Aba aba: Reproduction

Summary: How do Aba aba make more Aba aba? Join Kiersten to find out about the reproductive behavior of Gymnarchus niloticus.

 

For my hearing impaired followers, a complete transcript of this podcast follows the show notes on Podbean

 

Show Notes: 

“Abundance, Distribution, Morphometric, Feeding Evaluation and the Reproductive Strategies of Gymnarchus niloticus in the Lower River Niger at Agenebode, Edo State Nigeria,” by Mo Agbugui, Fe Abhulimen, and Ao Adeniyi. J. Apple. Sci. Environ. Manage Vol. 25 (8). 1371-1377, August 2021.

“Gymnarchus niloticus Cuvier, 1829

“Some Ecological Factors of the Tropical Floodplain Influencing the Breeding and Conservation of Gymnarchus niloticus (Cuvier 1829): A Review,” by Oladosu O. O., Oladosu G. A. And Hart A. I.

Music written and performed by Katherine Camp

 

Transcript

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Kiersten - This is Ten Things I Like About…a ten minute, ten episode podcast about unknown or misunderstood wildlife.

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Kiersten - Welcome to Ten Things I Like About… This is a podcast about misunderstood or unknown creatures in nature. Some we’ll find right out side our doors and some are continents away but all are fascinating. 

This podcast will focus ten, ten minute episodes on different animals and their amazing characteristics. Please join me on this extraordinary journey, you won’t regret it.

Episode three of Aba aba is here and we are talking about reproduction. The end of episode two hinted at reproduction kicking off with the rainy season so that’s where we’ll begin. Join me for the third thing I like about Aba abas, reproduction.

It all begins when two Aba aba love each other, no really, it all begins with the rainy season. In the continent of Africa many animals rely on the abundance of the rainy season. This season brings rain that is a necessary resource for survival of all living things, as well as flooding the rivers. Flooded rivers overflow into flood plains where food becomes abundant. Terrestrial invertebrates are often caught off guard and drown leaving them to be consumed by aquatic carnivores, like the Aba aba. The Aba aba already lives in the water but when those waters rise nutrients increase and aquatic vegetation gets thicker. Then it’s time to start looking for a mate.

In studies performed in the Lower River Niger, two breeding peaks were observed. One from May to July, the other from October to January. The breeding behavior of Gymnarchus niloticus is heavily dependent on the flooding of the rivers. Beyond the food resources that increase at this time the aquatic plants that increase are important for the nest making of the Aba aba.

Now, the males of the species are the ones that make the nests. This is not uncommon in fish na the Aba aba is no exception. Their nests can be pretty big, but that is not a surprise for a fish that can get 5 feet in length. The male Aba aba makes a nest with uprooted aquatic plants. He pulls up the plants himself and weaves them into a floating nest that can be 1 meter, or 39 inches, in width. The perimeter of the nest is molded with the mud from the roots of the plants. It is expertly woven. It will be anchored to other plants and have an opening through which the male can enter and depart when needed. A little bit of the top of the nest will stick out of the surface of the water. If the nest becomes dislodged the male will remain with it as it floats down the river.

Inside the plants the male will create a bubble nest. This portion of the nest is made of air bubbles and this is where the eggs will be nestled.

The nest is important for several reasons: The first is to attract a mate. The ladies are attracted by large, well made nests, so the gentlemen will take their time picking the right plants for just the right nest. A few studies have indicated that they prefer plants in Family Poaceae, which are the grasses. The oblong leaves of the grass are perfect for weaving. We have to remember that this animal is weaving a nest. An animal that has no hands is weaving a nest. How extraordinary it that!

The second reason the nest is important is that this is where the eggs will be hidden and held until they hatch. Eggs are between 7mm-8mm, some papers have even said 10mm. That is a very large fish egg. 

Once the eggs are in the nest and fertilized, the male aggressively protects the nest from all predators. It will not hesitate to attack any living thing that comes near, including humans. These guys have no fear, especially when protecting their young. 

As I mentioned before, the nest have an opening for the Aba aba to enter and leave. When they are inside the nest, the male has been seen agitating the water around the eggs. We are not sure why they do this, but it could be to make sure the eggs are well oxygenated and/or keeping the eggs clean of debris. Either way the male is doing a great job keeping the eggs healthy.

I did not find any reference to how long it takes the Aba aba fry, that’s right baby fish are called fry, to hatch and leave the nest. They will remain in the nest until the yolk is completely absorbed. Until then they are vulnerable to predation and they will stay in the nest under papa’s protection. The fry have long gills to help absorb oxygen from the water, but will also gulp air from the center of the nest as well.

How many eggs are we talking about here? Good question! I love it when you think ahead listeners. Females can lay 800-1000 eggs in a nest. That is a lot a fry to keep track of, but it’s actually a low number compared to other species of fish. Aba aba seem to put more energy into larger, but fewer eggs, and more parental involvement to ensure future generations’ survival. 

I could not find any information about how many nests a female will visit in one breeding season. This may be due to the fact that it is difficult to follow them in the rivers where they live, especially during the rainy season when sediment is stirred and flowing freely in the rivers, or it could be that no one has pursued this avenue of study.  

Male and females both have singular reproduction organs. The males have a single testis and the females have a single ovary. This probably limits the amount of eggs they can lay and fertilize. 

Aba abas will complete this reproductive cycle twice a year in the wild following the rainy seasons. In captivity, it may be a different story. The Aba aba I worked with at the zoo was a male. We know this because we gave him enrichment toys such as weighted pool toys and copious amounts of plastic aquatic plants. The only thing he ever did with them was make a floating nest. He would weave the plants together and then shove the pool toys up inside the nest. Sometimes he used the nest like a hammock. Just relaxing inside it and not moving at all. Several times he gave me gave me heart palpitations as I thought he was dead, but it was just one more thing that made me like him.

I’m so happy you joined me for episode three of Aba abas because my third favorite thing about them is their reproductive behaviors.

If you're enjoying this podcast please recommend me to friends and family and take a moment to give me a rating on whatever platform your listening. It will help me reach more listeners and give the animals I talk about an even better chance at change. 

Join me next week for another exciting episode about the Aba aba.  

    

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This has been an episode of Ten Things I like About with Kiersten and Company. Original music written and performed by Katherine Camp, piano extraordinaire.