| dc.contributor.author | Shackell, Nancy Louise. | en_US |
| dc.date.accessioned | 2014-10-21T12:34:51Z | |
| dc.date.available | 1991 | |
| dc.date.issued | 1991 | en_US |
| dc.identifier.other | AAINN64489 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/55196 | |
| dc.description | Aquaculture genetic improvement programs may be ineffective if the sole objective is to increase growth rate. Stress resistance is equally important but is difficult to measure. In this study, developmental stability was used to characterize dietary stress resistance of 2 strains of tilapia (Oreochromis niloticus). Developmental stability was measured as the inverse of (1) asymmetry of bilateral traits, e.g. paired fins (Asymmetry index) and (2) the amount of scale circulus deformation (Circulus Deformation index). Growth and developmental stability of inbred, outbred and inter-strain hybrid lines of tilapia were studied in 2 dietary regimes. Growth rate was significantly faster in the constant high protein regime (CE) than in the fluctuating low-high-low protein regime (FE). Hybrid progeny of the "Nifi" and "Israel" strains grew the fastest, followed by the Israel strain and lastly the Nifi strain. | en_US |
| dc.description | As measured by the Asymmetry index, developmental stability was unexpectedly higher in regime FE than in regime CE; partially because the data was dependent on size. In contrast, developmental stability was higher in regime CE using the Circulus Deformation index. The Asymmetry index showed that (1) the inbred Nifi line had the lowest developmental stability and that (2) the Nifi strain had lower developmental stability than the Israel and hybrid strains. The Circulus Deformation index showed that (1) inbred lines had lower developmental stability than outbred lines, (2) the Nifi strain had lower developmental stability than the Israel strain and that (3) the hybrid progeny had higher developmental stability than their mid-parent value. The Asymmetry index is difficult to measure and was found to distinguish poorly between diets and among lines. Its use is therefore better suited to the controlled environments of laboratories than to the variable environments on farms. The Circulus Deformation index is more practical, and was found to be a more discriminative index of developmental stability. It has potential application as (1) an indicator of environmental and/or genetic stress and as (2) a selection criterion, in conjunction with growth, in genetic improvement programs. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 1991. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Genetics. | en_US |
| dc.subject | Agriculture, Fisheries and Aquaculture. | en_US |
| dc.title | Growth and developmental stability of inbred, outbred and inter-strain hybrid tilapia (Oreochromis niloticus) in two diet regimes. | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
