Department of Marine and Fisheries Sciences

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    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.
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    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.
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    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.
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    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.
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    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.
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    Distribution of Macroalgae in the Intertidal Zone of Ghana
    (University of Ghana, 2019-07) Amamoo, P.A.
    Marine macroalgae or seaweeds, as they are generally referred to, are primary producers which play a central role in the productivity of coastal habitats and also serve as a source of ecosystem goods and services. They are used directly or indirectly in the production of food products, fertilizer, animal feed additives, bioenergy, nutraceutical, confectionary, textiles, paper, paint, and varnish among others. How far this can be exploited depends on the knowledge of available species. In Ghana, there have been sporadic studies of seaweeds or macroalgae since the 1950s, when inventory of the species began, until recent investigation which considered community structure analysis. Following from what is known about this biological community, this study was designed to comprehensively evaluate macroalgal distribution across the coast of Ghana. The key objectives of the research were to: (1) assess of species diversity within the intertidal zone of Ghana; (2) characterize the distribution and community structure of the macroalgae in the intertidal zone of Ghana; and (3) determine the effect of nutrients on observed distributional patterns. Ten sampling locations were selected in a manner that allowed the entire Ghana coast to be covered – i.e. Dixcove, Takoradi, Aminano, Mumford, Kokrobite, Christianborg Castle, Teshie (Next Door), Tema, Prampram and Old Ningo. The macroalgae were purposively sampled using a 1m x 1m quadrat constructed from polyvinyl chloride pipes. Species abundance were estimated as percentage cover within each quadrat, from the high to the low water mark on selected days where the tidal height was lowest. Water quality at each location was analysed for five nutrients (i.e. phosphate, nitrate, ammonia, silicate and sulphate). The sampling period was from 11th October, 2018 to 5th January, 2019. The data was subjected to various statistical analyses using Plymouth Routines in Multivariate Ecological Research (PRIMER version 6). Altogether, forty-one species belonging to 25 families were identified. Of these, ten species played an important role in influencing the spatial community structure, i.e. Ulva fasciata, Ulva flexuosa, Ulva lactuca, Hydropuntia dentata, Hypnea musciformis, Ralfsia expansa, Lithothamnion bisporum, Centroceras clavulatum, Chaetomorpha linum and Caulerpa taxifolia. This study identified these species as keystone species in terms of their dominance and contribution to observed spatio-temporal patterns in community structure, and zonation within the intertidal region; from the supra-littoral across the mid-littoral to sublittoral zones. This study did not find any evidence of the role of nutrients on the observed macroalgal distributional pattern, and attributed it possibly to the short-term temporal nature of the study. Therefore, it is recommended that long-term investigation, in relation to the effect of nutrients on macroalgae community characterization, be undertaken in future studies. Furthermore, adoption of molecular techniques to assist taxonomic characterization of macroalgae and use of unmanned aerial vehicle in field assessment should be explored towards a more comprehensive assessment.
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    Macrobenthic Infaunal Assemblage Structure in Nearshore and Offshore Seabeds of Ghana
    (University Of Ghana, 2017-06) Commey, N.A.
    The increased need for energy self-sufficiency has caused an extensive search for various sources of energy (especially, oil and gas) in the marine environment. Globally, the magnitude of impacts of the activities on the marine environment is increasing over the years and most felt on the seafloor. The study of seafloor (benthic) organisms therefore, are vital determinants of impacts on the seafloor. This thesis sought to determine the community structure of nearshore and offshore benthic macrofaunal assemblages and sediment characteristics of the two environments. It further provides a baseline of benthic macrofaunal assemblages prior to the proposed coal-powered facility at Ekumfi Aboano (nearshore), as well as, determine the current (2015) state of benthic macrofaunal assemblages in the Jubilee Fields (deep-sea). The study was carried out within the nearshore Ekumfi Aboano (av. depth–15 meters) and offshore regions (av. depth–1250 meters) of the Jubilee Fields. Sediment samples were obtained using a Van Veen grab and box corer for the nearshore and deep-sea environments respectively. Benthic macrofaunal distribution was investigated using PRIMER. Using GRADISTAT, nearshore sediment (mean grain size of 99.80 μm) was characterized as moderately sorted with very fine sand. Conversely, offshore sediment (mean grain size of 109.79 μm) was characterized as poorly sorted with very coarse silty fine sand. From the macrobenthic infauna analyses, 1113 individuals with an average density of 38 individuals/m2 were found at the nearshore environment and 2205 individuals with an average density of 47 individuals/m2 were found in the deep-sea environment. Numerical abundance showed polychaetes were 194 and 983, crustaceans were 827 and 696, molluscs were 35 and 229, echinoderms were 14 and 37 and “others” (foraminiferans, nematodes, nemerteans, sipunculids) were 43 and 260, for iv the nearshore and offshore environments respectively. The order of dominant taxa was; crustaceans > polychaetes > molluscans > others > echinoderms–for shallow Ekumfi seabed and; polychaetes > crustaceans > molluscans > others > echinoderms–for the offshore Jubilee seabed. Species identified nearshore were 116, whereas 188 species were identified within the deep-sea environment. Both sites were evenly spread (J’ > 0.8) and showed high diversity (H’ > 4; 1-D > 0.9). Polychaetes dominated (44.58 %) offshore as arthropods dominated nearshore (74.30 %). Macrobenthic infauna abundance was higher deep-sea than nearshore and were 75 % dissimilar, possibly due to varied anthropogenic influence within the two environments.
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    Assessment of the Security of Coastal Fishing Operations in Ghana from the Perspectives of Safety Poverty and Catches
    (University of Ghana, 2015) Amponsah, S.K.K
    The study was conducted in four fish landing sampling stations along the southern coastline of Ghana, namely: Vodzah and Denu (both in the Volta Region) as well as Jamestown and Tema (both in the Greater Accra Region) from June, 2014 to January, 2015. The purpose of the study was to assess the security of coastal fishing operations in Ghana from three main perspectives, namely safety, poverty and fish catches. Data was obtained from both primary sources (field data) and grey literature by courtesy of FSSD and MCSD. A number of factors were found to impact the security of coastal fishing from the perspective of safety. These included total fines and the number of IUU infractions recorded in Ghana’s coastal waters; awareness of fisheries regulation measures, compliance with fisheries regulations and the absence of government officials as the prominent enforcement agent of fisheries regulation measures. From the perspective of poverty, the security of coastal fishing was found to be under high risk with respect to high poverty head count, vulnerabilities and marginalization indicators. Similarly, the security of coastal fishing operations from the perspective of catches was also under high risk. This was because the calculated fishing mortality rates (F) (ranging from F=1.48 yr-1 to F= 2.92 yr-1, compared to Fopt = 0.4M) were beyond the limit for sustainable fishing. Consequently, the estimated exploitation rates (E) for majority of the assessed fish species ranging from 0.53 to 0.76 were greater than the optimum level of 0.5, implying heavy exploitation. Further, the calculated lengths at first capture (Lc) (3.71 cm – 13.19 cm) were less than the calculated lengths at first maturity (Lm) (7.4 cm – 17.9 cm) indicating the presence of growth overfishing. It was concluded that the overall security of coastal fishing operations was under very high risk requiring urgent management attention. Some recommendations for effective management have been provided including initiating community sensitization programmes and partition of marine patrols between Ghana Navy and Ghana Marine Police.