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In September of 2010, thousands of live fish of the species Gambusia affinis were transported by air from a rural fish farm in the Mississippi Delta region of the southern United States to one on the outskirts of Port-au-Prince, Haiti, where they are to be raised in tanks and released into freshwater ecosystems all over the country. These fish, one of two Gambusia species commonly known as “mosquitofish” in English, are native to the southeastern United States, and no sightings of the fish have previously been reported in freshwater ecosystems in Haiti or elsewhere on the island of Hispaniola. The reason given for this mass introduction is to aide in malaria eradication efforts in Haiti: malaria is transmitted by mosquitoes, mosquitoes lay their eggs on the surface of standing bodies of freshwater, and the omnivorous mosquitofish, in addition to any other food source available, will certainly eat mosquito eggs and larvae as their name suggests. Intentional introductions of these fish as a biological method of mosquito control have been carried out all over the world since 1905, with many introductions resulting in long-term establishment of mosquitofish populations outside of their native range [1].

Although widely introduced as mosquito control agents, recent critical reviews of the world literature on mosquito control have not supported the view that Gambusia are particularly effective in reducing mosquito populations or in reducing the incidence of mosquito-borne diseases (Courtenay and Meffe 1989; Arthington and Lloyd 1989). Because of their aggressive and predatory behavior, mosquitofish may negatively affect populations of small fish through predation and competition (Myers 1967; Courtenay and Meffe 1989). In some habitats, introduced mosquitofish reportedly displaced select native fish species regarded as better or more efficient mosquito control agents (Danielsen 1968; Courtenay and Meffe 1989). Introduced mosquitofish have been particularly destructive in the American West where they have contributed to the elimination or decline of populations of federally endangered and threatened species (Courtenay and Meffe 1989).

Successful invasions of alien species in island ecosystems often have severe ecological and socioeconomic impacts [2], and mosquitofish meet two important criteria which suggest that a successful invasion would likely result from their introduction into an area [3]: they can survive under a large range of environmental conditions, especially temperature [4] and salinity [5], allowing them to successfully establish populations wherever they are introduced, and they are highly mobile [6], allowing established populations to spread rapidly. Also, mosquitofish have a history of successful, and ecologically disruptive, invasions outside their native range. They often populate the ecosystems they invade at high densities, and since zooplankton constitute the overwhelming majority of their diet, their presence often results in elevated phytoplankton levels, and even algal blooms [7]. They attack native fish in the ecosystems they invade, compete with them for food, and eat their minnows [8] [9]. Amphibian species, some of which are also important mosquito predators [10], have been shown to be particularly threatened by mosquitofish introductions [11] [12] [13], as moquitofish eat their eggs and tadpoles. There are at least three related Gambusia species endemic to Hispaniola, and it appears that the proponents of this project have completely overlooked these fish both as a potential native species for use in biological mosquito control and also as species that would be potentially impacted by a mosquitofish invasion. Competition and hybridization with invading mosquitofish have threatened multiple rare species of Gambusia endemic to the southwestern United States, and the invasion of mosquitofish almost certainly contributed to the recent extinction of G. amistadensis in Texas [14] [15].

"The difference between G. holbrooki and G. affinis is minor. They are both known as "mosquitofish" in American English and though they are two separate species, they are often treated as one in the scientific literature because their biology is very similar. Some of literature that I cited, especially those by Australian scientists, actually deal with G. affinis, since that was the species introduced there (G. holbrooki was introduced in Europe, Asia, and Africa).

I'm not sure if I believe their claim that G. affinis already exists in Haiti, though. When I wrote the article, I searched pretty hard for any evidence that either species had been introduced to the island, but found none. If it was already there, why did they have to fly fish in from Mississippi? And why aren't they using native fish? Perhaps I could contact Dr. Abe personally to clarify this.

They claim that they are not going to release G. affinis into open water, which is good. This doesn't mean that G. affinis won't successfully invade freshwater ecosystems though, especially in the event of a flood.

So, although I will certainly edit my article to reflect their claim that it was G. affinis that they introduced, I certainly will not change my analysis. I'm working on drafting an open letter Bill Horan, which I will post on my website. I plan to address the fact that the press release seems to imply that they didn't just introduce a species of fish into Haiti, which they did. It also does not accept that what they are doing will have ecological consequences, which it will."