Spatial variability in branchial basket meristics and morphology of southern African sardine Sardinops sagax

Incorporating parasite data in population structure studies of South African sardine Sardinops sagax

“…Analyses of variability in branchial basket meristics (gill raker number) and morphology (gill arch length and gill raker gap) of sardine from around southern Africa have also been conducted (Idris, 2010), with significant spatial differences seen in most of these characteristics although not always consistently across all size classes. Sardine from the South African west and south coasts showed significant differences in gill arch length and gill raker number (Idris, 2010), and subsequent analysis of fish from the east coast showed that they also differed in terms of gill arch length and gill raker gap (Idris et al unpublished data). These significant differences in most of the sardine phenotypic characteristics studied were taken as support for the hypothesis of multiple sardine stocks off South Africa (van der Lingen et al .…”

Spawning patterns provide further evidence for multiple stocks of sardine (Sardinops sagax) off eastern Australia

“…The peak spawning times for each of the three SA spawning groups occur within different temporal/environmental conditions. For example, the western SA group which is located between the Luderitz upwelling and Cape Agulhas (Idris et al., ) spawns in summer in SSTs of 15–18.5°C (Mhlongo et al., ), while the southern group that occurs between Cape Agulhas to Port Alfred spawns in waters at 18–21.5°C (Mhlongo et al., ). While no selection of specific spawning SSTs have been documented for the eastern South African group, a distinct behavioural selection of spawning habitat has been observed.…”

“…The Luderitz upwelling cell off southern Namibia produces persistent offshore advection and cold temperatures. This upwelling system is believed to be a pelagic barrier (Lett, Veitch, van der Lingen, & Hutchings, 2007) to exchange between the northern Benguela stock, which resides in Namibian/southern Angolan waters north of the Luderitz upwelling (Kreiner, Yemane, Stenevik, & Moroff, 2011), and the western, southern and eastern South African stocks located south of the Luderitz upwelling (Idris, Moloney, & van der Lingen, 2016). Sea surface temperatures for spawning between the northern Benguela and western South African stocks differ by up to 3°C (Mhlongo, Yemane, Hendricks, & van der Lingen, 2015).…”

Concentrations and relative compositions of metallic elements differ between predatory squid and filter-feeding sardine from the Indian and South Atlantic oceans

“…Although we only had two sardine sampling sites, our data supports the hypothesis of multiple sardine stocks off South Africa. Multiple stocks are also implied by other studies that compared morphometric, meristic, genetic, and parasite load characteristics of sardines from the west, south, and east coasts (Groenewald et al, 2019;Idris et al, 2016;Teske et al, 2018;van der Lingen et al, 2015;Weston et al, 2015). A recent study (Hampton et al, 2018) showed that otolith microchemistry of South African sardine juveniles differed between collection sites in the same ocean -most of the compositional differences were site specific and varied annually.…”

“…While phytoplankton is the most commonly-ingested prey, zooplankton provides most of the fish's sustenance in both the South Atlantic and Indian oceans (van der Lingen, 2002). Spatial variability in sardine diet is apparent, with phytoplankton and smaller zooplankton more important in the South Atlantic Ocean (van der Lingen, 2002; Idris et al, 2016). This difference in diet, and spatial differences in natural background concentrations arising from different oceanographic conditions and anthropogenic sources, may explain the differences in sardine muscle metallic concentrations between collection sites.…”