FISH INTRODUCTIONS WITHIN LAKE MALAWI

The introduction of exotic fish species to areas where they do not naturally belong is a global problem. Apart from cases of exotic species, there are also many more cases of species transplant within the same watershed, this is the issue which mainly affects most of African and indeed Malawian water ecosystems.

What is of great concern to ecologists, enviromentalists, biologists and genetists alike is what happens next after an introduction has occurred. Mainly a concern is whether a fish species which has been introduced to a new ecosystem is going to establish itself in that new environment.

The law of nature dictates "survival of the fittest", this is equally true with the new introduced fish species to any ecosystem, whether it is a lake, river, reservoir or pond. The new species needs to have an added advantage over the native species in order to do well in the new habitant. If the ecosystem is already diverse enough and strong the new species has problems to deal with its survival. In most areas in the wolrd, aquatic ecosystems have been tampered enough so that their structures are no longer strong to resist the establishment of new species in their territories. This has been due to high human population in most shorelines, which have impacted these ecosystems to the extent of affecting their assemblages.

Lake Malawi is one of those ecosystems which has suffered human impacts due to increasing settlements and farming activities near or in the shore line. This has affected the breeding grounds of many fish species including, the most totted Lake Malawi Tilapia commonly known as 'Chambo". As if this is not enough, the Lake Malawi ecosystem is also at the moment suffering from fish transfers or what ecologists call it fish translocations. This is happening mostly with the most colourful species which are commonly known as "Mbuna". The high demand of the Malawian Mbuna to European and Asian markets has led fishermen to capture these tiny spcies as far as the northern waters and send them to the southern waters where they are freighted to outside markets. It is during these processes that some of the Mbuna species are dropped on the way and hence found to be where they do not belong.

At the moment it is not yet known whether these small species will be able to establish themselves in the new ecosystems. But the questions which we should aks ourselves as Malawians are: why do we have so many fish species coexisting in lake malawi? what mechanisms are these species using to coexists? why different fish colours in different geographic areas within the lake? what will be the response of the native species?

As one way of trying to answer these questions, I have put forward a proposal which is being funded by British Council. Anyone willing to help or collaborate in this venture just contact me using my email.