Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

Mullaney, Thomas J.; Miskiewicz, Anthony G.; Baird, Mark E.; Burns, Pippa; Suthers, Iain M.

doi:10.1111/j.1365-2419.2011.00594.x

Cited by 18 publications

(40 citation statements)

References 40 publications

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“…The inner-shelf water in this region has previously been shown to be distinctively enriched in nitrate (Suthers et al 2011), phytoplankton (Condie et al 2011), zooplankton , and larval fish (Mullaney et al 2011;Syahailatua et al 2011a). In this study, satellite imagery showed the inner-shelf water to have enhanced levels of Chl a (.…”

Section: Discussionsupporting

confidence: 54%

“…A region of mixed EAC, Tasman Sea, and coastal water exists off the coast of Sydney and over 100 km offshore , known as the western Tasman Front (wTF; Mullaney et al 2011). The cyclonic eddy observed here is part of the same process forming the wTF and its mixture of water types.…”

Section: Discussionmentioning

confidence: 66%

“…The eddy was distinguished by a larval abundance of taxa that are known to spawn on the continental shelf (Ward et al 2003;Syahailatua et al 2011a,b). Larval Clupeidae, Scombridae, Carangidae, and Bothidae have been previously described as coastal or shelf families off eastern Australia , and Clupeidae and Bothidae are particularly characteristic of the inner-shelf water type (Mullaney et al 2011). S. sagax spawn off northern New South Wales from June to October at inner-shelf , 50 m isobath (Ward et al 2003), whereas S. australasicus spawns on the outer shelf between 25uS and 35uS and is readily entrained into the EAC (Mullaney et al 2011).…”

Section: Discussionmentioning

confidence: 99%

“…Larval Clupeidae, Scombridae, Carangidae, and Bothidae have been previously described as coastal or shelf families off eastern Australia , and Clupeidae and Bothidae are particularly characteristic of the inner-shelf water type (Mullaney et al 2011). S. sagax spawn off northern New South Wales from June to October at inner-shelf , 50 m isobath (Ward et al 2003), whereas S. australasicus spawns on the outer shelf between 25uS and 35uS and is readily entrained into the EAC (Mullaney et al 2011). T. novaezelandiae is more associated with EAC water than S. sagax and is likely to have a spring spawning distribution similar to S. australasicus (Syahailatua et al 2011a,b).…”

Section: Discussionmentioning

confidence: 99%

“…Shelf water in this region is already enriched with phytoplankton, zooplankton, and larval fish (Mullaney et al 2011) compared to the EAC or Tasman Sea (Baird et al 2008). Our aim, therefore, was to examine entrainment of preconditioned shelf water into a short-lived, submesoscale frontal eddy of the EAC and determine whether such eddies can emulate longer-lived mesoscale eddies (Bakun 2006) in larval fish entrainment, larval retention, and larval survival.…”

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confidence: 99%

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Entrainment and retention of the coastal larval fish assemblage by a short‐lived, submesoscale, frontal eddy of the East Australian Current

Mullaney

Suthers

2013

Limnology & Oceanography

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We examined the fate of larval fish assemblages after the East Australian Current (EAC) had separated from the coast and larval fish were advected eastward along the Tasman Front. There was no difference in the assemblages at four stations as the EAC meandered from the continental shelf to 220 km eastward. At a fifth station, we sampled a submesoscale, frontal eddy that had formed at the EAC separation zone 11 d earlier and had entrained shelf water. Zooplankton biomass was greater within the eddy compared to the adjacent shelf. The larval fish assemblage in the eddy was significantly different from all other stations. There was an order of magnitude greater abundance of three species characteristic of the shelf: sardine (Sardinops sagax; Clupeidae), blue mackerel (Scomber australasicus; Scombridae), and yellowtail scad (Trachurus novaezelandiae; Carangidae), which were also significantly larger than larvae from a station on the adjacent shelf. In particular, S. sagax in the eddy were , 5 mm longer and , 10 d older, although growth rates were similar. Larval retention in the eddy was inferred from the co-occurrence of small and large larvae of all three species compared to the adjacent shelf. The EAC is only 20-30 km from the inner-shelf water, where frontal eddies may facilitate three stages of successful recruitment: entrainment, enrichment, and retention. Frontal eddies off southeastern Australia entrain preconditioned shelf water, move slower than the mean flow of the EAC, decreasing transport rates, and may sustain planktonic communities through eddy uplift. These eddies are frequent and short-lived (2 to 4 weeks), and we suspect they are of fisheries importance as their duration is sufficient for fish larvae to complete their early life history and, presumably, recruit back to the coast.

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Section: Discussionsupporting

confidence: 54%

Section: Discussionmentioning

confidence: 66%

Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

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Entrainment and retention of the coastal larval fish assemblage by a short‐lived, submesoscale, frontal eddy of the East Australian Current

Mullaney

Suthers

2013

Limnology & Oceanography

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Cyclonic entrainment of preconditioned shelf waters into a frontal eddy

et al. 2015

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The volume transport of nutrient-rich continental shelf water into a cyclonic frontal eddy (entrainment) was examined from satellite observations, a Slocum glider and numerical simulation outputs. Within the frontal eddy, parcels of water with temperature/salinity signatures of the continental shelf (18)(19) C and >35.5, respectively) were recorded. The distribution of patches of shelf water observed within the eddy was consistent with the spiral pattern shown within the numerical simulations. A numerical dye tracer experiment showed that the surface waters (50 m depth) of the frontal eddy are almost entirely (95%) shelf waters. Particle tracking experiments showed that water was drawn into the eddy from over 4 of latitude (30-34.5 S). Consistent with the glider observations, the modeled particles entrained into the eddy sunk relative to their initial position. Particles released south of 33 S, where the waters are cooler and denser, sunk 34 m deeper than their release position. Distance to the shelf was a critical factor in determining the volume of shelf water entrained into the eddy. Entrainment reduced to 0.23 Sv when the eddy was furthest from the shelf, compared to 0.61 Sv when the eddy was within 10 km of the shelf. From a biological perspective, quantifying the entrainment of shelf water into frontal eddies is important, as it is thought to play a significant role in providing an offshore nursery habitat for coastally spawned larval fish.

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Frontal eddies provide an oceanographic triad for favorable larval fish habitat

Suthers

Schaeffer

Archer

et al. 2023

Limnology & Oceanography

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Frontal eddies form on the shoreward edge of boundary currents, on average at weekly intervals and can last up to several weeks. This duration allows zooplankton production and completion of the larval stage of fish but may be too ephemeral for longer food chains with planktonic predators to establish. Therefore, frontal eddies may provide a suitable offshore nursery habitat, by entraining and retaining inner-shelf water, preconditioned with coastal plankton and ichthyoplankton, into an upwelling favorable cyclonic eddy. Here, we briefly describe the behavior of frontal eddies formed by western boundary currents in the context of the fundamental ocean triad, which incorporates three processes for the successful reproduction of fish: nutrient enrichment, food concentration, and retention of larvae. We adapt this hypothesis for frontal eddies adjacent to the substantial fisheries production of continental shelves, creating conditions for enhanced recruitment potential of larval cohorts at a finer scale than previously considered. We review the evidence and investigations of frontal eddies in their capacity to entrain coastal water, sustain the plankton community through eddy uplift and retain distinctive coastal communities of larval fish offshore until larval development is complete. The process of frontal eddy formation is complex and such habitats are irregular yet ubiquitous, which present challenges and opportunities for their study. With the advance of ocean observing systems and integration of physical and biological sampling, frontal eddies provide a novel focus for understanding fisheries production and connectivity of coastal ecosystems.

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Entrainment of larval fish assemblages from the inner shelf into the East Australian Current and into the western Tasman Front

Cited by 18 publications

References 40 publications

Entrainment and retention of the coastal larval fish assemblage by a short‐lived, submesoscale, frontal eddy of the East Australian Current

Entrainment and retention of the coastal larval fish assemblage by a short‐lived, submesoscale, frontal eddy of the East Australian Current

Cyclonic entrainment of preconditioned shelf waters into a frontal eddy

Frontal eddies provide an oceanographic triad for favorable larval fish habitat

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