Showing papers on "Nile tilapia published in 1989"

Ontogenetic Changes in Behavior and Sense Organ Morphogenesis in Largemouth Bass and Tilapia nilotica

Abstract: The development of sensory systems and the coincident acquisition of associated behaviors were examined in two paternal brooders, largemouth bass Micropterus salmoides and Nile tilapia Tilapia nilotica. In newly hatched eleutheroembryos of largemouth bass, the eyes are unpigmented, the nares are closed, and the free neuromasts and taste buds are not developed. Six hours after hatching (when the epithelium of the otic vesicle is ciliated), the eleutheroembryos are able to aggregate by responding to the movements of neighboring siblings. Thereafter, four correlations between sense organ development and initiation of fish behavior were observed: appearance of the first free neuromasts on the head and positive rheotaxis; morphological completion of the larval-type retina and positive phototaxis; formation of twin cones in the retina and optomotor reaction; and appearance of taste buds in the oral cavity and selective feeding. The ontogenetic development of the sense organs of Nile tilapia reflects ad...

Culture of Nile tilapia, Oreochromis niloticus (L.), at three stocking densities in outdoor concrete tanks using drainage water

Abstract: . Effects of stocking density on water quality and on the growth, survival and food conversion of Oreochromis niloticus (Linnaeus) were evaluated. Fingerlings of tilapia (average weight 40.25 ± 94 g) were stocked in six 3.75-m3 concrete tanks at 16, 32 and 42.6/m3 and reared for 164 days. A water flow rate of 1 l/min/kg fish biomass was maintained in all the tanks. The growth rate was inversely related to stocking density with mean weights of 337.25g, 327.0g and 323.5g at the low, medium and high densities respectively. At harvest, standing crop biomass averaged 5.36 kg, 10.44kg and 13.24kg for the three densities. The respective food conversion ratios (FCR) were 1.85, 1.88 and 1.95, while the survival rates were 99.2, 99.6 and 95.9%. However, the survival rate, growth rate and food conversion efficiencies were not significantly different at the three stocking densities. Water quality did not deteriorate in different tanks as the oxygen was continuously replenished and metabolites and waste products removed by the water flowing through the tanks. These data suggest that culture of tilapia at a density of 42.6/m3 and production of 13.24 kg/m3 in 164 days with a production of 18–20 kg/m3 in a growing season (April-October) of 210 days is possible using the drainage water in flow-through water systems.

Digestibility of a Commercial Fish Feed, Wet Algae, and Dried Algae by Tilapia nilotica and Silver Carp

Abstract: We stimulated growth of microbial food in ponds by silage grass enrichment and investigated the digestibility by fish of a harvestable mat of biomass produced in this way. Synthetic ponds, enriched with silaged grass, produced a high-protein microbial bloom (19–24% dry weight), which attached to the silage forming a slimy matrix at the pond surface. Silver carp (Hypophthalmichthys molitrix) and Nile tilapia (Tilapia nilotica) were fed rations of the microbial mat, and digestibility of fresh and dried samples was compared with that of commercial fish feeds. The fresh microbial mat was 81% digestible by Nile tilapia and 75% digestible by silver carp. The dried form was significantly less digestible by both species. Fresh microbial mat compared favorably with commercial catfish feed in digestibility by Nile tilapia.

[Aeromonas hydrophila-related septicemia in the Nile tilapia Oreochromis niloticus].

Abstract: From diseased wild and cultured Oreochromis niloticus in Lower Egypt, 17 Aeromonas hydrophila isolates were recovered. The mortality was between 10% and 70% in among cultured fish. The course of the disease ran in an acute manner. For cultured fish, the disease outbreaks were found mainly in winter and for the wild Nile fish, mortalities were observed in late spring and summer. Additionally wild fish were affected with ectoparasites. The LD50 values of the isolates ranged between 10(3) and 10(7). Isolates of high virulence were resistant to 1 hr boiling and to the bactericidal effect of fresh normal guinea pig serum. Moreover, they did not agglutinate in acriflavin. Only the virulent isolates could agglutinate tilapia erythrocytes. The above effects were reversed for avirulent isolates while moderately virulent isolates showed no consistency in their reactions. Tube agglutination test using O and WC antisera prepared against 6 isolates versus O and WC antigens of 17 isolates indicated an antigenic heterogenicity of different isolates. While some isolates were identical, 4 antigens out of 17 did not react with any of the sera.

Induction of autoantibodies against spermatozoa by injection of allogeneic sperm in the Nile Tilapia, Oreochromis niloticus

Abstract: 1. 1. The sperm-agglutinating factor (SAF) could be induced in the serum of male Nile tilapias, Oreochromis niloticus, by injection of allogeneic sperm. 2. 2. Only one class of molecules was demonstrated to be SAF in the serum. 3. 3. Analysis on purified SAF revealed it to be a tetrameric molecule of IgM with a mol. wt of 760kD. 4. 4. Cross reaction of the IgM with sperm of other teleost species suggests that sperm-specific surface antigens may be in evolution.

Fishing gear selectivity in relation to their manufacture and to the management of fisheries of the Nile perch, the Nile tilapia, and Rastrineobola argentea (Mukene) in Lakes Victoria and Kyoga

Abstract: The fisheries of Lakes Victoria and Kyoga have changed from the native tilapiine species and are now dominated by two introduced species; Nile perch and Nile tilapia, and one native species; Rastrineobola argentea (mukene). Because of the differences in the size of the species, it may be necessary to change the type and sizes of nets used.