Analyses of field moult data: prediction of intermoult period and assessment of seasonal growth in Antarctic krill, Euphausia superba Dana

1989 ◽  
Vol 1 (4) ◽  
pp. 301-306 ◽  
Author(s):  
Friedrich Buchholz ◽  
David J. Morris ◽  
Jonathan L. Watkins
Keyword(s):  
Food Availability ◽  
Antarctic Krill ◽  
Marked Effect ◽  
Laboratory Data ◽  
Euphausia Superba ◽  
Simple Relationship ◽  
Daily Growth ◽  
Growth Increments ◽  
Data Prediction ◽  
Field Samples

A technique for moult staging Antarctic krill (Euphausia superba Dana) was used in the analysis of field samples to predict intermoult periods and hence assess growth and the effects of seasonal changes in food availability. The proportion of moulting krill was used, in conjunction with laboratory data on the duration of this phase, to predict the moulting frequency (intermoult period, IMP). The moulting frequency was then combined with appropriate daily growth increments from laboratory study to assess overall growth in the krill sampled. The effects of seasonal fluctuations in food availability on moulting frequency were examined for samples taken at five different locations and times of year. Moulting rate was not linearly related to the availability of phytoplankton, although it is likely that this factor has a marked effect. Similarly, although temperature affects IMP, the data indicate that this is not a simple relationship either. These preliminary data indicate the value of utilizing this technique in the analysis of field samples of Antarctic krill.

Seasonal reproduction, multiple spawning, and fecundity in northern krill, Meganyctiphanes norvegica, and Antarctic krill, Euphausia superba

2000 ◽  
Vol 57 (S3) ◽  
pp. 6-15 ◽  
Author(s):  
Janine Cuzin-Roudy
Keyword(s):  
Antarctic Krill ◽  
Size Structure ◽  
Euphausia Superba ◽  
Batch Size ◽  
Effect Of Temperature ◽  
Multiple Spawning ◽  
Field Samples ◽  
Meganyctiphanes Norvegica ◽  
Reproductive Cycles ◽  
Antarctic Krill Euphausia Superba

Both northern krill, Meganyctiphanes norvegica, and Antarctic krill, Euphausia superba, release eggs seasonally in multiple spawning events. Fecundity estimates were determined based on counts of mature oocytes in the ovary of females in preserved field samples. Principal components analysis and allometry were used to analyze the covariation of egg-batch size with female characteristics. In both krill species, egg-batch size scaled isometrically with ovarian weight but showed a positive allometry with body size. Predicted egg-batch size ranged from 200 to 4000 eggs for M. norvegica of 25.5-35 mm body length and from 1500 to 6000 eggs for E. superba of 36-55 mm. Allometric relationships can be used to predict annual fecundity from size structure data of krill populations. In this study, the effect of temperature on the duration of molting and spawning cycles was used to infer a number of reproductive cycles per year, taking into account climate and seasonal variation.

Observation on behaviours of Antarctic krill (Euphausia superba) in lighting condition

2012 ◽  
Vol 36 (2) ◽  
pp. 300
Author(s):  
Peng-xiang XU ◽  
Ying-chun LI ◽  
Guo-ping ZHU ◽  
Hui XIA ◽  
Liu-xiong XU
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Lighting Condition ◽  
Antarctic Krill Euphausia Superba

scholarly journals Antarctic krill (Euphausia superba) exhibit positive phototaxis to white LED light

Polar Biology ◽  
2021 ◽  
Vol 44 (3) ◽  
pp. 483-489
Author(s):  
Bjørn A. Krafft ◽  
Ludvig A. Krag
Keyword(s):  
Antarctic Krill ◽  
Light Exposure ◽  
Euphausia Superba ◽  
Marine Species ◽  
Artificial Light ◽  
White Led ◽  
Light Emitting ◽  
Positive Phototaxis ◽  
Led Light ◽  
Exposure Experiment

AbstractThe use of light-emitting diodes (LEDs) is increasingly used in fishing gears and its application is known to trigger negative or positive phototaxis (i.e., swimming away or toward the light source, respectively) for some marine species. However, our understanding of how artificial light influences behavior is poorly understood for many species and most studies can be characterized as trial and error experiments. In this study, we tested whether exposure to white LED light could initiate a phototactic response in Antarctic krill (Euphausia superba). Trawl-caught krill were used in a controlled artificial light exposure experiment conducted onboard a vessel in the Southern Ocean. The experiment was conducted in chambers with dark and light zones in which krill could move freely. Results showed that krill displayed a significant positive phototaxis. Understanding this behavioral response is relevant to development of krill fishing technology to improve scientific sampling gear, improve harvest efficiency, and reduce potential unwanted bycatch.

scholarly journals Experimental determination of reflectance spectra of Antarctic krill (Euphausia superba) in the Scotia Sea

2021 ◽  
pp. 1-13
Author(s):  
Anna Belcher ◽  
Sophie Fielding ◽  
Andrew Gray ◽  
Lauren Biermann ◽  
Gabriele Stowasser ◽  
...  
Keyword(s):  
Antarctic Krill ◽  
Euphausia Superba ◽  
Reflectance Spectra ◽  
Spectral Signature ◽  
Absorption Feature ◽  
Scotia Sea ◽  
Surface Ocean ◽  
Measuring Surface ◽  
Ground Truthing

Abstract Antarctic krill are the dominant metazoan in the Southern Ocean in terms of biomass; however, their wide and patchy distribution means that estimates of their biomass are still uncertain. Most currently employed methods do not sample the upper surface layers, yet historical records indicate that large surface swarms can change the water colour. Ocean colour satellites are able to measure the surface ocean synoptically and should theoretically provide a means for detecting and measuring surface krill swarms. Before we can assess the feasibility of remote detection, more must be known about the reflectance spectra of krill. Here, we measure the reflectance spectral signature of Antarctic krill collected in situ from the Scotia Sea and compare it to that of in situ water. Using a spectroradiometer, we measure a strong absorption feature between 500 and 550 nm, which corresponds to the pigment astaxanthin, and high reflectance in the 600–700 nm range due to the krill's red colouration. We find that the spectra of seawater containing krill is significantly different from seawater only. We conclude that it is tractable to detect high-density swarms of krill remotely using platforms such as optical satellites and unmanned aerial vehicles, and further steps to carry out ground-truthing campaigns are now warranted.

Observations on moulting in Antarctic Krill (Euphausia superba Dana)

1982 ◽  
Vol 33 (1) ◽  
pp. 71 ◽  
Author(s):  
T Ikeda ◽  
P Dixon
Keyword(s):  
Phaeodactylum Tricornutum ◽  
Antarctic Krill ◽  
Dry Weight ◽  
Euphausia Superba ◽  
Dunaliella Tertiolecta ◽  
Antarctic Ocean ◽  
Fish Food ◽  
Antarctic Waters ◽  
The Antarctic ◽  
Antarctic Krill Euphausia Superba

Live E. superba were transported from Antarctic waters to a tropical laboratory where observations at the temperature of -0.5�C (0 to - 1.0�C), were made of intermoult period of specimens fed a mixture of microalgae (Dunaliella tertiolecta and Phaeodactylum tricornutum) or artificial pet fish food or starved. Mean intermoult period was 26.4-27.1 days for fed specimens and 29.6 days for starved specimens, with no relation to the size of specimens. The moult accounted for a loss of 2.63-4.35% of animal dry weight, which is equivalent to 1.1-1.8% of animal nitrogen or 1.4-2.3% of animal carbon. The contribution of moults to detritus in the Antarctic Ocean was estimated as 0.11 g C m-2 per year.

scholarly journals Sea-ice habitat minimizes grazing impact and predation risk for larval Antarctic krill

Polar Biology ◽  
2021 ◽  
Author(s):  
Carmen L. David ◽  
Fokje L. Schaafsma ◽  
Jan A. van Franeker ◽  
Evgeny A. Pakhomov ◽  
Brian P. V. Hunt ◽  
...  
Keyword(s):  
Sea Ice ◽  
Predation Risk ◽  
Water Column ◽  
Antarctic Krill ◽  
Standing Stock ◽  
Euphausia Superba ◽  
Grazing Impact ◽  
Water Interface ◽  
Winter Habitat ◽  
Ice Water

AbstractSurvival of larval Antarctic krill (Euphausia superba) during winter is largely dependent upon the presence of sea ice as it provides an important source of food and shelter. We hypothesized that sea ice provides additional benefits because it hosts fewer competitors and provides reduced predation risk for krill larvae than the water column. To test our hypothesis, zooplankton were sampled in the Weddell-Scotia Confluence Zone at the ice-water interface (0–2 m) and in the water column (0–500 m) during August–October 2013. Grazing by mesozooplankton, expressed as a percentage of the phytoplankton standing stock, was higher in the water column (1.97 ± 1.84%) than at the ice-water interface (0.08 ± 0.09%), due to a high abundance of pelagic copepods. Predation risk by carnivorous macrozooplankton, expressed as a percentage of the mesozooplankton standing stock, was significantly lower at the ice-water interface (0.83 ± 0.57%; main predators amphipods, siphonophores and ctenophores) than in the water column (4.72 ± 5.85%; main predators chaetognaths and medusae). These results emphasize the important role of sea ice as a suitable winter habitat for larval krill with fewer competitors and lower predation risk. These benefits should be taken into account when considering the response of Antarctic krill to projected declines in sea ice. Whether reduced sea-ice algal production may be compensated for by increased water column production remains unclear, but the shelter provided by sea ice would be significantly reduced or disappear, thus increasing the predation risk on krill larvae.

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