Upwelling, downwelling, and cross-shelf transport of bivalve larvae: test of a hypothesis

Shanks, Alan L.; Brink, Laura

doi:10.3354/meps302001

Cited by 206 publications

(175 citation statements)

References 48 publications

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“…Spawning releases can occur continuously over months or in a few short events. Biotic factors, such as active swimming and vertical migration, also contribute to movement patterns (12,14,15). A small fraction of the larvae settle at suitable sites, and an even smaller fraction recruit to adult stages where they can reach reproductive age and contribute to fishery yields.…”

mentioning

confidence: 99%

“…3i) because more larvae are found in the nearshore environment during their settlement competency window compared with the base case (thus increasing f sv ). Importantly, different connectivity patterns arise from the same flow field for organisms with different life histories.Movement by individual larvae, both ontogenetic vertical migrations and late-period active swimming toward suitable habitat, also can shape connectivity patterns (12,14,15). Ontogenetic descents should affect larval transport by moving larvae from higher-speed surface flows to deeper, slower flows.…”

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confidence: 99%

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The stochastic nature of larval connectivity among nearshore marine populations

Siegel

Mitarai

Costello

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

359

356

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Many nearshore fish and invertebrate populations are overexploited even when apparently coherent management structures are in place. One potential cause of mismanagement may be a poor understanding and accounting of stochasticity, particularly for stock recruitment. Many of the fishes and invertebrates that comprise nearshore fisheries are relatively sedentary as adults but have an obligate larval pelagic stage that is dispersed by ocean currents. Here, we demonstrate that larval connectivity is inherently an intermittent and heterogeneous process on annual time scales. This stochasticity arises from the advection of pelagic larvae by chaotic coastal circulations. This result departs from typical assumptions where larvae simply diffuse from one site to another or where complex connectivity patterns are created by transport within spatially complicated environments. We derive a statistical model for the expected variability in larval settlement patterns and demonstrate how larval connectivity varies as a function of different biological and physical processes. The stochastic nature of larval connectivity creates an unavoidable uncertainty in the assessment of fish recruitment and the resulting forecasts of sustainable yields.coastal oceanography ͉ fisheries ͉ marine ecology N earshore ecosystems host a wide variety of marine organisms and are among the most productive environments on Earth. Yet many species harvested from these ecosystems are overfished (1-3), a problem that is especially acute for those invertebrates and fishes with a relatively sedentary adult life stage. One potential cause of overfishing is mismanagement because of a poor understanding and accounting of stochasticity in these systems (4,5). Stochasticity caused by climate variations has long been known to influence the dynamics of ocean ecosystems and the fisheries they support (6). Climate variation affects rates of fecundity and recruitment by altering water temperature, coastal circulation patterns, or the availability of spawning grounds (7,8); such effects can be understood and, given sufficient data, may be predictable. Here, we introduce a mechanism that generates stochasticity in spatial and temporal patterns of larval transport on annual time scales. This stochasticity is inherently unpredictable because of the chaotic nature of coastal circulations and the relatively short larval time scales.Many harvested fish and invertebrates from nearshore ecosystems have a life cycle that includes a pelagic larval stage that can last up to months and a localized benthic adult stage (9, 10). These relatively sedentary adults release hundreds to millions of larvae that are advected and dispersed by ocean currents as they develop competency to settle (9-13). Spawning releases can occur continuously over months or in a few short events. Biotic factors, such as active swimming and vertical migration, also contribute to movement patterns (12,14,15). A small fraction of the larvae settle at suitable sites, and an even smaller fraction recruit to adult...

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mentioning

confidence: 99%

mentioning

confidence: 99%

The stochastic nature of larval connectivity among nearshore marine populations

Siegel

Mitarai

Costello

et al. 2008

Proc. Natl. Acad. Sci. U.S.A.

359

356

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“…Coarse-to large-scale 12 hydrodynamic features (10 to 100s km, sensu Haury et al, 1978) such as downwelling, 13 relaxation events, internal tidal bores, and wind driven currents influence transport and larval 14 supply of benthic invertebrate taxa (e.g., Bennell, 1981;Hawkins and Hartnoll, 1982;Farrell et 15 al., 1991;Pineda, 1991;Poulin et al, 2002). The effects of coarse-to large-scale hydrodynamics 16 on larval supply have been inferred from measurements of larval concentrations and time series 17 of physical measurements that characterize the hydrodynamic processes (e.g., Garland et al, 18 2002;Shanks and Brink, 2005). In other studies, coarse-to large-scale hydrodynamic processes 19 are correlated to time series of larval settlement, but larval concentrations in the water are not 20 measured (e.g., Bertness et al, 1996;Jacinto and Cruz, 2008).…”

mentioning

confidence: 99%

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

Pineda

Porri

Starczak

et al. 2010

Journal of Experimental Marine Biology and Ecology

184

100

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Marine broadcast spawners have two-phase life cycles, with pelagic larvae and benthic adults. 2 Larval supply and settlement link these two phases and are crucial for the persistence of marine 3 populations. Mainly due to the complexity in sampling larval supply accurately, many 4 researchers use settlement as a proxy for larval supply. Larval supply is a constraining variable 5 for settlement because, without larval supply, there is no settlement. Larval supply and 6 settlement may not be well correlated, however, and settlement may not consistently estimate 7 larval supply. 8This paper explores the argument that larval supply (i.e., larval abundance near settlement sites) 9 may not relate linearly to settlement. We review the relationship between larval supply and 10 settlement, from estimates and biases in larval supply sampling, to non-behavioral and 11 behavioral components, including small-scale hydrodynamics, competency, gregarious behavior, 12 intensification of settlement, lunar periodicity, predation and cannibalism. Physical and structural 13 processes coupled with behavior, such as small-scale hydrodynamics and intensification of 14 settlement, sometimes result in under-or overestimation of larval supply, where it is predicted 15 from a linear relationship with settlement. Although settlement is a function of larval supply, 16 spatial and temporal processes interact with larval behavior to distort the relationship between 17 larval supply and settlement, and when these distortions act consistently in time and space, they 18 cause biased estimates of larval supply from settlement data. 19Most of the examples discussed here suggest that behavior is the main source of the decoupling 20 between larval supply and settlement because larval behavior affects the vertical distribution of 21 3 larvae, the response of larvae to hydrodynamics, intensification of settlement, gregariousness, 1 predation and cannibalism. Thus, larval behavior seems to limit broad generalizations on the 2 regulation of settlement by larval supply. Knowledge of the relationship is further hindered by 3 the lack of a well founded theoretical relationship between the two variables. 4The larval supply-settlement transition may have strong general consequences for population 5 connectivity, since larval supply is a result of larval transport, and settlement constrains 6 recruitment. Thus, measuring larval supply and settlement effectively allows more accurate 7 quantification and understanding of larval transport, recruitment and population connectivity. 8 9 4

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“…Consequently, these authors suggested that the strength and temporal variation of upwelling might explain the variations in recruitment in these particular ecosystems. However, recent studies have pointed out that the hypothesis of rapid larval transport during upwelling/downwelling may be incorrect (Shanks et al 2003;Shanks and Brink 2005;Shanks and Shearman 2009;Morgan et al 2009a, b;Morgan and Fisher 2010). In fact, these studies found no consistent differences in the cross-shelf distribution of invertebrate larvae during upwelling and downwelling periods.…”

Section: Introductionmentioning

confidence: 43%

Mesoscale advection of Upogebia pusilla larvae through an upwelling filament in the Canaries Coastal Transition Zone (CTZ)

2012

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Larval transport has a strong influence on marine populations and ecosystem function. Traditional hypotheses establish that larvae of coastal species are swept offshore during strong upwelling periods producing low recruitment rates; however, recent studies have demonstrated that this hypothesis is not supported by larval distribution data. The present study examines the influence of upwelling filaments on larval advection and wastage. During August 1993, the transport of Upogebia pusilla was analysed in relation to an offshore filament off Northwest Africa. This mesoscale structure was generated by a trapped, quasi-permanent cyclonic eddy located between the Canary Islands and the African shelf and extended 150 km westward into the oligotrophic open ocean waters. The horizontal distribution depicted by U. pusilla larvae was strongly influenced by the oceanographic features of the Canaries Coastal Transition Zone (CTZ). Specifically, the larvae were closely associated with upwelling front and filament position, showing that these neritic larvae can be advected 10-100s of kilometres offshore through the filament. However, the low larval densities observed in the samples suggest that many larvae might remain close to the coast, thus avoiding seaward transport. This implies that filaments probably do not significantly affect the recruitment success of intertidal invertebrates such us U. pusilla in upwelling systems.

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Upwelling, downwelling, and cross-shelf transport of bivalve larvae: test of a hypothesis

Cited by 206 publications

References 48 publications

The stochastic nature of larval connectivity among nearshore marine populations

The stochastic nature of larval connectivity among nearshore marine populations

Causes of decoupling between larval supply and settlement and consequences for understanding recruitment and population connectivity

Mesoscale advection of Upogebia pusilla larvae through an upwelling filament in the Canaries Coastal Transition Zone (CTZ)

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