Jeremy M. Shelton
I completed undergraduate and honours degrees in zoology and ecology, and an MSc in conservation biology at the University of Cape Town. During this time I became interested in freshwater ecology. Alien invasive predatory fish are one of the greatest threats to freshwater biodiversity in South Africa, and much of my research has focussed on the ecological effects of these fish. As an honours project I investigated the effect of alien smallmouth bass on the native fish community in the Witte River in the Western Cape. The results of that study were shocking, showing that the alien bass almost completely eliminated once-abundant native fishes from a stretch of stream. Additional work by Dr Steve Lowe (post-doctoral associate at the C·I·B) has shown that not only did the bass decimate native fish populations, but they also had strong affects at the ecosystem scale, altering aquatic invertebrate and algal communities severely. My MSc research examined whether alien largemouth bass alter abundance, population structure and behaviour of a unique and ancient freshwater fish – the Cape galaxias. The bass appeared to be having an impact, but this was subtle, possibly because bass numbers were low due to lack of suitable habitat.
Due to factors such as habitat destruction and alien predatory fish like bass, catfish and carp, stream communities in the lower parts of South African rivers are generally in a degraded state. At present, intact natural stream communities are largely restricted to mountain streams where terrain is unsuitable for agriculture and waters are too cold for most of the introduced, invasive fish species to inhabit. Trout, however, is a coldwater fish, adapted to the low temperatures and swift currents associated with mountain streams. Since their introduction to South Africa about 100 years ago, they have invaded several mountain streams and potentially pose a severe threat to remaining pristine mountain stream communities.
Although the harmful ecological effects of trout have been documented elsewhere, there is practically no information on their impact in South Africa. Information on their ecological impact is needed to inform management decisions and to conserve South Africa’s unique and threatened stream biodiversity. My PhD research will address this knowledge gap by investigating the ecological effects of rainbow trout in the Cape Floristic Region of South Africa – a global biodiversity hotspot.