Comparative Evaluation of Growth, Survival and Disease Resistance of Nile and Red Tilapia Strains | |
| Author | Ataguba, Gabriel Arome |
| Call Number | AIT Diss. no.AQ-17-01 |
| Subject(s) | Nile tilapia Red tilapia Fishes--Diseases |
| Note | A dissertation submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Aquaculture and Aquatic Resources Management |
| Publisher | Asian Institute of Technology |
| Abstract | Nile tilapia (Oreochromis niloticus) and the red hybrid tilapia culture is a major economic activity in Thailand. The latter strain can grow under saline conditions and customers prefer its red colour. Production of both strains is fluctuating due to bacterial infections and erosion of genetic quality. A survey was conducted to evaluate if there is a difference in survival between the red and the Nile tilapia strains among farms in Thailand. Results showed that majority of cage farmers (85%) perceive the red strain is more susceptible to mortality. Survival rates reported by farmers is dependent on the strain and training received by the farmers. Majority of trained red tilapia (63%) reported survival rates between 70 to 89% survival rates as against 37% in the untrained category. Three experiments were conducted after the survey. The first experiment was conducted to evaluate the genetic diversity of four strains farmed in Thailand. Genetic diversity within the strains was variable. Average Kimura-2-parameter (K2P) distance for nucleotide diversity within GIFT was 0.032, the highest among the strains, followed by Taiwanese red (0.024). Ecuador red and Thai red strains have low distances within them (0.001 and 0.003 respectively). Inter-strain genetic divergence shows a clear distinction between GIFT and the other strains. Taiwanese red has the least distance from GIFT (~0.044) and the distance between GIFT and Thai red was the highest (0.053). Sampling site map of BOLD systems software showed that GIFT and Taiwanese red have good global spread. The second experiment was conducted to investigate growth, survival and CIELAB colour space of F1offspring from a half diallel cross of: GIFT (G), Ecuador red (E), Taiwan red (T) and Thai red (D). Two hundred offspring each from 57 families were reared under two spatial conditions (3m2 and 0.81m2: 67 and 247 fish/ m2, respectively) in hapas. Stocking density significantly (p <0.05) affected mean final weight (MFW), mean final length (MFL), specific growth rate (SGR) and survival. At 67 fish.m-2E×G, E×T, D×T, D×G and D×E had significantly high MFW. Top performers at 247 fish.m-2 were E×E, D×G and D×T. The odds of mortality against G×G was high for all other crosses but T×T had the lowest odd ratio at 67 fish.m-2. The cross E×G had positive heterosis for survival (10.25% and 25.26%) in both densities respectively. While E×G had the highest heterosis (46.41%) for growth at 67 fish m-2, D×G had the highest heterosis for growth (49.6%) at 247 fish m-2. Skin colour ratio of intercolour crosses (E×G and D×G) was mixed red and black. Colour cluster discrimination produced four clusters; cluster 4 had the highest red colour intensity value (22.84). Cross E×G had relatively higher colour variability. The third experiment investigated the potential for garlic(Alliumsativum) and betel (Piper betle) leaf extracts to enhance immune response of Nile tilapia against Streptococcusagalactiae. Ethanol extract of betel leaf had a minimum inhibitory concentration (MIC) of 0.42mg.L-1 against S. agalactiae. Addition of 10-times of MIC dosage (PH) to tilapia feed and feeding for 7-days prior to challenge test effectively controlled S. agalactiae infection in Chitralada strain with 100% survival. Relative risk of mortality is at least 99.9% if fish do not receive PH treatment.PH treatment increased white blood cell count (WBC) and mean corpuscular haemoglobin concentration (MCHC). In conclusion, farmer’ training is crucial in ensuring survival of strains. There is a less genetic diversity within the Ecuador red and the Thai red population. Crossing GIFT with red tilapia strains led to heterosis for survival and growth from the ♀E × ♂G cross. Digital image analysis can be applied to fish skin to detect better red colour for further selection. Ethanol extract from Piper betle leaf is effective in controlling S. agalactiae infection in tilapia. |
| Year | 2017 |
| Type | Dissertation |
| School | School of Environment, Resources, and Development (SERD) |
| Department | Department of Food, Agriculture and Natural Resources (Former title: Department of Food Agriculture, and BioResources (DFAB)) |
| Academic Program/FoS | Aquaculture and Aquatic Resources Management (AQ) |
| Chairperson(s) | Salin, Krishna R. |
| Examination Committee(s) | Yakupitiyage, Amararatne ;Anal, Anil Kumar |
| Scholarship Donor(s) | Tertiary Education Trust Fund ;University of Agriculture, Makurdi, Nigeria |
| Degree | Thesis (Ph. D.) - Asian Institute of Technology, 2017 |