method—which was christened “ovarian lavage”—during
downtime from another breeding project.
Our first attempt involved three pairs. The females were given
the hormone via ovarian lavage, and we placed each one in a
separate aquarium (filled with artificial seawater) with a male to
see if they would spawn on their own. After three days of waiting,
we thought it was a failure. But when we removed the fish and
were cleaning the tanks, we found eggs in one aquarium. A small
percentage hatched three days later, producing about 100 fry. It
wasn’t an adequate result, but this renewed our enthusiasm.
In the second attempt, we used four females, but this time
we gently expressed the eggs after 36 hours and fertilized them
artificially. We had a hatch rate of close to 100 percent. Female
spotted green puffers are extremely fecund—eggs can constitute
up to a quarter of their body weight, and a big one can produce
7000 eggs—so you don’t need many adults to produce fry on a
In the third attempt, we used three females and repeated the
procedure from the second attempt. We had an even higher hatch
rate, and a large percentage survived long enough to begin feeding
on brine shrimp. At that point, I was confident that ovarian lavage
worked and decided it was time to start showing producers how
we were doing it.
The author inspects the spotted green puffer fry at the University of
Florida’s Tropical Aquaculture Laboratory in Ruskin.
Since then, we’ve demonstrated ovarian lavage several times, and
I’ve given presentations at a World Aquaculture Society meeting
on the method. We have distributed captive-bred broodstock to at
least five farms in Florida, and I expect them to be in commercial
production this year.
Completing the Process
We’ve been doing this long enough that some of the captive-bred baby puffers have reached adulthood, and we’ve bred them
successfully. That means the loop is closed, so to speak, and we
know that captive-bred puffers can be used for heredity studies.
We’ve submitted one journal article, an overview of ovarian
lavage (which has been accepted for publication in the journal
Marine Genomics), and we’re working on an article about the
embryology. We also expect to produce articles investigating the
age of sexual maturity of spotted green puffers, and the acclimation
of juveniles to brackish and freshwater rearing conditions.
We’ve also obtained a U.S. Department of Agriculture grant
to demonstrate ovarian lavage in other species. This is a formal,
proof-of-concept study where we are attempting to rule out the
possibility that some other factor has led to our success with the
spotted green puffers. That’s not very likely, but as scientists, it’s
important that we eliminate all doubt. Early results are positive
that the technique works on goldfish.
Ultimately this method may be useful in other hard-to-breed
species, especially those with physical characteristics that make it
difficult to give them injections with a needle.
There are about 15 other species of puffers with commercial
value, either as ornamentals or food fish. The latter group is, of
course, the famous—or infamous—fugu fish, edible puffers that
are considered a delicacy in Japan. Some of their internal organs
are highly toxic, and by law, the fish is only prepared by licensed
chefs. There’s a substantial commercial aquaculture industry in
Japan that breeds fugu fish, typically the species Takifugu rubripes,
using hormone injections. Ovarian lavage might be a more cost-efficient method for them, but that remains to be seen.
There can be up to 7000 T. nigroviridis eggs produced in a single brood, and
the author’s team was able to achieve a nearly 100-percent hatch rate.
Tropical Fish Hobbyist www.tfhmagazine.com