Food and Agriculture Organization of the United Nations
for a world without hunger
Fisheries and
Aquaculture Department
Cultured Aquatic Species Information Programme
Rana catesbeiana (Shaw, 1862)
I. Identity
V. Status And Trends
VI. Main Issues
a. Biological Features
b. Images Gallery
a. Responsible Aquaculture Practices
II. Profile
a. Historical Background
b. Main Producer Countries
c. Habitat And Biology
VII. References
a. Related Links
III. Production
a. Production Cycle
b. Production Systems
c. Diseases And Control Measures
IV. Statistics
a. Production Statistics
b. Market And Trade
Identity
Rana catesbeiana Shaw, 1802
[Ranidae]
FAO Names: En - American bull frog, Fr - Grenouille-taureau américaine, Es - Rana toro
americana
Biological features
One of the largest frogs of the genus Rana, which can reach up to 20 cm in snout-to-vent length (SV-L), and up
to 800 g in weight.
Body robust, with wide, flat head. Skin smooth and plain (no wrinkles, warts or spikes), dominantly pale green
with brown spots on the dorsal and lateral parts of the body, including limbs and head. Abdominal side white.
In adult males, upper abdomen temporarily turns yellowish as sexual maturity approaches. Anterior limbs short.
Posterior legs robust and long (representing up to 50 percent of total body length, and up to 40 percent of total
body weight). Both anterior and posterior limbs possess inter-digital swimming webs. Sexual dimorphism is
present in this species, although it is only conspicuous when pre-adult stage is reached.
FAO Fisheries and Aquaculture Department
Images gallery
Rana catesbeiana
Semi-natural bullfrog breeding pen (Central Brazil)
Controlled-environment breeding pen (Yucatan,
Mexico)
Nursery tank, attached to a tadpole rearing tank
(Guatemala)
Profile
Historical background
The American bullfrog is native to North America. Its natural geographical distribution extends from the southeastern Canadian province of New Brunswick in the north, southwards through eastern United States to
Florida, Alabama and the south-eastern part of Texas. It has been introduced to a number of other regions,
including Central and South America, the Caribbean islands, and Northeast and South-eastern Asia.
The first documented attempts to cultivate the American bullfrog date back to the late XIX century in the
United States. Primitive farms consisted of fenced earthen ponds, where tadpoles were stocked to feed on
natural productivity. Young frogs would congregate along the edge of the pond to feed on insect larvae
hatched on decomposing meat or other kitchen wastes deliberately placed as spawning substrates. Poor yields
soon discouraged such pioneering attempts. By the late 1930s, bullfrogs had been introduced in Brazil, and the
first frog farm outside the United States was established. Success was marginal due to the lack of sufficient
food, cannibalism and disease problems. Bullfrog farming re-gained popularity in Brazil in the mid 1970s.
Small ventures multiplied and academic groups got involved in research until late 1980s, developing a range of
culture facility designs and culture techniques for bullfrogs, whose systems are described in the production
section of this fact sheet.
FAO Fisheries and Aquaculture Department
Taiwan Province of China imported the first batch of bullfrogs as a potential alternative aquaculture species in
the 1950s. A research programme aimed at the cultivation of Rana catesbeiana was then established.
The first attempts to cultivate this species in Mexico began in the early 1960s, when this species was
introduced. The first farm was established with the objective of meeting the growing demand for live frogs in
the United States. The farm had breeding, tadpole rearing and fattening facilities and eventually became an
extensive tadpole-producing facility for stocking natural water bodies that later became frog fishing grounds.
Between 1968 and 1990, two research groups in United States, at the University of Michigan, and at Louisiana
State University, carried out research on culture techniques for bullfrogs as laboratory animals, and on its
reproductive physiology, pathology and nutrition.
In the early 1990s Thai farmers also began culturing frogs, and R. catesbeiana (along with Rana tigerina, a species
native to Southeast Asia) became a popular culture species, technically supported by Chulalongkorn
University.
Between 1991 and 2001, the Center for Research and Advanced Studies (Cinvestav) of Mexico, carried out a
comprehensive applied research programme for its cultivation, resulting in further advances in reproductive
physiology, nutrition, pathology and ecophysiology, which led to the development of an inundated-type culture
system that is currently in commercial use in a number of regions of Mexico and Central America.
Main producer countries
Although production of this species is reported to FAO by only two countries, commercial farms also exists in
Mexico, Guatemala, Salvador, Panama, Ecuador, Argentina, Thailand, Indonesia, the Lao People's Democratic
Republic, Viet Nam and Malaysia, while experimental farms exist in the United States of America, Cuba and
Puerto Rico. It is likely that production from the other commercial farms is reported to FAO under the more
general statistical category 'frogs (Rana spp.)'.
Main producer countries of Rana catesbeiana (FAO Fishery Statistics, 2006)
Habitat and biology
Bullfrogs readily adapt to and occur throughout a wide range of climatic conditions. They are found in
temperate regions, where they hibernate to withstand below-freezing ambient temperatures, and also in tropical
regions, where temperatures reach 40 °C during summer months.
The reproductive physiology of bullfrogs is highly influenced by temperature, photoperiod, ambient humidity,
and barometric pressure. Consequently, the closer a population is to the Equator, the wider the length of its
FAO Fisheries and Aquaculture Department
reproductive period. While year-round spawning is common in bullfrog stocks from Panama and Ecuador,
wild stocks in Mississippi (United States of America) have a three-month reproductive season.
Metamorphosis of tadpoles is dependent upon two types of ecological factors:
Adequate environmental conditions (temperature, water quality, availability of food).
Competitive interactions (intra- and inter-specific competition and presence of predators).
All these factors act as natural selection 'sieves', thus only allowing the fittest individuals to survive through to
adult stages. In culture situations, where such factors are artificially eliminated, genetic variability expresses
itself through size disparities and vulnerability of the weakest organisms.
In general, bullfrogs from the northern hemisphere (i.e. Asia, North and Central America) reproduce from
March through August, while populations from countries south of the Equator (i.e. Brazil, Uruguay and
Argentina) reproduce from September through February. The fecundity of bullfrogs is a function of age, rather
than body mass. In farmed females, between 1 300 and 33 000 laid eggs have been recorded from firstspawning and 3-year females, respectively.
Embryonic development and timing to metamorphosis are highly temperature-dependent. In tropical regions
(>26 °C) hatching occurs within 48 hours. The concentration of dissolved oxygen is of particular importance at
this stage, therefore egg masses have to be kept near the surface. DO levels should be >3 mg/litre. Newlyhatched larvae are approximately 10 mm in length and attach to smooth surfaces by means of an oral sucker.
They have a yolk sac that is consumed in approximately 72 hours at ≥26 °C. Immediately after the yolk sac is
exhausted, larvae become free-swimming, filter feeding tadpoles.
Ontogenic transition of feeding habits include filter-feeding of phytoplankton, grazing on benthic algae,
detritophagy and a gradual shift towards animal protein ingestion, before reaching the metamorphic climax
when nourishment becomes briefly autogenic. After tail resorption, froglets become carnivores.
Farmed frog stocks can achieve a survivorship of more than 50 percent. Genetic variability expresses through a
significant asynchrony in growth and timing to sexual maturity within every cohort, therefore, under tropical
conditions, fitter individuals can reach market size (>180 g), in 3 months after metamorphosis, and sexual
maturity in as early as 7 months after hatching, while weakest may take over one year.
Production
Production cycle
FAO Fisheries and Aquaculture Department
Production cycle of Rana catesbeiana
Production systems
Seed supply
Various strategies are employed by bullfrog farmers to obtain seed. These include collection of egg masses or
tadpoles from the wild, as well as semi-natural breeding in captivity (semi-controlled reproduction), and more
recently, environmental and hormonal manipulation for controlled reproduction.
Collection from the wild
Many small farmers of Latin America, in areas where wild bullfrog populations occur, collect tadpoles during
the breeding season. Smaller tadpoles (<50 mm) are transported in oxygen-saturated water in plastic bags at 1
500-2 000/litre. Metamorphosing tadpoles are also collected. These are placed on soaked cotton sheets, and
transported in perforated cardboard boxes at 250/m2 of box bottom area.
Semi-natural reproduction
This consists of stocking adult males and females in breeding pens where practically no management other than
feeding is practiced. Breeding pens are of two types. Asian farmers employ 10-20 m2 square concrete tanks,
with 1 m walls and an 8-12 cm permanent water layer. Water flows through the tank continuously. Breeders
are stocked at 1-5/m2 , and a sex ratio of 1 male: 1-3 females. Feeding consists of 40 percent protein floating
pellets, provided once a day at 2.5-3 percent bodyweight/day.
Latin American bullfrog farms generally employ a semi-dry type of breeding pen. This consists of an area of
variable dimensions (they range from 10 to 1 600 m2 ), constructed of cinder block or agricultural shade cloth.
Some pens also have a top mesh to prevent avian predation. Between 75 and 90 percent of the total floor
surface area of the pen is covered by grass, while the rest has shallow (<10 cm) concrete-lined puddles. These
FAO Fisheries and Aquaculture Department
latter are used as spawning sites and can be small (1 m2 ), for one breeding couple at a time, or large enough for
collective breeding (20-60 m2 ). Feeding points and shelters are also present. Feeding consists of a 40 percent
protein pellet, fed once daily at 2.5-3 percent bw/day, together with 2-3 percent bw/day fly (Musca domestica)
larvae.
Controlled reproduction
Controlled reproduction involves the manipulation of ambient and water temperature, ambient humidity and
photoperiod in indoor breeding facilities. Such strategies are usually sufficient to stimulate reproduction
throughout the year, especially in thermally stable latitudes. However, hormonal stimulation is occasionally
employed. Intensive bullfrog farms in Mexico and Guatemala employ indoor breeding facilities, which retain
heat through a greenhouse effect. Buildings are divided into three sections:
1. A series of 3-5, 25 m2 , sex-segregated broodstock-holding tanks.
2. A collective meeting area for males and females.
3. A series of small (1 m2 ) spawning puddles.
The temperature within the building oscillates between 28 ºC and 42 °C in a 24-hour cycle most of the year.
Water temperature remains constant at 26-28 °C. Light bulbs are evenly distributed in the building, and are
automatically time-regulated to maintain a photoperiod of 10D:14L Ambient humidity is kept at 95-98 percent,
by using water sprinklers. Breeders are stocked at 10/m2 in section 1, from which ripe individuals are
transferred to section 2 at a male: female ratio of 1:1. The stocking density is reduced to 1/m2 . Breeders spawn
in section 3.
Hatchery
Most farms use their tadpole rearing tanks to incubate fertilized spawns. However, some others have specific
incubation facilities. These involve concrete buildings where eggs are placed in small (1 m2 ) plastic or
fibreglass containers. Fertilized eggs are kept in a shallow (5-8 cm), static, chlorine-free, clean water layer in a
shaded, ventilated (25-26 °C) site. No aeration is employed. Hatching takes place within 48 hours at 26 °C.
Nursery
Tadpole rearing
Once tadpoles reach the first-feeding stage, they are transferred to the tadpole rearing tanks. Phytoplankton
inoculation is carried out for the first two weeks, and then supplementary feeding is provided 2-4 times a day.
The recommended stocking density is 50/m2 .
Water quality is maintained by running freshwater continuously through the tank (1-1.5 times/day), or through
aeration. Culling is a routine procedure to lower intra-specific competition. Timing to metamorphosis varies
greatly among individuals. Precocious tadpoles become froglets in 45 days, while most of the population
achieves this in 90-120 days, and a small portion of the cohort (7-12 percent) will metamorphose after one year
or more, even in tropical conditions.
Nursery
Nursery tanks are only used in the wet, Mexican system. These are 5.0 x 2.5 x 0.40 m and attached to the
tadpole rearing tanks (see photograph in the images gallery). Here froglets are trained to feed on inert, floating
pellets. Through routine culling, weaker, slow-growing individuals are removed. Froglets are stocked at
between 50 and 75/m2 . A 2 cm water layer is maintained permanently. Young frogs are fed ad libitum at least 6
times a day with 1/16', 40 percent crude protein, floating crumbles, until they reach 30-45 g, which normally
takes between 30 and 45 days at 26 °C.
Ongrowing techniques
Ongrowing systems can be classified into two major types: dry, and semi-dry and wet (inundated) systems.
FAO Fisheries and Aquaculture Department
Dry systems
These include the Brazilian designs mentioned in the following table.
System
Main physical characteristics
Countries
Earthen or concrete, shallow, narrow, long open canals with sloped,
Aquaterrarium
Brazil, Mexico
grass-covered banks and terraces
Square 20-30 m2 walled, roofless, grass-covered floor, with a central
Brazil, Taiwan
Tank-Island concrete platform (10% surface area), surrounded by a shallow (<0.10 m)
Province of China
canal
Confinement Square, 12 m2 , concrete floored, walled rooms. Floor is a ramp with its
Brazil
Rooms
lower part under a water layer and roofed
Concrete, closed buildings containing 8-12, 20-25 m2 , concrete floored
Amphifarm on-growing rooms. Floor has two narrow canals, pre-fabricated shelters Brazil, Ecuador
and feeding troughs
Brazil, Argentina,
Wooden or concrete 4-8 m2 tanks with partially flooded floor. Tanks are
Greenhouses
Uruguay, México,
placed in wooden or metallic-framed, plastic or tarpaulin-roofed building
Guatemala
Vertical array of wooden or fibreglass, heated boxes with water and feed
Ranabox
Brazil, Argentina
trays
Semi-dry and wet systems
This category comprises a number of systems employed in Southeast Asia, as well as some Latin American
versions employed in Mexico, Guatemala, Argentina and Uruguay. The following table summarizes the main
operational and productive characteristics.
Wet surface area
30-50% of total bottom area of fattening tank
Water dynamics
Static
Nursery stage
No
Average yield
12-16 kg/m2
Type of feed
Supplementary + live (fly larvae)
Functional versatility Limited
100% of total bottom area of fattening tank
Flow-through
Yes
14-22 kg/m2
100% supplementary feed
High
Feed supply
Specific frog feed is used in some Asian countries, while Latin American farmers employ chiefly tilapia or
trout feeds.
Harvesting techniques
Once frogs reach market size, they are prepared for harvest. Frogs are starved for 24 hrs before harvest. In
semi-dry systems, ongrowing rooms are drained and frogs are collected manually. Harvesting is carried out in
much the same way in wet systems although, in some farms, iced water is pumped into the tanks to
hypothermally anaesthetize the frogs to allow for better handling.
Handling and processing
Processing of frogs is carried out in certified processing facilities. Frogs are hypothermally anaesthetized (12´at
4 °C) and then slaughtered. Processing includes bleeding, skinning and cutting off the lower limbs, which are
then thoroughly cleansed using chlorinated water. Then the legs are individually bagged, frozen and packed by
size in master boxes for transport. Frog legs are kept frozen at -15±2 °C which gives them a shelf life of up to 6
FAO Fisheries and Aquaculture Department
months.
Frogs for the live or scientific markets are manually rinsed and packed in 25-lb waxed perforated cardboard
boxes. Live frogs are transported under cool and dry conditions by plane. Survival is usually up to 99 percent
when the journey does not exceed 72 hrs.
Production costs
The annual operating costs for a 36 tonnes/yr bullfrog farm (in Mexico) have been reported to total USD 67
560 (41 percent feed; 31 percent labour). Fixed investment costs were USD 130 000 (land USD 20 000;
infrastructure USD 90 000; equipment USD 16 000; and initial broodstock USD 4 000).
Diseases and control measures
The major disease problems affecting American bullfrogs are included in the table below.
In some cases antibiotics and other pharmaceuticals have been used in treatment but their inclusion in this table does not imply an FAO
recommendation.
DISEASE
AGENT
TYPE SYNDROME MEASURES
Antibiotics;
Occurrence of several bacteria, either synergistically
biosecurity;
'Red leg'
or mono-specifically. The most common genera are Bacteria Red legs; red movement of
disease.
anus
Aeromonas , Pseudomonas , Klebsiella, Edwardsiella, Myma,
non-infected
Streptococcus
organisms only
Antibiotics;
biosecurity;
General
Most common causative genera are Streptococcus and Bacteria General
movement of
oedema
Staphylococcus
swelling
non-infected
organisms only
Antibiotics;
biosecurity;
'Swirling'
Most commonly found genera in diseased organisms
Bacteria
–
movement of
disease
are Aeromonas, Streptococcus and Staphylococcus
non-infected
organisms only
Antibiotics;
Tuberculosis; biosecurity;
Tuberculosis Mycobacterium spp.
Bacteria surface ulcers movement of
may appear
non-infected
organisms only
Ulcers,
sometime with
Fungicides;
Mycosis
Achlya spp., Saprolegnia spp.
Fungus visible
biosecurity
mycelia; skin
reddening
Good
Environmental Various (congenital, nutritional, environmental)
–
–
management
practices
Suppliers of pathology expertise
Assistance can be obtained from the following sources:
FAO Fisheries and Aquaculture Department
Dr. Marcio Hipolito, Instituto Biológico de Sao Paulo, Brazil
.
Dr. Putsatee Paryanonth, Chulalongkorn University, Bangkok, Thailand.
Dr. Victor Vidal, Center for Research and Advanced Studies (CINVESTAV), Merida, Mexico
Dr. Daniel Carnevia Instituto Nacional de Pesca, Montevideo, Uruguay.
.
Statistics
Production statistics
Global Aquaculture Production for species (tonnes)
Source: FAO FishStat
6k
4k
2k
0k
1950
1960
1970
1980
1990
2000
2010
Rana catesbeiana
The figure above is based on national statistical returns to FAO for aquaculture production of this species.
Nearly all is from Taiwan Province of China (1551 tonnes in 2002), with very small annual production
reported by Uruguay. Other frog aquaculture production is not identified by species, simply being reported as
'frogs, Rana spp.'; this category undoubtedly contains production of R. catesbeiana but the proportion is unknown.
However, it is known that there is substantial production of this species in Brazil, Mexico, Ecuador and
Guatemala.
Market and trade
In 1980, it was estimated that 3 percent of the global market of frogs (all species) was supplied by aquaculture,
while the current (2002) estimated contribution is 15 percent, taking into account the calculated growth rate of
the industry.
Market statistics for frogs are scarce and unreliable. Some documented demand statistics place the United
States of America as the highest consumer of frogs (all species), followed by France, Canada, Belgium, Italy
and Spain.
There are three major market niches for bullfrogs, namely:
Frog legs.
Live frogs.
Educational and scientific requirements.
The market for frog legs is by far the largest niche worldwide. The main producers (capture and aquaculture)
are Indonesia and Taiwan Province of China. Prices are weight-related, fluctuating from USD 3.86-10.14/kg at
current (2004) prices.
FAO Fisheries and Aquaculture Department
The demand for live frogs for food has increased especially amongst Asian groups living in Canada and the
United States of America. Wholesaler prices range between USD 2.25 and USD 3.75/kg of whole frog,
depending on weight. The main producers (capture and aquaculture) are Taiwan Province of China, Brazil and
Mexico.
Live bullfrogs for educational or scientific purposes are sold in the United States of America to processing
companies. Three size-categories are marketed: 4-5', 5-6', and 6-7' (S-VL); prices range from USD 1.30-3.25
each.
Status and trends
Continued research efforts focusing on nutrition, pathology and reproduction are expected to result in important
improvements that will boost production in the future. However, there is still much to be done on genetics.
Marketwise, prices will tend to gradually increase, as trading of wild-caught frogs becomes restricted, thus
being replaced by farmed animals; nonetheless, important efforts should focus on marketing and advertising,
since frog meat and its attributes are far from being widely known.
Main issues
As in any other type of aquaculture, bullfrog farming can cause problems if not managed properly. The
following table summarizes a series of externalities likely to be generated by frog farming, as well as the risks
involved and some suggestions for their prevention or mitigation.
Externality
Risks
Mitigation strategies
Eutrophication and ecological alteration of
Organic
On farm wastewater treatment; wastewater re-use
surrounding waters; organic pollution of
discharges
in agriculture; use of low-polluting feeds
water used for human consumption
Release of
Discourage use of antibiotics; replace drugs with
Stimulation of natural bacterial resistance
antibiotics
efficient management and prophylaxis
Introduction of non-native pathogens; out- Implement preliminary ecological impact studies;
Introduction of
competition of local species; unwanted
adopt strict bio-security measures to prevent
exotic species
hybridization
escapes; quarantine introduced organisms
Water or land that is or can be used in a
Make a comparative cost/benefit analysis with
Resources use
more efficient way to generate more social other economic or social activities already in
conflicts
benefits
place or potential
Collection of
eggs and
Diminishes recruitment of commercially
Carry out population dynamics studies; use
tadpoles from important frog fisheries
aquaculture to re-stock natural fishing grounds
the wild
Responsible aquaculture practices
All countries request sanitary certification when buying frog legs but no CITES paperwork is required.
It is important to develop specific regulatory frameworks for bullfrog farming, as it is becoming an important
aquaculture activity in many regions. It should also follow the general principles adopted by the Code of
Conduct for Responsible Fisheries, Article 9 (see http://www.fao.org).
References
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FAO Fisheries and Aquaculture Department
Related links
Aquafind
Aquatic Animal Pathogen and Quarantine Information System - AAPQIS
Aquatic Network
Database on Introductions of Aquatic Species - DIAS
European Aquaculture Society - EAS
FishBase
FAO FishStatJ – Universal software for fishery statistical time series
GLOBEFISH
Network of Aquaculture Centres in Asia-Pacific - NACA
World Aquaculture Society - WAS
FAO Fisheries and Aquaculture Department