Madagascar RAP: Where are all the fish?

As part of a CI-organized Rapid Assessment Program (RAP) off the northeastern coast of Madagascar, an international team of marine scientists is spending three weeks exploring ecosystems, documenting species – and reporting back to us about what they’ve found. Read all of the team’s posts from the field here.

To be among the first to survey the coral reef fishes of Madagascar’s northeastern coast, and to do so together with my colleague Bemahafaly Randriamanantsoa, who has surveyed most other reefs in Madagascar, is a fantastic opportunity for me, and an honor.

This expedition has brought me to the southernmost reefs I have ever visited in the Indian Ocean. I came armed with my identification books, monographs and lists of species drawn up on underwater paper, hoping I was adequately prepared for the myriad species I’m likely to encounter in any one dive.

On this trip, I am comparing data from northeastern Madagascar with locations in Tanzania, Comoros and Mozambique that I am surveying as part of a regional study in the Western Indian Ocean. We are trying to determine what drives high diversity on coral reefs, with the hypothesis that northern Madagascar might be a significant area of high biodiversity.

So far, the expedition has certainly brought surprises, but they haven’t all been positive. I was expecting this part of Madagascar to still be relatively remote, with small coastal populations, limited fishing technology and therefore low fishing pressure. I expected a variety and abundance of reef fish like snappers, emperors and groupers. This is not the case so far; the numbers of groupers have been some of the lowest I have come across in the Western Indian Ocean (except on reefs severely damaged by dynamite fishing) which has surprised and disappointed me, since I love groupers! So is this coastline heavily fished after all, or are we seeing something different?

Perhaps these reefs are just not as productive as we expected. They face large oceanic swells which bear the brunt of the strong southeast monsoon, and cyclones are frequent. The “food fish” aren’t the only ones that are in low numbers; I’m also not seeing the variety of damselfishes I expected – those species are a key indicator group of reef fish diversity.

Still, we are only halfway through the expedition, so I’m hoping these numbers might change.

In any case, the surprise and excitement of seeing species I have never seen before has been wonderful. I’m also finding occasional species that defy my ID sources! I’ve found some that occur across the entire Indo-Pacific , all the way to the Solomon Islands; others that are found only in Madagascar and nearby islands; and others also found in the Red Sea but not on mainland Africa.

All of this makes me wonder more about ocean currents, the evolutionary origins of these species, what processes drive these populations today and what their future holds. Research always generates even more questions, but on this expedition I will at least quantify the number of species (from 19 families) that comprise the bulk of coral reef fishes residing in this part of Madagascar. This research, I hope, will lay a foundation for future conservation planning for Madagascar’s coral reefs.

Melita Samoilys is the coral reef specialist of the RAP team. She is co-director of CORDIO, based in Nairobi, Kenya.

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