Robert J. M. Crawford

Robert J. M. Crawford
South Africa Government · Department of Environmental Affairs

Doctor of Philosophy

About

280
Publications
65,116
Reads
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11,811
Citations
Additional affiliations
June 1982 - May 2015
South Africa Government
Position
  • Contract Scientist Specialist

Publications

Publications (280)
Article
Full-text available
Aim Climate change will likely lead to a significant redistribution of biodiversity in marine ecosystems. We examine the potential redistribution of a community of marine predators by comparing current and future habitat distribution projections. We examine relative changes among species, indicative of potential future community-level changes and c...
Article
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Cape Cormorants Phalacrocorax capensis breed in southern Africa’s Benguela upwelling system and in 2013 were listed as Endangered by the IUCN following a population decrease of >50% over their three most recent generations. This decrease was associated with reduced prey availability, particularly of the pelagic shoaling fishes Cape anchovy Engrauli...
Book
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The book writes on birds as challenges and opportunities for business, conservation and research. The main chapter explains how the new genetic research has and will change the taxonomy and number of bird species in the world.
Article
Populations of the macaroni penguin Eudyptes chrysolophus and the eastern rockhopper penguin E. filholi breeding at Marion Island (Prince Edward Islands) in the sub-Antarctic Indian Ocean decreased from 1994 to 2018. We examined their diets when rearing chicks during this period. There was substantial overlap in the diets of the two species, with c...
Chapter
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The Benguela Current is used by c. 82 seabird species, of which seven are endemic to it. Eggs and guano of formerly abundant seabirds were heavily harvested in the 19th and 20th centuries but decreases in seabird populations led to cessation of these industries at islands. Guano is still scraped from platforms. Seabird ecotourism has grown. There w...
Article
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The designation of Marine Protected Areas has become an important approach to conserving marine ecosystems that relies on robust information on the spatial distribution of biodiversity. We used GPS tracking data to identify marine Important Bird and Biodiversity Areas (IBAs) for the Endangered northern rockhopper penguin Eudyptes moseleyi within th...
Article
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Forage fish populations often undergo large and rapid fluctuations in abundance. However, most of their predators are buffered against such fluctuations owing to their slower pace of life, which allows them to maintain more stable populations, at least during short periods of food scarcity. In this study, we investigated top‐down processes exerted...
Article
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This paper presents a new, updated, temporally dynamic Ecosim model for the Southern Benguela (1978–2015) by capturing recent advancements in our understanding of the dynamics and newly available data series from an additional decade of research in the region. The paper documents the model development and the thinking behind incorporating a newly a...
Article
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Understanding changes in abundance is crucial for conservation, but population growth rates often vary over space and time. We use 40 years of count data (1979–2019) and Bayesian state‐space models to assess the African penguin Spheniscus demersus population under IUCN Red List Criterion A. We deconstruct the overall decline in time and space to id...
Article
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Southern Ocean ecosystems are under pressure from resource exploitation and climate change1,2. Mitigation requires the identification and protection of Areas of Ecological Significance (AESs), which have so far not been determined at the ocean-basin scale. Here, using assemblage-level tracking of marine predators, we identify AESs for this globally...
Article
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Remote oceanic islands harbour unique biodiversity, especially of species that rely on the marine trophic resources around their breeding islands. Identifying marine areas used by such species is essential to manage and limit processes that threaten these species. The Tristan da Cunha territory in the South Atlantic Ocean hosts several endemic and...
Article
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The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for mul...
Article
The Retrospective Analysis of Antarctic Tracking Data (RAATD) is a Scientific Committee for Antarctic Research project led jointly by the Expert Groups on Birds and Marine Mammals and Antarctic Biodiversity Informatics, and endorsed by the Commission for the Conservation of Antarctic Marine Living Resources. RAATD consolidated tracking data for mul...
Preprint
Full-text available
African Penguin Spheniscus demersus numbers have declined steadily over three generations, resulting in a loss of nearly 60% since of 1989. The breeding population reached an historic low of ~20,850 pairs in 2019. We use count data and JARA, a generalized Bayesian state-space tool for estimating extinction risk estimates under IUCN Red List Criteri...
Article
The Bank Cormorant Phalacrocorax neglectus is endemic to the Benguela upwelling ecosystem off southwest Africa and is classified as Endangered owing to a recent large reduction in its number. It is thought that food scarcity, including a decreased abundance of West Coast rock lobster Jasus lalandii, has been a major driver of the decrease, yet its...
Article
Full-text available
The Cape Gannet Morus capensis is one of several seabird species endemic to the Benguela upwelling ecosystem (BUS) but whose population has recently decreased, leading to an unfavourable IUCN Red List assessment. Application of ‘JARA’ (‘Just Another Red-List Assessment,’ a Bayesian state-space tool used for IUCN Red List assessments) to updated inf...
Technical Report
Full-text available
Previously referred to as the “State of the Oceans and Coasts around South Africa Report Card". Consists of research and monitoring report cards for 2018 by multiple different authors, edited by Kirkman, Huggett and Crawford. This is the low resolution, web-site version
Article
Full-text available
Over the past three decades, marine resource management has shifted conceptually from top-down sectoral approaches towards the more systems-oriented multi-stakeholder frameworks of integrated coastal management and ecosystem-based conservation. However, the successful implementation of such frameworks is commonly hindered by a lack of cross-discipl...
Preprint
Full-text available
Remote oceanic islands harbour unique biodiversity, especially of species that rely on pelagic resources around their breeding islands. Identifying marine areas used by such species is important to reduce or limit threats that may put these species at risk. The Tristan da Cunha group of islands in the South Atlantic Ocean hosts several endemic and...
Article
Large recent decreases of Cape gannets Morus capensis, Cape cormorants Phalacrocorax capensis and African penguins Spheniscus demersus in South Africa resulted in their being listed as Endangered. These seabirds, endemic to the Benguela upwelling system (BUS), primarily rely on anchovy Engraulis encrasicolus and sardine Sardinops sagax for food, ye...
Article
Full-text available
Numbers of eight seabird species that have bred in coastal areas of South Africa’s arid Northern Cape province have all shown substantial decreases since initial estimates of their abundance were made in the latter part of the twentieth century. Likely drivers of these decreases include reduced availability of food and the loss of suitable breeding...
Article
Full-text available
Demographic parameters of wild animals are often closely associated with their foraging distribution and behaviour, and understanding these attributes can assist in identifying causes of population changes. The Indian Yellow-nosed Albatross (Thalassarche carteri) is endangered but little information is available on its at-sea distribution and behav...
Article
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Global forage-fish landings are increasing, with potentially grave consequences for marine ecosystems. Predators of forage fish may be influenced by this harvest, but the nature of these effects is contentious. Experimental fishery manipulations offer the best solution to quantify population-level impacts, but are rare. We used Bayesian inference t...
Article
The distribution of marine predators is driven by the distribution and abundance of their prey; areas preferred by multiple marine predator species should therefore indicate areas of ecological significance. The Southern Ocean supports large populations of seabirds and marine mammals and is undergoing rapid environmental change. The management and...
Article
Worldwide, in recent years capture fisheries targeting lower-trophic level forage fish and euphausiid crustaceans have been substantial (∼20 million metric tons [MT] annually). Landings of forage species are projected to increase in the future, and this harvest may affect marine ecosystems and predator-prey interactions by removal or redistribution...
Article
Ten of the 15 seabird species that breed in the Benguela upwelling ecosystem, including six species that are endemic to it, are now classified as threatened or near-threatened in terms of Red List criteria. Both bottom-up (operating from lower in the food chain) and top-down (operating from higher in the food chain, or outside it) processes have in...
Article
Human activities are important drivers of marine ecosystem functioning. However, separating the synergistic effects of fishing and environmental variability on the prey base of non-target predators is difficult, often because prey availability estimates on appropriate scales are lacking. Understanding how prey abundance at different spatial scales...
Article
Full-text available
King penguins make up the bulk of avian biomass on a number of sub-Antarctic islands where they have a large functional effect on terrestrial and marine ecosystems. The same applies at Marion Island where a substantial proportion of the world population breeds. In spite of their obvious ecological importance, the at-sea distribution and behavior of...
Article
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Human activities are important drivers of marine ecosystem functioning. However, separating the synergistic effects of fishing and environmental variability on the prey base of nontarget predators is difficult, often because prey availability estimates on appropriate scales are lacking. Understanding how prey abundance at different spatial scales l...
Article
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To help meet the high energy demands of raising the young, some seabirds alternate between short, frequent foraging trips to maximize food delivery to the young, and infrequent, long foraging trips that serve towards self-maintenance. Our study is the first to investigate the foraging behaviour of gentoo penguins at Marion Island, which we did thro...
Article
Full-text available
Numbers of Cape cormorants Phalacrocorax capensis breeding in South Africa decreased by nearly 50% from approximately 107 000 pairs in 1977–1981 to 57 000 pairs in 2010–2014. Although four colonies had >10 000 pairs in 1977–1981, there was just one such colony in 2010–2014. Almost all the decrease occurred after the early 1990s off north-west South...
Article
Full-text available
Human activities are important drivers of marine ecosystem functioning. However, teasing apart the synergistic effects of fishing and environmental variability on the prey base of non-target predators is difficult, often because estimates of prey availability on appropriate scales are lacking. Hence, understanding the links between direct measures...
Article
Sub-Antarctic Marion Island is one of the few islands where both species of Phoebetria albatrosses breed sympatrically. The last published assessment of their population trends, which reported counts up to 2008, concluded that the numbers of breeding pairs of sooty albatross P. fusca (Endangered) were decreasing, whereas numbers of light-mantled al...
Research
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Edited by Dr Hans Verheye and Dr Robert Crawford, this report attempted to summarized the state of the oceans around South Africa. Top Predators are covers in Chapter 5 and list of authors acompany this post
Article
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Marine no-take zones can have positive impacts for target species and are increasingly important management tools. However, whether they indirectly benefit higher order predators remains unclear. The endangered African penguin (Spheniscus demersus) depends on commercially exploited forage fish. We examined how chick survival responded to an experim...
Article
Full-text available
Overfishing and human-induced climate change are putting severe pressure on marine ecosystems. In the southern Benguela, most of South Africa's commercial fisheries have a long history of exploitation and this, coupled with spatio-temporal changes in key species over the last three decades has severely impacted some of South Africa's fisheries and...
Article
Full-text available
Seabirds are upper trophic level predators, and are often highly sensitive to changes in the availability of their prey. Altered prey assemblages resulting from fluctuations in oceanographic conditions may be mirrored by shifts in seabird diet. Long-term studies of dietary change in seabirds therefore provide valuable insight into the nature of env...
Article
Full-text available
In the southern Benguela ecosystem off South Africa, there were recent shifts to the south and east in the distributions of three forage resources (anchovy, sardine, rock lobster), which probably were influenced by environmental change although fishing too may have played a part. In this study, we review information on trends in distributions and n...
Article
Full-text available
Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means...
Article
Cumulative human impacts across the world's oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means...
Article
Cumulative human impacts across the world’s oceans are considerable. We therefore examined a single model taxonomic group, the penguins (Spheniscidae), to explore how marine species and communities might be at risk of decline or extinction in the southern hemisphere. We sought to determine the most important threats to penguins and to suggest means...