Influence of the annual flood-pulse on catch per unit effort, condition and reproduction of Clarias gariepinus from the upper Okavango Delta, Botswana

Journal article

Authors/Editors

Bokhutlo, Thethela

Research Areas

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Publication Details

Author list: Bokhutlo T, Weyl OLF, Mosepele K, Wilson GG

Publisher: National Inquiry Services Centre (NISC) / Taylor & Francis: STM, Behavioural Science and Public Health Titles

Place: GRAHAMSTOWN

Publication year: 2016

Journal: African Journal of Aquatic Science (1608-5914)

Journal acronym: AFR J AQUAT SCI

Volume number: 41

Issue number: 2

Start page: 235

End page: 239

Number of pages: 5

ISSN: 1608-5914

eISSN: 1727-9364

Languages: English-Great Britain (EN-GB)

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Abstract

Catch per unit effort (CPUE), length, weight and maturity data for Clarias gariepinus were collected during monthly gillnet surveys in the upper Okavango Delta between 2001 and 2009 to investigate their relationship with the annual flood-pulse. CPUE, condition factor (K) and the proportion of ripe-running fish (P-RR) in the population followed a unimodal annual cycle that could be modelled using water temperature and flood-pulse hydrology. Increased CPUE during declining water levels was most likely a result of feeding migrations and aggregation behaviour. The observed increase in K during low floods in October and November preceded the increase in P-RR, which increased mainly with increasing temperature but appeared less dependent on flow. This study provided quantitative evidence that the biology of fish in the Okavango Delta is mainly dependent on the annual flood regime and, therefore, that conservation efforts should be focused on maintaining natural flow patterns in the face of climate change and potential water extraction schemes upstream.

Keywords

catfish run, Flow, spawning, temperature

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