scholarly journals TEMPERATURE, SALINITY AND OXYGEN CLIMATOLOGY OF AFRICAN CONTINENTAL SHELF WATER, SOUTH OF THE EQUATOR, AND CHANGES SINCE 1945

2021 ◽  
Author(s):  
Stephanie de Villiers
Keyword(s):  
Continental Shelf ◽  
Environmental Variability ◽  
Marine Ecosystem ◽  
Ecosystem Approach ◽  
Shelf Water ◽  
Classification Schemes ◽  
Continental Shelf Water ◽  
Large Marine Ecosystem ◽  
Oceanographic Data ◽  
Spatial Grid

The first temperature, salinity and oxygen climatologies for waters of the continuous southern African continental shelf is presented. It is based on oceanographic data collected since 1945, sub-sampled at depths of 5, 50 and 100 m on a mixed-spatial grid with 0.25° to 0.5° resolution. The climatologies capture spatial heterogeneities and seasonal variability in key ocean variables for the southern African shelf in unique detail. The results correspond relatively well with biogeographic boundaries informed by classification schemes grounded in taxonomy, but questions the value of the Large Marine Ecosystem approach. Analysis of decadal trends demonstrates the inherent complexity and spatial heterogeneity associated with environmental variability, and suggest the possibility that decadal periodicities are in the process of being disrupted by a longer-term trend. The overall pattern is that southern African West and South coast shelf waters are becoming warmer, except for some upwelling areas, where cooling is evident. Benguela and Agulhas Bank shelf water are also becoming more oxygen depleted.

scholarly journals Sex-specific variation in the use of vertical habitat by a resident Antarctic top predator

2020 ◽  
Vol 287 (1937) ◽  
pp. 20201447
Author(s):  
Theoni Photopoulou ◽  
Karine Heerah ◽  
Jennifer Pohle ◽  
Lars Boehme
Keyword(s):  
Habitat Use ◽  
Continental Shelf ◽  
Weddell Sea ◽  
Water Masses ◽  
Shelf Water ◽  
Top Predator ◽  
Marine Animals ◽  
Deep Diving ◽  
Continental Shelf Water ◽  
Oceanographic Conditions

Patterns of habitat use are commonly studied in horizontal space, but this does not capture the four-dimensional nature of ocean habitats (space, depth, and time). Deep-diving marine animals encounter varying oceanographic conditions, particularly at the poles, where there is strong seasonal variation in vertical ocean structuring. This dimension of space use is hidden if we only consider horizontal movement. To identify different diving behaviours and usage patterns of vertically distributed habitat, we use hidden Markov models fitted to telemetry data from an air-breathing top predator, the Weddell seal, in the Weddell Sea, Antarctica. We present evidence of overlapping use of high-density, continental shelf water masses by both sexes, as well as important differences in their preferences for oceanographic conditions. Males spend more time in the unique high-salinity shelf water masses found at depth, while females also venture off the continental shelf and visit warmer, shallower water masses. Both sexes exhibit a diurnal pattern in diving behaviour (deep in the day, shallow at night) that persists from austral autumn into winter. The differences in habitat use in this resident, sexually monomorphic Antarctic top predator suggest a different set of needs and constraints operating at the intraspecific level, not driven by body size.

scholarly journals Diverse integrated ecosystem approach overcomes pandemic-related fisheries monitoring challenges

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Jarrod A. Santora ◽  
Tanya L. Rogers ◽  
Megan A. Cimino ◽  
Keith M. Sakuma ◽  
Keith D. Hanson ◽  
...  
Keyword(s):  
Marine Ecosystem ◽  
Ecosystem Approach ◽  
Ecosystem Monitoring ◽  
Stock Assessments ◽  
Ecosystem Indicators ◽  
Modeling Techniques ◽  
Large Marine Ecosystem ◽  
Effort Reduction ◽  
Strategic Advice ◽  
Management And Conservation

AbstractThe COVID-19 pandemic caused unprecedented cancellations of fisheries and ecosystem-assessment surveys, resulting in a recession of observations needed for management and conservation globally. This unavoidable reduction of survey data poses challenges for informing biodiversity and ecosystem functioning, developing future stock assessments of harvested species, and providing strategic advice for ecosystem-based management. We present a diversified framework involving integration of monitoring data with empirical models and simulations to inform ecosystem status within the California Current Large Marine Ecosystem. We augment trawl observations collected from a limited fisheries survey with survey effort reduction simulations, use of seabird diets as indicators of fish abundance, and krill species distribution modeling trained on past observations. This diversified approach allows for evaluation of ecosystem status during data-poor situations, especially during the COVID-19 era. The challenges to ecosystem monitoring imposed by the pandemic may be overcome by preparing for unexpected effort reduction, linking disparate ecosystem indicators, and applying new species modeling techniques.

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