Research Article
Sep 10, 2021
Dietary shifts in Juvenile and Adult Nile Tilapia, Oreochromis Niloticus.
Oreochromis niloticus (Nile tilapia) is an important fish in the ecology of tropical waters as well as aquatic systems in other subtropical regions. It is the most commercially important and preferred fish species in Ethiopia. It is also a candidate fish for aquaculture. In recent years, the fish community structure and ecosystem dynamics of the Lake Ziway have changed, but no studies have been carried out to assess whether the fishes have altered their diets in the lake. Indeed the food of Nile tilapia with respect to size was conducted from April to August 2017 in Lake Ziway, Ethiopia.A total of 365 Nile tilapia specimens (170 adults and 195 juveniles) were collected ranging from 2.5 to 30 cm TL and 0.5 to 459.7 g TW. Guts of 165 (85%) juveniles and 115 (73.5%) adults’ contained food items. Specimens that contained food items in their stomachs were analyzed using frequency of occurrence, volumetric methods and Schoener’s index. Nile tilapia originally known to be phytoplanktivorous has shifted to omnivorous feeding mainly on macrophytes. Volumetrically, the major diets of juveniles were zooplankton (33.79%), phytoplankton (25.44%), insect (18.69%) and detritus (14.02%) while the diet of adults were mainly macrophytes (36.2%) followed by phytoplankton (34.36%) and detritus (18.41%). Adult Nile tilapia which was a phytoplanktivorous has now shifted to macrophytes even though phytoplankton is the second dominant food item while juvenile mainly depends on zooplankton and insect larvae. Ontogenetic diet shift was observed in the present study demonstrating juveniles mainly feeding on animal based food items whereas adults depend on plant origin.
Editorial
Sep 02, 2021
Fish Disease and Parasites.
Not applicable.
Commentary
Aug 26, 2021
Bio Toxins in Marine Life.
Not applicable.
Commentary
Aug 24, 2021
Tuna Fish Farming.
Not applicable.
Research Article
Aug 02, 2021
Offshore Marine Environment and Mammal Habitation with the Changing Climate in the Gulf of Guinea.
Understanding environmental baseline parameters within Gulf of Guinea offshore areas as relevant delineating conditions favorably ensuring the survival of marine life bounded within was examined against Environmental Baseline Surveys (EBS) conducted during the Environmental Impact Assessment (EIA) by licensed oil and gas operators of the region. The case of the EBS within Ghana’s western basin is mainly because offshore marine habitation over a decade has seen a rise in anthropogenic activities. Current concerns span pollution, over-exploitation of natural resources, air emissions, growing anthropogenic activity, and climate change. A series of samplings were taking at essential offshore and coastal facility locations to investigate baseline ocean environment; understand the nature of ecology and identify issues of vulnerabilities that could ensure destructive tendencies. The paper observes EBS conditions were consistent with findings of EIAs. The tropical nature of the region meant high radiation influx from the sun leading to the thermal insulation of the area. Temperatures recorded are a direct function of solar energy absorbed in the atmosphere delimiting humidity over infrared wave outputs, atmospheric precipitations and occasional poor visibility. Absorbed heat energy in the ocean depicted a generalized thermocline under 300 meters depth at the surface. Several surface and underwater factors such as wind influenced the salinity, and temperature along water-depth, sound velocity, and dissolved oxygen concentrations useful to marine animals such as turtles, seagull, pilot whales, dolphins, and sharks; clustered along with various webs of the food chain influenced by the seasonality of upwelling. The main challenge to the environment was the concerns of growing anthropogenic activities, plastic pollution and oil spills from operations and possible blowouts.
Miscellaneous
Jul 29, 2021
Recreational (Sport) Fishing.
Not applicable.
Miscellaneous
Jul 29, 2021
Marine Farming
Not applicable.
Editorial
Jun 29, 2021
Marine Protected Areas.
Not applicable.
Research Article
Jun 21, 2021
Effect of Season on the Concentration of Nutrients in the Lakes.
Water resource contamination is still a major concern in several regions of developing countries especially in sub-Saharan countries in which polluted waters pose serious risks to human health and the environment. The research was aimed to evaluate the current water quality status of highland Lakes (Ardibo, Logo and Tana) of Ethiopia in different season and to identify potential pollution sources sites. Physico-chemical water quality parameters have been determined by taking duplicate samples from three sampling sites of each lake and the results were compared with WHO and FAO standards. The result of the study indicates nutrients concentration to be Alkalinity (428, 269.945, 109.935 mg/L), calcium (31.542, 46.873, 77.12 mg/L), chloride (89.165, 77.5, 40.125 mg/L), magnesium (94. 755, 93.165, 39.396 mg/L), NH3 (0.418, 0.184, 0.6493 mg/L), NH4 (0.433,0.145, 0.753 mg/L), potassium (1.299,19.325, 6.547 mg/L), sodium (22.489,39.5, 10.671 mg/L) and sulphate (2, 2.075, 1.479 mg/L) in Lake Logo, Ardibo and Tana, respectively. The concentration of Calcium and NH4 were significantly more abundant in rainy season than dry season (p<0.01) and the concentration of Chloride, magnesium, Potassium, Sodium and Sulphate were significantly more abundant in dry season than rainy season in lake Ardibo (p<0.01). The concentration of NH4 were significantly more abundant in rainy season than dry season and the concentration of magnesium were significantly more abundant in dry season than rainy season in lake Tana (p<0.01) and also the concentration of alkalinity, magnesium, and sulphate were significantly more abundant in dry season than rainy season in Lake Logo and the concentration of NH3 and Potassium were significantly more abundant in rainy season than dry season (p<0.01). The concentration of NH3 and NH4 were 0.6088 mg/l, 0.679 mg/l in rainy season and 0.6897 mg/l, 0.8083 mg/l in dry season respectively in Lake Tana. As the result shown that the concentration is higher in rainy season and the main reason for these results were the storm water and sediment load from different catchment of the lake released in the form of run off and soil erosion. The farmers use fertilizer to increase their crop production since NH4 and NH3 are directly released in to the lake in the form of runoff hence the concentration of these nutrients increase in rainy season.
Research Article
Jun 11, 2021
Penaeus vannamei Stock, Genetic Variance and Parentage Identification.
A microsatellite DNA marker technique was used to monitor specific-pathogen-free Penaeus vannamei (white shrimp) stock in the hatchery of the University of Guam, mainly for assessment of genetic diversity and identification of the parentage for two consecutive generations. A panel of 16 loci was selected to analyze 36 families of P. vannamei, comprising of a total of 1,152 individual shrimp samples. The families showed high genetic variation. The average number of alleles per locus was 10.625 for the parents and 10.052 for their offspring. The average observed heterozygosity declined slightly from 0.891 in the parents to 0.813 in the offspring. Similarly the expected heterozygosity was 0.804 among the parents and 0.792 for their progeny. The inbreeding coefficient was -0.107 for the parents but -0.026 for the offspring. These two generations did not differ significantly in any foregoing measures (p>0.05). CERVUS and COLONY confirmed that any 12 loci from the panel could deliver 100% correct parentage identification when the genotyping error rate was set as 0.01.
Research Article
Jun 03, 2021
Fish Processing and Value Chain Analysis.
A 6-weeks study was conducted in the domestic fish markets and at the River Nile landing sites of Juba city to determine the demand of fish products. A total of 45 fish traders and 3 focus groups (8 individuals per group) discussions were selected by means of sampling techniques. 6 other government officials from different levels of institutions and academia were interviewed using a well-structured questionnaire. Focus group discussions were provided with a well- structured guide together with the key informant interviews. Results of the study showed that, fish traders have got very low savings while running the fish businesses in Juba, Kator and Munuki Payams of Juba city. Respondents in the study area mentioned poor transport networks and marketing structures, multiple levies and taxes imposed on the fish traders, high transport cost, high rental fees for the business premises in the fish markets, limited and poor storage facilities and the lack of credits from the financial institutions to the fish traders’ associations and individuals were the major challenges confronting the domestic fish marketing in Juba city. The experiences of the fish traders in fisheries business ranged from 2-5 years old and the motivations of the fish traders in joining fisheries business was the source of income generation activities and employment. Fish traders’ income generated from fisheries business not sufficient enough to cover their monthly expenses. Boats, small- sized trucks and motorbikes were the main transportation system for fish products from the production areas to Juba city. Fish traders used ice, sisal sacks, wooden boxes, woven baskets, plastic buckets on boats, defreezers, wooden tables, carpets and concrete slaps to handle their fish products during the transportation and selling processes at the fish markets. Marketing structures observed to be dominated by traditionally made systems causing high fish spoilage and loses. Majority of the fish traders were not members to any business associations or cooperatives. Few fish traders mostly women were members to Konyokonyo Women SACCO and the fish traders from Uganda were members in their country of origin. There is no fisheries policy framework to regulate domestic fish marketing in Juba city. Central Equatoria State Ministry of Animal Resources and Fisheries has a Fishery draft bill laying before Central Equatoria Revitalarised Legislative Assembly for readings and amendment. Long term planning by the government and partners for the development of fisheries sector with a focus on fish marketing structures and the landing sites to strengthened fish value chain in Juba city is required.
