This study was designed to investigate for the first time in the region of Ouargla, Algeria, the events and timing of the embryonic development of African catfish, C. gariepinus (Burchell, 1822). The embryonic development was carefully monitored using a binocular magnifier 10 and 20 lenses that reveal details on live specimens from fertilization to the first take of food. The offensive and foul odor continues to be the characteristic smell of the hatching stage. Pigmentation and continuous spread of cephalo-caudal melanophore in fry hatched on the first day. The barely hatched larvae are photo-phobic. The yellow reserve is reduced and leads to the ability to swim easily, and the majority starts feeding on the fourth day. The vitellin reserve is significantly reduced, allowing the larvae to feed exogenously. The events observed in our opinion demonstrate the presence of two exceptionally critical parameters: the use of a high-quality diet and the guarantee of a clean and quality source of water, meeting the standards of aquaculture farming.
Hence, the interest in variations in feeding frequencies in captive Nile tilapia fry. Two hundred forty mixed-sex fries, intended to test the feeding frequency, with an initial average weight of 0.03 0.04g; corresponding to an average size of 1.4 cm, randomly distributed in (12) boxes each containing 4 fry/L. Fry are fed with Naturalleva import pellets for 30 days. A single photoperiod is studied for long days (18L: 6D) and to maintain an intensity of 2500 lux. The Statistics data are analyzed using software (R) and tested for normality and homogeneity of variance before being subjected to variance analysis (ANOVA; p≤0.05) and Duncan’s method. A multiple range test was used to compare the mean differences. A feed frequency of 4 times and six (06) times a day shows more efficient use of food than once, twice, and three times a day of food intake. The overall growth parameters for larval tilapia rearing are satisfactory, with the feeding regime set at 35% of the biomass of captive residents for two weeks of rearing, and 17.5% for the remaining two weeks. These results represent standards for the launch of captive breeding of the Nile tilapia strain, which will allow freeing themselves from the often expensive and foreign currency imports of fry for the country.
The assessment of the impacts of the expansion of the invasive species on taxonomic diversity, the abundance and dominance of groups of algae, the presence and/or absence of species of ecological interest that may or may not be indicative of water quality well mentioned, through the installation of a 20 × 20 cm quadrat representing the minimum area. The observation stations were visited monthly, during a repetitive three-year cycle, during the spring, summer and autumn seasons, periods of maximum growth and development of the algal flora and the results suggest the following facts. The invasive alga Caulerpa cylindracea Sonder, 1845 tends to colonise disturbed ecosystems reflecting a reduction in native algal diversity; in fact, we note a drastic impoverishment of the invaded algal community, represented by a limited number of Macrophyte algae accompanying the invasive taxon in phytosociological surveys and a Shannon-Weaver Diversity Index (H’) and Equitability reduced by 4.49 and 0.77 n the heavily affected station. The number of macroalgal species accompanying the invasive species has dropped by 52% in Salamandre. In addition, the multidimensional analysis, represented by the Hierarchical Ascendant Clustering applied to this case, confirms our results.
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