Wednesday, April 5, 2017

Cichlids and Sex

Things here at Kande Beach are as beautiful as ever. The rainy season brings lush greenery, growth and new life wherever one looks. Sex is in the air and you can feel it. The pintail whydah, a native bird here does its beautiful courtship dance for a female; singing and waving its long tail (3 times the length of its body) to show her what he can do. The flat backed toads sing every night luring the females with their chorus louder than the engine of a diesel truck. The flap-necked chameleon does an amazing colour change display for its girlfriend. These courtship rituals play an important role in what Charles Darwin called sexual selection: when the female of a species bears most of the cost of reproduction, males use extravagant displays and gifts to represent their “reproductive fitness” and females choose between them.  For many male humans, muscular displays, or shards of a crystalline form of carbon can serve to win over the female.



Sexual selection often actually works against natural selection. In situations of mainly female parental care, the reproductive success of the male is almost completely in the hands of the female. So even if a male is well camouflaged and can survive for a long time, if he doesn’t impress the female, he wont have any babies, and his genes will cease to be passed forward. In this way female choice selects for traits that sometimes actually increase the survival risks of the males. For example the agama lizard of east Africa have lost any camouflage capability when compared with their female counterparts. 



Here in Lake Malawi many cichlids have evolved a unique form of attraction. Over 200 cichlid species here build special structures to attract their females. These structures are called bowers, named after the structures built by the famous bowerbirds of Papua New Guinea. Like the bowerbirds these structures are built by male cichlids solely for the purpose of showing the girls what they can do.  In essence, the size and structure of the bower is a direct indicator of the fitness of the male. This is because, after all, if you are able to spend time digging and pushing around sand rather than finding food, you must be a strong individual with good genes to pass on.

video



There are two general bower types; either castles or pits and they are often built in large groups or congregations of many males called leks. Here, on Kande island there are species that build both types of bowers, but the most impressive, in my opinion, are those belonging to the species Dapidiochromis kawinge. The males of these species dig large pits often with diameters and depths greater than one meter. They do this by pushing the sand out of the way with their snouts. Every week here we do a survey of a lek near the island, and we try to track when the bowers are usually
inhabited. 

After the bowers are constructed, the males will remain in or above the structure and display for any passing female. If the courtship is successful, the female will lay her eggs and the male will fertilize them within the bower. The female will then scoop up the eggs with her mouth and carry them away to care for them herself. 

Female cichlids do not have to build any nests or structures, as many of them have evolved an amazing ability to brood their babies in their mouths!!! This behavior allows the mother to be mobile all the while providing round the clock parental care.

video


Here at the island we have found a couple mouth brooding resident mothers of the species Tyrannochromis nigriventer who we love to go watch whenever we have a chance. Cichlids are some of the most caring mothers of the animal kingdom, and this puts immense evolutionary pressure on the males to be more brightly coloured, or have better mating displays, or build better bowers. Cichlids can mouth brood their offspring for upto a month! Once the babies grow up, this sexually selective cycle repeats itself. As new tastes are developed or enhanced over generations whole new species with different preferences arise, continuing the ancient process that has led to the species and behaviours that we see today.

Share/Bookmark

Sunday, February 12, 2017

News from the Beach from our new Research Assistant Neha!

I got off of the plane in Lilongwe, exhausted after my journey from Canada. I was met by a smiling man who I was to drive with for the next five hours north to the village of Kande, on the shores of Lake Malawi. We drove through the beautiful countryside and countless villages that all had their little hub of shops and restaurants nestled around the main road. We reached Kande at around 7:30; it was dark, and only the bright stars and the fireflies lit the road.

I was asleep as soon as my head hit the pillow in my cozy cabin. The next morning I was up and at it, taking a new diver out to explore the reef. It was my first dive in the lake as well.  Right away fish of many different shapes and colours surround me. I know Lake Malawi is known as the most biologically diverse lake on the planet, but wow! The manifestation of this diversity astounds me.

The cichlid fishes are one of the largest animal groups on the planet. The group itself is thought to predate the continental drift events that separated Africa and South America around 140 million years ago as they are found in Africa, Latin America, Madagascar, and some parts of South East Asia.  However, the African cichlids represent one of the most striking examples of adaptive radiation (rapid evolutionary divergence) in the animal kingdom.

There are over 600 identified species, and many more unidentified species that live only in Lake Malawi! The lake basin is thought to be around 8.6 million years old, yet the majority of the cichlid species have been thought to have diverged from each other much more recently than the origin of the lake. To give you an idea of that insane speed, it is thought that we diverged from our closest living relative, the chimpanzee, around 13 million years ago!

There are many hypotheses as to how this group of fish has diversified so spectacularly. The geological history of the African lakes and their rising and falling cycles have given rise to many smaller lakes that have disconnected and reconnected over evolutionary time. This has allowed for many separate, but startlingly parallel, evolutionary trajectories. There are many highly behaviourally similar species that live in different regions or lakes, yet share less genetic similarity with each other than with the other species in close range.

Like Darwin’s finches of the Galapagos Islands the Cichlids of Africa have all specialized to specific ecological niches. There are species that remove parasites from the skin of catfish, and another that eats the catfish skin itself. There are scale eaters, fin-biters, sediment sifters, and zooplankton feeders. There is a group that inhabits snail shells, another that eats snails, crabs, or flies on the surface, and yet another that flips rocks to find insect larvae hidden underneath. Some species have evolved huge eyes to enable them to see in the dim lights at depths of over 100 meters, and others have evolved lateral line systems to enable them to find creatures in the mud.

These different morphological and behavioural adaptations are associated with changes in body shape and colour, jaw structure and orientation, and teeth size and form. As I float through this underwater realm I can see these novel adaptations in action. The evolutionary history of this lake, and the resulting diversity amaze me.
It is one of the many reasons that I chose to come to Malawi, and I am looking forward to my time here amongst these crazy fish!



Share/Bookmark

Friday, December 2, 2016

News from the Beach!

-So lets get the sad news out of the way quickly before we move on to the good stuff.  Unfortunately work on our poor research vessel has been put on hold due to its sinking.  A freak storm blew it off its mooring and it smashed against the rocks.  We are all in a bit of mourning here but don't worry our explorations of the lake will continue undetered!

- On the bright side we are looking forward to welcome our new Research Assistant Neha Acharya-Patel.  She will be arriving just after Christmas.  We will leave it to her to introduce herself when she arrives.  We've got big plans for next year so we are excited to welcome her aboard!

-Speaking of those plans next year the Maru is happy to announce that it will be working with Operation Wallacea from the United Kingdom to help educate students from all over the world about Lake Malawi.  Stay tuned for more info on this great new venture!

- We've also made one more step towards getting all of the data we collect at the Maru online in an informative, real-time, and interactive platform.  Getting the back end of this to work is still a challenge but to take a look at the pages we do have live go to www.themaru.org/research-conservation.html.  As always this is a work in progress but take a look around at the working links and let us know what you think!

-Finally summer is in full swing down here on the Lake and we are LOVING it. Hot sun, calm lake, and the water temperature just right.  The holidays are coming and there is no better place to spend them than a Kande Beach.  This year we are doing a whole pig on a spit for New's Years and you are all invited!
Share/Bookmark

Thursday, July 14, 2016

We're doing SASSE!




As part of our research at The Maru we monitor the water quality of three local rivers; the Kande River, the Masembe River and the Fua River. This month, alongside collecting data on water temperature, current, turbidity, pH and TDS (total dissolved solids), we have introduced a Stream Assessment Scoring System (miniSASS) to our water quality monitoring. This is a tool used to monitor the health of a river and measure the general quality of the water. MiniSASS scores the sensitivity to water quality of various macro-invertebrates living in rivers and classes the health of the river using five categories ranging from natural to very poor.


MiniSASS method:

At each site a small net is held in the current. Whilst ranging across the river to different habitats; stones, vegetation, sand etc. are disturbed using your feet or hands. After five minutes the content of the net is emptied into a white tray filled with some water. Using a magnifying glass, each insect is studied and identified using the dichotomous key (Figure 1). We are not concerned with the number of insects; we are simply interested in the presence or absence of a group. Each group found scores a certain number based on its sensitivity (Table 1). The sum of the sensitivity scores for each group found at the site is then divided by the number of groups to give an average. This average score is compared to the Ecological Category Table (Table 2) which tells us which health class the river is in.

Figure 1
The Dichotomous Key


Table 1
Sensitivity Score Table
Groups
Sensitivity Score
Flat worms
3
Worms
2
Leeches
2
Crabs or shrimps
6
Stoneflies
17
Minnow mayflies
5
Other mayflies
11
Damselflies
4
Dragonflies
6
Bugs or beetles
5
Caddishflies
9
True flies
2
Snails
4
Total Score
76
Number of groups
13
Average Score
5.8


Table 2
Ecological Category Table
Ecological category (condition)
River category
Sandy
Rocky
Unmodified (natural)
>6.9
>7.9
Largely natural/few modifications (good condition)
5.8-6.9
6.8-7.9
Moderately modified (fair condition)
4.9-5.8
6.1-6.8
Largely modified (poor condition)
4.3-4.9
5.1-6.1
Seriously/critically modified (very poor)
<4 .3="" o:p="">
<5 .1="" o:p="">


Whilst this water quality monitoring technique is still very new for The Maru, we have already found some interesting results. So far all of our sample sites fall in the ecological categories between unmodified (natural), and largely modified (poor condition). For examples as Figure 1 shows, the health class of each site along Kande River has varied from natural to poor within 4 weeks. More data is needed in order to see if this will stabilise and how conditions may vary seasonally. However, it is good to see that the majority of the samples (75%) are either ‘natural’ or ‘good’ and a smaller proportion of the data (25%) fall in the ‘fair’ and ‘poor’ categories.  





Figure 1. Graph showing the health class of 4 sites along Kande River over 4 weeks where an ecological score of 1 is ‘natural’, 2 is ‘good condition’, 3 is ‘fair condition’, 4 is ‘poor condition’ and 5 is ‘very poor’.




Our data will be uploaded onto the miniSASS website (www.minisass.org) in order to help map river health across Southern Africa. Once more research has been done using this method, communities can use the information and knowledge of the rivers to investigate why the river is in good condition and how to keep it that way or to identify pollution sources in areas of poor condition. Locals are already very interested and curious and enjoy learning about what we are doing and having a look at the insects we find. 

(This post was written by by Karin Johannson one of our current interns! Good job Karin!  To find out how you can intern or volunteer with us just CLICK HERE)
Share/Bookmark

Thursday, July 7, 2016

News from the Beach! Some analysis of our fisheries monitoring data

Well the windy season is in full swing down here at Kande Beach but we are keeping busy nonetheless.  Rob, our research assistant, has done a great job going through our fisheries monitoring program data.  See the results below!  And here is a nice photo of our current Maru team.  We have fun here too!





And now Rob's report -

Over the past four years, we here at the Maru have regularly undertaken fisheries surveys at the local fishing village of Masakuhunju.  This village is home to fishers who primarily target the “Utaka” fishery.  Utaka are cichlids in the genus Copadichromis. Our data provides us with three indicators of the pressure on these fisheries; fishing effort in terms of working canoes each day (both landed and boats still coming in when we arrive); total canoes at the village (both working and non-working – so as to provide an idea of the total number of fishermen operating out of the village at any given point; and finally total estimated landed catch. In order to calculate the total estimated landed catch we weigh 20% of the working canoes on the beach when we arrive. A mean figure is calculated for all the boats weighed, and this is extrapolated to 100% of the working boats.

Our findings thus far have enabled us to chart seasonal and annual patterns.

Figure 1 shows the total number of canoes in the village.

Figure 1.

We started recording this aspect of the dataset in late 2013, and for the most part we have counted somewhere in the region of 40-60 canoes each day. The only deviation from this is a clear peak occurring in the second half of 2014. The total number of canoes at Masakahunju almost doubles to around 80-100 canoes each day. This number did fall as the year closed out, and unfortunately apart from the end of 2013, data is insufficient for the third quarter of each other year we have been recording. This was due to having a lack of interns at the research centre during these months. One explanation for this pattern could be that because the windy season on the lake finishes around the end of July, a number of part-time fishermen use the seasonal opportunity to ply their trade at fishing, whilst holding a different occupation for the rougher months.

While total number of boats at the village is a relevant indicator of potential fishing pressure, it is a more telling statistic when compared to the total number of working canoes. Figure 2 shows how this number has varied over the past four years.

Figure 2.


The total number of working canoes shows very much a similar story to the total number of canoes at the village. For the most part, in the first half of the year the number varies between 10 and 20 boats going out each day; we see in the second half of 2014 that the numbers start to increase to almost double again (as with total canoes in the village), this time to around 20-30 boats each day. In general there are two more points of note in Figure 2 than in Figure 1. Firstly there seems to be very little working boats heading out for the entirety of 2015. Data was missing for August, September and December for that year, but the number barely exceeds a mean of 5 working canoes per day for any month that year. The second point of note is that in February 2016, the number of working canoes per day averaged just fewer than 30. This seems unseasonably high given all the data we have reviewed hitherto, as the figures for the month of February in 2013 and 2014 were half this and the figure for February in 2015 was as low as 3.8.

Perhaps our most direct indicator of fishing effort is the total estimated landed catch. Figure 3 shows the seasonal variation for the mean daily values in total estimated landed catch.


Figure 3.

Immediately one can some consistencies with the seasonal patterns of the other two indicators. For the first half of all four years the total estimated catch varies between 50 and 300lbs per day. Again, in 2014 this increases for the second half, and starts to fall in the final months of the year. Interestingly, in 2013 there is an increase in total estimated landed catch, though this appears to happen from October to December, slightly later than in 2014. The only other year in which there is data for any point in the fourth quarter is 2015 – and here for the months of October and November, the total estimated catch was between 350 and 400lbs on average each day. This is an impressive feat, as Figure 2 shows that very few boats were going out each day for any month that year.

We at the Maru are still in the process of going through the statistical analysis of this data, but these graphs allow us to make qualitative inferences on the amount of fishing pressure exerted by the fishermen at Masakahunju. In terms of working boats and total boats at the village, there seems to be a fair amount of sporadic variation between the daily, monthly and yearly scale. Crucially, 2015 showed fewer working canoes in general than the other years, yet their total estimated catches did not seem to be significantly lower than for 2013, 2014 or 2016. In the second half of 2014 there was evidently an increase in fishing pressure, as for all three indicators the figures effectively double, with the onset starting around the end of July. Whether this was just for 2014, or rather a typical seasonal pattern observed year in year out, is currently unclear due to the gaps in our dataset. Ultimately we can say that there has been no visible crash in the total estimated landed catch, and that has resulted in a seemingly similar stability in the total working boats, and total boats in the village; this would suggest that the fisheries in this part of the lake are currently being fished to a sustainable level.

The only way to know for sure, is of course to continue collecting this data, which is exactly what we intend to do.



Share/Bookmark

Saturday, June 4, 2016

It's coming! Our very own research vessel!


So we are really excited about this. To further our research capabilities at the Maru we have started constructing our own research vessel!  It will be fully equipped with a small laboratory, dive compressor and scuba gear, kitchen, lounge, solar electricity and beds for 8 researchers.  There are so many unexplored places in Lake Malawi, particularly in the north, and with this new boat we will be able to comfortably and afford-ably visit them like no one has!  As you can see from the picture it is still very much under construction but we hope to have our first researchers, interns, and volunteers move in in 2 months time.  Watch this space as we will be updating regularly with new pictures.

Share/Bookmark

Sunday, May 29, 2016

News from the Beach and Rob! Fisheries Monitoring at the Maru Edition

Every weekday morning, our research interns head down the lake shore to the local fishing village, leaving at 8.15 on the dot so as to coincide with the fishermen coming back from a long night’s fishing. Upon arrival in the village, locally referred to as Masakurunju, one can encounter as many as 60 wooden canoes scattered along the sandy shoreline, with the recently landed boats surrounded by groups of people, sorting through the fine gauge fishing nets that were cast across the deeper waters of the lake the night before. The catch invariably contains small open water fishes know as utaka in the local Chitonga. Most of these fish belong to the genus Copadichromis, a type of cichlid fish, and they make up a large proportion of the diet of the villagers in this immediate coastal region of Malawi, especially at this time of year.  Also potentially found in the catch are usipa – a sardine like fish, gongo – another cichlid and nkholokolo (synodontis njassae) - a small species of catfish with a mottled leopard style pattern.

At the Maru, we aim to collect baseline data, every week, over long periods of time. For the last four years we have strove to create a comprehensive data set for charts almost daily the fish caught at Masakahunju, the fishing conditions and the fishing effort (in terms of working boats). Data sets that track the same variables over such long time frames hopefully provide useful context and history about the exploitation of local fisheries in Lake Malawi that can be used by local people and government officials to make better environmental management decisions.

Incidentally, one of the real pleasures of walking to the fishing village everyday, is bumping into the beach venders; well spoken salesmen, of whom many have adopted bizarre names hailing from all sorts of random English words, phrases and celebrities. So far I have had the pleasure of meeting Sweet Bananas, Gift, Brown Bread, Michael Jackson, Sugar and Spice, Cheese on Toast, Spiderman, Donald Duck, Wiseman and my personal fave, Mel Gibson. These men earn a living by selling whatever bits and bobs they can to tourists, but it can also be helpful to have them around when the fish are being sorted from the nets, as their translation and enthusiasm make the whole process slightly less awkward.

For the fishermen themselves, it is a hard life. It is currently the windy season here at Kande, and conditions have oft been too choppy to go out in little one-man canoes. Sometimes the need for food and money is such that personal safety gets put aside and there is no other option but to brave the forces of the lake. But this is the harsh reality of living off the land in the manner that these people do. It is a difficult living, but for now it would seem there is ample food, enough to sustain the population in this part of the lake. Recalling that old adage of ‘give a man a fish and he can eat for a day, but teach a man to fish and he can eat for a lifetime’; well perhaps if we can learn to fish sustainably in other fisheries around the world, as it appears here, then people will be able to eat for more than just one lifetime but for the lifetimes of generations to come.

Share/Bookmark