Common Name: Spotted Blue-eye or
Family: Pseudomugilidae (Blue eyes)
P. gertrudae was named for the wife of Dr. Hugo Merton (Gertrude
Merton), a scientist who visited the Aru Islands.
Pseudomugil means false mullet.
The fish were first collected in the early 1900’s by Dutch collectors
in the Aru Islands.
Pseudomugil gertrudae is found in northern Australia, southern New
Guinea and the Aru Islands. There are many different populations of
this species. They have been collected in New Guinea from Pahoturi,
lower Fly, and the Bensbach river systems. There are at least 5
populations known just from Australia. These populations are fairly
scattered. They include: northern Cape York, the Murray Swamps (QLD.),
Finniss River system (near Darwin), Melville Island, and eastern Arnhem
Land, NT. The latter is where my fish comes from originally.
The body of these fish is a basic silvery grey colour.
The scales seem to be outlined lightly in black. Eyes are blue, of
course. Pectoral fins can be variable in colour since there are so many
locales of gertrudae. They can range from yellow to orange to an almost
red colour. Many of the fins are tinged on the edge with white. The
dorsal, anal and caudal fins can be white or yellow. These fins are
covered in dark spots.
Males have elongated dorsal, anal and pelvic fins. They also have more
spots than females. Variable fin shapes are possible due to the many
These are a delicate looking fish that reach a maximum of about 3.8 cm
(approx. 1 ½”). They eat mainly insects, insect larvae and
crustaceans as their main diet in their natural habitat.
In the wild, spawning usually occurs between October and December.
Males display to females and chase them. The display usually consists
of the male raising up his dorsal fins and spreading the anal fin. Each
female will lay approximately 10-12 eggs during the day. Eggs are clear
and are quite large for such a small fish.
These eggs generally hatch in 9 to 11 days depending on conditions.
Pseudomugil gertrudae prefers to live in small creeks, lagoons,
billabongs, swampy marshes, and rainforest streams. They also like
backwaters next to major rivers. It likes these areas to but
gertrudae are usually found in fairly soft waters with a temperature
range of 23 to 30° Celsius (73-86°F), and pH 5.2 to 7.6.
We received a
shipment of fish and eggs from a fellow ANGFA-NA member (Kevin Hosmer).
The live fish was a surprise since we had requested eggs. It was a
wonderful surprise though!
It turned out to be a lucky surprise as only one of the eggs actually
hatched and survived for us. I placed the small group of 10 fish into a
20 gallon tank. The tank has floating hornwort and a spawning mop in
it. I have the tank at room temperature since there is no heater in
this tank. The group consisted of a few adults and some juveniles. I
was really impressed by the pretty little males. The pectoral fins are
a nice orange colour and the other fins were a delicate yellow (some
with spots of course!). This tank gets fed a supply of live baby brine
shrimp and flake. I added a small amount of salt to this tank as they
prefer some salinity to their water.
I started checking the mops a few weeks after I received the fish and
since I had a group, I had what I considered decent numbers of eggs
every day. I collected approximately 40 eggs over a couple of days. I
removed the eggs from the mop and placed them into a small clear
corningware baking dish on top of a tank that has a strong lid on it. I
used the water from the parents tank for this. I placed a small
airstone in the container to keep the water moving slightly. From what
I can tell, it appears that all the eggs hatched. In about 10 days or
so, they started hatching. The first week we fed the fry exclusively
microworms. After that they still got microworms in the morning but
started getting some feedings of baby brine shrimp in the evenings.
They grew well on this diet and have now been placed back into the
parents tank. I grew these fry out separately for breeders points, but
it appears that I didn’t have to do this as many fry have appeared in
the parents tank. It looks as if the adults don’t eat their fry if they
are well fed.