Age validation, growth and mortality of introduced Tilapia zillii in Crater Lake Nkuruba, Uganda
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Date
2016
Journal Title
Journal ISSN
Volume Title
Publisher
Fisheries Management and Ecology
Abstract
Periodicity and timing of opaque zone formation in otoliths of introduced redbelly tilapia, Tilapia zillii
(Gervais), in Crater Lake Nkuruba, Uganda, were validated using marginal increment. Age and growth were assessed
through readings of biannuli in thin-sectioned sagittal otoliths. Deposition of opaque zone formation in T. zillii otoliths
was bimodal (March–May and September–November), corresponding to two seasonal peaks of precipitation
characteristic of this equatorial region. Ages of T. zillii ranged from 2 to 8 years, with fish gillnetted offshore having
a faster growth and attaining larger size-at-age than fish captured inshore in minnow traps, suggesting that use of
multiple gears is needed when estimating the growth of T. zillii. Total instantaneous mortality (Z), estimated using
catch curve analysis, was 0.74 for gillnetted fish and 0.71 for trapped fish. These estimates were at the low end of the
total mortality reported for other tilapia species. Natural mortality (M) was estimated as 0.52–0.54 by applying Rikhter
and Efanov’s maximum age at maturity and Hoenig’s maximum age methods, respectively. Fishing mortality (F) in
Lake Nkuruba was 0.17–0.22, indicating a low exploitation level in the lake.
Description
Keywords
Ageing, Cichlid fishes, Growth, Life history, Tropical lakesgrowth
Citation
Efitre, J., Murie, D. J., & Chapman, L. J. (2016). Age validation, growth and mortality of introduced Tilapia zillii in Crater Lake Nkuruba, Uganda. Fisheries Management and Ecology, 23(1), 66-75. doi: 10.1111/fme.12163