Fluorescent Transgenic Aquarium Fish: Origin, Species and Regulation

Fluorescent transgenic aquarium fish: origin in zebrafish research, the species on sale, their legal status in the US, EU, UK, Canada and Brazil, and what risk assessments say about care.

What fluorescent transgenic fish are

Fluorescent transgenic fish (sold under a trademark) are aquarium fish that carry an inserted gene for a fluorescent protein. Their colour is inherited, unlike dyed or tattooed fish, whose colour is applied artificially and fades. They are also different from colour strains made by selective breeding within a species, which are covered in separate genetics guides.

Origin in zebrafish research

According to Wikipedia, scientists at the National University of Singapore inserted a gene for green fluorescent protein (GFP) from a jellyfish into zebrafish (Danio rerio) embryos in 1999. Their aim was to develop fish that could signal pollution. Genes for red fluorescent protein from corals, and for orange-yellow variants derived from jellyfish genes, were added later. A 2019 Canadian risk assessment states that the colours of the transgenic tetras it reviewed come from fluorescent proteins derived from sea anemones and corals.

Wikipedia reports that fluorescent fish were first authorised for sale in Taiwan in spring 2003 and reached the US market in late 2003. The Canadian assessment describes how one transgenic line is made: a gene construct is injected into newly fertilised eggs, and the line is maintained by breeding descendants of a single founder fish.

Species available

Zebrafish (Danio rerio): the original species, on sale in the US since 2003 (Wikipedia).
Black tetra (Gymnocorymbus ternetzi): produced from a naturally occurring albino (white) line of the species, according to Fisheries and Oceans Canada; Wikipedia dates the first green versions of tetras and tiger barbs to 2012.
Tiger barb (Puntigrus tetrazona): green, red, purple and orange lines were assessed in Canada in 2022.
Rainbow shark: orange, green and purple versions since 2016 (Wikipedia).
Betta: green versions released in February 2020 (Wikipedia).
Angelfish and Corydoras: Wikipedia lists these as also developed.

Regulatory status by country

United States (FDA): in December 2003 the US Food and Drug Administration stated that, because tropical aquarium fish are not used for food, they pose no threat to the food supply, that there was no evidence they pose more environmental threat than unmodified zebrafish, and that it found no reason to regulate them (Wikipedia).
California: sale and possession were made illegal in 2003 under a state regulation restricting genetically modified fish; the fish became legal for import and sale in 2015 (Wikipedia). Title 14 of the California Code of Regulations, section 671.1, still prohibits releasing transgenic aquatic animals or their progeny into state waters.
European Union: Wikipedia states that import, sale and possession are not permitted in the EU. Under Directive 2001/18/EC on the deliberate release of GMOs, a genetically modified organism may be placed on the market only after notification to a competent authority and written consent (Articles 13 and 19). In 2006 Dutch authorities found about 1,400 fluorescent fish on sale in aquarium shops (Wikipedia). A 2020 study in Transgenic Research describes PCR tests used to detect illegally imported transgenic fish in two European countries.
United Kingdom: Practical Fishkeeping reported that importing, acquiring, releasing or marketing any GMO is prohibited without consent under the Environmental Protection Act 1990. The head of the UK GM Inspectorate told the magazine that no GM fish had been authorised in the UK or the EU.
Canada: under the Canadian Environmental Protection Act, 1999 (CEPA) and its New Substances Notification Regulations (Organisms), transgenic fish must be notified and assessed before import. Several lines have been assessed as low risk, including transgenic black tetras (Fisheries and Oceans Canada, 2019) and four tiger barb lines, which were added to the Domestic Substances List in November 2022 (Environment and Climate Change Canada).
Brazil: according to the São Paulo Research Foundation's Pesquisa FAPESP magazine, imports have been banned since 2008, although wild-type zebrafish can still be imported.

Care compared with the parent species

The Canadian tetra assessment notes that no formal studies have compared disease susceptibility between transgenic and wild-type tetras. Veterinary statements supplied by the producer reported no sign of increased susceptibility to water-borne pathogens and stated that the fish need the same husbandry as non-transgenic tetras. The assessment did measure some differences, however. All five tetra lines tolerated cold slightly less well than white tetras, and some lines had lower reproductive success. In fluorescent zebrafish research lines, survival is generally similar to non-transgenic fish, but effects on reproduction and on the ability to avoid predators are inconsistent. Wikipedia notes that some of these fish are fertile and breed in captivity, although purchase terms prohibit breeding and selling the offspring.

The environmental fluorescence myth

The fluorescent proteins do not spread into water, plants or other animals. Fisheries and Oceans Canada concluded that if live or dead fish entered the environment, both the fish and their fluorescent proteins would biodegrade normally and would not bioaccumulate. Sequence analyses found no similarity to known toxins or allergens. The colours are also visible under ordinary light: the Canadian assessment describes each tetra line as appearing blue, orange, pink, purple or red under ambient light, while the 2020 Transgenic Research study notes that the colours fluoresce under UV light.

Escape is a real risk, especially in warm climates. A 2014 peer-reviewed screening by Hill, Lawson and Hardin in Transactions of the American Fisheries Society used the Fish Invasiveness Screening Kit (FISK). It rated transgenic zebrafish, black tetras and tiger barbs as a low invasiveness risk in the conterminous US, with any risk limited to warmer regions. The authors cited no potential to hybridise with native species, little history of invasiveness, and small body size combined with fluorescence that makes the fish easier for predators to find. Wikipedia reports a second study that found no difference in risk compared with wild-type zebrafish. However, Pesquisa FAPESP reported in 2022 that more than 100 transgenic zebrafish were found in two headwater creeks of the Paraíba do Sul basin in Minas Gerais, Brazil. They had probably escaped from a nearby ornamental fish farm, and the creeks stay at 24–30 °C all year, which allows breeding in every season. In Canada, by contrast, the assessed tetras could not survive long periods below 9 °C, so they are not expected to establish there.