size: 5036KB - Crocodile Specialist Group

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Lake Cahora Bassa has a shoreline ofapproximately 1200 km'zand a surface area of 2665 km'?
when at the planned operating level of 326 m a.s.l. @ernacsek and topes, 1984). Since 1981
the mean operating level has dropped to 315 m a.s.l. and this has led to an unstable situation
at the head of the lake close the Zimbabwean border (the Zumbo basin) with a fluctuating
lakehiver interface. Most samDles were collected in this basin.
trlgure 1: The Zambezi River rhowing Lsk€s Kaiiba and Cahora Bassa
NIMBERS AND POPI]LATION STRUCTURE
The age structure and size of two populations was estimated for $e Zambezi river, the second
study site being located 300 km downstream fi:om Lake Kariba in Mozambique using methods
summarised in Bayliss (1988) and Graham (1988). The investigation
the Mozambican study
site was an opportunistic one with its principal aim to obtain a sample of larger orocodiles as
these were proving difficult to catch in Lake Kariba. Extensive work went into estimating the
size of the Mozambican population using several methods (aerial survey, spotlight munts,
cropping and nest counts) were available and was possible to ascertain if they gave similar
results. Population estimates from nesting data did agree with other methods and consequently
this puts confidence in the population estimates flom nest counts fo. Lake Kariba. The mean
populatio[ estimate for the Zimbabwean side of Lake Kariba was 6 500 crocodiles of all sizes
with approximately 3 500 of these being larger than 1.2 m total lengtl (i.e. sub-adults and
adults). This gives an estimate density of 3.51 animals per kilometre of shoreline. The
maximum estimate using correction factom from Hutton and Woolholse (1990) was
approximately l1 500 animals with nearly 6 000 ofthese being sub-adults and adults. However,
it should be remembered that in recent years aftempts are being made to collert all eggs fiom