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.

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Abstract. Ghellai M, Bachir-Bouiadjra MEA, Dahloum L, Megharbi A, Bachir-Bouiadjra B. 2021. Distribution of phytobenthosis in the presence of an invasive alga Caulerpa cylindracea on the Algerian west coast. Biodiversitas 22: 5644-5653. We have targeted and followed the speed of expansion of Caulerpa cylindracea Sonder 1845 through visiting sixteen sites on the Algerian west coast, out in five provinces which are; Tlemcen, Aïn Témouchent, Oran, Mostaganem and Chlef, where it was listed in eight stations; the coastal lines of Oran and Mostaganem, and in a single station in the province of Aïn Témouchent. The phytosociological surveys were established, made it possible to see the frequency of each identified taxon, mentioning a high degree of disturbance in the appearance of benthic macrophytes regarding the dominance of the invasive species. The calculation of the Shannon index and equitability identify the ecological state of the sites, varies from average (H’ around 3.29 for sites little and not invaded by Caulerpa) to poor (H’: 1.74 for Salamandre), with low macrophytic biodiversity (0.4?E?0.64). The calculation of the Caulerpa racemosa (ICar) index on sandy to rocky substrates with algae does not appear to be a limiting factor for the spread of the invasive species. The previous analyses were validated statistically using Factorial correspondence analysis (FCA), Ascending hierarchical classification (AHC), Principal component analysis (PCA), justifying the unbalanced state according to the degrees of pollution.

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