Aquatic Science and Technology

Tagelus adansonii, a Bivalve with Unknown Potential in the Mangrove Ecosystems of Senegal

2023-08-11T01:23:23+00:00

Shell molluscs are an important resource for island and coastal populations around the world. In Senegal, these resources constitute a significant contribution to the economy, food and cultural practices of the populations. The species commonly exploited are few in number, only about ten, whereas Senegal has a great diversity of shell molluscs that are still little known and exploited, including Tagelus adansonii. This is a bivalve of the solecurtidae family, the only species of the genus found on the West African coast. The study showed that this species is not widely exploited and not well known, especially among young farmers. The exploitation for self-consumption was practised in the past, but currently this species is more of an accessory catch. Its nutritional and taste qualities have also been demonstrated. The species is available and has been found in all four sites sampled, but is most abundant in Joal-Fadiouth and the Saloum estuary. The areas where densities are zero correspond to the hyper-salted environment, or exposed to silting and erosion. Moreover, its size is greater in the Senegal River Delta where the salinity is lower. Thus the physico-chemical parameters of the environment affect the distribution, growth and even survival of this species.

The majority of the people interviewed have a low level of education, and their awareness of the potential of T. adansonii will certainly open up prospects for diversifying the range of resources exploited and thus their economic contribution.

Diversity of Large and Medium Sized Mammals and Their Challenges in Abay (Blue Nile) Gorge in the Amhara Region of Ethiopia

2023-01-26T12:22:23+00:00

The diversity and threats of medium and large‐sized mammals was studied in Abay (Blue Nile) Gorge, Amhara Region, Ethiopia using direct and indirect survey techniques on transect lines crossing natural forest, riverine forest and woodlands. Footprints, camera traps and group discussions were used. Data were analyzed using detrended correspondence analysis, cluster analysis, non-metric multidimensional scaling, and diversity indices. A total of 25 medium and large mammal species belonging to 6 orders and 12 families were recorded. Order Carnivora was the most abundant followed by Artiodactyla, whereas Tubulidentata, Lagomorpha and Procaviida were rare. Leopard is threatened species. The plotting of the detrended correspondence analysis between mammal species and districts showed 61% on axis 1 and 22% on axis 2 and Gozamin district stood at the left side of the plot and Andabet, Enebise Sar Midir and Borena at the extreme right, contributing to the observed association. The mammal species were found lined up along axis 1, where Lycaon pictus and Reducna redunca were closely associated to Gozamin. The cluster analysis based on the Bray-Curtis single linkage similarity index showed differences and similarities between the mammals species composition recorded in the six districts. P. anubis, C. pygerythrus, S. grimmia, O. oreotragus, G. genetta, P. pardus pardus, H. hyaena, G. sanguinea, H. brucei, P. capensis, H. cristata stood out clearly separated from the rest of them and showed linkage at almost 50% similarity. The highest similarity (at about 96% similarity) was a cluster of four species, i.e., T. sylvaticus, T.strepsiceros, S. scrofa and K. ellipsiprymnus. Non-metric multidimensional scaling also gave clusters of similar districts but not mammal species. Species diversity (H′) ranged from low (1.1) to average (1.9). Anthropogenic impacts were associated with decline in abundance of species and populations. Conservation schemes (nature reserves) need to be launched as soon as possible.

Effects of Vermicompost on Growth of Cyprinid Fish and Water Quality of Warm Water Earthen Ponds

2023-02-22T00:59:05+00:00

Experiment was conducted in 0.0-ha earthen ponds to promote growth performance of silver carp and Cyprinus carpio and big head (cyprinid) plus phytoplankton and zooplankton and were estimated in a pond receiving mixed fertilizer with vermicomposting, with 6000 and 12000 kg per/ha/year mixed with fertilizer (VC₆and VC₁₂) and 6000, 12000 kg per/ha/year without vermicomposting (CO₆and CO₁₂). All treatments were compared finally. Significant differences were found in diversity and abundance of plankton in the pond exposed to fertilizer having CO₆, CO₁₂ and VC6, VC12 The used fertilizer and manure could be graded in the following descending order VC₁₂, VC6, CO₁₂, and CO6. The least concentration was accounted in control sets with 6000 kg manure. The highest production of fish was found in vats treated with VC₁₂ (12000kg/ha/year) followed by VC₆ (6000 kg / ha/year), CO₁₂ (12000 kg/ha/year), CO₆ (6000 kg/ha/year). The highest yield of fish in vats applied with VC₁₂ may be related to its highest manorial value.

Diversity, Composition, and Abundance of Avian Species in and around SemienMecha District Wetlands North Western, Ethiopia

2023-01-26T12:33:29+00:00

The objective of the present study was assessing the species composition, relative abundance and species diversity of avifauna found in wetlands of Semin Mecha District. The diversity, relative abundance and distribution of the avian species were investigated from January 2019 to August 2019 both wet and dry seasons. Both point count and line transect methods were employed to identify birds from the three wetlands. A total of 39 species, 28 genera 14 families and 8 orders were identified. The order Charadriiformes dominated the list (4 families with 14 species) followed by Pelecaniformes (2 families with 9 species), Gruiformes (2 families with 4 species), suliformes 2 families with 3 species), psseriformes (1 family with 6 species), the rest Accipitriformes, phoenicopteriformes and podicipediformes(1 family with 1 species) each. Out of total 39 species, one species (Black billed gull) was endangered, two species (wattled crane and Black crowned crane were vulnerable, one specie (Rouget's rail) was near threatened, and thirty five bird species recorded were under the Least Concern category. Species abundance and diversity varied between the three habitats. Weinner Simpson index showed significant diversity of birds in Koga reservoir had higher species diversity (H’=5.9) followed by kurt Bahir dembar(H’=4.15) and lower species diversity Kurt Bahir (H’=2.53).The study shows that habitat destruction due to anthropogenic activities:- over-grazing, sedimentation, poor management of catchment, recession farming, over-utilization of resources, lack of awareness , Lack of sense of ownership, giving less attention to conservation were the main threats to the survival of wetland birds in the study area. The current management of wetlands is poor because of misuse of wetlands as the result birds are endangered. Thus urgent conservation measures are recommended to conserve the bird species.