Lionfish were most likely introduced through ten or more release events by aquarium owners. The first established Atlantic lionfish populations were documented in 2000 off South Carolina, Georgia and Bermuda. They spread to the Bahamas in 2007, and lionfish densities in many areas of the Caribbean have now reached hundreds of adult organisms per hectare. Lionfish populations in these densities can consume 460,000 prey fish/acre annually. They feed on over 70 species of Caribbean fish and in heavily invaded areas have been shown to reduce the populations of these fish by 90%. Invaded reefs in the Bahamas lost 65% of 42 prey fish species in biomass over just a two-year timespan. Lionfish can consume 80% of a reef's juvenile fish population in just five weeks, and a 2007 study of the Bahamas showed that "recruitment" (settlement of fish larvae from other reefs) was down 79% in invaded areas. Research has shown that the typically crepuscular lionfish appears to be hunting not just at dusk but throughout the day as well. They're also growing larger and eating larger prey. Part of their rapid proliferation in the Caribbean also has to do with their reproductive strategy. Lionfish, like all fish, are rapid-life history organisms with type 3 survivorship, but unlike other fish their eggs are rarely eaten by fish and other marine organisms because of their toxicity. These eggs are released in mucosal balls by the female of up to 15,000 eggs per ball, and are then fertilized by the male. Under favorable conditions, females can produce eggs every few days, up to two million a year. Lionfish develop quickly – just four days after conception, they are free-swimming larvae. Young lionfish eat primarily invertebrates and have had a negative impact on many Caribbean invertebrate species.
Lionfish can live at temperatures from 10-35 degrees Celsius and inhabit depths of up to 250 meters, far beyond the reach of SCUBA divers. Thus, eradication of lionfish in the Caribbean through spearfishing efforts is unlikely. However, spearfishing efforts have been shown to greatly reduce the impact of lionfish on reefs. Lionfish venom, a proteinaceous mixture of neuromuscular toxin and neurotransmittive acetylcholine delivered through two grooves in the lionfish's bony spines (of which there are typically 18), can be very painful and cause severe illness in humans. However, once the spines have been removed, they're a very tasty fish.