American bullfrogs turn up in irrigation ditches and ponds across Japan. Find a tadpole the size of your hand and the urge to take it home is understandable. The bullfrog is a designated invasive alien species, so some restriction must apply — but where the line sits was not obvious to me until I opened the statute. It is not at the catching.
The short answer first.
- Catching one is not restricted. Releasing it on the spot straight away is not restricted either
- Carrying it home alive is an offence. That counts as "transport" in the statute, which breaches the ban on keeping (Article 4)
- The penalty is up to one year's imprisonment or a fine of up to ¥1 million. Both may be imposed, and a corporation faces a separate ceiling of ¥50 million
- Tadpoles and eggs are treated the same. A Ministry of the Environment leaflet says so explicitly
- Killing it on the spot, in a way that brings death swiftly and reliably, and then carrying it home is not restricted
- For a school to keep one for teaching, a ministerial permit and an escape-proof facility are required
- Only two species — the red swamp crayfish and the red-eared slider — were moved to the lighter conditional regime. The bullfrog was not
The rest of this article traces each point back to the source.
This article organises what the statute and public documents say. Whether a particular case falls under the rules is for the authorities to decide. Provisions are quoted from the versions I checked on 14 August 2026. Translations of Japanese legal text are my own and are given for orientation, not as official renderings.
1. The line is at transport, not at catching
What the Invasive Alien Species Act prohibits is "keeping and the like". Article 1 sets out what that covers.
This Act, by regulating the keeping, cultivating, holding or transporting (hereinafter "keeping and the like") of designated invasive alien species, their import and their other handling, and by providing for measures such as control by the State and others, prevents damage to ecosystems and the like caused by designated invasive alien species (the remainder omitted)
Invasive Alien Species Act, Article 1 (extract, my translation)Of the four, the two that bite in a field situation are holding and transporting. Article 4 prohibits keeping and the like in principle. The word "catching" does not appear there.
The Ministry of the Environment states the consequence plainly.
Where you have caught a designated invasive alien species in the wild, taking it home is prohibited (this falls under transporting), but releasing it on the spot straight away is not subject to the restrictions (what anglers call catch and release is likewise not subject to the restrictions).
Ministry of the Environment, "What is prohibited?" (my translation)The Q&A adds what to do on finding one.
Since a designated invasive alien species that you have found cannot be transported alive without a permit, we recommend not catching it carelessly and instead first consulting the manager of the site or the administrative authority. That said, even if you have caught one, there is no problem provided you release it on the spot straight away.
Ministry of the Environment, "Q&A on the Invasive Alien Species Act", Q8 (my translation)The penalty is in Article 33. A breach of Article 4 that is not for the purpose of sale or distribution carries up to one year's imprisonment or a fine of up to ¥1 million, and both may be imposed. Article 36 adds a separate ceiling of ¥50 million for a corporation.
2. Tadpoles and eggs count too
This is not only about adults. A leaflet from the ministry's Chugoku-Shikoku Regional Environment Office spells it out.
Keeping bullfrogs, transporting them alive, or releasing them in another place is prohibited by the Invasive Alien Species Act, so please take care. *This includes tadpoles and eggs.
Ministry of the Environment, Chugoku-Shikoku Regional Environment Office, "Designated invasive alien species: the bullfrog" (my translation)Ishikawa Prefecture makes the same point while nodding at an older habit.
Bullfrog tadpoles grow enormous, and used to be kept quite commonly. Now that the species is designated, however, bullfrog tadpoles cannot be kept or transported without a permit.
Ishikawa Prefecture, "Bullfrog" (my translation)Size is the handle the public material offers. The same leaflet lines the larvae up.
| Species | Larva | Adult |
|---|---|---|
| American bullfrog | 12–15 cm | 12–18 cm |
| Black-spotted pond frog | 7 cm | 5–9 cm |
| Japanese tree frog | 5 cm | 3–4 cm |
For adults the leaflet points to the absence of dorsolateral folds and the large eardrum — bigger than the eye in males, about the same size in females. The black-spotted pond frog does have those folds. Bullfrogs commonly overwinter as tadpoles and metamorphose the following year.
The ministry's identification manual for amphibians has no section on the bullfrog's morphology or larvae. Nor could I find any public document stating that bullfrog tadpoles are easily confused with native ones. The material above is written from the other direction: the sizes are far apart.
3. What changes if it is killed on the spot
The ministry's Q&A draws a second line, in the angling context.
Even where a species is designated, you may still fish for it. What is prohibited is, for example, taking the fish home to keep it, or moving it and releasing it. Accordingly, releasing a designated invasive alien species you have caught on the spot — catch and release — is not a problem. Nor is there a problem in killing it on the spot and taking it home to eat.
Ministry of the Environment, "Q&A on the Invasive Alien Species Act", Q9 (my translation)Why that holds is set out in the article-by-article commentary, under the definition of "holding". Holding means keeping a creature within one's sphere of control so as to prevent its death or injury. Where the purpose is disposal, where the measures needed to bring about death have been put in place beforehand, and where the creature is held in a state in which death follows swiftly, that is in principle not "holding". The same reasoning is applied to transport.
The examples name a frog directly.
For instance, putting a largemouth bass into a cool box with no water in it, or putting a frog into a highly airtight container such as a film case in which swift asphyxiation is certain, (omitted) are envisaged as examples that do not constitute "holding". Conversely, where an animal caught in a trap is deliberately left there, and more generally where the measures needed to bring about death have not been put in place beforehand, this may constitute holding even though the purpose is disposal.
Ministry of the Environment, article-by-article commentary on the Act (1 July 2026 version, my translation)The second half seems to be the load-bearing part. It is not enough that the intention is disposal; the distinction turns on whether a state in which death follows swiftly and reliably has actually been prepared. A bucket in the back of a car does not sit on that side.
Article 2, paragraph 1 also limits designated invasive alien species to living individuals. Once frozen or processed, they fall outside the Act.
4. How far may it be moved
"Transport" has its own definition in the commentary.
"Transport" means carrying a creature under one's factual control and moving it to a different place. "A different place" means a place lacking sameness and unity with the original, and moving a designated invasive alien species within a place having sameness and unity does not fall under "transport" for the purposes of this Act.
Ministry of the Environment, article-by-article commentary (my translation)Where that boundary runs is worked out in the Q&A, using largemouth bass. Moving a fish within a range that does not reach the road adjoining the bank of the water it was caught in is treated as no problem; carrying it alive along a lakeside road to a weigh-in station is treated as a breach. The Q&A also explains how waters are divided.
As for lakes and rivers, even where they are connected within one system, each lake or river named on a map published by the Geospatial Information Authority of Japan is regarded as a separate lake or river. Where a weir or similar restricts the movement of fish, a river is not regarded as having sameness and unity across that structure.
Ministry of the Environment, "Q&A on the Invasive Alien Species Act", Q9 (my translation)That table is written around largemouth bass, though the opening of Q9 speaks of designated invasive alien species generally. I could not find a table setting out transport ranges for the bullfrog specifically.
5. A school needs a permit
The permit for keeping sits in Article 5, and the permitted purposes are limited by Article 3 of the Enforcement Regulation. Item (ii) is education. A school is in a position to obtain a permit; it cannot keep one without.
How far "education" reaches is also in the commentary.
This is directed in principle at educational activities carried out by educational institutions of high public benefit, namely schools under the School Education Act. Awareness-raising by NPOs is in principle not accepted, and private cram schools are not accepted either. Nursery centres, certified centres for early childhood education and care and the like (omitted) become eligible where the purpose is found to be educational.
Ministry of the Environment, article-by-article commentary, on Article 3(ii) of the Regulation (my translation)A permit also requires an escape-proof facility. Article 5, paragraph 3 lists the absence of such a facility as a ground for refusal.
On dissection, there is a ministry survey of the situation before designation.
Bullfrogs are used for dissection in biology practicals at universities and elsewhere. (omitted) At least 100 universities across the country use bullfrogs for experiments, with a further 50 or more other institutions (vocational colleges, medical research institutes and so on). Beyond these, they are also used for dissection experiments in primary and lower secondary school science clubs and the like, so the total is difficult to establish.
Ministry of the Environment, "On the distribution of bullfrogs (edible frogs)", 4th expert group meeting, document 1-7 (my translation)That was 2005, before designation. It does not describe the situation now. For the period since, the regional office leaflet says that bullfrogs "are still used in numbers as food and as laboratory animals, though a keeping permit from the Ministry of the Environment is required in advance where live individuals are used."
For the red-eared slider and the red swamp crayfish, MEXT circulated a notice to boards of education on 22 May 2023. For the bullfrog, I could not find any national notice or material addressed to schools.
6. Culling also needs a procedure
Besides the permit, Article 4 exempts "capture and the like in connection with control". Control here means control under Chapter 3 of the Act: confirmation by the competent minister for a municipality, or accreditation for a body other than the State or a local government.
There is a small-scale exemption that dispenses with the procedure, but its scope is narrow.
For small-scale control such as control by local volunteers, the following cases are exempt from the prohibition on keeping and the like (keeping, cultivating, holding, transporting) under the Act without going through the procedures of public notice, confirmation or accreditation.
(i) Plants (omitted)
(ii) The family Cerambycidae (omitted)
The bullfrog is in neither category. A local group that wants to carry frogs away alive for disposal needs the confirmation or accreditation route.
Cases exist. Nanae Town in Hokkaido holds a confirmation for bullfrog control running from 5 September 2024 to 31 March 2034. An accreditation held by the Freshwater Ecology Institute, covering six prefectures in the Kansai region, lists the bullfrog alongside the snapping turtle and the Chinese stripe-necked turtle.
The guidelines also address what happens to the animals taken. Where they are not disposed of on site, the requirement is that there be "no personal taking home by workers or third parties and no abandonment in the wild" before proper disposal. Even on the control side, taking one home is carved out.
7. Why it is here
The bullfrog's arrival is dated to 1918. The National Institute for Environmental Studies invasive species database records the route as "brought in from New Orleans in the southern United States for food and for farming". A ministry document puts it as "first brought to Japan in 1918, and for a time farmed in various places for food".
Designation took effect on 1 February 2006, together with 43 species and species groups including western mosquitofish. Non-native crayfish other than the red swamp crayfish followed in 2020, and the red swamp crayfish and red-eared slider in 2023 — so the bullfrog was designated comparatively early.
The impacts public material points to are predation and competition.
Concern centres on effects such as predation on rare native species and competition for food resources with native frogs living by the water, including the black-spotted pond frog and the Daruma pond frog. There are ponds where the forest green tree frog, once present, is no longer seen after bullfrogs moved in and established, and islands where native frogs became almost absent as bullfrog numbers rose.
Ministry of the Environment, Chugoku-Shikoku Regional Environment Office (my translation)The invasive species database describes the diet as "carnivorous; eats almost any animal that fits in its mouth" and notes that the species appears on both the global and the Japanese lists of 100 worst invasive alien species.
The people who wrote the rules could see the taking-home problem. Explaining why the red swamp crayfish and red-eared slider were moved to the conditional regime in 2023, the commentary says: "citizens, including children, who do not know the content of the regulation would catch them, transport them home and keep them, and would thereby breach Article 4; on top of that, the burden of the permit procedure and the fear of penalties would induce unpermitted keeping and release, and damage to ecosystems would in fact expand." That relaxation was applied to two species. The bullfrog was not among them.
Closing
Finding a bullfrog is not an offence, and neither is catching one. The restriction attaches the moment you put it in a bucket and start walking. That the line sits there is hard to see without opening the statute. It is not "designated, therefore do not touch", and it is not "found one, so cull it" either.
The other side of the same regime — the crayfish, which may be kept but with conditions attached — is in a separate article.
What is written here is one way of looking at it. Statutes and notices get amended, and local ordinances may set their own rules. If you notice something, I would be glad to hear it through the contact form.
Sources
- Act on the Prevention of Adverse Ecological Impacts Caused by Designated Invasive Alien Species (Act No. 78 of 2004), Articles 1, 2, 4, 5, 9, 17-4, 18, 32, 33 and 36 e-Gov (Japanese)
- Enforcement Order (Cabinet Order No. 169 of 2005), Appended Table 1 e-Gov (Japanese) / Enforcement Regulation (MAFF/MOE Ordinance No. 2 of 2005), Articles 2 and 3 e-Gov (Japanese)
- Ministry of the Environment, article-by-article commentary on the Act (1 July 2026) PDF / index page
- Ministry of the Environment, "What is prohibited?" page / "Penalties" page
- Ministry of the Environment, "Q&A on the Invasive Alien Species Act", Q8 and Q9 page
- Ministry of the Environment and MAFF, "Points to note when fishing" (revised 2 November 2020) PDF
- Ministry of the Environment, Chugoku-Shikoku Regional Environment Office, "Designated invasive alien species: the bullfrog" (updated June 2014) PDF / amphibian materials
- Ministry of the Environment, identification manual for amphibians PDF / list of designated species by date PDF / list page
- Ministry of the Environment, "Guidelines for implementing control of designated invasive alien species" PDF / public notices of control page
- Ministry of the Environment, "On the distribution of bullfrogs (edible frogs)", 4th expert group meeting on reptiles and amphibians, document 1-7 PDF / minutes
- National Institute for Environmental Studies, Invasive Species of Japan, "American bullfrog" page
- Ishikawa Prefecture, "Bullfrog" (updated 18 July 2017) page / Hokkaido Blue List, identifying common alien species (amphibians) page