Department of Marine and Fisheries Sciences
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Item Evaluating The Performance Of CMRI For Estimating The Spatial Distribution Of Mangroves At The Keta Lagoon Complex In The Volta Region Of Ghana(University of Ghana, 2020-10) Sackey-Addo, S.Data obtained from remote sensing is useful for evaluating and mapping infrastructure and natural resources including vegetation. Over the past years, a number of vegetation indices have been developed to detect vegetation with the use of satellite imageries to monitor the distribution and phenology of mangroves. Forest managers and environmental scientists have developed a wide range of indices for delineating and assessing the health of different vegetation and forest cover. This study will evaluate the performance of Combined Mangrove Recognition Index (CMRI) for estimating and distinguishing mangroves in the Keta Lagoon Complex. The CMRI was compared to the Normalized Vegetation Index (NDVI), a widely used vegetation index and supervised classification (maximum likelihood) which were selected based on their classification accuracies of about 80% in the estimation of vegetation. Sentinel-2 imagery was used to generate vegetation maps for the NDVI and CMRI indices and a land cover map generated using the supervised classification (maximum likelihood) technique. The threshold value method was used to extract the values of mangrove areas for each index and used to delineate areas of mangrove and non-mangrove using binary data with the use of UAV imagery for validation. Random points with their coordinates were generated as reference points on the UAV imagery and overlaid on the other maps. Areas of mangroves were denoted “1” and areas with non-mangroves were denoted “0”. The Cochran’s Q test, used for statistical analysis of binary data was used to derive the p-value after which the area coverage of mangroves in the study area was estimated. From the study, the threshold values used to mask out mangroves were observed to be between 0.27 and 0.37, and between 0.51 and 0.70 for NDVI and CMRI respectively. UAV imagery was used to validate the area coverage due to its high resolution. The imagery covered an area of 1.8 km2 and was used as a subset for the mangrove area coverage comparison. Mangrove area coverage was estimated to be 0.32km2, 0.30km2, and 0.25km2 for NDVI, supervised classification and CMRI respectively. All techniques used in classification showed no statistical significance (>0.05) when compared to ground truth data. The CMRI was observed to have performed better and hence confirmed its sensitivity in estimating mangroves and that other satellite missions with optical sensors and multiple bands can be used to generate the index with high accuracy.Item The Ecological Statusof The Keta Lagoon Using Physicochemical And Biological Indicators Of Water Quality(University Of Ghana, 2021-09) Danso, P.The Keta Lagoon and its catchment areas are under the influence of intensive agriculture which depend heavily on agrochemical usage. It is necessary that, the quality of water in the lagoon is assessed to broaden our understanding of how the lagoon and its associated biota are responding to agro-related activities in its watershed. This study carried out a comprehensive assessment of the ecological status of the lagoon using physicochemical parameters (temperature, DO, turbidity, pH, nitrate, phosphate, silicate, ammonia), Trophic State Index and diversities of benthic macroinvertebrates and phytoplankton communities. The lagoon was partitioned into five zones (A to E) to depict the intensity of human impact as reflected through farming along the bank of the lagoon. Zone A is the area in close proximity to Anloga, Zone B, covers the mid-section of the lagoon and falls between Anloga and Woe, Zone C is main Woe area, Zone D represents the area between Woe and Afedome and finally Zone E which represents the area beyond Afedome extending towards Keta. The average physicochemical parameters reported during the study showed that Zones A and B recorded the highest levels of pH, 9.6 0.16 which was above the acceptable range levels by Ghana’s EPA and USEPA (6.0 to 9.0). The least pH level was recorded for Zone C at 8.5 0.03 which was within the acceptable range of pH. Dissolved oxygen levels measured was highest in Zone D (8.1 0.26 mg/l) and least in Zone A (6.5 0.13 mg/l), all within Ghana EPA and USEPA as well as the World Health Organization tolerable limits. Zones A recorded the higest nitrate values of 3.4 0.03mg/l and least in Zone E, 1.9 0.02 mg/l. All zones recorded nitrate levels that were above the Ghana and US EPA permissible ranges. Ammonia was highest in Zone A (0.12 0.02 mg/l) and least in Zone E (0.03 0.02 mg/l), and Phosphate levels was highest in Zone A (0.26 0.01mg/l) and least in Zone E (0.13 0.01 mg/l). Both phosphate and ammonia measured were within the permissible limits. The Trophic State Index based on Chlorophyll-a estimation indicated that the lagoon was hypereutrophic (61.3-64.9). However, Zone A recorded the highest TSI value (64.9) and the least TSI was recorded by Zone E (61.3). Zones A, B and C (4.9-6.5) were in poor ecological conditions. D (3.0-3.8) was in fair ecological conditions. Zone E was in good ecological conditions. The mean Plankton Index of Biotic Integrity (P-IBI) for the entire lagoon, however, was 3.96 and that shows a mesotrophic lagoon with diverse populations of phytoplankton.The total number of macrobenthic species counted in the Keta lagoon was 1018 which consisted of 83% mollusks and 17% polychaetes as the major taxa. Generally, Macrobenthic assemblage richness, evenness and diversity were 1.2, 0.8 and 1.7 respectively for the lagoon. The trends of physicochemical parameters (temperature, DO, turbidity, pH, nitrate, phosphate, silicate, ammonia), Trophic State Index, diversities of benthic macroinvertebrates and phytoplankton communities showed that the lagoon is in the state of deterioration with time.Item Evaluating The Performance Of CMIR For Estimating The Spatial Distribution Of Mangroves At The Keta Lagoon Complex In The Volta Region Of Ghana(University of Ghana, 2020-10) Samuel, S-A.Data obtained from remote sensing is useful for evaluating and mapping infrastructure and natural resources including vegetation. Over the past years, a number of vegetation indices have been developed to detect vegetation with the use of satellite imageries to monitor the distribution and phenology of mangroves. Forest managers and environmental scientists have developed a wide range of indices for delineating and assessing the health of different vegetation and forest cover. This study will evaluate the performance of Combined Mangrove Recognition Index (CMRI) for estimating and distinguishing mangroves in the Keta Lagoon Complex. The CMRI was compared to the Normalized Vegetation Index (NDVI), a widely used vegetation index and supervised classification (maximum likelihood) which were selected based on their classification accuracies of about 80% in the estimation of vegetation. Sentinel 2 imagery was used to generate vegetation maps for the NDVI and CMRI indices and a land cover map generated using the supervised classification (maximum likelihood) technique. The threshold value method was used to extract the values of mangrove areas for each index and used to delineate areas of mangrove and non-mangrove using binary data with the use of UAV imagery for validation. Random points with their coordinates were generated as reference points on the UAV imagery and overlaid on the other maps. Areas of mangroves were denoted “1” and areas with non-mangroves were denoted “0”. The Cochran’s Q test, used for statistical analysis of binary data was used to derive the p-value after which the area coverage of mangroves in the study area was estimated. From the study, the threshold values used to mask out mangroves were observed to be between 0.27 and 0.37, and between 0.51 and 0.70 for NDVI and CMRI respectively. UAV imagery was used to validate the area coverage due to its high resolution. The imagery covered an area of 1.8 km2 and was used as a subset for the mangrove area coverage comparison. Mangrove area coverage was estimated to be 0.32km2 , University of Ghana http://ugspace.ug.edu.gh iv 0.30km2 , and 0.25km2 for NDVI, supervised classification and CMRI respectively. All techniques used in classification showed no statistical significance (>0.05) when compared to ground truth data. The CMRI was observed to have performed better and hence confirmed its sensitivity in estimating mangroves and that other satellite missions with optical sensors and multiple bands can be used to generate the index with high accuracy.Item Food and Feeding Habits of Three Tuna Species Landed in Ghana(2020-08) Tuga, A.Food and feeding habits of the three tuna species landed in Ghana were investigated for a period of six (6) months from October 2019 to March 2020. The species are Thunnus albacares, Katsuwonus pelamis, and Thunnus obesus. The study sampled a total of 210 individuals of the three tuna species, out of which 90 individuals were Katsuwonus pelamis, 60 individuals of Thunnus albacares, and 60 individuals of Thunnus obesus. The study sampled 90 specimens for Katsuwonus pelamis because they are of high abundance and very common in Ghanaian waters than Thunnus albacares and Thunnus obesus. These tuna species were sampled for stomach content analysis, to determine which type of prey item is most important and preferred as food for these three tuna species. The samples were transported to the Fisheries Scientific Survey Division (FSSD) laboratory in Tema, under the Ministry of Fisheries and Aquaculture Development for analysis. At the laboratory, some morphometric measurements of the samples were taken. The fish samples were dissected and their guts were removed for examination. Gut content analysis was conducted on each of the fish sampled. The gut fullness was determined on a scale of 0/4 to 4/4 by visual inspection. The commonest prey items discovered in the stomachs during the studies were Engraulis encrasicolus, Exocoetus spp, Penaeus kerathurus, Sepia hierredda, Loligo spp, and Metapenaeus monoceros. Engraulis encrasicolus was found to be the most preferred food item accounting for 58% occurrence by number, with Diplodus spp being the least preferred food item accounting for 2% for Thunnus albacares. For Katsuwonus pelamis, Penaeus kerathurus was found to be the most preferred food item accounting for 57% occurrence by number, with Sepia hierredda being the least preferred food item accounting for 10% of total prey items found. Exocoetus spp was also found to be the most preferred food item accounting for 86% occurrence by number, with Metapenaeus monoceros being the least preferred food item accounting for 12% for Thunnus obesus. Similarly, the most important food items identified using Index of relative importance were Engraulis encrasicolus, Penaeus kerathurus and Exocoetus spp with Diplodus spp, Sepia hierredda and Metapenaeus monoceros recording the least important for Thunnus albacares, Katsuwonus pelamis and Thunnus obesus respectively. There was a significant difference among these three tuna species with respect to Engraulis encrasicolus, Penaeus kerathurus Exocoetus spp, Sardinella aurita, Caranx crysos, Sepia hierredda, Loligo spp, and Brachyuran spp. Continuous research on food and feeding habits of these Tuna species to cover all the yearly seasons was recommended owing to their commercial importance to Ghana and the international community.Item Assessment of Beach Litter at the Sakumono and La Pleasure Beaches(University of Ghana, 2019-07) Adjei, O.Ghana faces a major challenge when it comes to waste management, especially in the urban areas. Population growth even makes the situation more exacerbated in the coastal urban areas. Most of the waste that is generated and lost inland end up in the coastal and marine environment when the rains fall and wash the solid wastes downstream. Some of the waste is also produced on the beaches by revelers when they use the beaches for tourist and entertainment purposes. This study was carried out on two beaches in the Greater Accra Region, namely Sakumono and La Pleasure beaches. The main objective of this study was to assess the amount of beach litter at the two beaches. A transect of 1000 m2 was used in the study. A total of 2,697 litter items were collected from the two beaches. The total weight of the litter throughout the survey was 50.07 kg from both sites. Weight of litter collected from Sakumono beach was 31.79 kg accounting for 63.49% of the total weight of litter surveyed whereas the weight of litter collected from La was 18.28 kg, also accounting for 36.51% of total litter surveyed. Plastics were found to be the most abundant both by number as well as weight. For both beaches, plastics made up 72.56% composition by number or quantity at 1975 items and 65.53% by weight at 32.81 kg. Sakumono beach was found to be more littered than La Pleasure beach. This was significant at an alpha value of 0.05 (p value = 0.02). Continuous monitoring, intensive education, and the enforcement of appropriate policy initiatives remain crucial to addressing the beach litter menace along the coasts of Ghana.Item Investigating Pathological Agents Associated With the Rusty-Brown Spots on Farmed Nile Tilapia (Oreochromis Niloticus Linnaeus, 1758) in Ghana(University of Ghana, 2019-07) Deho, R.E.A.The outbreak of disease in fish farming has become a worldwide problem. The aquaculture industry in Ghana has seen a major rise in the rate of fish mortality in recent times with significant economic losses. New and emerging diseases maybe associated with these mortalities including the rusty brown spot recorded on cultured Oreochromis niloticus (Nile tilapia). However, there is no much information on the pathological agents associated with the condition. The rusty brown spots have been observed in tilapia cultured in earthen ponds and concrete ponds. This work looks at isolating and identifying the possible organisms that are likely to be the cause of the rusty brown spots. Preliminary culture of the fish skin on Tryptone soy agar (TSA) and Tryptic Yeast Extract salt agar (TYES) recorded the following bacteria species Psuedomonas aureginosa, Klebsiella pneumoniae, Staphylococcus aureus, Staphylococcus chonii and Flavobactrium. Data obtained shown that Aspergillus niger and Flavobacterium spp. were the primary pathogens associated with the rusty brown spots. However, molecular identification is yet to be done to determine the exact strain of Flavobacterium and Aspergillus niger and to confirm their virulence in a challenge infection experiment.Item Effects of Broodstock Sex Pairing Ratios and Resting Periods of the Nile Tilapia Oreochromis Niloticus (Linnaeus, 1758) on Fry Production(University of Ghana, 2019-07) Oblie, E.N.A.The Nile tilapia, Oreochromis niloticus (Linnaeus, 1758) forms about 80% of farmed fish in Ghana. However, the unavailability of its seed all year round for culture is a major constraint. This study evaluated the effects of varying male to female broodstock pairing ratios of 1:1, 1:2 and 1:3 with resting intervals of 0, 3 and 7 days on fry production performance of the Akosombo strain of the Nile tilapia at the Ashaiman Aquaculture Demonstration Centre, Ghana. Nine (9) treatments were arranged according to a 2 x 3 factorial design with three replicates giving a total of 27 spawning hapas (1 m3). Male and female brooders of mean body weight (200±50 g and 171±23.7 g respectively) were paired according to the three different sex ratios. Water quality parameters for temperature and DO were taken daily while’s pH, salinity and ammonia were measured weekly. The total mean fry output for the sex pairing ratios (1:1, 1:2, 1:3) were 716±344, 973±325 and 723±577 respectively. The total fry output for 0, 3 and 7 days of resting were 1503±868, 2030±637 and 3051±1054 respectively with an observed 35% (3 days rest) and 103% (7 days rest) fry production increment over the 0 resting treatment. With respect to the combined effect of varying sex ratios and resting periods, the highest mean fry production (701±405) was attained under the 7 days resting period at a pairing ratio of 1:2. Although results subjected to ANOVA showed no significant differences (p>0.05) among the treatments, the relatively high reproductive performance observed for broodstock pairing ratio 1:2 and resting period of 7 days under this study confirms that it is a more efficient broodstock management technique for an increased Nile tilapia fry production.Item Studies on Abundance of Jellyfish in Beach Seine Landings along the Coast of Greater Accra Region of Ghana(University of Ghana, 2019-07) Adongo, P.A.The study was conducted in three landing villages along the coast of Greater Accra Region of Ghana, namely; Ada, La and Bortianor from November 2018 to April 2019. The purpose of the study was to assess the abundance of jellyfish in beach seine landings. Biological data was obtained primarily from local fishermen who deployed beach seine net. The jellyfish families that were encountered were four in number and a total of 2,676 individuals from 72 beach seine hauls. These were; Catostylidae (35%), Chirodropidae (31%), Rhizostomatidae (30%) and Pelagiidae (4%). Ada had 37% of jellyfish, La 49% and Bortianor 14% of the total jellyfish landings. Rhizostomatidae was the most abundant at Ada, whereas Chirodropidae and Catostylidae were the most abundant at La and Bortianor respectively. The fish families that were encountered together with the jellyfish were thirteen and consisted of 352,228 individuals. They were; Carangidae > Portunidae > Penaeidae > Dasyatidae > Sciaenidae > Haemulidae > Cynoglossidae > Sphyraenidae > Sparidae > Stromateidae > Lutjanidae > Trichiuridae > Sepiidae; in order of decreasing abundance. Physico-chemical parameters at each site where fishing was carried out were collected. Five water quality parameters (DO, Conductivity, TDS, Phosphate and Chlorophyll-a) out of the eleven water parameters measured were identified to contribute significantly to the biological variations observed. A Canonical Correspondence Analysis (CCA) was used to identify which of the principal water quality parameters influenced abundance of both jellyfish and fish at each site. Decreasing DO, Conductivity and Chlorophyll-a levels influenced a decrease of jellyfish at Ada while increasing DO, Conductivity and Chlorophyll-a influenced an increase of jellyfish at La. Conversely, decreasing levels of TDS and Phosphate led to a decrease in Bortianor.Item Predicting Nutrient Distribution Patterns in Some Coastal Lagoons in Ghana Using Mike 3 Model(University of Ghana, 2019-07) Kwame-Biney, M.The study assesses the levels of phosphate, nitrate and ammonia in water and sediments from the Mukwe, Sakumono II, Gao and Laloi lagoons situated within the central coast of Ghana alongside other physicochemical parameters (pH, Dissolved Oxygen, Total Dissolved Solids and Temperature). Data collected over a six-month period was used in calibrating and predicting nutrient concentrations in the Sakumono II and Gao lagoons using the MIKE 3 model. High pH measurements beyond USEPA and Ghana’s EPA permissible limits of 6.5 to 8.5 and 6.0 to 9.0, respectively, were recorded in the Sakumono II and Mukwe lagoons whiles Gao and Laloi recorded pH values within these permissible limits. With the exception of the Laloi lagoon which had an average dissolved oxygen value of 5.1mg/l, dissolved oxygen concentration in all the other lagoons were lower than the EPA and WHO permissible limits of 5.0mg/l to 6.5mg/l and 5.0mg/l to 6.0mg/l, respectively. Total Dissolved Solid measurements in all the lagoons were above the EPA permissible limit of 500mg/l. Phosphate, nitrate and ammonia concentrations in all the four lagoons were generally above Ghana’s EPA and USEPA permissible limits. Discharge rates measured were highest for the Laloi lagoon and lowest for the Gao lagoon, which may be linked to the width and depth of the lagoons. Sediment nutrient concentrations were used together with the instantaneous sediment discharge formula to calculate the rate of discharge of sediment nutrient for the four lagoons. The results indicated that sediment nutrient concentration has a positive correlation with sediment discharge rate. Apart from few discrepancies in the results which was caused by poor rainfall data and non-point discharges, the correlation analysis indicated that MIKE 3 model was able to generally predict nutrient concentrations and show the distribution patterns in the Sakumono II and Gao lagoons. Average sediment nutrient concentrations recorded for phosphate during the dry and rainy season for Sakumono II, Mukwe, Gao and Laloi lagoons were (0.121 and 0.128mg/kg), (0.146 and 0.113mg/kg), (1.42 and 1.22mg/kg) and (0.112 and 0.103mg/kg) respectively. The average sediment nutrient concentrations recorded for ammonia during the dry and rainy season for Sakumono II, Mukwe, Gao and Laloi lagoons were (37.18 and 25.85 mg/kg), (41.49 and 37.46mg/kg), (4.58 and 4.31mg/kg) and (41.74 and 40.93mg/kg) respectively. The average sediment nutrient concentrations recorded for nitrate during the dry and rainy season for Sakumono II, Mukwe, Gao and Laloi lagoons were (14.54 and 11.55mg/kg), (15.15 and 15.41mg/kg), (3.83 and 3.46mg/kg) and (13.22 and 11.77mg/kg) respectively. Average sediment discharge rates recorded in the Sakumono II, Mukwe, Gao and Laloi lagoons for ammonia, nitrate and phosphate were (0.00000399 m3/s, 0.00000133m3/s and 0.0000000143m3/s), (0.0000377m3/s, 0.0000126m3/s and 0.00000131m3/s), (0.000021m3/s, 0.0000073m3/s and 0.0000000746m3/s) and (0.00001624m3/s, 0.0000537m3/s and 0.0000000465m3/s) respectively.Item Induced Breeding of the African Catfish (Clarias Gariepinus Burchell, 1822) Under Varying Brood Stock Ratios Using Ovaprim(University of Ghana, 2019-06) Ameti, S.K.Modern methods of producing African catfish (Clarias gariepinus) fingerlings require that the male brooder is sacrificed to obtain milt for artificial fertilization of the eggs stripped from the female under hormonal induction. The objective of this research was to study the semi artificial technique of producing catfish larvae with different brood stock ratios using Ovaprim. The experiment was made up of three (3) treatment groups and each treatment had three (3) replicates each. The treatments were T1 (artificial spawning with 1:1 female: male ratio), T2 (semi artificial spawning with 1:1 female: male ratio) and T3 (semi artificial spawning with 2:1 female: male ratio). The relative fecundity of female brooders in T1, T2 and T3 were 68 ± 6.31, 78 ± 12.29 and 65 ± 8.18 respectively and they were not significantly different (p>0.05). Percentage fertilization for T1 (81±1.52%), T2 (75 ± 2.51%) and T3 (62 ± 2.50%) were significantly different (p<0.05). The observed percent hatchability (85 ± 2.51%, 83 ± 3.21% and 82 ± 2.50%) in respect of T1, T2 and T3 were not statistically different. Differences in total egg weight (96 ± 3.30 g, 72 ± 10.53 g and 59 ± 0.50 g), and total larval production (57,700 ± 3672; 42,423 ± 6972 and 34,078 ± 762) for T1, T2 and T3 respectively were statistically significant (p<0.05) between artificial spawning and semi artificial spawning. Larval survival was statistically (p<0.05) different between T1 (84 ± 2.31) and T3 (92 ± 2.50) but both did not differ significantly from T2 (87 ± 2.51). In conclusion, semi artificial spawning of C. gariepinus with Ovaprim could be beneficial to fish farmers if done at a brood stock sex pairing ratio of 1:1.