Stock - The Inhabitants
Fish Aggression. A Pictorial Guide
Written by Thursday, 04 July 2002 01:00
Sometimes fish aggression causes wounds, even severe ones. Then you have to isolate your fish and treat their wounds to avoid secondary infections. Isolating the fish means that you have a tank which is set up with the right temperature and is ready to receive the wounded fish. What happens if all your tanks are already occupied with recovering fish and / or breeding pairs ? You simply have to transfer one of the partially recovered fish to one of those tanks. Recently, my male Nimbochromis venustus (3 years old; 24 cm) was badly wounded by the male Cyrtocara moorii (5 years old; 24 cm). In order to treat it I needed an empty tank since its situation was really bad and any tankmate would take advantage of it. The only tank with only one inhabitant was a 140 liter one housing a recovering male Cyrtocara moorii (2 years old; 15 cm). The fish was found nearly dead following a very serious fight with a wild caught Fossorochomis rostratus (22 months old; 18 cm). At the time of the incident the C.moorii had partially recovered from the wounds so I thought there would be no risk to transfer it to a tank housing a breeding trio of Haplochromis nyererei (Lake Victoria rock fish). The latter is known to be extremely aggressive but I thought the difference in size would keep aggression at bay. I turned off the lights in the nyererei tank, waited for one hour and then transferred the C. moorii hoping that this red devil had gone to sleep.
After exactly 23 seconds the tank was boiling. I turned on the lights again only to find the two gladiators making big circles progressively closing in. Both fish are really aggressive but fight in different ways. The smaller (H. nyererei) is much faster and more versatile thus prefers to strike in the side while the C.moorii is more powerful, less fast and will go for a direct hit, preferably a jaw lock. Under normal circumstances, the H. nyererei might choose not to engage with such a bigger opponent but there were three reasons that forced it to: Firstly, it was its own tank for over a year, secondly, there were two of its females in that tank so it had to protect its territory (one female can be seen next to it) and thirdly, it is far more aggressive than mbuna.
It soon became apparent that nobody would retreat or give in. The first signs were obvious: both fish displaying and closing in. The C. moorii was trying to catch the much faster nyererei which was in turn trying to avoid its mouth (see photo) while at the same time aiming at the sides of its opponent.
Since I was still keeping the net in hand I decided to take some more pictures and then separate them unless one of them was in danger. Both fishes are excellent specimens so losing either of them was out of the question.
The tactics are shown in this photo. The H. nyererei always in the move while the bigger C. moorii is just changing its position to have its mouth pointing to its opponent. Both fish are completely focused on this "war game". You can also see some of the wounds on C. moorii's sides. Some of them were made during the old fight while the H. nyererei has already managed to hit twice.
The next photo shows the H. nyererei winning a point. The C.moorii is not only longer but also much taller than its slender opponent. Yet, thanks to its speed, the H. nyererei was able to hit the side of the C. moorii before the latter could change its position. The moorii got really mad at this point. It was only a matter of time...
Finally, "game, set and match" went to the C. moorii. After being hit several times, it managed to do what it was after. A direct hit. Not a jaw lock but grasping the whole head of the H. nyererei and hitting it on the rocks. After releasing it, the H. nyererei decided to keep some distance but after a couple of minutes there were circling again. It became evident that with this kind of aggression, sooner or later I would lose one of the two opponents. So the C. moorii made one more trip to a newly setup tank to stay for one week, till its wounds are completely healed. Then it is going to go back to the 500 liter tank with its brother.
Big fish may be less nervous than mbuna however, when they decide to fight they can really show who the boss is!
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