In order to improve the production of Clariidae, a study on the type of cultivation of Heterobranchus longifilis and Clarias gariepinus in post fingerlings growth phase was carried out in tanks. It took place from March to May 2018 at the IRAD fish station in Koupa-Matapi (LN: 5º 21 ‘to 5º 58’ and LE: 10º 17 ‘to 11º 02’) west region Cameroon. For this fact 180 fry therefore 90 Heterobranchus longifilis and 90 Clarias gariepinus with an average weight 3.55 ± 0.68 g; 8.46 ± 0.41cm of total length and 7.37 ± 0.30 cm of standard length were used. The 180 fry were divided into three treatments of 60 individuals (T1 treatment: Clarias gariepinus, T2 treatment Heterobranchus longifilis and T3 treatment: Clarias gariepinus + Heterobranchus longifilis). Each treatment was repeated twice. The fish were fed twice per day at a rate of 10% of the ichthyobiomass readjusted each month after control fishing with a feed at 42% crude protein. From the results of this trial, it appears that unlike the higher mortality rates (11.66 ± 2.36%) recorded in monoculture Clarias gariepinus, the highest cannibalism rates were obtained in monoculture of Heterobranchus longifilis (13.33 ± 4.71%). The survival rate was not influenced by the type of culture. Nevertheless, the highest rate (94.44 ± 0.00%) was observed in Heterobranchus longifilis in polyculture. The highest growth values were recorded for C. gariepinus in polyculture and the weakest for H. longifilis in polyculture. For linear growth, the highest values were recorded in C. gariepinus in monoculture. In order to reduce the rate of cannibalism and mortalities in Clarias gariepinus and Heterobranchus longifilis in post f ingerlings growth phase, it is preferable to combine these two species.

This study examined the use of supplemental oxygen and two temperatures (1° and 11°C) during the four hour storage of unfertilized landlocked fall Chinook salmon (Oncorhynchus tshawytscha) eggs from Lake Oahe, South Dakota, USA. There was a significant and positive effect of oxygen use on egg survival to the eyed-stage and hatch. In addition, survival to egg eye-up and hatch was significantly affected by storage temperature, with decreased survival at 1°C. However, there was no significant interaction observed between the use of oxygen and storage temperature. Mean survival to hatch ranged from 50% for those eggs stored with oxygen at 11°C compared 17.8% for those eggs stored on ice at 1°C in air. To maintain landlocked Chinook salmon egg fertility, storage with supplemental oxygen at 11°C is recommended.

Many industries discharge their effluents in to aquatic ecosystems without proper treatment. As they contain several heavy metals, they affect aquatic organisms. Acute toxicity tests provide rapid estimates of lethal concentrations of toxicants. Hence, the present work has been designed to test the acute toxicity of mercury, cadmium and their combinations to the fingerlings of the Indian major carp, Labeo rohita. Among these four types of toxicants, Hg was the most toxic followed by (Cd)+Hg, (Hg)+Cd and Cd.

Industries discharge their effluents in to the environment and some of them reach aquatic systems. Trace metals present in such effluents as mixtures affect fish. Hence in the present work, an attempt has been made to estimate the effects of nickel and chromium separately and in combination on the mineral content of the fish, C.mrigala. Both nickel and chromium individually resulted in the decline of Ca, Na, K and Mg but increase in P content. Both the combinations increased Ca, Mg, and P content in the fish. (Ni)+Cr combination alone caused an elevation in Na and K content of the whole fish under chronic exposure.