Assignment (MPhil)--Stellenbosch University, 2003. / ENGLISH ABSTRACT: Many species of tilapia such as Oreochromis mossambicus are
euryhaline, able to adapt to different salinity waters. Their ability to
withstand high salinity levels has given rise to the possibility of using
tilapia as baitfish for tuna line fishery. The purpose of the study was to
determine the survival rate of tilapia O. mossambicus during direct
transfer from freshwater to the salinity levels of 0, 15, 20, 22.5, 25, 27.5,
30, 32.5, and 35 ppt. The data was analysed through means of
univariate ANOVAand regression analysis.
O. mossambicus showed no mortality to all salinity regimes up to
25 ppt. Mortality was observed at 27.5 ppt, with 100% mortality at 35
ppt. LC 50 and LC 90 were found to be 30.5 and 34.2 ppt, respectively.
The results indicate that tilapia (0. mossambicus) will survive a direct
transfer to salinities up to 25 ppt. acclimation will be required in the
event of transfer to salinity levels above 25 ppt, in order to prevent
significant levels of mortalities. / AFRIKAANSE OPSOMMING: Meeste van die tilapia spesies soos Oreochremis mossambicus het die
vermoë om by water van verskillende soutgehaltes aantepas. Dit is
hierdie vermoë om hoë sout vlakke te weerstaan wat die moontlikheid vir
gebruik as lewende aas in die tuna langlyn visvangbedryf moontlik maak.
Die doel van hierdie studie was om die oorlewingsvlak van tilapia, O.
mossambicus te bepaal by die oorplasing van varswater direk na
soutwater by vlakke van 0, 15, 20, 22.5, 25, 27.5, 30, 32.5, en 35 dele
per duisend. Die data is verwerk deur gebruik te maak van eenvariant
ANOVAen regressie analises.
O. mossambicus het geen mortaliteite tot gevolg gehad by al
die oorplasings van vlakke tot en met 25 dele per duisend sout nie.
Mortaliteite is wel gevind vanaf 27.5 dele per duisend, met 100 %
mortaliteite by 35 dele per duisend. LC 50 en LC90 was gewees 30.5 en
34.2 dele per duisend onderskeidelik. Die resultate toon aan dat tilapia
(0. mossambicus) sal oorleef by direkte oorplasing na soutwater by
vlakke van tot en met 25 dele per duisend. Tilapia wat na hoër vlakke as
25 dele per duisend oorgeplaas wil word, sal eers geleidelik moet
akklimatiseer om mortaliteite te beperk.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/53355 |
| Date | 12 1900 |
| Creators | Fitwi, Biniam Samuel |
| Contributors | Brink, D., Stellenbosch University. Faculty of AgriSciences. Dept. of Animal Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | viii, 38 p. : ill. |
| Rights | Stellenbosch University |
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