Hong Kong Goby
This species is from Asia: southern Chinese highlands, numerous in the New Territories of Hong Kong, in creeks. Not certain when discovered, probably about 1960.
(©1997 by Kaycy Ruffer)
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On March 1st, 1999 I received an E-mail from a gentleman, Chan Pui-lok Bosco, from the University of Hong Kong, and he was very nice to offer me the following information that he thought I might like to have. He said he was studying freshwater species in Hong Kong:
1)Rhinogobius wui is actually an old synonym of Ctenogobius duospilus, it has also been named as Ctenogobius whitleyi, but Ctenogobius duospilus is the up-to-date recognized scientific name. For more information on fishes in Hong Kong (see Pan et al.1990 The freshwater fishes of Guangdong Province.)
2)As far as I have seen/read, this species is 100% freshwater, at least in Hong Kong and various locations in China I visited. It occurs together with other primary freshwater species and is not found in lower reach of streams/rivers.
3)It occurs in riffles and shallow pools in clean streams with a sandy/gravel bed, the habitat it's found normally do not have any aquatic plants.
In the beginning of 1994 I was walking through my local fish store, Capitol Aquarium, just to see what they may have that I couldn't live without. I noticed a tank with some cute little fish in it on the back wall on the bottom row. At first I thought something was wrong with the fish because they stayed on the bottom of the tank. When they went to swim to the surface is when I thought they had swim bladder problems. I managed to get the attention of an employee that I had known for a couple of years and she told me these fish didn't have a problem. They were gobies. "What is a goby?", I asked her. I purchased about a dozen of them at approximately $5 each and took them home.
I started with the Hong Kong Goby (Rhinogobius wui) and I placed a male and two females in a twenty gallon tank with a heater set at 80° F. I put in a few rock formations, some plastic plants and a fine layer of gravel with a sponge filter for filtration. My salinity is 1.005, pH is 7.2 and my hardness is 7.5
I fed the adults tubifex worms, flakes, and frozen brine shrimp. Of course, they preferred the worms. I noticed that the females were beginning to get plump. The belly region gets a dark green colorationwhen the female is full of eggs.
After about four days I noticed one of the females was thinner than the previous day. I looked for the male and found him under a rock, picking at something on the roof part of the rock formation. Sure enough, eggs. I was a bit saddened to find the next day that all the eggs were gone.
Two weeks later I noticed the female's ovipositor was showing and her belly was a "hot-pink" orange. The pair chose a rock formation that had a flat rock for the base, two round rocks for the walls, and a long rock for the roof.
The female kept crawling over the male's head area and nudging his head and side and bending her body around the front part of his head. The male then (finally, to the females' relief) turned himself upside down and held onto the roof of their "house" with his suction ventral fins. When the female went to join him, he released his hold and went back down to the floor of the cave. Her body movements began all over again. I almost feel for her. He doesn't seem interested and she is trying her hardest to get her mate to join her. Twelve minutes later the roles were reversed and he is having trouble getting her to join him.
It was getting late so I decided to turn out their light and hit the "hay" myself. To my surprise, the pair started getting really active again. Thirty minutes later her belly seemed to be having muscle spasms. I hope this means she is about to spawn.
At times, when the female goes over the males' back, she will rest her tail on his head. He doesnt like this and shows her by raising his head and opening his mouth wide as if in anger. Still nothing. Maybe tomorrow.
I came home the next day and couldn't believe there were eggs. Her first spawn only netted thirteen eggs. This time there must have been at least fifty eggs! The male is guarding the spawn. I'm going to leave the eggs with him this time and see how things go.
The eggs are connected to the rock by short strands and the male goes over, around and into the clutch to fan them with his pectoral fins. The eggs appear to be oblong in shape, like a chicken egg. The wider part contains the developing fry.
The male quit tending his brood after the third day so I removed them to a basket hanging in their tank. The adults didn't seem to notice the basket of eggs.
Seven days later the fry hatched and I could see large orange yolk sacs attached to a thin thread with two black eyes at one end. They could only scoot on their sides so they would just go around in circles when they tried to move. It took 14 more days to absorb their yolk sacs at 80° F. I sucked one of the fry into an airline tube at this point and could actually see a tail, head and pectoral fins. The fry was about an eighth of an inch long.
I found that if I kept my fry at 80° F. they did much better. At a lower temperature than this I lost fry from what I guess was a chill. The fry began taking newly hatched brine shrimp after three more days. I managed to get them past level one. I got them to the free swimming state. I then transferred them from the net basket to a ten gallon tank I had previously set up for them. Two months later the fry were about 3/4 " long. After another four weeks the fry were 1 1/4" long. They were moved to a twenty gallon semi-brackish tank (this means I am slowly bringing the salinity down to zero). After reading what I can find about them it appears they can live in fresh water as well.
I was able to start sexing the young at two months. You must look at them from underneath and any you see that have red markings under the chin are the males. Females do not have these red markings.
Three months later the females were ready for spawning but I noticed they didnt know they were supposed to spawn with the males because they were releasing their eggs all over the tank! Now nature begins again.
These are quite easy fish to spawn and will spawn readily in either fresh or brackish water though brackish water is preferred. It is really a sight to watch the male(s) display for their females by raising their heads and bellowing out their throat showing off all the bright red striping!