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Trainer V.L.,National Oceanic and Atmospheric Administration | Pitcher G.C.,South African Department of Environmental Affairs and Tourism | Pitcher G.C.,University of Cape Town | Reguera B.,Spanish Institute of Oceanography | Smayda T.J.,University of Rhode Island
Progress in Oceanography | Year: 2010

Comparison of harmful algal bloom (HAB) species in eastern boundary upwelling systems, specifically species composition, bloom densities, toxin concentrations and impacts are likely to contribute to understanding these phenomena. We identify and describe HABs in the California, Canary, Benguela and Humboldt Current systems, including those that can cause the poisoning syndromes in humans called paralytic shellfish poisoning (PSP), diarrhetic shellfish poisoning (DSP), and amnesic shellfish poisoning (ASP), as well as yessotoxins, ichthyotoxins, and high-biomass blooms resulting in hypoxia and anoxia. Such comparisons will allow identification of parameters, some unique to upwelling systems and others not, that contribute to the development of these harmful blooms. Source

Pitcher G.C.,South African Department of Environmental Affairs and Tourism | Pitcher G.C.,University of Cape Town | Figueiras F.G.,CSIC - Institute of Marine Research | Hickey B.M.,University of Washington | Moita M.T.,Institute Investigacao das Pescas e do Mar IPIMAR
Progress in Oceanography | Year: 2010

The upwelling systems of the eastern boundaries of the world's oceans are susceptible to harmful algal blooms (HABs) because they are highly productive, nutrient-rich environments, prone to high-biomass blooms. This review identifies those aspects of the physical environment important in the development of HABs in upwelling systems through description and comparison of bloom events in the Benguela, California and Iberia systems. HAB development is dictated by the influence of wind stress on the surface boundary layer through a combination of its influence on surface mixed-layer characteristics and shelf circulation patterns. The timing of HABs is controlled by windstress fluctuations and buoyancy inputs at the seasonal, event and interannual scales. Within this temporal framework, various mesoscale features that interrupt typical upwelling circulation patterns, determine the spatial distribution of HABs. The inner shelf in particular provides a mosaic of shifting habitats, some of which favour HABs. Changes in coastline configuration and orientation, and bottom topography are important in determining the distribution of HABs through their influence on water stratification and retention. A spectrum of coastline configurations, including headlands, capes, peninsulas, Rías, bays and estuaries, representing systems of increasing isolation from the open coast and consequent increasing retention times, are assessed in terms of their vulnerability to HABs. © 2010 Elsevier Ltd. All rights reserved. Source

Pichegru L.,Percy FitzPatrick Institute | Gremillet D.,CNRS Center of Evolutionary and Functional Ecology | Crawford R.J.M.,University of Cape Town | Crawford R.J.M.,South African Department of Environmental Affairs and Tourism | Ryan P.G.,Percy FitzPatrick Institute
Biology Letters | Year: 2010

No-take zones may protect populations of targeted marine species and restore the integrity of marine ecosystems, but it is unclear whether they benefit top predators that rely on mobile pelagic fishes. In South Africa, foraging effort of breeding African penguins decreased by 30 per cent within three months of closing a 20 km zone to the competing purse-seine fisheries around their largest colony. After the fishing ban, most of the penguins from this island had shifted their feeding effort inside the closed area. Birds breeding at another colony situated 50 km away, whose fishing grounds remained open to fishing, increased their foraging effort during the same period. This demonstrates the immediate benefit of a relatively small no-take zone for a marine top predator relying on pelagic prey. Selecting such small protected areas may be an important first conservation step, minimizing stakeholder conflicts and easing compliance, while ensuring benefit for the ecosystems within these habitats. © 2010 The Royal Society. Source

Hutchings K.,University of Cape Town | Griffiths M.H.,South African Department of Environmental Affairs and Tourism
African Journal of Marine Science | Year: 2010

Biological data for Umbrina robinsoni were obtained from fish sampled monthly during 2001-2002 by shore-angling in the warm-temperate De Hoop Marine Protected Area (MPA) (n = 312), and by means of spearfishing during three trips (May, September and January 2001-2002) in the Kosi Bay region of the subtropical Maputaland MPA (n = 354). Annuli in otolith sections were validated by means of marginal increment analyses and fluorochrome marking (oxytetracycline). Maximum ages recorded were 12 and 16 years at Kosi Bay and De Hoop respectively. Kosi Bay fish obtained a significantly greater asymptotic length than De Hoop fish and mean length-at-age (for ages 2-10 years) was significantly greater. The fitted von Bertalanffy growth equations for combined sexes were: Lt = 594 (1 - e-0.183 (t + 2.42)) for De Hoop and Lt = 875 (1 - e-0.151 (t + 2.49)) for Kosi Bay. Trends in mean monthly gonadosomatic indices and proportions of histologically validated macroscopic gonad stages indicated a summer spawning season (November-February) at De Hoop and year-round spawning at Kosi Bay. Relative condition peaked in both spring and autumn at De Hoop but showed little seasonal variation in the Kosi Bay region. Kosi Bay females attained 50% sexual maturity at a significantly larger size (48 vs 39 cm) but at younger age (2.8 vs 3.4 years) than those at De Hoop. Analysis of maturity schedules indicates that current sizes at maturity are plastic responses that maximise lifetime fecundity within local regimes of somatic growth and natural mortality. The instantaneous rate of natural mortality was substantially higher at Kosi Bay than at De Hoop (M = 0.35 vs M = 0.26). © NISC (Pty) Ltd. Source

Soule M.A.,Fisheries Resource Surveys Cc | Hampton I.,Fisheries Resource Surveys Cc | Lipinski M.R.,South African Department of Environmental Affairs and Tourism
ICES Journal of Marine Science | Year: 2010

Estimates of the target strength (TS) of the loliginid squid Loligo reynaudii at 120 kHz were made from ex situ experiments on 38 caged, but free-swimming animals, and at 38 and 120 kHz from 17 in situ experiments on spawning aggregations in the wild conducted from a research vessel and from small boats. The cage experiments suggested that the backscattering cross section is proportional to mantle length (ML), which would not be expected from simple considerations of ML in relation to wavelength. A similar relationship was found during the in situ experiments conducted from the research vessel. The TS estimates from the research vessel agreed well with those from the cage experiments, for both of the two methods used to extract squid TS distributions from the overall TS distributions, but were some 2-3 dB lower than those from the small boats. This suggests that in situ estimates are affected by the vessel and/or the way in which squid react to it. It is concluded that ex situ experiments on L. reynaudii TS are of most value as a complement to in situ experiments, which should be made concurrently while surveying, using systems capable of having higher volume resolution than in the current experiments, to maximize the applicability of the estimates to the survey data. © 2010 International Council for the Exploration of the Sea. Published by Oxford Journals. All rights reserved. Source

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