A growth comparison among three commercial Tilapia species in a biofloc technology system in South Africa

Day, Scott Bowerbank (2015-12)

Thesis (MSc)--Stellenbosch University, 2015.

Thesis

ENGLISH ABSTRACT: With environmental conservation playing a growing role in decision making today, the aquaculture industry has sought new innovative ways to reduce the impact on the environment, and maximize efficiency. Much of the focus of such developments has included lower water usage and better feed utilization, with the emergence of biofloc technology systems addressing such needs. Tilapia has been identified as a fish for the future, with its production having already risen to make it an important food fish globally, and an increase in its market share is predicted going forward. Although it is common around the world, the production of tilapia has failed to take off in South Africa, with the reasoning being put forward including; legislative restrictions, unfavourable climate, incorrect species choice and shortage of expertise and supporting industry. The major aims of this study were to address the main constraints and uncertainties facing the local tilapia industry in terms of species choice, and to investigate the biofloc technology concept under local conditions. Being restricted to the use of the Mozambique tilapia (Oreochromis mossambicus), and with the recent changes allowing the use of the Nile tilapia (Oreochromis niloticus), the question whether O. niloticus will in fact outperform O. mossambicus under South African conditions, was raised. With the production of the Three Spot tilapia (Oreochromis andersonii) also prevalent in southern Africa, this species was also included in the study. The secondary aim of the study was to create a profile of key water quality parameters during the start-up period of the biofloc technology system prior to fish being introduced, and throughout the course of the trial. With the biofloc technology concept being expected to play a role in the development of the South African tilapia industry, the study was conducted in a biofloc technology system. Twelve tanks, connected through airlift pumps to homogenize the water quality, were stocked with fish. Each of the three species were stocked randomly into four tanks with each tank being considered an independent replicate. The growth trial was conducted within a greenhouse, and commenced at the start of the summer grow out period for tilapia in South Africa, in October 2014, running for 10 weeks. Fish were sampled fortnightly from the system, with the mass data being used to fit a linear regression. Water quality measurements were taken from the start-up period in mid-September, for 12 weeks. Profiles for temperature, dissolved oxygen, pH, salinity, electro-conductivity, total dissolved solids, floc volume, total ammonia nitrogen, nitrite, nitrate, orthophosphate, total suspended solids and turbidity were successfully documented over the trial period. Two spikes in total ammonia nitrogen and nitrite were recorded, one during start-up, and one following a water loss event during the trial. A regression fitted to the mass data showed O. niloticus to have the highest growth rate with an average daily gain of 0.693±0.018 g/day, followed by O. mossambicus of 0.405±0.025 g/day, and then O. andersonii of 0.185±0.025 g/day, with significant difference between all three species. The lowest feed conversion ratio was also recorded for O. niloticus being 1.00±0.05, followed by O. mossambicus of 2.24±0.16, and O. andersonii with 2.53±0.28. These results suggest that of the three species investigated, O. niloticus performs best in a biofloc technology system in South African conditions. It is recommended that this species should therefore be used in biofloc technology systems as they develop in South Africa.

AFRIKAANSE OPSOMMING: Omgewingsbewaring speel vandag ‘n toenemend groter rol in besluitnemingsprosesse. In hierdie lig is die akwakultuurbedryf op soek na nuwe, innoverende maniere om impak op die omgewing te verminder en doeltreffendheid te maksimeer. Heelwat van die fokus in sulke ontwikkelinge is op laer waterverbruik en meer effektiewe voerbenutting gebaseer. Met die ontwikkeling van biofloc tegnologie sisteme, kan sulke behoeftes aangespreek word. Tilapia is geidentifiseer as 'n vis vir die toekoms. Die produksie van tilapia is toenemend besig om te styg en is reeds 'n belangrike voedselbron wêreldwyd terwyl 'n verdere verhoging in markaandele voorspel word. Alhoewel die produksie van tilapia regoor die wêreld algemeen voorkom, het produksie nog nie werklik in Suid-Afrika posgevat nie. Die redes hiervoor is onder andere: wetlike beperkings, ongunstige klimaat, verkeerde spesie-keuses, 'n tekort aan kundigheid en gebrekkige ondersteuning van die bedryf. Die hoofdoelwitte van die studie was om die belangrikste beperkinge en onsekerhede wat die plaaslike tilapia-bedryf in terme van spesie-keuse ervaar te identifiseer en om die biofloc tegnologie-konsep onder plaaslike omstandighede, te ondersoek. Beperk tot die gebruik van die Blou Kurper (Oreochromis mossambicus) en met die veranderinge wat die gebruik van die Nyl Kurper (Oreochromis niloticus) wettig gemaak het, was die vraag: Watter van of O. niloticus of O. mossambicus beter onder Suid-Afrikaanse toestande sal presteer. Die Driekol Kurper (Oreochromis andersonii), algemeen geboer in suidelike Afrika, was ook vir die studiedoeleindes ingesluit. Die sekondêre doel van die studie was om 'n profiel op te bou van die belangrikste waterkwaliteit-parameters vanaf die begin van die aanvangstydperk van die biofloc tegnologie systeem, voor vis ingesit was, en deurlopend tot aan die einde van die hele studie. Met die konsep, wat verwag was om 'n belangrike rol te speel in die ontwikkeling van die Suid-Afrikaanse tilapia-bedryf, het die studie in 'n biofloc tegnologie sisteem plaasgevind. Vier herhalingtenks vir elk van die drie spesies (behandelings) was opgestel. Die aanwasproef het binne 'n kweekhuis plaasgevind. Dit het met die aanvang van die somer-uitgroei-tydperk in Oktober 2014 begin, en vir 10 weke geduur. Vismonsters was twee-weekliks geneem en die massadata was gebruik om 'n lineêre regressiekurwe op te stel. Waterkwaliteitmetings was vanaf die aanvangstydperk in middel-September 2014, vir 12 weke geneem. Profiele vir temperatuur, suurstof, pH, soutgehalte, elektro-konduktiwiteit, opgeloste vastestowwe, floc volume, totale ammoniakstikstof, nitriet, nitraat, ortofosfate, totale gesuspendeerde vastestowwe en troebelrigheid was suksesvol gedokumenteer oor die proeftydperk. Twee uiterstes in totale ammoniakstikstof en nitriet is aangeteken: een aan die begin, tydens die aanvangstydperk, en ‘n ander na 'n waterverlies-geval tydens die proef. Oreochromis niloticus het die hoogste groeitempo van 0.693±0.018 g/dag gehad, gevolg deur O. mossambicus van 0.405±0.025 g/dag en dan O. andersonii van 0.185±0.025 g/dag, met 'n beduidende verskil tussen al drie spesies. Die laagste voeromsettingsverhouding van 1.00±0.05 was aangeteken vir O. niloticus, gevolg deur 2.24±0.16 vir O. mossambicus en dan 2.53±0.28 vir O. andersonii. Die uitslae dui daarop dat O. niloticus die beste presteer in 'n biofloc tegnologie sisteem onder Suid-Afrikaanse toestande. Dit word dus aanbeveel dat O. niloticus gebruik moet word in biofloc tegnologie sisteme soos dit verder in Suid-Afrika ontwikkel.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/98040
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