South Africa

Augustyn, Johann; Cockcroft, A. C.; Kerwath, Sven E.; Lamberth, Stephen J.; Githaiga-Mwicigi, Jean; Pitcher, Grant C.; Roberts, Michael J.; Lingen, CD van der; Auerswald, Lutz

doi:10.1002/9781119154051.ch15

Cited by 12 publications

(10 citation statements)

References 88 publications

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“…These studies demonstrated the very clear need for implementation of a consistent sampling protocol with respect to sampling intervals and station locations to enable meaningful analyses of trends. Nevertheless, in the absence of any detected change in bottom oxygen concentrations, it is likely that the decline of rock lobsters on the west coast be attributed to an increase in events of episodic anoxia due to an increased occurrence of red tides (Augustyn et al, 2018).…”

Section: Known Trends and Susceptibility To Further Deoxygenationmentioning

confidence: 99%

System controls of coastal and open ocean oxygen depletion

Pitcher

Aguirre-Velarde

Breitburg

et al. 2021

Progress in Oceanography

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The epoch of the Anthropocene, a period during which human activity has been the dominant influence on climate and the environment, has witnessed a decline in oxygen concentrations and an expansion of oxygendepleted environments in both coastal and open ocean systems since the middle of the 20th century. This paper provides a review of system-specific drivers of low oxygen in a range of case studies representing marine systems in the open ocean, on continental shelves, in enclosed seas and in the coastal environment. Identification of similar and contrasting responses within and across system types and corresponding oxygen regimes is shown to be informative both in understanding and isolating key controlling processes and provides a sound basis for predicting change under anticipated future conditions. Case studies were selected to achieve a balance in system diversity and global coverage. Each case study describes system attributes, including the present-day oxygen environment and known trends in oxygen concentrations over time. Central to each case study is the identification of the physical and biogeochemical processes that determine oxygen concentrations through the tradeoff between ventilation and respiration. Spatial distributions of oxygen and time series of oxygen data provide the opportunity to identify trends in oxygen availability and have allowed various drivers of low oxygen to be distinguished through correlative and causative relationships. Deoxygenation results from a complex interplay of hydrographic and biogeochemical processes and the superposition of these processes, some additive and others subtractive, makes attribution to any particular driver challenging. System-specific models are therefore required to achieve a quantitative understanding of these processes and of the feedbacks between processes at varying scales.

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Section: Known Trends and Susceptibility To Further Deoxygenationmentioning

confidence: 99%

System controls of coastal and open ocean oxygen depletion

Pitcher

Aguirre-Velarde

Breitburg

et al. 2021

Progress in Oceanography

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“…The one exception is yellowtail, which has successfully recovered from collapse following the closure of the purse-seine fishery in the early 1980s. Diminishing returns in the commercial line-fishery have been exacerbated by an increase in storminess and a drop in the number of days that the fleet can fish (Augustyn et al, 2017). To partly compensate for declining yields and accommodate demand for participation in commercial fisheries, new resources are currently being explored, e.g., through an experimental octopus fishery.…”

Section: Biologymentioning

confidence: 99%

A synthesis of three decades of socio-ecological change in False Bay, South Africa: setting the scene for multidisciplinary research and management

Pfaff

Logston

Raemaekers

et al. 2019

Elementa: Science of the Anthropocene

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“…This is particularly important as the environmental conditions influence the squid life cycle and catches (e.g., Roberts, 2005;Jury, 2019). Moreover, changes in small pelagic fish species (anchovy and sardine), attributed to environmental factors, were observed off the south coast of Africa during 2013 (Augustyn et al, 2017), which further favours the hypothesis of environmental change affecting the pelagic species' abundance. Although efforts towards a more sustainable management strategy of the squid resource have been on-going (Augustyn et al, 1992;Zantsi et al, 2013;Mwicigi et al, 2018), no studies have examined the influence of long-term environmental changes on the squid catches based on observations, and very few model-based investigations have attempted to address the squid catch declines.…”

Section: Introductionmentioning

confidence: 99%

“…Despite the fishing effort control measures implemented since the late 1980s (Zantsi et al, 2013;DAFF., 2013), the squid catch declined to extremely low levels in 2013, impacting many fishers' income and employment (Joyner, 2015;Mthembu, 2019). Overexploitation and environmental controls have since been debated as potential causes of the squid fish stocks crash and production loss in 2013 (Joyner, 2015;Augustyn et al, 2017). Investigating changes in the marine environment can help understand potential environmental drivers of low catches and guide the level of response required in case of future similar situations.…”

Section: Introductionmentioning

confidence: 99%