Publication Date:
2021-05-19
Description:
Most reports on the distribution of spawning areas of
sardine (Sardinops sagax) in the northern Benguela
originate from the 1970s and 1980s. The northern
Benguela system was in a high upwelling regime during
those decades. Since the early 1990s upwelling
favourable winds have decreased and a trend of
increasing sea surface temperature (SST) has been
observed. Changes in the structure of sardine stock in
the northern Benguela have been observed and it has
been suggested that a reduced biomass and changes in
stock structure has led to decreased spawning in the
favourable southern locations, thus preventing a
recovery of the sardine stock. The present paper on
the contrary shows that there has been a shift in
spawning location from the less favourable northern
areas in the early 1980s to spawning areas further
south in the 2000s. Thus, the failure of the northern
Benguela sardine stock to recover since its collapse in
the late 1960s cannot be explained by spawning in less
favourable areas. The shift in preferred spawning
location to more southern areas since the 1980s was to
be expected with a general warming of the northern
Benguela system. Alternative explanations for the
failure of the sardine stock to recover such as a
reduction in average length as well as length at 50%
maturity, leading to a reduction in reproductive output,
increased predation pressure, and increased low
oxygen waters are proposed.
Description:
The northern Benguela upwelling system is one of four
major eastern boundary upwelling systems in the
world. Its dynamics have been extensively reviewed by
several authors (Nelson and Hutchings, 1983; Shannon,
1985; Lutjeharms and Valentine, 1987; Fennel,
1999). The system is characterized by strong seasonal
signals with higher water temperatures during austral
summer and autumn (December to March) and lower
temperatures during winter and spring (August to
November) (Bartholomae and van der Plas, 2007),
when upwelling favourable southwesterly winds are
strongest.
Description:
Published
Description:
Environment
Description:
Northern Benguela
Description:
Sardine
Description:
Spawning location
Description:
Stock structure
Keywords:
Coastal upwelling
;
Upwelling
;
Temperature
;
Spawning
;
Seasonal changes
Repository Name:
AquaDocs
Type:
Journal Contribution
,
Non-Refereed
,
Article
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