Swimming in formation in krill (Euphausiacea), a hypothesis: dynamics of the flow field, properties of antennular sensor systems and a sensory-motor link

Patria, Mufti Petala; Wiese, K.

doi:10.1093/plankt/fbh122

Cited by 28 publications

(33 citation statements)

References 35 publications

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“…Therefore, studies on tethered specimens do not provide an accurate representation of the induced flow fields. The free-swimming E. pacifica flow field more closely resembled the findings of tethered studies, with a distinct downward-directed jet (Kils, 1982;Yen et al, 2003;Patria and Wiese, 2004), whereas the non-uniformity and K. B. Catton and others variation in direction produced by each stroke of the pleopods was more apparent in the E. superba flow fields. Unlike the study by Patria and Wiese (Patria and Wiese, 2004), the larger species (E. superba) did not produce vortex rings from the side view, which suggests that the observed vortex rings were an artifact of the aquarium or tethering in their study.…”

Section: Flow Fieldssupporting

confidence: 62%

“…The free-swimming E. pacifica flow field more closely resembled the findings of tethered studies, with a distinct downward-directed jet (Kils, 1982;Yen et al, 2003;Patria and Wiese, 2004), whereas the non-uniformity and K. B. Catton and others variation in direction produced by each stroke of the pleopods was more apparent in the E. superba flow fields. Unlike the study by Patria and Wiese (Patria and Wiese, 2004), the larger species (E. superba) did not produce vortex rings from the side view, which suggests that the observed vortex rings were an artifact of the aquarium or tethering in their study. Vortex rings were also not produced in the flow field of a model lobster (235mm body length) performing pleopod swimming (Lim and DeMont, 2009), thus suggesting that vortex rings may not form, even at larger Reynolds numbers.…”

Section: Flow Fieldssupporting

confidence: 62%

“…Past studies on euphausiid flow fields are limited to studies of tethered specimens of Meganyctiphanes norvegica (Kils, 1982;Patria and Wiese, 2004), E. pacifica (Yen et al, 2003) and E. superba (Ebina and Miki, 1996). Tethered specimens generate flow fields with higher velocities and more rotation in the flow (Catton et al, 2007) because the tether imparts an unbalanced force on the fluid.…”

Section: Flow Fieldsmentioning

confidence: 99%

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The hydrodynamic disturbances of two species of krill: implications for aggregation structure

Catton

Webster

Kawaguchi

et al. 2011

Journal of Experimental Biology

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Swimming capacity is dependent on size (Johnson and Tarling, 2008) and organism size is directly related to the spatial extent of the hydrodynamic disturbance, which potentially provides a sensory field for prey, predators and conspecifics (Abrahamsen et al., 2010 Accepted 15 February 2011 SUMMARY Krill aggregations vary in size, krill density and uniformity depending on the species of krill. These aggregations may be structured to allow individuals to sense the hydrodynamic cues of neighboring krill or to avoid the flow fields of neighboring krill, which may increase drag forces on an individual krill. To determine the strength and location of the flow disturbance generated by krill, we used infrared particle image velocimetry measurements to analyze the flow field of free-swimming solitary specimens (Euphausia superba and Euphausia pacifica) and small, coordinated groups of three to six E. superba. Euphausia pacifica individuals possessed shorter body lengths, steeper body orientations relative to horizontal, slower swimming speeds and faster pleopod beat frequencies compared with E. superba. The downward-directed flow produced by E. pacifica has a smaller maximum velocity and smaller horizontal extent of the flow pattern compared with the flow produced by E. superba, which suggests that the flow disturbance is less persistent as a potential hydrodynamic cue for E. pacifica. Time record analysis reveals that the hydrodynamic disturbance is very weak beyond two body lengths for E. pacifica, whereas the hydrodynamic disturbance is observable above background level at four body lengths for E. superba. Because the nearest neighbor separation distance of E. superba within a school is less than two body lengths, hydrodynamic disturbances are a viable cue for intraspecies communication. The orientation of the position of the nearest neighbor is not coincident with the orientation of the flow disturbance, however, which indicates that E. superba are avoiding the region of strongest flow.

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Section: Flow Fieldssupporting

confidence: 62%

Section: Flow Fieldssupporting

confidence: 62%

Section: Flow Fieldsmentioning

confidence: 99%

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The hydrodynamic disturbances of two species of krill: implications for aggregation structure

Catton

Webster

Kawaguchi

et al. 2011

Journal of Experimental Biology

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“…Owing to the complex social behaviour of krill aggregations recently observed (Price 1989, Greene et al 1992, Heywood 1996, Patria & Wiese 2004, we can also assume that the short-term velocity fluctuations around w z for a krill aggregation do not contribute to dispersal but rather to maintenance of the aggregation against turbulent diffusion. It is therefore difficult to assume that the nonlinearity of individual krill movements could be simulated by an additional diffusion term (Visser & Thygesen 2003), as proposed by Wroblewski (1982) and used by Zakardjian et al (1999) for copepods.…”

Section: Methodsmentioning

confidence: 99%

Krill aggregation in the St. Lawrence system, and supply of krill to the whale feeding grounds in the estuary from the gulf

Sourisseau¹,

Simard²,

Saucier³

2006

Mar. Ecol. Prog. Ser.

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Persistent high-density krill aggregations make the St. Lawrence Estuary and the Gulf of St. Lawrence important feeding-grounds for large marine mammals. To estimate the effects of the circulation on the seasonal krill distribution, a krill biomass-concentration equation with active vertical migration was coupled to a 3D regional sea ice-ocean circulation model. The results show recurrent spatial patterns of aggregation and advection controlled by the circulation and a high sensitivity to the parameters of the biological model. The time spent in the surface layer is crucial for the retention of organisms in the estuary. The simulated krill aggregation areas are associated with 3 processes (tidal interactions with bathymetry, wind-driven upwelling and mean circulation). Zooplankton generally aggregate near the edges of the Laurentian Channel and other secondary channels, at locations that are consistent with the sparse synoptic information on the distributions of large marine mammals in the gulf. The simulations also indicate that changes in the seasonal circulation significantly affect the krill distribution within the gulf through gyre intensities, the seasonal thermocline and the strength of the estuarine circulation. Finally, the variability of zooplankton transport to the estuary from the gulf appears to be controlled by processes acting on the circulation mode at the mouth of the estuary and estuarine pumping of the krill layer towards the head of the Laurentian Channel. The simulated krill biomass imported into the estuary changed by a factor of 2 over the 3 simulated years.

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“…Estimates of euphausiid sensing distance have been made from a number of sources, including diver observations (1-2 m for E. superba; Ragulin, 1969), net avoidance (1.7-2.3 m for Nematoscelis megalops; Wiebe et al, 1982), and rheotactic sensing abilities (0.16-1 m for E. superba; Wiese 1996, Patria andWiese, 2004). From such measurements of responses mostly to large objects, it is difficult to estimate at what distance a krill might be able to respond to conspecifics.…”

Section: 23a Threshold Volume Backscattering Strengthmentioning

confidence: 99%

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

Lawson¹

2006

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The physical and biological forces that drive zooplankton distribution and patchiness in an antarctic continental shelf region were examined, with particular emphasis on the Antarctic krill, Euphausia superba. This was accomplished by the application of acoustic, video, and environmental sensors during surveys of the region in and around Marguerite Bay, west of the Antarctic Peninsula, in the falls and winters of 2001 and 2002. An important component of the research involved the development and verification of methods for extracting estimates of ecologically-meaningful quantities from measurements of scattered sound. The distribution of acoustic volume backscattering at the single frequency of 120 kHz was first examined as an index of the overall biomass of zooplankton. Distinct spatial and seasonal patterns were observed that coincided with advective features. Improved parameterization was then achieved for a theoretical model of Antarctic krill target strength, the quantity necessary in scaling measurements of scattered sound to estimates of abundance, through direct measurement of all necessary model parameters for krill sampled in the study region and survey period. Methods were developed for identifying and delineating krill aggregations, allowing the distribution of krill to be distinguished from that of the overall zooplankton community. Additional methods were developed and verified for estimating the length, abundance, and biomass of krill in each acoustically-identified aggregation. These methods were applied to multifrequency acoustic survey data, demonstrating strong seasonal, inter-annual, and spatial variability in the distribution of krill biomass. Highest biomass was consistently associated with regions close to land where temperatures at depth were cool. Finally, the morphology, internal structure, and vertical position of individual krill aggregations were examined. The observed patterns of variability in aggregation characteristics between day and night, regions of high versus low food availability, and in the presence or absence of predators, together reinforced the conclusion that aggregation and diel vertical migration represent strategies to avoid visual predators, while also allowing the krill access to shallowly-distributed food resources. The various findings of this work have important implications to the fields of zooplankton acoustics and Antarctic krill ecology, especially in relation to the interactions of the krill with its predators.

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Swimming in formation in krill (Euphausiacea), a hypothesis: dynamics of the flow field, properties of antennular sensor systems and a sensory-motor link

Cited by 28 publications

References 35 publications

The hydrodynamic disturbances of two species of krill: implications for aggregation structure

The hydrodynamic disturbances of two species of krill: implications for aggregation structure

Krill aggregation in the St. Lawrence system, and supply of krill to the whale feeding grounds in the estuary from the gulf

Distribution, patchiness, and behavior of Antarctic zooplankton, assessed using multi-frequency acoustic techniques

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