Salinity tolerance of Oreochromis niloticus and O. mossambicus F1 hybrids their successive backcross /
Mateo, Dennis Almazan
Salinity tolerance of Oreochromis niloticus and O. mossambicus F1 hybrids their successive backcross / by Dennis Almazan Mateo. - Miag-ao, Iloilo : University of the Philippines in the Visayas, 2002. - xv, 97 pages : illustrations ; 28 cm.
Thesis (MS Fisheries -- Aquaculture) University of the Philippines in the Visayas
Includes bibliographical references.
The effect of backcrossing on the salinity tolerance of the offspring of the hybrid O. mossambicus (Mo) x O. niloticus (Ni) was determined using median lethal salinity (MLS) and optimum salinity tolerance (OST) as indices of tolerance. The reciprocal Hybrids 1 (H1)(Mo x Ni and Ni x Mo), the first hybridization, were backcrossed with parental O. mossambicus in reciprocal crosses (i.e. with O. mossambicus as mother or father) to produce the reciprocal Hybrids 2 (H2) (HI x Mo and Mo x H1), the backcross 1 and reciprocal Hybrids 3 (H3) (H2 x Mo and Mo x H2) and the backcross 2. These reciprocal hybrids and pure parental species were exposed to progressive changes in salinity at 6 ppt intervals until total mortality. Standard length (SL) was measured to correlate the size to salinity tolerance. Clinical signs and social behavior were observed during the test.
Parental O. mossambicus showed the highest salinity tolerance, followed by reciprocal H3, H2 and HI, while parental O. niloticus had the lowest. There was an increase of salinity tolerance in the offspring as they were backcrossed to the saline-tolerant parent O. mossambicus.
Both parents (O. mossambicus) contributed to the salinity tolerance of the offspring. Maternal inheritance was observed in reciprocal H1 and reciprocal H2, while paternal inheritance was observed in reciprocal H3. HI had the highest heterosis. Both H2 and H3 stocks had negative and slight positive heterosis, indicating that they are good candidates as base population for selection.
Size and salinity tolerance were significantly related in H'2 and H'3 compared to the other group of fishes. Bigger fish survives longer in elevated salinities compared to smaller one. In the selection phase for growth, salinity tolerance might be indirectly selected, because larger fish survives longer regardless of age.
Social behavior during acclimation to salinity was observed. Generally, there was a decrease in the dominance of dominant individuals with the increase in salinity. O. niloticus and HI stocks were increasingly aggressive at 30-36 ppt. H1 still had a residual dominant individuals until 96 ppt. Dominance disappeared in the other groups (H2 and H3 and pure O. mossambicus) at 48 ppt.
Loss of dominance among dominant individuals, cessation of feeding/minimal food intake, sunken eyes and abdomen, color changes and sluggish movement were observed before fish mortality.
Aquaculture
Nile tilapia
Mozambique tilapia
Fish culture
639 / M41 2002
Salinity tolerance of Oreochromis niloticus and O. mossambicus F1 hybrids their successive backcross / by Dennis Almazan Mateo. - Miag-ao, Iloilo : University of the Philippines in the Visayas, 2002. - xv, 97 pages : illustrations ; 28 cm.
Thesis (MS Fisheries -- Aquaculture) University of the Philippines in the Visayas
Includes bibliographical references.
The effect of backcrossing on the salinity tolerance of the offspring of the hybrid O. mossambicus (Mo) x O. niloticus (Ni) was determined using median lethal salinity (MLS) and optimum salinity tolerance (OST) as indices of tolerance. The reciprocal Hybrids 1 (H1)(Mo x Ni and Ni x Mo), the first hybridization, were backcrossed with parental O. mossambicus in reciprocal crosses (i.e. with O. mossambicus as mother or father) to produce the reciprocal Hybrids 2 (H2) (HI x Mo and Mo x H1), the backcross 1 and reciprocal Hybrids 3 (H3) (H2 x Mo and Mo x H2) and the backcross 2. These reciprocal hybrids and pure parental species were exposed to progressive changes in salinity at 6 ppt intervals until total mortality. Standard length (SL) was measured to correlate the size to salinity tolerance. Clinical signs and social behavior were observed during the test.
Parental O. mossambicus showed the highest salinity tolerance, followed by reciprocal H3, H2 and HI, while parental O. niloticus had the lowest. There was an increase of salinity tolerance in the offspring as they were backcrossed to the saline-tolerant parent O. mossambicus.
Both parents (O. mossambicus) contributed to the salinity tolerance of the offspring. Maternal inheritance was observed in reciprocal H1 and reciprocal H2, while paternal inheritance was observed in reciprocal H3. HI had the highest heterosis. Both H2 and H3 stocks had negative and slight positive heterosis, indicating that they are good candidates as base population for selection.
Size and salinity tolerance were significantly related in H'2 and H'3 compared to the other group of fishes. Bigger fish survives longer in elevated salinities compared to smaller one. In the selection phase for growth, salinity tolerance might be indirectly selected, because larger fish survives longer regardless of age.
Social behavior during acclimation to salinity was observed. Generally, there was a decrease in the dominance of dominant individuals with the increase in salinity. O. niloticus and HI stocks were increasingly aggressive at 30-36 ppt. H1 still had a residual dominant individuals until 96 ppt. Dominance disappeared in the other groups (H2 and H3 and pure O. mossambicus) at 48 ppt.
Loss of dominance among dominant individuals, cessation of feeding/minimal food intake, sunken eyes and abdomen, color changes and sluggish movement were observed before fish mortality.
Aquaculture
Nile tilapia
Mozambique tilapia
Fish culture
639 / M41 2002