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Aspects of the reproductive biology of the brown mussel Perna perna at the Iture rocky beach near Cape Coast, Ghana, were studied from September 2014 to August 2015. The current study was aimed at providing information useful for managing the mussel fishery in this locality and also that would form the basis for designing appropriate culture methods for the species. Microscopic examination of fresh smears of gonadal material, as well as histological preparations of the gonad, were used to study the sexuality and breeding pattern of the species. Monthly gonadal and condition indices were also determined. Perna perna exhibited gonochoristic sexuality with a sex ratio of approximately 1:1 throughout the study period. Sexes were identifiable at shell lengths of 15.0–19.9 mm. Five stages of gonadal development were identified in both sexes. Gametogenic activity was continuous throughout the year, with two major spawning activities, from April to June and from August to December. These periods coincided with the major and minor rainy seasons, respectively, as well as the major upwelling period in August. Condition indices suggest that the mussels were in better condition for harvesting in March and August prior to the major spawning events. 相似文献
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Paul William Kojo Yankson Alex Barimah Owusu George Owusu John Boakye-Danquah Jacob Doku Tetteh 《Natural Hazards》2017,85(2):691-707
In this paper, the extent to which the potentially transit-dependent portion of the population is vulnerable to the effects of a hurricane is estimated. The vulnerability of an area is defined as a composite measure of the proportion of disadvantaged persons, distance to transit, and flooding potential of people within an area. Unlike past studies which have focused on the vulnerability of the population in relatively large geographic areas, this study estimates the vulnerability of the population in 30 m × 30 m areas as defined in the National Land Cover Database. Population estimates from the national census at block level are disaggregated to the 30 m × 30 m units using a modified dasymetric mapping method in ArcGIS. The modified mapping method assigns population to each small areal unit using weights estimated by regressing the area of each land use in a census block against the population in that block. The coefficients in the regression analysis are “weights” associating population with each land use, and are used to distribute the population in each census block to the small geographic units based on their land use. In a case study of New Orleans, the results show that some areas are not well served by the existing transit pickup locations, as evidenced by their high vulnerability scores. Reassignment of pickup point locations to cover higher vulnerability score areas was investigated using integer linear programming. The results show that the optimally located pickup points serve areas with a larger average vulnerability score than the current pickup points in the study area. The method appears to be helpful in identifying vulnerable areas that, subsequently, could receive improved hurricane evacuation service in the future. 相似文献
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Paul W.K. Yankson 《Singapore journal of tropical geography》2000,21(2):200-214
House-based enterprises (HBEs) as well as small enterprises located in residential neighbourhoods are common to all urban areas of developing countries, especially low-income residential neighbourhoods. In Accra, the capital city of Ghana, there is an increasing use of houses and residential neighbourhoods as places of work. A survey of small-scale production and service-oriented enterprises located in three low income residential areas in Accra examines three issues: space use, growth patterns, and health and environmental effects. The study found that although HBEs derived some advantages from being sited in houses and in residential neighbourhoods, half of the sampled operators would have preferred to locate their business outside the residential neighbourhood in order to attract more customers, overcome the problem of inadequate workspace and to expand their enterprises. Most of the sampled enterprises had no appreciable growth over time. Enterprises had unintended negative health and environmental consequences on the operators, their workers and also on the house and residential environment in general. These effects tended to compound the already serious household environmental conditions in low-income residential neighbourhoods. The paper offers some suggestions to improve the accommodation of HBEs in order to promote business growth and ultimately to reduce the health and environmental impacts. 相似文献
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Spatial and social transformations in a secondary city: the role of mobility in Sekondi-Takoradi,Ghana 总被引：1，自引：1，他引：0
Paul W. K. Yankson Katherine V. Gough James Esson Ebenezer F. Amankwaa 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2017,117(2):82-92
AbstractExisting research on urban Ghana mainly focuses on processes occurring within the country’s major cities, thereby reproducing a trend within the social sciences to overlook the role of intermediate and secondary cities. This paper aims to address this shortcoming by exploring spatial and social transformations in Sekondi–Takoradi, one of Ghana’s secondary cities and the metropolitan area serving the region’s emerging rubber industries as well as the country’s oil and gas economy. Using qualitative interviews conducted with residents in five of the city’s neighbourhoods, and a modified version of Kaufmann’s typology of mobility, we examine migration into Sekondi–Takoradi, residential mobility within the city and the daily mobility of the city’s residents. The paper highlights how these diverse forms of mobility interact with processes taking place both within and outside Sekondi–Takoradi, most notably influencing and being influenced by livelihood strategies. It is argued that the city and its hinterlands can best be envisaged as a mobile networked whole, rather than consisting of disconnected and compartmentalized locales. The paper thus contributes to broader debates on how mobility shapes urbanization by providing new empirical data on events unfolding in Africa’s secondary cities, and extends existing research by providing a counter-narrative to literature that examines the city and its surrounding rural areas separately. 相似文献
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Gerald Atampugre De-Valera N. Y. M. Botchway Kobina Esia-Donkoh Stephen Kendie 《GeoJournal》2016,81(3):367-378
Ghana is endowed with surface and ground water resources. These resources prior to the colonial era were managed by traditional societies through various conventional methods embedded in their cosmovision. However during the colonial and postcolonial regimes, in response to climate change, economic globalization, and population pressure, there has been a conscious shift from customary water management systems towards paradigms cast in the contemporary mould (legislation, policies, and institutions). These modern approaches have been shown over the years to be insufficient in ensuring water sustainability. This insufficiency manifests itself in the increasing water scarcity through anthropogenic-induced water resources degradation and severe climatic variability. Using content analysis, this paper reviews this transition, first to fully understand the intricacies of the evolution and second to draw lessons for better water resources management in Ghana. This paper contends that although Ghana’s water related institutions, laws, and policies are undergoing significant reforms, implementation and practice remains embedded in weak ecological modernization (EM). Institutionalizing a narrow conception of EM will only perpetuate ‘organized irresponsibility’ and permit the continued production of ecological problems, leaving open the question of whether modernization is compatible with ecological sustainability. Though customary water management approaches are not entirely devoid of limitations, simply branding them as obsolete may obviate an important vehicle for water sustainability. In the spirit paradigmatic complementarity, ecosystem-friendly indigenous approaches must be integrated with contemporary management systems for the long term goal of sustainability. 相似文献
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The brown mussel, Perna perna, is an ecologically important species which has a great potential for aquaculture in Ghana. Though it is harvested from the wild for consumption locally, there is no information on its population parameters to guide its management and subsequent culturing. The species inhabiting Iture rocky beach near Cape Coast (Ghana) was therefore investigated to elucidate its growth and other population parameters. Specimens had shell length ranging from 5.00 to 78.0 mm, a modal shell length class of 35.0–39.9 mm, and exhibited negative allometric growth. The asymptotic length (L∞), growth coefficient (K), and growth performance index (Φ') were 80.10 mm, 0.49 per year, and 3.49, respectively. The recruitment pattern showed that P. perna has year-round recruitment with a single peak between April and July. Total mortality (Z) was estimated at 2.79 per year, while natural mortality (M) and fishing mortality (F) were 0.87 and 1.92 per year, respectively. The calculated exploitation level of the population (E = 0.69) suggests possible overfishing of the mussels at Iture rocky beach. These results could serve as baseline information for management of the mussel population in Ghana. 相似文献
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Lasse Møller-Jensen Richard Y. Kofie Paul W. K. Yankson 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):39-47
Geografisk Tidsskrift, Danish Journal of Geography 105(2):39–47, 2005 A multi-scale classification algorithm based entirely on computation of image texture in moving windows is presented and discussed. The rationale for using kernel-based methods as opposed to segment-based methods for texture-based land cover classification is discussed, as well as, the need for identifying strategies that may limit the effects of the inherent weaknesses of the kernel-based methods. Part of the proposed solution to this problem is to omit the search for an optimum kernel size and rather use different sizes concurrently followed by a weighted summary overlay process based on associated scores. The spatial growth pattern of the city of Accra, Ghana, is assessed over a 17 years period using the algorithm. Land-cover maps showing the extension of the new residential areas on the fringe of Accra are produced from Landsat ETM satellite imagery. These areas constitute the rapidly expanding frontier of urban Accra into its rural surroundings. The classification discriminates between new residential areas that have a distinct urban appearance and areas that are in a transition phase between rural and urban use. Finally, comparisons are made to a previous satellite-based study of land cover changes for the period 1985–1991. 相似文献
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Paul William Kojo Yankson Alex Barimah Owusu George Owusu John Boakye-Danquah Jacob Doku Tetteh 《Natural Hazards》2017,89(2):661-689
Coastal towns along the coast of Africa are among the most vulnerable to climate change impacts such as flooding and sea level rise. Yet, because coastal conditions in many parts of the region are poorly understood, knowledge on which population groups are at the most risk is less known, particularly in the Greater Accra Metropolitan Area (GAMA) of Ghana, where the capital city Accra is located. Without adequate information about the risk levels and why, the implementation of locally appropriate adaptation plans may be less effective. This study enriches our understanding of the levels of flood risks along the coast of GAMA and contributes knowledge to improve understanding of place-specific adaptation plans. The study uses data from a 300-household survey, stakeholder meetings, and interviews with local community leaders to construct an integrated vulnerability index. The index includes seven components made up of: dwelling type; house and house environment; household socioeconomic characteristics; experience and perception of flood risk; household and community flood adaptation strategies; house location, and physical characteristics. Our findings show that exposure to floods, particularly from local flash floods is relatively high in all communities. However, significant differences in sensitivity and adaptive capacity of the communities were observed due to differences in location, socioeconomic characteristics, and perception of risks to flooding and sea level rise. The complexity of factors involved in the determination of local-level vulnerability requires that the implementation of adaptation strategies needs to involve cross-sectorial partnerships, involving local communities, in building a comprehensive multi-risk adaptation strategy. 相似文献
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