Month: March 2013

Above: Julidiochromis ornatus – the masked bandit of Lake Tanganyika.

Like a few other species here in Lake Tanganyika, J. ornatus is a cooperative breeder; meaning that they form groups in which smaller individuals don’t reproduce (usually) and help raise the offspring of the breeding pair.

The cooperative system in the Julies gets a bit more complex however. In the breeding pairs the male or female can be larger, and fish preferentially form groups so that one or the other is substantially larger. When the male is larger, the social system is typically polygynous. This means the male mates with multiple females in the group. In most cases, the female is larger and the system is the opposite. The term for this is polyandrous, meaning “many males,” and she keeps a harem of males around.

 

I should start by saying I have a love-hate relationship with these fish. As you can see, they are very attractive fish. At a certain level, they can be considered ecosystem engineers for the shell beds they construct; shell beds that a number of species (including last weeks cichlid of the week) rely on. Territorial males collect shells and defend patches of shell bed. Successful males maintain a harem of females who live inside the shells where they lay their eggs. Less successful males are on the lookout for great shells they can steal.

The males are far too big to fit inside, but because of the drastic size dimorphism between the sexes the females have no issues. These are reasons I really like these fish, now for the reasons they test my patience…

As I said, territorial males are much larger than females, and they don’t grow that big overnight. Juveniles form schools sometimes numbering in the hundreds that move all around the lake floor where they essentially pillage the territories of other fish. As “the mob” descends onto territories, they all start picking up mouthfuls of sand, eating whatever they come across, send the other fish into a panic, then leave just as fast as they arrived. They do a fine job of messing up observations, and they also have a gift for getting caught in our fence nets. And it’s never just one that gets caught in the net either.

In the end these are pretty cool fish, in spite of their gift for frustrating me.

Having dove twice a day more or less every day since arriving, we have decided to take a couple of days to rest up and recuperate before the final drive of our field season. Its been a fun, relaxing, and entertaining few days!

On both Friday and today a number of police, navy, and other government officials have been at the lodge learning how to SCUBA dive. They’re a very friendly bunch, but none of us had any idea they’d be here. Apparently most of them learned to swim last week and from my perspective they’ve gotten comfortable with the whole thing very quick.

Yesterday we went back to Katoto for a fun dive to see all the fish in the rock garden. The rock garden is an area in 3-5 meters of clear water that has huge boulders as well as abundant aquatic plants. For whatever reason, this site has tons of fish, and most of them are way brighter than they are here. It was a great time, and both our bottle filler Fernandez and our boat drivers Damias and Mr. Kupembwe joined in for a fun swim. A bunch of kids on shore who in all likelihood may have never seen a Muzungu were waving from shore and yelling “Hey, Muzungu!” for our entire visit.

Above: A little “multi,” sadly where we found them was at 15 m off the east coast of Mbita Island; a little too deep for my camera, so you have to settle for a shot of this little guy we brought up with us.

Last week I wrote about the worlds largest cichlid, its only fitting that this weeks feature be the worlds smallest, which also lives in this lake. Neolamprologus multifasciatus is a tiny fish maxing out just over 2 cm. They live in shell beds in which each male defends a plot of shells and all the lady multi’s that call those shells home. The shell bed we were working on was huge, empty gastropod (snail) shells as far as the eye could see (which depending on the visibility was 1-7 meters). 

Don’t let the small size fool you, these little guys are kings of their domain. The males duke it out to make sure their neighbors don’t get too close to their territory, and the males “police” the females living in his territory to make sure their fights don’t get out of line. Of course, each fish has its own little shell for safety in case a bigger (any) fish comes along looking for a meal. The plan works great until the predator happens to be a researcher who just picks up the shell. Eventually getting them out of the shell was a huge pain however…

 

The past week or so has been interesting in terms of weather; we had an intense rainstorm a few nights ago that lasted about 8 hours, and before that (and coincidentally right now) the wind has begun to pick up and lead to waves around 2 m. Combining those waves with a rocky shoreline makes it a bit unsafe to dive so we already had to take one afternoon off. The first day, we were still debating the dive as the wind kicked up, and I walked by Fernandez our bottle filler, navigator, and general advisor on what not to do. I asked whether it was thumbs up or thumbs down for the afternoon, to which he responded “oh, yes.” When I looked back confused and asked if it was safe to dive, he promptly responded “oh, no,” then laughed. Some of the other team members were on the boat by Mbita Island when it started up, and they were stranded at the dock at fisheries until the early evening. Their return trip included a frantic boat ride to shore, a car ride from town to the wrong village, from which they had to walk to our lodge.

Our fearless leader Susan has headed home. It was sad to see her go, but she trained us all well and I’m confident we’ll survive without her.

It seems National Geographic has taken an interest in Lake Tanganyika recently. Hopefully you find it interesting!

http://newswatch.nationalgeographic.com/2013/03/07/warming-lakes-climate-change-threatens-the-ecological-stability-of-lake-tanganyika/

 

Above: A pair of Nkupi defending a swarm of fry.

Twice I have found myself swimming along in midwater to find the water around me rippling as though I’m in a swarm of gnats. It then becomes clear I’m in a cloud of fry, thousands of them. The next thing I’ve noticed is the parents circling around me nervously. Boulengerochromis microlepis, also known as Nkupi or Yellow Belly, are the largest cichlid in the world, growing up to 70 cm in length. They are beautiful fish and very graceful in the water. They form at least socially monogamous pairs (to my knowledge nobody has actually done paternity work on them to look for cheating). These pairs fiercely defend the eggs, fry, and juveniles.

It seems at least some of them have an issue with divers wearing yellow masks or snorkels. On a previous expedition, one diver got rammed by a Nkupi multiple times.

They are also delicious.

Above: It turns out jellyfish are tough to photograph…

This morning started up like any other, with us eating breakfast, going over the dive plan, and getting our gear set up. The water was smooth, and fairly clear on shore. That doesn’t always mean it will be clear deeper, but this morning it was there too. As we swam out, we all started to notice small blobs floating around. Upon closer inspection it became clear that they were jellyfish. And they were everywhere!

Once we got deeper, the fish were also clearly excited about the jellyfish too, and there were large aggregations of fish a few meters off the bottom going after any jellyfish that floated by. All this made it a great dive. But it got even better.

On my way back to shore, I was swimming along and noticed the water was rippling all around me. I then realized I was in the middle of a school of thousands of Nkupi fry, and both parents were circling around me nervously. We’ve seen a good number of them, but this was the closest I’d been, and the visibility in the water made it even better. I’ll talk more about this fish at some point, but they’re the biggest cichlid in the world, they are amazing parents, and they’re delicious.

This afternoon in our second dive the waves had kicked up a bit, and we only saw a few jellyfish, but it was still a great dive. To cap off the day, Kelly and Joe went into Mplungu to run some errands, managed to refill our peanut butter and soda reserves, and as a bonus found hot sauce and chocolate bars! it will be a great dinner!

This week’s cichlid is one of several species commonly known as Featherfins. One look at their fins should make it perfectly clear why. That’s hardly what is most interesting about them however. As I alluded to in my last post, it’s about that time that a young male C. furcifer starts to think about finding a mate and making some little C. furcifers. The first step is to build a bower, which essentially is an underwater sand castle. Right now there are tons of these just offshore from where we are staying. Each male builds a ring of sand up to about a meter or so in diameter and roughly 30 cm in height. They are meticulous in their maintenance of their bower, and continuously add more sand, smooth out edges, and run off any fish that tries to get too close.

Once their bower is ready, the show begins! As females pass by to check out the quality of the castle, the males flare out their fins, brighten their colors, and show off more or less continuously. If the female approves, she lays a few eggs in the middle of the bower. When she turns around to pick up the unfertilized eggs (more on why in a moment), the male drags his pelvic fins in the sand in front of her. The yellow tips are known as “egg mimics”. The female thinks she’s missed a few eggs and swims after them, at which point the male ejaculates in order to fertilize the eggs in her mouth. This may repeat several times until the female has a mouthful of fertilized eggs.

C. furcifer is a maternal mouth brooder, which means the female will keep those eggs, and eventually the fry in her mouth until they’re old enough to live on their own. When the fry are free-swimming, they will swim out of their mother’s mouth to go catch food, and dart back in at the first sight of danger.