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Management of the linefish resource in Southern Mozambique : a case study for Marreco (Chrysoblephus puniceus).Lichucha, Ivone Delfina Lourenco Tivane. January 2001 (has links)
This study provides information on the biology, stock status and the management of C.
puniceus, a key linefish resource in southern Mozambique. This is regionally endemic to
Mozambique and KwaZulu-Natal. Fairly resident species, is found on the continental
shelf ranging north to Zavora and south to KwaZulu-Natal and Transkei, and inhabits
rocky seabeds, ranging between 20 and l00m. In Mozambique is manly exploited by
semi-industrial fleet, and exported to South Africa.
The reproductive biology, assessed through gonad somatic index as well as microscopic
and macroscopic assessment, indicates that spawning extends over the spring months
from August to November, peaking in September. It is a protogynous hermaphrodite,
relatively slow growing and long lived species.
The length-weight relationships for male and female C. puniceus show to be different,
and the overall length frequency distribution shows clear difference in size between male
and female C. puniceus, with male length frequency distribution restricted to the larger
size classes. The monthly length frequency distribution of female C. puniceus is
unimodal and peak at 300 mm FL, male shows unclear year classes.
Age determination was carried out using otoliths and growth was estimated using the
model developed by Punt et al (1993) for protogynous hermaphrodites reproductive
styles. Validation of annuli was done by examining the outer margin of otolith, and also
through mark and recapture information. Validation following the first method indicated
that the opaque band is laid down twice a year, but the mark recapture results were
inconsistent. This contradicts previously published information on C. puniceus, and thus;
both single and double scenarios were modelled. The Von Bertalanffy growth parameters
found for C. puniceus suggest relatively slow-growth, with the number of rings found
from reading the sectioned otolith ranging from 2 to 18. Reproducibility of age estimates
was evaluated using the average percentage error (APE) technique, and was equal to
22%. The age at full recruitment was found to be 2.5 and 5 years for bi-annual and annual banding, respectively. The analysis of the age-at-50% maturity, based on double band
scenario, suggests that C. puniceus mature at 1.5 year-old, which corresponds to a mean
FL of 240mm.
A preliminary yield per recruit assessment revealed that at the current fishing mortality,
C. puniceus fishery is moderately overfished, with the spawning biomass-per-recruit at
35.43% and 36.57%, for one and two bands, respectively, of its unexploited level.
Fishing mortality was equal to 0.2 year-1 and 0.41 year-1, for single and double band,
respectively. YPR analysis shows that the single band scenario is less conservative than
the double band assessment, which has a bearing on the management approach.
It is suggested as the preliminary management strategy a reduction of the number of
boats. Indeed the average number of crew per boat, needs to be evaluated in terms of
overall effort. To complement this management measures, there is a strong and urgent
need to establish marine reserves in order to protect spawning stock, and also, to develop
an overall linefish management plan, which will help in the management of the whole
linefish resource in Mozambique. Furthermore, an age and growth study for C. puniceus
over a larger geographical area needs to be done as a mean to overcome the differences
between previous study and this study, once C. puniceus is being shared between the two
countries (Mozambique and KwaZulu-Natal). / Thesis (M.Sc.)-University of Natal, Durban, 2001.
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Numerical Analysis of Convective Storm Development over MaldivesShareef, Ali January 2009 (has links)
In the Asian and other monsoon regions of the world most of the severe weather observed is local or mesoscale in nature. Forecasting convective storms or mesoscale systems in the monsoon regions, especially in the tropics, has always been a challenging task to operational meteorologists.
Maldives Islands, being situated in the tropical Indian Ocean, are affected by monsoon depressions and tropical cyclones. Thunderstorms and the passage of squall lines are well known sources of heavy rainfall. However, due to the lack of professional people and necessary equipment the weather systems around these islands are seldom studied. Therefore the aim of this thesis is to investigate whether the small islands can create sufficient perturbations in the mesoscale environment to result in the development of convective systems. In this regard, two numerical models, Weather Research and Forecasting model (WRF version 2.2.1) and Regional Atmospheric Modelling System (RAMS version 6.0) were used in this study.
Two experiments were performed using the WRF model. In the first experiment, a case study was investigated where the selected day experienced heavy rainfall and thunderstorms. In the second experiment, the same case study was used but with the topographical and surface properties removed in order to investigate the influence of the island in modifying the mesoscale environment. All the experiments were initialized using the re-analysis data from NECP. WRF was able to predict the large scale synoptic features with reasonable accuracy when compared to the observations. Development of the boundary layer and the downstream advection of the temperature anomaly generated by the island were well represented. However, the magnitude of the effects was shown to be weak, probably due to the influence of large scale synoptic features. Even though the model was able to predict the large scale features and some of the mesoscale features, it did not predict any storm development and underestimated the precipitation. Therefore, it was decided to idealize the storm development using the RAMS model.
RAMS model was used in a two-dimensional framework. The model was initialized horizontally homogenous using a single sounding and six simulations were performed. The simulation results clearly depicted that the small island can generate its own circulation and influence the mesoscale environment. The daytime heating of the island and the downstream advection of the temperature anomaly in a moist unstable atmosphere could trigger a thunderstorm later in the day. The storm becomes mature approximately 40-80 km offshore. This also suggests that triggering of a storm on one side of an atoll could influence the islands on the downstream side. Sensitivity of storm development to the thermodynamics showed that even with an unstable atmosphere, enough moisture in the lower and mid-troposphere is needed to trigger the storm. Sensitivity to the change of SST showed that convective development was suppressed with a drop of 1 oC. However, this needs further investigation. Assessment of sensitivity to the size of the island showed that the time of triggering of the storm was later and the scale of influence was smaller with a smaller island.
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A Sea of Debt: Histories of Commerce and Obligation in the Indian Ocean, c. 1850-1940Bishara, Fahad Ahmad January 2012 (has links)
<p>This dissertation is a legal history of debt and economic life in the Indian Ocean during the nineteenth and early-twentieth century. It draws on materials from Bahrain, Muscat, Bombay, Zanzibar and London to examine how members of an ocean-wide commercial society constructed relationships of economic mutualism with one another by mobilizing debt and credit. It further explores how they expressed their debt relationships through legal idioms, and how they mobilized commercial and legal instruments to adapt to the emergence of modern capitalism in the region.</p><p>At the same time, it looks at the concomitant development of an Indian Ocean-wide empire of law centered at Bombay, and explores how this Indian Ocean contractual culture encountered an Anglo-Indian legal regime that conceived of legal documents in a radically different way. By mobilizing written deeds in imaginative ways, and by strategically accessing British courts, Indian Ocean merchants were able to shape the contours of this growing legal regime.</p><p>Most broadly, the dissertation argues that law and courts became increasingly central to economic life in the Indian Ocean, and that economic actors in the region employed a wide range of different legal strategies in adapting to a changing world of commerce. In the Indian Ocean, as elsewhere, the histories of commerce and law were inextricably intertwined.</p> / Dissertation
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Testing hypotheses with regard to measurement of primary productivity by 14C techniques: International Indian Ocean ExpeditionNewhouse, Jan January 1967 (has links)
Typescript. / Thesis (Ph. D.)--University of Hawaii. 1967. / Bibliography: leaves 211-218. / xi, 218 l illus., maps, tables
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Habitat structure, degradation and management effects on coral reef fish communitiesYahya, Saleh A.S. January 2011 (has links)
Coral reefs are among the most diverse and productive ecosystems on earth, and are critical to the survival of tropical marine ecosystems and sustenance of local human populations. However, coral reefs are quite vulnerable to disturbances, both natural and anthropogenic. This thesis looks at how coral reef communities have responded to climactic disturbances, particularly the 1997-98 El Niño Southern Oscillation (ENSO) and subsequent coral bleaching and mortality that affected much of the Indian Ocean, including the coastal waters of Tanzania, where the study was conducted. In particular, it investigates the effects of coral bleaching, habitat degradation and reef spatial arrangement on reef fish assemblages. Habitat structural complexity and spatial arrangement of reefs had an effect on reef fish communities. Fish communities showed patterns in distribution among habitats and between patch and continuous reefs. Fishes preferred live to bleached/dead or eroded coral, but trophic groups reacted differently to patch and continuous reefs. There were slight changes in fish abundance and significant changes in fish diversity on experimental, bleached branching Acropora coral plots over a period of one year. While fish abundance on one site increased shortly after a bleaching event, 6 years later fish abundance had decreased significantly. Conversely, coral reef communities in northern Tanzania had changed little over an 8-year period, with minor changes associated with the 1997-98 ENSO and the presence or absence of fisheries management. The coral reefs in the region were found to show high variability in community structure and responses of associated fish and invertebrate communities. The findings of this thesis indicate the importance of habitat structure and spatial arrangement of reefs, the detrimental effects of coral bleaching, and the possibility that some reefs and some (generalist) reef fish taxa may exhibit resilience to climate change. / At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 3: Manuscript. Paper 4: Manuscript.
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Reproduction and recruitment of scleractinian corals on equatorial reefs in Mombasa, KenyaMangubhai, Sangeeta Unknown Date (has links)
This study examined patterns of coral reproduction and recruitment on lagoonal reefs adjacent to Mombasa in Kenya, at latitude 4ºS. Very little detailed research has been done on the reproductive patterns of scleractinian corals on equatorial reefs, where it has been suggested that seasonality and spawning synchrony may break down due to the weak environmental cues that are thought to govern the onset and timing of reproduction. Gametogenic data were collected for three faviid (Echinopora gemmacea, Platygyra daedalea and Leptoria phrygia) and three Acropora species (A. tenuis, A. valida and Acropora sp.1) in the Mombasa Marine National Park and Reserve between April 2003 – May 2005. A further 20 species of Acropora were identified (9 species represented range extensions) and marked to examine intra- and inter-specific spawning synchrony within this genus. In comparison to other regions, the overall pattern of coral reproduction in Kenya was found to be asynchronous, with spawning occurring over 9 months of the year from August – April, with some level of ‘temporal reproductive isolation’ occurring between species in relation to the main lunar month and lunar quarter when spawning occurred. Proximate cues governing the timing of reproduction could not be clearly discerned in Kenya with spawning occurring during both rising and maximum temperatures, during both neap and spring tides and across all lunar phases. Acropora species spawned over a 7-month period between October – April and faviid species over a 5-month period from December - April. The timing of reproduction in Acropora varied both within and among species, with the main release of gametes occurring from January – March when sea surface temperatures were at their summer maximum. Individual species released gametes over 2-5 months. The greatest overlap in spawning Acropora species occurred in February, which coincided with the spawning months of P. daedalea and E. gemmacea and suggests that some degree of multispecific spawning is a characteristic of Kenyan reefs. Within the main spawning period individual Acropora species had their main spawning in different lunar months. Acropora species released gametes in all lunar quarters, with the highest number of colonies and species spawning in the 3rd lunar quarter (i.e. in the 7 nights after full moon). Spawning in the faviids was more synchronised than Acropora species with the majority of faviid corals spawning in the 3rd lunar quarter. Single annual cycles of gametogenesis were recorded in E. gemmacea, A. tenuis, L.phrygia, most colonies of A. valida and Acropora sp.1, and in 84% of P. daedalea colonies. Biannual cycles of gametogenesis were recorded in 16% of P.daedalea colonies, which included two morphotypes identified in the Mombasa lagoon through morphometric and genetic studies. The presence of different oocyte sizes in L.phrygia during gametogenesis suggested that in some colonies there were two slightly overlapping oogenic cycles, which terminated in spawning within 1-2 months of each other. Overlapping oogenic cycles have not previously been recorded in hermaphroditic broadcast spawning corals in the tropics. The findings from Kenya support the hypothesis of protracted breeding seasons and a breakdown of spawning synchrony nearer the equator. It is hypothesised that the high fecundities recorded in faviid and Acropora species in Kenya compared to other regions, may allow reef corals to stagger their reproduction over 2-5 months, without incurring a significant reduction in fertilisation rates. Spat from the Family Pocilloporidae dominated settlement tiles in the Marine National Park and Reserve comprising 93.7% of spat, which contrasts with other tropical reefs where Acroporidae spat dominate. Patterns of settlement of Acroporidae spat generally coincided with the timing and extended spawning season in Acropora species in Kenya. The density and relative composition of coral recruits and juvenile corals on natural substrata recorded during this study were similar to those recorded before the 1997-98 bleaching event. There is no evidence to suggest that Kenya’s reefs have undergone a phase-shift in community structure, and reef recovery is occurring post-bleaching with mean percent hard coral cover currently at 25%. The slow rate of recovery of Kenya’s reefs is likely to reflect the scale of the mortality, source and availability of coral larvae as well as post-settlement processes operating at individual sites. In the medium-term, the recovery of Kenya’s reefs appears to be more strongly dependent on larvae from local reefs.
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Reproduction and recruitment of scleractinian corals on equatorial reefs in Mombasa, KenyaMangubhai, Sangeeta Unknown Date (has links)
This study examined patterns of coral reproduction and recruitment on lagoonal reefs adjacent to Mombasa in Kenya, at latitude 4ºS. Very little detailed research has been done on the reproductive patterns of scleractinian corals on equatorial reefs, where it has been suggested that seasonality and spawning synchrony may break down due to the weak environmental cues that are thought to govern the onset and timing of reproduction. Gametogenic data were collected for three faviid (Echinopora gemmacea, Platygyra daedalea and Leptoria phrygia) and three Acropora species (A. tenuis, A. valida and Acropora sp.1) in the Mombasa Marine National Park and Reserve between April 2003 – May 2005. A further 20 species of Acropora were identified (9 species represented range extensions) and marked to examine intra- and inter-specific spawning synchrony within this genus. In comparison to other regions, the overall pattern of coral reproduction in Kenya was found to be asynchronous, with spawning occurring over 9 months of the year from August – April, with some level of ‘temporal reproductive isolation’ occurring between species in relation to the main lunar month and lunar quarter when spawning occurred. Proximate cues governing the timing of reproduction could not be clearly discerned in Kenya with spawning occurring during both rising and maximum temperatures, during both neap and spring tides and across all lunar phases. Acropora species spawned over a 7-month period between October – April and faviid species over a 5-month period from December - April. The timing of reproduction in Acropora varied both within and among species, with the main release of gametes occurring from January – March when sea surface temperatures were at their summer maximum. Individual species released gametes over 2-5 months. The greatest overlap in spawning Acropora species occurred in February, which coincided with the spawning months of P. daedalea and E. gemmacea and suggests that some degree of multispecific spawning is a characteristic of Kenyan reefs. Within the main spawning period individual Acropora species had their main spawning in different lunar months. Acropora species released gametes in all lunar quarters, with the highest number of colonies and species spawning in the 3rd lunar quarter (i.e. in the 7 nights after full moon). Spawning in the faviids was more synchronised than Acropora species with the majority of faviid corals spawning in the 3rd lunar quarter. Single annual cycles of gametogenesis were recorded in E. gemmacea, A. tenuis, L.phrygia, most colonies of A. valida and Acropora sp.1, and in 84% of P. daedalea colonies. Biannual cycles of gametogenesis were recorded in 16% of P.daedalea colonies, which included two morphotypes identified in the Mombasa lagoon through morphometric and genetic studies. The presence of different oocyte sizes in L.phrygia during gametogenesis suggested that in some colonies there were two slightly overlapping oogenic cycles, which terminated in spawning within 1-2 months of each other. Overlapping oogenic cycles have not previously been recorded in hermaphroditic broadcast spawning corals in the tropics. The findings from Kenya support the hypothesis of protracted breeding seasons and a breakdown of spawning synchrony nearer the equator. It is hypothesised that the high fecundities recorded in faviid and Acropora species in Kenya compared to other regions, may allow reef corals to stagger their reproduction over 2-5 months, without incurring a significant reduction in fertilisation rates. Spat from the Family Pocilloporidae dominated settlement tiles in the Marine National Park and Reserve comprising 93.7% of spat, which contrasts with other tropical reefs where Acroporidae spat dominate. Patterns of settlement of Acroporidae spat generally coincided with the timing and extended spawning season in Acropora species in Kenya. The density and relative composition of coral recruits and juvenile corals on natural substrata recorded during this study were similar to those recorded before the 1997-98 bleaching event. There is no evidence to suggest that Kenya’s reefs have undergone a phase-shift in community structure, and reef recovery is occurring post-bleaching with mean percent hard coral cover currently at 25%. The slow rate of recovery of Kenya’s reefs is likely to reflect the scale of the mortality, source and availability of coral larvae as well as post-settlement processes operating at individual sites. In the medium-term, the recovery of Kenya’s reefs appears to be more strongly dependent on larvae from local reefs.
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Numerical Analysis of Convective Storm Development over MaldivesShareef, Ali January 2009 (has links)
In the Asian and other monsoon regions of the world most of the severe weather observed is local or mesoscale in nature. Forecasting convective storms or mesoscale systems in the monsoon regions, especially in the tropics, has always been a challenging task to operational meteorologists. Maldives Islands, being situated in the tropical Indian Ocean, are affected by monsoon depressions and tropical cyclones. Thunderstorms and the passage of squall lines are well known sources of heavy rainfall. However, due to the lack of professional people and necessary equipment the weather systems around these islands are seldom studied. Therefore the aim of this thesis is to investigate whether the small islands can create sufficient perturbations in the mesoscale environment to result in the development of convective systems. In this regard, two numerical models, Weather Research and Forecasting model (WRF version 2.2.1) and Regional Atmospheric Modelling System (RAMS version 6.0) were used in this study. Two experiments were performed using the WRF model. In the first experiment, a case study was investigated where the selected day experienced heavy rainfall and thunderstorms. In the second experiment, the same case study was used but with the topographical and surface properties removed in order to investigate the influence of the island in modifying the mesoscale environment. All the experiments were initialized using the re-analysis data from NECP. WRF was able to predict the large scale synoptic features with reasonable accuracy when compared to the observations. Development of the boundary layer and the downstream advection of the temperature anomaly generated by the island were well represented. However, the magnitude of the effects was shown to be weak, probably due to the influence of large scale synoptic features. Even though the model was able to predict the large scale features and some of the mesoscale features, it did not predict any storm development and underestimated the precipitation. Therefore, it was decided to idealize the storm development using the RAMS model. RAMS model was used in a two-dimensional framework. The model was initialized horizontally homogenous using a single sounding and six simulations were performed. The simulation results clearly depicted that the small island can generate its own circulation and influence the mesoscale environment. The daytime heating of the island and the downstream advection of the temperature anomaly in a moist unstable atmosphere could trigger a thunderstorm later in the day. The storm becomes mature approximately 40-80 km offshore. This also suggests that triggering of a storm on one side of an atoll could influence the islands on the downstream side. Sensitivity of storm development to the thermodynamics showed that even with an unstable atmosphere, enough moisture in the lower and mid-troposphere is needed to trigger the storm. Sensitivity to the change of SST showed that convective development was suppressed with a drop of 1 oC. However, this needs further investigation. Assessment of sensitivity to the size of the island showed that the time of triggering of the storm was later and the scale of influence was smaller with a smaller island.
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Physical processes controlling circulation and frontal zones in Shark Bay, Western AustraliaNahas, Elizabeth Leila January 2005 (has links)
Shark Bay is a large inverse estuary, located in Western Australia. It has a number of unique habitats that support important species. The dynamics of circulation in Shark Bay have an influence on the species that inhabit the region, on small, local scales as well as on large Bay-wide scales. Numerical modeling and field data were used to examine small-scale dynamics in relation to an important recreational fish, pink snapper (Pagrus auratus). Icthyoplankton surveys collected and recorded egg density in regions where snapper are found. A barotropic three-dimensional hydrodynamic model was coupled with a two-dimensional Lagrangian particle-tracking program to simulate the passive transport of eggs through regions where spawning is known to occur. Circulation modeling results indicated residual flows on small scales that served to retain the eggs in the region where they were originally spawned. Results corroborate genetic work on adult snapper, which found no evidence intermixing of populations in Shark Bay. The numerical model was then further refined to run in a baroclinic mode. Simulations of salinity and temperature gradients were used to recreate frontal systems in Shark Bay. Frontal regions divide the Bay into a northern and a southern section as well as separate it from the ocean. Application of an analytical method for calculating front locations was consistent with the observed results and indicated that the primary forces determining frontal locations in the Bay are tides and gravitational circulation. Winds are a secondary influence, and solar heating is minimal in influence
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Explorations of social capital and physical activity participation among adults on Christmas IslandLee, Poh Chin January 2007 (has links)
[Truncated abstract] This research investigates social capital within the everyday space and actions of sociability on Christmas Island. The theory of social capital as proposed by Robert Putnam (1995) provides the framework for this investigation which was conducted in two phases. Quantitative and qualitative approaches and a mixed methods concurrent nested strategy were used in both phases of the investigation and the analyses. The analyses also incorporated multiple perspectives of both social capital and physical activity processes. In the first phase, I sought to: (a) uncover the determinants of social capital within the Christmas Island community; (b) develop a social capital typology; and (c) establish the relationship between the determinants of social capital and adults’ physical activity involvement. In all, 212 participants took part in the study . . . Overall, several factors affected women’s social capital and physical activity. These included: (a) women’s societal roles and positions; (b) household and cultural norms relating to gender-based time and space negotiations; (c) ideologies surrounding ethic of care; and (d) role commitment. These factors also influenced women’s recruitment into becoming active in their community. Network embeddedness and autonomy, assimilation and acculturation as well as language and knowledge competency further distinguished the community and physical activity status of European and Asian women. Analysis related to the two physical activity programmes in part 3 showed how various forms of latent social capital within the community can be synergized to produce physical activity benefits and empower inactive and minority-group women. Findings in this study also support trust as an important element in the establishment of relatedness in a physical activity setting.
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