Maximum Sustainable Yield Estimates from Lake Nasser Fisheries, Egypt with Special Reference to Nile Tilapia Oreochromis niloticus using ASPIC Software

The lakes’ fisheries play an important role in the Egyptian economy. Egyptian lakes face many challenges such as over-fishing, illegal and destructive fishing methods, human activities and pollution which affected the fish production from it. The lakes’ contribution to the Egyptian fish production decreased from about 50% in 80’s to the only 10% during 2017. Lake Nasser, as one of the largest artificial lakes in the world, plays a significant role in Egyptian fisheries. Its mean annual fish production is about 28,000 ton, this constituted 18% of the total fish harvested from Egyptian lakes. The catch and effort data over 15 years were collected from the lake and analyzed to assess its status and to summerize the main problems facing its development and management. Maximum Sustainable Yield of Nasser lake with special reference to the Nile tilapia, the main species in the lake, is estimated based on catch and effort data from 2003 to 2017. The computer software packages of ASPIC had been used. The surplus production model of Schaefer was applied in this study. The obtained results proved the over exploitation situation for the lake fishery and to achieve the sustainability many applicable measures are recommended.

DNA barcoding revels first records of three rare coleopteran genera in Northern lakes of Egypt.

One aquatic coleopteran species from family Dytiscidae and two aquatic coleopteran genera from family Hydrophilidae were recorded in the summer period and represent first records in the Egyptian lakes. Beetles were collected from two northern lakes, Lake Idku and Lake Burullus. They were identified by morphological characteristics as well as the mtDNA barcoding method. A molecular phylogenetic approach was used to determine the genetic identity of the collected samples based on the mitochondrial cytochrome oxidase I (COI). Prodaticus servillianus (Dytiscidae) from Egypt showed no significant difference in the COI region and they are highly similar to P. servillianus from Madagascar. The phylogenetic analysis revealed that the other two coleopteran genera belong to family Hydrophilidae. Based on COI only, there is no clear evidence for their genetic identity at the species level. So, we defined them to the closest taxon and denoted them as Cymbiodyta type A and B. The results indicated that resolving the molecular identity of the aquatic beetles from northern lakes of Egypt need more considerations in the field of biological conservation. We concluded that utilization of COI as a barcoding region for identifying some coleopteran species is not sufficient and additional molecular markers are required to uncover the molecular taxonomy at deep levels.

Short-term changes in phytoplankton assemblages and their potential for heavy metal bioaccumulation – a laboratory study

This study focused on phytoplankton changes in polluted waters of Lake Manzala and the assessment of heavy metal bioaccumulation capacity during the 15-day laboratory experiment. Phytoplankton samples were analyzed every day and the concentration of zinc, iron and lead in water, in phytoplankton and in filtrate – every fifth day of the experiment. Significantly higher phytoplankton abundance was recorded in water from the El-Boom station (basin I) compared to the New Bahr El-Baqar drain (basin II), followed by distinct differences in its composition and chlorophyll content. However, the most abundant species were the same in both basins, i.e. Chroococcus minor, Microcystis aeruginosa, Actinoptychus octonarius, Aulacoseira granulata, Pantocsekiella ocellata, Kirchneriella obesa and Nephrocytium limneticum. Water in basin I was more polluted with heavy metals compared to basin II. Basin I was characterized by the dominance of cyanobacteria and high relative abundance of chlorophytes compared to basin II, where either cyanobacteria and/or diatoms dominated in the phytoplankton. In the former basin, the highest uptake factors (UFs) were recorded for iron and zinc and the lowest UF for lead. In basin II, the highest UF was determined for zinc, but relatively high UFs were recorded also for iron and lead. The presented results suggest that phytoplankton can contribute to natural biosorbents of heavy metals in Egyptian lakes.