Thursday, January 16, 2014

Colonization and succession of fishes in Lake Liambezi, an ephemeral floodplain lake in northeastern Namibia




Lake Liambezi
Research Update 

Richard Peel (PhD Student)


Supervisors: Dr OLF Weyl; Dr S Kaehler; Dr CJ Hay

In conjunction with the Ministry of Fisheries and Marine Resources, Directorate Aquaculture and Inland Fisheries, Namibia.


Funders: Southern African Science Service Centre for Climate Change and Adaptive Land Management; Nedbank Namibia Go Green; South African Institute for Aquatic Biodiversity/National Research Foundation





The lake dried up in 1985 and remained so until the early 2000s. It eventually filled in 2009 after exceptionally high floods in the Zambezi and Kwando rivers, and filled again in 2010 and 2011. The floodwaters brought with them a diverse fish fauna that quickly colonized the newly flooded environment, and has undergone significant changes as the lake has matured. The aim of this research is to describe and understand the colonization process and species successions by assessing the recruiting fish fauna from the Zambezi and Kwando, describing trends in species composition since inundation in 2007, assessing the life-histories of species representative of different life-history strategies, and analysing the food web using stable carbon and nitrogen isotopes.


The colonising fish assemblage was dominated by Barbus paludinosus, Barbus poechii, and the catfishes Clarias gariepinus and Schilbe intermedius. After filling completely in 2009, the abundance of C. gariepinus declined markedly, and the barbs were rapidly replaced by two small characins Brycinus lateralis and Rhabdalestes maunensis. The tilapiine cichlids on which the fishery is based, and several other larger, slower growing species including Serranochromis macrocephalus and Hepsetus cuvieri have increased more gradually in abundance since inundation. Preliminary food web analysis showed that the food chain is short and influenced primarily by bottom-up (productivity related) factors. Consumer δ13C values indicate that algal primary production (associated with particulate organic matter) contributes most to consumer biomass, while C3 macrophytes and detritus contribute relatively little. Further analysis will investigate the potential role of competition and predation on species successions.


The composition and abundance of recruiting fish fauna will be assessed during the 2014 and 2015 floods. Recruitment will be quantified by up-calculating relative abundance estimates over the brief flooding period to give species specific abundance and biomass estimates. The life-history traits, including age, growth, maturity, fecundity, spawning season and mortality, of twelve species representative of opportunistic, periodic and equilibrium life history strategies, will be assessed in relation to colonisation and establishment rates.

For more info contact Richard Peel at: richpeel1@gmail.com


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