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In Cameroon, wild strains of Clarias gariepinus (Burchell, 1822) are often used for artificial reproduction in hatchery facilities, but there is insufficient information on their reproductive capacity and progeny performance. The reproductive capacity of two strains of C. gariepinus from the Mezam and Mungo Rivers and the performance of their F1 larvae obtained following hybridization were assessed. Reproduction was carried out with four crosses as follows: Mezam (♂) x Mezam (♀) (T1), Mezam (♂) x Mungo (♀) (T2), Mungo (♂) x Mezam (♀) (T3) and Mungo (♂) x Mungo (♀) (T4). Thereafter, three days old larvae obtained following reproduction were subjected to a 30 day experimental trial with standard feeds. The performance of larvae obtained from T4 was not assessed since larvae obtained were too few for the experiment. Although the broodstock of the different strains did not differ significantly in size, Mezam stock had significantly (p = 0.00) bigger eggs when compared to Mungo stock. Fecundity of 52480 was recorded for Mezam stock compared to 32985 for Mungo stock. Fertilization and hatchability rates differed significantly (p < 0.05) among the crosses, with the highest (82.28 and 81.31%, respectively) in T1, followed by T3 (65.96 and 61.28%, respectively), and the least (38.61 and 2.81%, respectively) in T4. The best larval survival was recorded in T1 (37.17%) and the least in T2 (15.67%), meanwhile T3 recorded best growth after 30 days. In terms of fertilization and hatchability, T1 was more suitable for artificial reproduction, but T3 is more encouraged for aquaculture based on its reproductive capacity and larval performance.

Jatropha curcas Linnaeus, 1753 is a plant with several uses for communities in Cameroon and other African countries. However, present methods of detoxifying J. curcas kernel cake (JKC) to add value to its further utilization are too sophisticated for cottage operations in rural areas. This study sought to evaluate two auto-detoxification methods using the shellfish brine shrimp, Artemia salina (Linnaeus, 1758). Two identical J. curcas auto-detoxification apparatuses (JADA) were developed: one simulating diffuse daylight (DJADA) and the other solar irradiation (SJADA) conditions. JKC was pretreated by either soaking or boiling in water or lye. The pretreated samples were then placed in the JADA and either re-moistened to 66% dry matter (DM) or left un-moistened. Among the 14 pretreated samples, water soaked solar without re-moistening (WS1), lye soaked solar without re-moistening (LS1), and water soaked solar with re-moistening (WS2) had LC50 values above 1000 ppm after four weeks. On the other hand, un-moistened diffuse daylight spread (UDC), boiled in water and exposed to diffused daylight without remoistening (WD3), and un-moistened solar spread (USS) were the least detoxified within the same period of four weeks with LC50 values less than 60 ppm. Irrespective of the pretreatment, extracts from the SJADA had higher LC50 values when compared to that of DJADA. This finding suggests that sunlight is an important factor in auto-detoxification. The top three most efficient detoxified treatments: WS1, LS1 and WS2 are recommended for further development and testing with livestock and fish models. This study confirms that JKC is toxic, but under natural conditions is exposed to auto-detoxifying factors which are both endogenous and environmental. When these conditions are optimally manipulated, the detoxification rate is enhanced. Farmers in rural communities can use this strategy to detoxify JKC, transform it into livestock and fish dietary ingredient and consequently enhance its contribution to climate change mitigation. Key words: Jatropha curcas, auto-detoxification, solar irradiation, Artemia salina.

The African River prawn Macrobrachium vollenhovenii is the largest of the local Palaemonidae prawns along the Cameroonian coast and an important target species for fisheries and aquaculture. A preliminary study on larviculture of this species was carried out at the IRAD-AQUASOL hatchery in Kribi, Cameroon. Berried females M. vollenhovenii were obtained from the Lobe and Lokoundje Rivers in the Southern Region, typical Lower Guinea rainforest streams. The larval rearing system consisted of a single recirculation system of four 65 L cylindrical plastic containers connected to a submerged biological filter container (65 L). Experiments were conducted three times in the same condition, with two batches of larvae reared separately in duplicate per experiment, at a density of 40/L, temperature 26°C, and salinity 16%. Larvae were fed from 1 day after hatching until metamorphosis to postlarvae (PL) with newly hatched Artemia nauplii, three times daily at the rate of 5 nauplii per mL water. The number of newly hat...