Janet Claire Coetzee

Janet Claire Coetzee

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Janet Claire Coetzee

Branch Fisheries, Department of Agriculture , Forestry and Fisheries , Private Bag X2, Rogge Bay, 8012, South Africa

Research Focus & Metrics

Academic Career Length

28Years (1999-Present)

(Calculated once Scilit publication data is synced: current year − year of first publication + 1)

Representative Publications

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1 December 2009 in Progress in Oceanography
Verified
Journal Article
Closed access
LHL. Hutchings
L. Hutchings
CLC.D. van der Lingen
C.D. van der Lingen
LSL.J. Shannon
L.J. Shannon
RCR.J.M. Crawford
R.J.M. Crawford
HVH.M.S. Verheye
H.M.S. Verheye
PMP.M.S. Monteiro
P.M.S. Monteiro

1 July 2006 in Current Biology
Verified
Journal Article
Closed access
CLChristopher P. Lynam
Christopher P. Lynam
MGMark J. Gibbons
Mark J. Gibbons
BABjørn E. Axelsen
Bjørn E. Axelsen
CSConrad Sparks
Conrad Sparks
JCJanet Coetzee
Janet Coetzee
ABAndrew S. Brierley
Andrew S. Brierley

1 February 2008 in Journal of Applied Ecology
Verified
Journal Article
Open access
PDF file
DGDavid Grémillet
David Grémillet
SLSue Lewis
Sue Lewis
LDLaurent Drapeau
Laurent Drapeau
CLCarl D. Van Der Lingen
Carl D. Van Der Lingen
JHJenny A. Huggett
Jenny A. Huggett
PRPeter G. Ryan
Peter G. Ryan
Summary: Remote‐sensing measurements of marine primary productivity are widely used to predict the distribution and movements of marine top predators, despite the fact that predators do not feed directly on phytoplankton but several trophic levels higher up the food chain. To test for potential links between primary productivity and top‐predator feeding hotspots, we assessed spatial match–mismatch across four trophic levels of the Benguela upwelling zone (south‐east Atlantic). The food chain studied consisted of phytoplankton, zooplankton (copepods), pelagic fish (anchovies and sardines) and two top predators (Cape gannets Morus capensis and human fisheries). Remote‐sensing data of sea‐surface temperature (SST) and chlorophyll_a concentration were used as indices of phytoplankton abundance throughout the study area. Copepod biomass and pelagic fish density were determined during at‐sea surveys in the South African section of the Benguela using net tows and hydro‐acoustics, respectively. Seabird (Cape gannet) home ranges and foraging zones were assessed from two Namibian breeding colonies (Mercury and Ichaboe) and two South African colonies (Lambert's Bay and Malgas) using global positioning system (GPS) tracking. Industrial fishing for anchovies and sardines was investigated using South African landing statistics and logbooks. Our spatial analyses revealed a strong match of seabird at‐sea habitat and zones of high primary productivity throughout the southern Benguela. Conversely, there was a marked spatial mismatch between copepods and pelagic fish, as well as between pelagic fish, seabirds and human fisheries: copepods were present in the southern Benguela but pelagic fish usually feeding upon them were located further east (Indian Ocean), outside of the Benguela sensu stricto. Consequently, the majority of these pelagic fish were out of reach for seabirds and fisheries confined to the southern Benguela. Synthesis and applications. Our study demonstrates the impact of an ecosystem shift across one of the world's most productive marine ecosystems and highlights the limitations of using remote‐sensed patterns of primary productivity to interpret the foraging behaviour of marine top predators. These findings underline the importance of a better knowledge of food web spatial dynamics to support ecosystem‐based fisheries management and the conservation of marine top predators.

1 December 2008 in ICES Journal of Marine Science
Verified
Journal Article
Open access
PDF file
JCJanet C. Coetzee
Janet C. Coetzee
CLCarl D. van der Lingen
Carl D. van der Lingen
LHLaurence Hutchings
Laurence Hutchings
TFTracey P. Fairweather
Tracey P. Fairweather
Coetzee, J. C., van der Lingen, C. D., Hutchings, L., and Fairweather, T. P. 2008. Has the fishery contributed to a major shift in the distribution of South African sardine? – ICES Journal of Marine Science, 65: 1676–1688. A major shift in the distribution of South African sardine (Sardinops sagax) has resulted in a significant spatial mismatch in fishing effort vs. fish abundance in recent years. The sardine fishery started on the west coast during the 1940s, and processing capacity there increased rapidly. This trend together with increases in annual landings continued up to the early 1960s, but then the fishery collapsed as a consequence of overfishing. The population then recovered steadily during the 1980s and 1990s, coincident with, but perhaps not entirely attributable to, the inception of conservative management practices, to support catches similar to pre-collapse levels. Since 2001, however, most of the sardine population has been situated on South Africa’s south coast, far from processing facilities. Fishing effort has increased concomitantly on that coast, particularly during the past three years, reflecting the continued decline in the abundance of sardine on the west coast. Three hypotheses explaining the change in the distribution of sardine have been proposed: (i) intensely localized (i.e. west coast) fishing pressure depleted that part (or functionally distinct unit) of the population; (ii) the shift was environmentally induced; and (iii) successful spawning and recruit survival on the south coast contributed disproportionately more towards the bulk of recruitment, and progeny spawned there now dominate the population and exhibit natal homing. The first of these hypotheses is evaluated, and management implications of the shift discussed.

1 December 2009 in Progress in Oceanography
Verified
Journal Article
Closed access
MBManuel Barange
Manuel Barange
JCJanet Coetzee
Janet Coetzee
ATAkinori Takasuka
Akinori Takasuka
KHKevin Hill
Kevin Hill
MGMariano Gutierrez
Mariano Gutierrez
VAVera Agostini
Vera Agostini

1 January 2000 in Aquatic Living Resources
Verified
Journal Article
Closed access
JCJ Coetzee
J Coetzee