Pterois volitans
(lionfish)

P. volitansis known as a venomous coral reef fish from the Indian and western Pacific oceans. It is the first Indo-Pacific marine fish to become established in Atlantic waters. It was likely first introduced off the Florida coast in the early to mid-1990s. For the past few years members of this species have been collected, photographed and observed from southern Florida to Cape Hatteras, North Carolina, and juvenile lionfish have been collected from Long Island, New York and Bermuda. The species is also spreading rapidly through the Caribbean. The large scale distribution of this invasive species over such a short time period, along with the presence of juveniles, suggests that lionfish are reproducing (Ruiz-Caruz et al., 2006). Along the North Carolina coast both the number and spatial distribution of lionfish have increased. In August 2000, there were three lionfish reported in three locations. By October 2002, 49 lionfish were reported in 15 different locations. Dispersal of lionfish in 2002 appears to have been both inshore and offshore of the lionfish locations in 2001. Lionfish have also been sighted in waters deeper than originally anticipated (Whitfield et al., 2006). The initial introduction was thought to have been through aquarium releases off the Florida coast during Hurricane Andrew, but this is now thought unlikely, with multiple aquarium releases in Florida considered a more likely cause. It is unknown what effects on the ecosystem this marine invasive fish will have along the Atlantic coast of the United States. Whitfield et al. (2002) reported that there should be a cause for concern as they are predators and appear to be permanent residents. ISSG (2010) added that this is the first time aquarium releases have resulted in the successful establishment of non-native marine fish.

The native distribution of the red lionfish is restricted to reef habitats of the Indo-Pacific. This distribution encompasses an enormous area extending from Western Australia and Malaysia east to French Polynesia and the Pitcairn Islands, north to southern Japan and southern Korea and south to Lord Howe Island off the east coast of Australia and the Kermadec Islands of New Zealand. In between, the species is found throughout Micronesia (Randall et al., 1997).

Froese and Pauly (2010) and Robins (2010) reported that P. volitans are replaced by the very similar P. miles from the Red Sea to Sumatra. Robins (2010) even claimed that a published record of P. volitans from Inhaca Island, Mozambique, is presumably an error and more likely represents the more westerly P. miles. However scientists working on fish parasites of the northern Red Sea claimed that they collected their specimens of P. volitans from Sharm El-Sheikh, Egypt (Hassanine, 2006) and from Eilat Gulf, Israel (Paperna, 1972). Since both of these study sites are in the area of the north Red Sea it possible that both references relied on same source for identification despite a time span of more than 30 years between the two studies. Kimball et al. (2004) studying the thermal tolerance of red lionfish on the east coast of the USA used the term P. volitans/ miles complex to describe lionfish they studied (apparently to avoid confusion).Hare and Whitfield (2003) citing the work Kochzius et al. (2003) which confirmed genetic differences between P. miles and P. volitans, had argued that Kochzius et al's work was inconclusive regarding the existence of two species or two populations of one species. Hence they too decided to use the term P. volitans/ miles perhaps to avoid confusion.

The introduced range includes much of the Caribbean and the southern part of the east coast of the USA. Up to date information can be found on the map published by the United States Geological Survey.

Since the lionfish is listed as invasive species only in the USA and the Caribbean most of the work on their invasiveness has been done in that area. Morris (2009) argued that as a venomous scorpionfish, lionfish are considered invasive by definition because of their probable impacts to native reef fish communities (Albins and Hixon, 2008; Morris and Atkins, 2009) and to human health (Vetrano et al., 2002).

Hixon et al. (2009) reported that lionfish have the potential to drastically reduce the abundance of coral reef fishes and leave behind a devastated ecosystem. They suggested that with few known natural predators, the lionfish poses a major threat to coral reef ecosystems in the Caribbean region by decreasing survival of a wide range of native reef animals via both predation and competition. While native groupers may prey on lionfish, they have been overfished and therefore unlikely to significantly reduce the effects of invasive lionfish on coral reef communities. Albins and Hixon (2008) conducted a controlled field experiment using a matrix of translocated coral and artificial patch reefs to examine the short-term effects of lionfish on the recruitment of native reef fishes in the Bahamas. They found that lionfish caused significant reductions in the recruitment of native fishes by an average of 79% over the 5 week duration of the experiment. They propose that this strong effect on a key life stage of coral-reef fish suggests that invasive lionfish are already having substantial negative impacts on Atlantic coral reefs. Hixon et al. (2009) on one occasion observed a lionfish consuming 20 small wrasses during a 30 minute period. They also observed that it was not unusual to see lionfish consuming prey up to two-thirds of its own length. Morris et al. (2008) claimed that the lionfish invasion in the northwestern Atlantic and the Caribbean represents one of the most rapid marine finfish invasions in history. Green and Cote (2008) estimated that the number of lionfish had increased 17 times between 2004 and 2008 in North Carolina.

In general, marine fish that do not have the ability to survive in brackish or fresh water at a certain stage of their lifecycle seldom become invasive (A Gittenberger, Gimaris, The Netherlands, personal communication, 2010).

Reproduction

P. volitans are gonochoristic, i.e. males and females exhibit sexual dimorphism only during reproduction. The male becomes darker and their stripes are much less visible, and any female whose eggs are ripe takes on a much paler hue with many areas of the body becoming silvery white. Lionfish samples collected off North Carolina and in the Bahamas suggest that lionfish are reproducing during all seasons of the year (Morris, 2009).

P. volitans perform external fertilization of eggs and a suite of complex courtship and mating behaviours (Ruiz-Carus et al., 2006). The adults are generally solitary outside of the reproductive season, but during courtship, males will aggregate with multiple females to form groups of three to eight fish.

The courtship has been described by divers and aquarists as a dance that entails the couple diving down to the seafloor, several times, and then coming face-to-face, they slowly rise while circling, as if doing a waltz. Just before reaching the surface, the female will expel a pair of mucus-encapsulated clusters, containing 2000-15000 eggs which float to the surface. Once the mucus tube reaches the surface, the male will release his sperm into the egg tube so fertilization can take place. After about 15 minutes these tubes fill up with seawater and become oval balls 2 to 5 cm in diameter. Within these mucosal balls lie one to two layers of individual eggs. After spawning the fish part and go their separate ways (Fishelson, 1975).

Egg development

Twelve hours after fertilization the embryo begins to form. Only 18 hours after fertilization, the head and eyes become moderately developed. Eventually, invading microbes deteriorate the mucus walls and 36 hours after fertilization, the larvae hatch. Four days after fertilization, the larvae are already good swimmers and are able to begin feeding on small ciliates (Fishelson, 1975; Wood, 2001). The planktonic larval stage lasts between 25 to 40 days before they settle out of the water column at a size of 10-12 mm in length (Morris, 2009; Robins, 2010).

Judging on the size, morphology and larval life of other species belong to Pterois, lionfish larvae have a large head, a relatively long and triangular snout, long and serrated head spines, a robust pelvic spine, and pigment confined to the pectoral fins. The larvae size has been estimated to be about 1.5 mm (Leis and Rennis, 2000).

Nutrition

Morris and Akins (2009) studying the ecology of P. volitans in the Bahamian archipelago found that the adults prey mainly upon fish (78%) and crustaceans (14%). They found that twenty-one families and 41 species of fish were represented in the diet of lionfish; the top 10 families of dietary importance were Gobiidae, Labridae, Grammatidae, Apogonidae, Pomacentridae, Serranidae, Blenniidae, Atherinidae, Mullidae, and Monacanthidae. They reported that younger lionfish mainly feed on crustaceans but increase their intake of fish as they grew older. Sano et al. (1984) also reported that the food of lionfish in Ryukyu Island consists of 95% fish and 5% crustaceans and other benthic invertebrates such as amphipods and isopods. Whitney (2003) reported lionfish in Columbia feed mostly on crustaceans (as well as other invertebrates).

P. volitans are very voracious feeders as they consume an average of 8.2 times their body weight per year and as juveniles they consume 5.5-13.5 g per day and 14.6 g a day as adults (Wood, 2001).

Lionfish hunt small fishes, shrimps, and crabs at night, using their widespread pectoral fins trapping prey into a corner, stunning it and then swallowing it. The lionfish glides along the substrate (rocks or sand) and vibrates the rays on its fins in order move the prey out of hiding. They are very swift in catching and swallowing their victims (Sano et al., 1984; Froese and Pauly, 2010).

Most literature, by hobbyists and scientists, state that lionfish are nocturnal and feed at night especially the first hours of the night when the coral community becomes active with night feeders coming out of their hiding places (Sano et al., 1984; Froese and Pauly, 2010). Conversely, Morris and Akins (2009) reported that lionfish were found to be diurnal feeders with the highest predation occurring in the morning (08:00–11:00). This contradiction could be as a result to availability of the food in a particular habitat. Robins (2010) suggested that despite lionfish being known to be nocturnal they have been observed to feed during the day and studies of captive specimens imply that lionfish that have taken up refuge may simply be those individuals that have recently fed and are full.

Fishelson (1997) found that under experimental conditions, the lionfish are inactive and only come out of their hiding places to feed on as many fish as possible when fish are plentiful, fasting when food is scarce. When food is plentiful, P. volitans becomes full and may not eat for at least 24 hours.

Lionfish invest most of their energy in growing to a large body size early in life. This tactic allows them to be more likely to avoid attack by predators and increase their chances of mating successfully (Wood, 2001).

Cannibalism

Evidence of cannibalism in lionfish has been either anecdotal or found in experimental work. NOAA’s (2004) Coral Reef News reviewed work suggesting that there was some evidence of cannibalism amongst lionfish as remains of two lionfish were found in the stomach of other lionfish sharing the same tank. A team from Kean University experimenting on lionfish demonstrated that they showed signs of cannibalism (Lane et al., undated). Morris (2009) observed one instance of cannibalism of lionfish in their experimental tank. However he quoted the work of Smith and Reay (1991) who suggested that cannibalism in teleost fishes while in captivity is common and may not reflect a natural event. Morris (2009) also mentioned that diet analyses of >1,000 adult lionfish from the Atlantic have provided no evidence of cannibalism.

Lionfish envenomation

Gallagher (2001) described Pterois spp.as the least venomous of the Scorpaenidae. Lionfish elongated dorsal spines, pelvic spines and anal spines all have a pair of venom glands at each of their bases and a loose sheath covers each spine. The sheath is pushed down the spine during envenomation, causing compression of the venom glands. Venom then travels along a groove in the spine into the wound. However, the fan-like array of pectoral fins, which may appear superficially the same as the dorsal fins in structure, are not equipped with these glands.

Lionfish use their venomous fins to sting as a defensive response, typically to being cornered or harassed in some way, with the dorsal spines being the predominant weapon. In the wild, they are not aggressive towards people and will almost always keep their distance when given the opportunity, hence pose a relatively low risk. Although not deadly, the lionfish’s sting is extremely painful and causes swelling, redness, bleeding, nausea, numbness, joint pain, anxiety, headache, disorientation, dizziness, nausea, paralysis, and convulsions (Ruiz-Carus et al., 2006; Fatherree, 2008).

Any broken spines should be removed, if possible, and the affected area soaked in non-scalding hot water (100-110°F or 38-43°C.) for 15-20 minutes. Lionfish venom contains proteins that are denatured by heat, thus preventing them from spreading in the bloodstream (Gallagher, 2001).

Predators

Lionfish have few known natural predators but groupers have been found with lionfish remains in their stomachs. However, studies of the closely related P. miles may provide us with some indication of the natural history of P. volitans. In the Gulf of Aqaba, Red Sea, the piscivorous cornetfish, Fistularia commersoni, appears to be a predator of P. miles. Judging by the presence of a specimen of P. miles in the stomach of a large F. commersoni, and its particular orientation therein, it was concluded that cornetfish in the Red Sea may utilize their ambush tactics to seize lionfish safely from the rear, consuming them tail first. As cornetfishes are widespread, effective piscivore species sympatric with P. volitans, they may also predate upon them (Fishelson, 1975).

Parasites

Morris (2009) reported that knowledge of the parasites infecting native and non-native lionfish is scant. No comprehensive survey of protozoan or metazoan parasites of either host (P. miles or P. volitans) has been published.

However some isolated studies, mainly in the Red Sea area, recorded the presence of trematode parasites on wild-caught specimens. Hamacreadium pteroisi and Haliotremapteroisi were found on lionfish specimens collected from two areas of the North Sea; Ghardaga in Egypt (Nagaty and Abdelaal, 1962) and southwest of the Elite Gulf in Israel (Paperna, 1972).

The intestinal trematode Proneohelicometra aegyptensis (Opecoelidae) was also isolated from specimens of P. volitans from Sharm El-Sheikh, Egypt in the Red Sea (Hassanine, 2006).

Copepods and leeches were reported from specimens from Japan (Paperna, 1976; Dojiri and Ho, 1988). A leech (Myzobdella lugubris) (Hirudinea, Piscicolidae) measuring 22 mm was found attached to the middle portion of the tongue of a lionfish caught on the Florida coast (Ruiz-Carus et al., 2006).

Few studies have been carried out on endoparasites; however, a new myxosporean species, Sphaeromyxa zaharoni was found in a lionfish gall bladder from the Red Sea (Diamant et al., 2004).

Recent observations of lionfish collected off North Carolina and in the Bahamas have found a low prevalence of endo- and ectoparasites when compared to parasites of native reef fishes (Morris, 2009).

General

• Pet/aquarium trade

Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authority should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used in a lawful manner, consistent with the product's label.

Although lionfish in their native range are considered one of the most valuable species as an aquarium fish and as food fish, lionfish in the northwestern Atlantic Ocean and the southwestern Caribbean Sea are recognized as a major threat to their ecosystem. The authorities and the public in those countries are concerned that this species is causing dramatic effects on people’s safety, biodiversity and habitat composition (Gonzalez, 2009).

However, ISSG (2010) reported that no specific preventative or control activities information has been recorded. Nevertheless countries, especially the USA and the Caribbean islands where lionfish has an established population or their establishment is imminent are putting together mitigating measures to deal with it as a potential threat. They are taking the following measures in order to control the problem as eradication is not likely (Whitfield, 2002; Morris, 2009).

1. Good planning

2. Involving people and community

3. Fisheries development

4. Undertake more research and use of new technology

5. Cooperation and liaison

USA: Centre for Coastal Fisheries and Habitat Research CCFHR, 101 Pivers Island Road, Beaufort, NC 28516, http://www.ccfhr.noaa.gov/ http://www.ccfhr.noaa.gov/

USA: Fish and Wildlife Conservation Commission National FWCC, 100 Eighth Avenue SE, St. Petersburg, FL, 33701-5020, http://research.myfwc.com

USA: National Oceanic and Atmospheric Administration/ National Centre for Research on Aquatic Invasive Species, Beaufort North Carolina, http://www.noaa.gov

USA: Reef Environmental Education Foundation REEF, REEF Headquarters P.O. Box 246, http://www.reef.org

25/02/10 Original text by:

Tagried Kurwie, Mahurangi Technical Institute1 Glenmore Drive, Warkworth, New Zealand