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Resilience of Coastal Systems and Their Human Partners: ecological and social profile of coastal systems in Kenya, Mozambique and Tanzania

  • The Nature Conservancy, Africa Region
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... New coastal developments (e.g. ports at Mtwara and Tanga in Tanzania, and Lamu in Kenya) pose a threat to the region's coastal ecosystems, mangroves and coral reefs (Samoilys et al. 2015). Recent studies have shown the importance of natural habitats to coastal protection (e.g. ...
The taxonomic history of the genus Manta has been questionable and convoluted, with Manta having one of the most extensive generic and species synonymies of any living genus of cartilaginous fish. Having previously been considered a monotypic genus with a single recognized species, Manta birostris (Walbaum 1792), new evidence, in the form of morphological and meristic data, confirm that two visually distinct species occur, both with wide ranging distributions through many of the world’s oceans. Manta birostris stands as the most widely distributed member of the genus, while Manta alfredi (Krefft 1868), resurrected herein, represents a smaller, more tropical species. Separation of the two species is based on morphometric measurements and external characters including colouration, dentition, denticle and spine morphology, as well as size at maturity and maximum disc width. The two species of Manta are sympatric in some locations and allopatric in other regions. A visual key was constructed which highlights the conspicuous, diagnostic features of the two species using data collected throughout their respective geographical ranges. A third, putative species, referred to here as Manta sp. cf. birostris, in the Atlantic may be distinct from M. birostris, but further examination of specimens is necessary to clarify the taxonomic status of this variant manta ray. The results of this study will aid in the differentiation of members of this genus both in the field and in preserved specimens. The splitting of this long-standing monospecific genus will help to highlight the specific threats facing the different species of Manta (e.g. targeted fishing, bycatch fisheries, boat strikes and habitat degradation) and will ultimately assist in the correct assessment of their respective worldwide conservation status.
The ocean thermal history of the 1997-98 El Nino episode is described in detail, with emphasis on developments along the equator and eastern Pacific coastlines. The temporal evolution of the warming and its causes are traced from the western Pacific, past the Galapagos Islands and on to the subpolar gyres off North and South America. Along the equator, the event was characterized by a subsurface warm anomaly that slowly made its way from west to east across the Pacific from mid-1996 until early 1997, whence it triggered the onset of surface anomalies at the eastern terminus of the equatorial waveguide. The thermocline depression off Ecuador intensified from mid-1997 through the end of the year, culminating in a mature phase with maximum sea surface temperature anomalies (SSTA) around November-December 1997. The event gradually abated thereafter until the beginning of the subsequent cool phase (La Nina) was detected in July 1998. Following their arrivals at the eastern boundary, equatorial Kelvin waves proceeded poleward into both hemispheres as coastal trapped waves, carrying the thermocline depression signal with them along with associated nutrient deficiencies and ecosystem impacts. The poleward propagation of SSTA was more uniform and faster south of the equator, reaching south-central Chile with amplitudes of 2 degreesC or greater. North of the equator the propagation was discontinuous, with decreased anomalies south of 20 degreesN and a revival of SSTA in excess of 2 degreesC, north of there, but with considerably larger time lags than observed off Chile. The possible reasons for these interhemispheric differences are discussed. The magnitude of the event is also discussed in an historical context, with emphasis on comparisons to the El Nino of 1982-83. Each of the two events, in its own way, set records. However, the two events are generally comparable in their magnitudes and the extent of their impacts, while both are top-ranked events for the period after 1950. In the centennial context, however, these events are not unprecedented, considering that they were probably enhanced by strong decadal warming during the 1980s and 1990s. An attempt is made to assess the accuracy of model forecasts of the 1997-98 event. Two recent studies are discussed which generally agree that statistical and dynamical models under-predicted the equatorial warming prior to its onset and failed to capture the strong, early onset at all. Predictions of the late-1997 climax, with shorter lead times, improved once the data showing large mid- 1997 anomalies were ingested into the models. However, the revised predictions were not in time to guide the successful atmospheric climate outlook for North America, which was issued in June 1997 on the basis of observed strong anomalies on the equator.
The evolutions of ENSO modes in the seasonal rainfall patterns over East Africa are examined in this study. The study covers the period 1961-1990. Both rotated empirical orthogonal function (EOF) and simple correlation analyses were used to delineate a network of 136 stations over East Africa into homogeneous rainfall regions in order to derive rainfall indices. Time series generated from the delineated regions were later used in the rainfall/ENSO analyses. Such analyses involved the development of composite rainfall map patterns for El Nino and post-ENSO (fl) years in order to investigate the associations between seasonal evolution of El Nino-Southern Oscillation (ENSO) signals and the space-time evolution of rainfall anomalies over the region. Analyses based on both EOF and simple correlation techniques yielded eight homogeneous rainfall regions over East Africa. The results showed unique seasonal evolution patterns in rainfall during the different phases of the ENSO cycles. East African rainfall performance characteristics were stratified to identify distinct rainfall anomaly patterns associated with ENSO and post-ENSO (+ 1) years. These can be applied in conjunction with skilful long lead (up to 12 months) ENSO prediction to provide guidance on likely patterns of seasonal rainfall anomalies over the region. Such information can be crucial for early warning of socio-economic disasters associated with extreme rainfall anomalies over East Africa. Copyright (C) 2000 Royal Meteorological Society.
Distribution records of white sharks in the tropical southwest Indian Ocean are both sparse and speculative. This paper provides the first confirmed records of white sharks from four localities in the region. A male white shark of about 5 m total length was taken by a fisheries vessel off Le Morne on the island of Mauritius in 1971. A white shark over 4 m long was caught at Matemwe Beach, Zanzibar, in 1993. A female white shark, estimated at 3.8 m, was taken in an artisanal net fishery near Antsiranana, in the Baie de Diego Suarez on the northeastern tip of Madagascar in 1994. A pregnant white shark, reported at 6.4 m, was taken in an artisanal net fishery near Malindi, Kenya, in 1996. At least seven embryos, 1.1 m long and weighing 10-20 kg, were found. White sharks in the tropical Indian Ocean may be predominantly large, possibly mature, specimens. Their occurrence in oceanic island waters may facilitate trans-oceanic movements, which has important consequences for the conservation and management of this species.