warned.

Divers recently reported spotting a lionfish, apparently nesting in the wreck of the L'Artington. Dive instructors have also seen them around Blue Hole and Marie Celeste as well.

Bermuda Biological Station for Research is monitoring the growth of the species amid concerns that it could have a harmful affect on local fish populations.

Lionfish are native to the Indo-Pacific region but are popular for home and public aquaria.

Many were accidentally released into the ocean when the hurricane ravaged Florida. Others were intentionally released by well-meaning private aquarium owners.

The film Finding Nemo has even been attributed for some of the deliberate releases. But while the intentions may have been good the effects could be damaging. Risk to humans is limited. Though the lionfish is poisonous and scientists say its sting should be treated as a medical emergency, no-one is known to have died from an encounter with the species.

And Lionfish are known to attack only as a defence mechanism.

Dr. Joanna Pitt, who is in charge of BBSR's research into the species, said: "If a predator tries to eat a lionfish (or if a person grabs or steps on it), pressure on the fins triggers venom glands at the base of the fin spines and venom runs out through a groove in the spine.

"Since the spine usually causes a puncture wound when it is triggered, the venom gets into the wound and causes severe local pain.

"For the lionfish, the venom is a defence rather than an attacking strategy, so people do not need to worry about avoiding the fish itself, they just need to treat this species with caution and remember not to touch it or do anything to provoke a defensive reaction.'

The far greater risk is to Bermuda's delicate ecosystem. If, as suspected, the lionfish are starting to breed, the growth of a 'voracious predator', into the island's waters could have a harmful affect — particularly on fish populations.

Dr. Pitt added: "To date, about 25-30 lionfish have been caught or sighted in the waters around Bermuda, and it does appear that they are becoming more common.

"At present, their numbers appear to be relatively low and their effects are probably negligible. However if the species is actually reproducing here, then the problem may be more significant.

"Invasive species often have no natural predators in their new environments, so their populations can grow faster than those of native species.

"This is particularly true of the lionfish, which has many venomous spines and is virtually impossible to eat. The invaders then compete with similar native species for resources such as food and habitat space."

She added that the lionfish's predatory tactics would be unknown to local fish populations, making it even more difficult for them to evade capture.

"There is a definite risk that, if their numbers increase, lionfish will begin to have an effect on local fish populations if they prey too extensively on juveniles.

"They may also compete with populations of other predatory fishes, and could cause particular problems for vulnerable grouper species that are only now beginning to recover from the over-fishing in the 1970s and '80s."

Dr. Joanna Pitt answers our questions about the Lionfish...

  • How and when did Lionfish arrive in Bermuda?
    The first lionfish to be found in Bermuda was collected in 2000. The timing of the first lionfish sightings in Florida, in about 1994, suggests that the destruction of property during Hurricane Andrew in 1992 may have been responsible for many accidental introductions. Red lionfish have now been reported from all over the U.S. east coast from Florida to North Carolina, and even as far north as New York. As Bermuda does not permit the live importation of marine species for aquarium use, it must be presumed that the lionfish here were transported as larvae by oceanic currents following reproduction by the U.S. populations. The fact that the first individual collected here was a juvenile supports this.

  • Where are they found?
    Lionfish are very versatile and, in Bermuda, they have been found everywhere from tide pools to 240 feet deep in lobster traps. SCUBA divers, particularly those who dive at deeper sites, and people fishing in water more than 100 feet deep are the most likely to encounter a lionfish.

  • What is the effect of being stung? What should you do if you are stung?
    Lionfish venom is very potent and [a sting] should be treated as a medical emergency. Localized symptoms include persistent, intense pain around the wound, tingling sensations, sweating and blistering. In the most severe cases, systemic reactions such as headache, nausea, abdominal pain, changes in blood pressure, breathing or heart problems, weakness or paralysis and even loss of consciousness may occur, although these are unlikely. There are no records of anyone having died as a result of a lionfish [poisoning]. Immediate first aid treatment for poisoning includes immersing the afflicted area in hot water (to 45° C, about as hot as your hand could normally tolerate) as certain components of lionfish venom may be inactivated by heat, but professional medical attention should be sought as soon as possible.

  • What should you do if you see a Lionfish?
    Lionfish sightings should be reported to the Bermuda Biodiversity Project, which in turn forwards the information to the Reef Environmental Education Foundation/NOAA Fisheries in the region. The public is discouraged from trying to capture lionfish because of the likelihood of injury. If you should happen to catch one on a hook and line, stay clear of the spines and lower the fish into a bucket of seawater then cut the line. Do not attempt to remove the hook. Specimens from any incidental captures can be dropped off to Dr. Joanna Pitt at BBSR, who is interested in examining the diet and age structure of the individuals in Bermuda.

    Report sightings to: jopitt@bbsr.edu

    Source: www.divester.com and www.bermudasun.bm


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