Acoustic and ecological investigations into predator-prey interactions between Antarctic krill (Euphausia superba) and seal and bird predators (original) (raw)
Related papers
Fisheries Research, 2000
Acoustic sampling has been used to investigate the ecology of Antarctic krill (Euphausia superba) and to provide information on dispersion and abundance necessary to manage their harvest. Population estimates based on multi-ship acoustic surveys have been used to set catch limits. More localized acoustic surveys have been conducted to study the response of landbreeding krill predators to local variations in their food supply. These and future surveys may result in additional controls on the ®shery. In this context, the use of acoustics to survey euphausiids is reviewed and major sources of uncertainty are discussed. These issues are organized as they pertain to the two broad steps of acoustic surveys: (1) estimating the volumetric density of krill (measurement uncertainty) and (2) mapping krill distribution and estimating abundance (sampling uncertainty). Published by Elsevier Science B.V.
Target strengths of Antarctic krill (Euphausia superba) at 38 and 120 kHz
The Journal of the Acoustical Society of America, 1990
Encaged aggregations of live krill in good to pristine condition have been ensonified at 38 and 120 kHz. Concurrent underwater television observations of behavior resemble those made by underwater divers in naturally occurring swarms, with comparably high densities of the order of 104 animals/m 3. Mean, single-animal target strengths have been inferred from measurements of echo energy. For aggregations with mean lengths in the range [ 30,39 ] mm, the mean single-krill target strengths are in the range [-88,-83 ] dB at 38 kHz and [-81,-74] dB at 120 kHz. Collateral measurements on some of the same encaged specimens determined a density contrast of 1.0357 q-0.0067 and sound-speed contrast of 1.0279-+-0.0024, relative to seawater. These numbers have been used with the fluid-sphere model as stated by Greenlaw [Limnol. Oceanogr. 24, 226-242 (1979) ]. Computed backscattering cross sections have been averaged over the length distributions of each measured aggregation, resulting in target strength predictions in the range [-86,-80] dB at 38 kHz and [-79,-76] dB at 120 kHz.
Acoustic characterization of the three-dimensional prey field of foraging chinstrap penguins
Marine Ecology-progress Series, 1996
Few studies of diving predators have explicitly addressed the 3-dimensional nature of interactions between predators and prey at the spatial and temporal scales relevant to an individual predator's search behavior Here, we present a new method for examining such interactions using the results from an acoustic survey of krill availability to foraging penguins Analyses of fine-scale krill distributions within a 1852 X 1852 X 50 m volume of ocean revealed substantial prey patchiness in all dimensions. Our survey detected the presence of at least 6 krill aggregations in the survey area. The surface distribution of penguins was associated with the edges of these aggregations and was nonrandomly associated with kl-ill dellsitirs above 0.1 krill m-' in the 30 to 40 m depth layer. The latter association was masked when krill abundance was integrated over the entire water column. Given that lilean daytlme dlve depths for chinstrap penguins fall betwccn 30 and 40 m, our data suggest penguins may fail to detect or choose to pass by shallow, denser prey aggregations and successfully forage on deeper, more homogeneously distributed krill offering higher encounter probabilities per unit volume searched. Thrse findings reveal biologically important features of prey patchiness that cannot be addressed within the limitations of a primarily 2-dimensional analysls of predator-prey distributions. We emphasize that if we hope to gain a predictive understanding of the foraging behavior of dlving predators, then we must consider fine-scale, 3-dimensional patterns of prey patchiness when assessing the availability of prey to diving predators.
Marine Ecology Progress Series, 2013
Interspecific competition is an important structuring element in marine ecosystems, especially in the Southern Ocean which offers few prey choices to comparatively large predator populations. We present the first simultaneous observations of at-sea behaviour and attendance patterns of 3 synchronously breeding, central place, krill foragers at Bouvetøya-a small, isolated, sub-Antarctic island in the South Atlantic. Time depth recorders and satellite transmitters were deployed during the austral summer of 2007/2008 on 47 lactating Antarctic fur seals Arctocephalus gazella (AFS) rearing pups and on 20 macaroni Eudyptes chrysolophus (MAC) and 30 chinstrap Pygoscelis antarctica penguins (CHIN) rearing chicks. All 3 species showed a strong preference for the west side of the island, and their foraging ranges overlapped markedly. Solar elevation influenced the timing of departures from, and arrivals to, the island with markedly different patterns between the seals and the penguins. Diving patterns also showed significant differences among the 3 species, with the frequency of diving being higher at night for the AFS, while both penguin species dove more frequently during the day. But a common, vertical diel pattern occurred in all 3 species, with shallow diving occurring at night and deep diving during the day, consistent with the vertical migration of krill. MACs targeted 2 depth layers for feeding, including a deep prey layer at ~70 m, which was not exploited by AFSs and CHINs. The results suggest that there is potential for competitive overlap among these 3 krill predators at Bouvetøya, but that it is reduced via both spatial (horizontal and vertical) and temporal partitioning of foraging areas.
2019
The primary objective for this krill research activity was twofold 1) to conduct a survey that provides updated estimates of the biomass and distribution of krill which are used in models to estimate sustainable yield in CCAMLR Area 48 and 2) to develop knowledge on the marine environment essential for the implementation of a FeedBack Management (FBM) system. The survey follows a similar design as a survey initiated by CCAMLR in year 2000 for comparative purposes, but in addition focuses on high krill-density areas, contains state-of-the art methods and employs modern technology for the research topics currently in focus. In terms of FBM, Marine Protected Area (MPA) development in CCAMLR Planning Domain 1 encompasses the major krill fishing grounds. Thus, data supporting FBM are critical if the fishery is to be managed by an empirical understanding of krill density, distribution, availability and predator needs as opposed to purely conservation-based measures. A future developed FBM system, requires acoustic data to be collected, processed and reported continuously during the fishing season as a measure of the available prey field. This information can be integrated with finer-scale knowledge of krill predator feeding strategies and updated through specific scientific studies at regular (multiyear) intervals. The survey and coupled FBM process studies took place during the Austral summer 2018-2019. The work was coordinated by Norway and involved collaborative international efforts as well as vessels from Norway, Association of Responsible Krill fishing companies (ARK) and the Norwegian fishing company Aker BioMarine AS, China, Korea, Ukraine and United Kingdom. This report presents preliminary results from the survey performed with the Norwegian RV Kronprins Haakon during 08th January-24th February 2019 and the land-based predator research carried out between 21st November 2018 and 20th February 2019. Content 1 Background 2 Krill Acoustics 3 Plankton, nutrients and environment 4 FlowCam studies 5 Fish and Cephalopods 6 Marine mammals and birds 7 Thermosalinograph and ADCP data 8 CTD data 9 Chemical indicators to monitor Ocean Acidification 10 Dissolved Oxygen 11 Sailbuoy with acoustics 12 LADCP measurements 13 Krill sound speed and density contrast 14 Acoustic backscatter of krill measured with lowered transducer 15 Echosounder moorings 16 Environmental toxicology 17 Metabolism balance in krill 18 Microbial communities 19 Trophic interactions 20 Land based predator research in support of adaptive management of the krill fishery 21 Acknowledgements 22 References 23 Appendix 1. Harstad-trawl rigging and procedures 24 Appendix 2. Scientific personell 25 Appendix 3. Crewlist KPH
Polar Science, 2011
From January to February 2008 the training research vessel TRV Umitaka Maru conducted a comprehensive oceanographic survey of the waters around the 140 E meridian off Adélie Land as part of the Collaborative East Antarctic Marine Census (CEAMARC) project. The acoustic component of this survey was conducted using a scientific echosounder operating at 38 and 70 kHz to estimate the distribution and density of Antarctic krill (Euphausia superba) and ice krill (E. crystallorophias). In addition, the relationship between the vertical distribution of Antarctic krill and the water temperature structure along the 140 E meridian was investigated. Antarctic krill were distributed in the waters of the continental slope at 65e66 S and the maximum value of the mean areal density r in 1 nautical mile (nmi) intervals was 4344 inds. m À2. Ice krill were distributed in the neritic waters of the continental shelf to the south of the 66 S and the maximum r in 1 nmi intervals was 23,669 inds. m À2. Along the 140 E meridian, Antarctic krill were mainly distributed at the water temperatures below 0.5 C. Although they were mostly distributed shallower than approximately 100 m, dense aggregations at approximately 180e200 m were also observed, which coincided with a depression of the water temperature structure.
Multifrequency acoustic target strength of Northern krill
2009
First, I would like to express my gratitude to my supervisor Professor Halvor Hobaek for his invaluable guidance and support throughout all these years. I sincerely thank him for following up my research work with such interest, encouraging me and believing in my abilities even when things have been difficult. A special thank goes to my colleague and friend Tor Knutsen, Research Group Plankton at the Institute of Marine Research (IMR) in Bergen, who contributed with fruitful discussions and ideas. Without his encouragement and experience this thesis would not have been possible. Dr. Webjørn Melle, research manager of the Research Group Plankton of IMR, is also thanked for promoting and supporting my research through the IMR internal program "New feed resources for the Aquaculture industry". The group leader Dr. Olav Rune Godø and all the colleagues and technicians of the Observation Metodikk Gruppen (OM) of IMR are sincerely thanked for the way they welcomed me as an "associated part" of the group. A particular acknowledgement goes to my co-supervisor John Dalen for his critical comments and helpful advice during the writing part of this thesis. I am deeply indebted to Professor Egil Ona for sharing with me his great knowledge in underwater acoustics and for always inspiring me. As for other young colleagues, I felt "victim" of his contagious enthusiasm. The group consultant Mrs Reidun Heggø Sørensen is also thanked for her great help in solving practical problems during my stay at OM.