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Thursday
Aug172017

Seagrass, Surveys And  Butterflies

Tropical sea grass beds are typically the highest in the world for seagrass species diversity and Mafia Island is no exception!

The team looked over the existing list of the eight most common seagrass species found on Mafia Island and headed out for an exploratory snorkel, in order to get a closer look in the water.

There is nothing better than getting into the water and seeing these species up close! At first you could dismiss seagrass for simply a layer of green on the floor, a plain background for the colourful array of tropical marine life, but the team were surprised to see that once you look the seagrass is indeed just as diverse and interesting!

We found many species including; Thalassodendrum ciliatum a meadow of extended waving hands; Enhalus acoroides one of the longest species of seagrass you will find; down to the smaller Halodule species you find at the edge of the seagrass beds.

The team were excited, because we found evidence of a new genus of seagrass present in the Utende meadows. So we took small specimens back to press for further species identification. In fact it appeared we found evidence of not only Halophila ovalis, but also Halophila stipulacea, meaning you can now find a total of nine species of tropical seagrass on Mafia Island!

On the hunt for anemone fish! We went out looking for anemone fish in order to observe their territorial behaviour and collate an ethogram of their ‘aggressive’ behaviours after inspiration from a paper by Camp et al., 2015. First by snorkelling we found a fantastic harlequin shrimp (Periclimenes brevicarpalis) and many juvenile three spot dascyllus (Dascyllus melanurus). Everything but anemone fish!

Take two was more successful spotting two different species of Amphiprion, firstly those that are more similar to the ‘Nemo’ style anemonefish that has become so recognisable. But we also spotted skunk anemonefish with their pale pink body and a dramatic white stripe down their back, that white stripe giving them the rather loveable name skunk anemonefish.

We observed their behaviour at a distance of least 2m looking for specific traits that had been discussed in the paper as displaying aggressive/territorial behaviour; rapid swimming towards other fish, head-dips, jaw clicking and excessive dorsal/ventral leaning. We found the most prominent territorial behaviour to be rapid swimming towards other fish. It was interesting to see just how they interacted with the other fish around them.

We dusted off the butterfly nets, jars and ID books and started compiling an ID list of butterfly species in Mafia! The butterfly database rapidly increased, showcasing just how diverse the butterflies of Mafia Island are.

We’ve taken the nets off to a few sites just to make sure we are sampling the greatest variety of butterflies. But also having lots of fun in the process trying to perfect our netting technique! But when we all finally get our own butterflies its super satisfying.

The plan is to start completing some 15 minute butterfly counts soon, as our database is beginning to reach saturation, so we have a good idea of the species present, which means it is time to see how prevalent each species is!

By Demi Mills - Tanzania Principle Investigator

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