Searching for freshwater fish in Mada - what it can say about forest conservation

In a new blog post from the field for The New York Times, John Sparks describes his search for an incredibly rare and recently discovered species (1990s) of Damba, a genus of fish endemic to Madagascar.

He highlights the plight of freshwater fish on the red island: 

“It should be painfully obvious to the reader from my earlier posts that Madagascar’s native freshwater fishes are in very serious trouble — narrow endemism and widespread habitat degradation are a dangerous combination. Throw in competition with an array of exotic species, and you have the ingredients for a full-blown disaster. Essentially, freshwater fishes are afforded little protection within the isolated patches of protected forest that remain throughout the country, and within which one can still find relatively healthy populations of lemurs, chameleons and other native vertebrates. Most of these forest reserves are at higher elevation, where there is little suitable habitat for fishes other than rheophilic gobioids (gobies and eleotrids). In addition, it is difficult, if not impossible, to find a watershed that has not been affected to some degree by deforestation throughout its course — and obviously, the negative effects of siltation persist downstream to the sea.”

But its not just fish that are threatened in freshwater systems: The lac alaotran lemur is critically endangered and the Alaotra grebe has recently been declared extinct.

One thing in his post that intrigued me is his emphasis on tilapia and their importance to local livelihoods:

"It has been extremely difficult and frustrating work — introduced tilapia provide much-needed protein and can thrive in even the most environmentally trashed habitats, so there is little incentive for change.”

My current NGO partners are funding tilapia projects all around the CAZ forest where I work. The NGO provides training and when the local forest management group digs a pond for the fish, then the NGOs provide the fish. I dont know isolated from existing bodies of water these ponds are but Sparks article certainly gives one pause.

When thinking about forest conservation here, habitat destruction and hunting are two big pressures that are consistently referred to. But invasives less so. Are invasives purely an aquatic issue here? I doubt it.

Prolemur simus, the greater bamboo lemur, is a current research interest of mine (more on that in the future). On my side of the forest it feeds primarily on one species of bamboo, Cathariostachys madagascariensis.

Cathariostachys madagascariensis, or volobe, great bamboo, exposed in a forest clearing. Photo credit: Sara Tolliver

In general, bamboos are not well known here. Two of the other species that this lemur has been seen eating aren’t yet described. But in conversation with a local conservation actor, I was told that there are lots of non-native bamboos on the island, starting to out-compete the native bamboos. Bamboo is cutivated, much like tilapia is, because they its incredibly useful for everyday life, as well as for building furniture and other items for sale. Yet, clearing forest opens up habitat for these non-native bamboos to compete with the local species, thereby potentially threatening the species that depend on the local species. This is all speculation, as so little is known, but it is an interesting question.

Hopefully our work this summer will help shed some light on it.

When livelihoods abut conservation concerns there are no easy answers. The bigger questions concern how we can keep exotic tilapia and bamboo out of largely native ecosystems, and still recognize the rights of locals and support them to make a living? And how much influence conservationists should have in deciding the answer...