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© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Melle, W., Klevjer, T., Drinkwater, K. F., Strand, E., Naustvoll, L. J., Wiebe, P. H., Aksnes, D. L., Knutsen, T., Sundby, S., Slotte, A., Dupont, N., Salvanes, A. G. V., Korneliussen, R., & Huse, G. Structure and functioning of four North Atlantic ecosystems - a comparative study. Deep-Sea Research Part II: Topical Studies in Oceanography, 180, (2020): 104838, doi:10.1016/j.dsr2.2020.104838., The epi- and mesopelagic ecosystems of four sub-polar ocean basins, the Labrador, Irminger, Iceland and Norwegian seas, were surveyed during two legs from Bergen, Norway, to Nuuk, Greenland, and back to Bergen. The survey was conducted from 1 May to 14 June, and major results were published in five papers (Drinkwater et al., Naustvoll et al., Strand et al., Melle et al., this issue, and Klevjer et al., this issue a, this issue b). In the present paper, the structures of the ecosystem are reviewed, and aspects of the functioning of the ecosystems examined, focusing on a comparison of trophic relationships in the four basins. In many ways, the ecosystems are similar, which is not surprising since they are located at similar latitudes and share many hydrographic characteristics, like input of both warm and saline Atlantic water, as well as cold and less saline Arctic water. Literature review suggests that total annual primary production is intermediate in the eastern basins and peaks in the Labrador Sea, while the Irminger Sea is the most oligotrophic sea. This was not reflected in the measurements of different trophic levels taken during the cruise. The potential new production was estimated to be higher in the Irminger Sea than in the eastern basins, and while the biomass of mesozooplankton was similar across basins, the biomass of mesopelagic micronekton was about one order of magnitude higher in the western basins, and peaked in the Irminger Sea, where literature suggests annual primary production is at its lowest. The eastern basins hold huge stocks of pelagic planktivore fish stocks like herring, mackerel and blue whiting, none of which are abundant in the western seas. As both epipelagic nekton and mesopelagic micronekton primarily feed on the mesozooplankton, there is likely competitive interactions between the epipelagic and mesopelagic, but we're currently unable to explain the estimated ~1 order of magnitude difference in micronekton standing stock. The resu, We greatly appreciate the Captain and crew of the R.V. G.O. Sars for their dedication and help during the BASIN survey. We also thank the technical support from the Institute of Marine Research that helped during the cruise and those that contributed to the processing and analysis of the data on land. The sampling, data analysis and reporting have been supported by IMR and University of Bergen through funding of ship time, laboratory costs and salaries of researchers through internally funded projects. We would also like to acknowledge the funding from Euro-BASIN, EU FP7, Grant agreement No 264933, HARMES, Research Council of Norway project number 280546 and MEESO, EU H2020 research and innovation programme, Grant Agreement No 817669. KD undertook this study as part of the Ecosystem Studies of Subarctic and Arctic Seas (ESSAS) programme.

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Klevjer, T., Melle, W., Knutsen, T., Strand, E., Korneliussen, R., Dupont, N., Salvanes, A. G. V., & Wiebe, P. H. Micronekton biomass distribution, improved estimates across four north Atlantic basins. Deep-Sea Research Part II: Topical Studies in Oceanography, 180, (2020): 104691, doi:10.1016/j.dsr2.2019.104691., Distribution of micronekton was investigated during early summer of 2013, using data from a cruise covering the central parts of four north Atlantic basins, the Norwegian Sea (NS), Iceland Sea (ICS), Irminger Sea (IRS), and Labrador Sea (LS). Continuous underway acoustics mapped vertical and horizontal distributions, and trawl sampling provided data on biomass and taxonomic composition. The hull mounted acoustics and trawl catches suggested that, among the four basins, biomass of epipelagic, larger nektonic species (>20 cm length) during the cruise was highest in the NS and ICS basins, while mesopelagic non-gelatinous micronekton biomass peaked in the IRS and LS basins. Biomass of Scyphozoa was also about 1 order of magnitude higher in IRS and LS compared to ICS and NS. In ICS and NS, crustaceans made up about 50% of total non-gelatinous micronekton biomass, with fish making up less than 20% of total biomass. In contrast, fish constituted more than 60% of non-gelatinous biomass of catches in IRS and LS. In catches from ICS and NS the myctophid Benthosema glaciale dominated the catches, whereas bathylagids, gonostomatids, barracudinas and stomiids contributed to the high biomass densities of fish in IRS and LS. In addition to the differences in biomass between the basins, the acoustic measurements suggested gradients within the north-eastern basins, and large differences in vertical distribution of biomass between the basins during the cruise., The detailed comments of two anonymous reviewers improved this paper. We gratefully acknowledge the cooperative effort and support provided by the Captains and Crew of the RV G.O. Sars during the six-week trans-Atlantic expedition. We are sincerely thankful for the financial support of the Institute of Marine Research that made the mission with G.O. Sars possible. The EU is thanked for support through EuroBasin (Integrated Project on Basin Scale Analysis, Synthesis and Integration), funded by Framework Programme 7, Contract 264933. The Research Council of Norway is thanked for the financial support through “Harvesting marine cold-water plankton species - abundance estimation and stock assessment” - (Harvest II, RCN 203871). The work is also a contribution to the Norwegian Sea Ecosystem Programme at IMR.

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Melle, W., Klevjer, T., Drinkwater, K. F., Strand, E., Naustvoll, L. J., Wiebe, P. H., Aksnes, D. L., Knutsen, T., Sundby, S., Slotte, A., Dupont, N., Salvanes, A. G. V., Korneliussen, R., & Huse, G. Structure and functioning of four North Atlantic ecosystems - a comparative study. Deep-Sea Research Part II: Topical Studies in Oceanography, 180, (2020): 104838, doi:10.1016/j.dsr2.2020.104838., The epi- and mesopelagic ecosystems of four sub-polar ocean basins, the Labrador, Irminger, Iceland and Norwegian seas, were surveyed during two legs from Bergen, Norway, to Nuuk, Greenland, and back to Bergen. The survey was conducted from 1 May to 14 June, and major results were published in five papers (Drinkwater et al., Naustvoll et al., Strand et al., Melle et al., this issue, and Klevjer et al., this issue a, this issue b). In the present paper, the structures of the ecosystem are reviewed, and aspects of the functioning of the ecosystems examined, focusing on a comparison of trophic relationships in the four basins. In many ways, the ecosystems are similar, which is not surprising since they are located at similar latitudes and share many hydrographic characteristics, like input of both warm and saline Atlantic water, as well as cold and less saline Arctic water. Literature review suggests that total annual primary production is intermediate in the eastern basins and peaks in the Labrador Sea, while the Irminger Sea is the most oligotrophic sea. This was not reflected in the measurements of different trophic levels taken during the cruise. The potential new production was estimated to be higher in the Irminger Sea than in the eastern basins, and while the biomass of mesozooplankton was similar across basins, the biomass of mesopelagic micronekton was about one order of magnitude higher in the western basins, and peaked in the Irminger Sea, where literature suggests annual primary production is at its lowest. The eastern basins hold huge stocks of pelagic planktivore fish stocks like herring, mackerel and blue whiting, none of which are abundant in the western seas. As both epipelagic nekton and mesopelagic micronekton primarily feed on the mesozooplankton, there is likely competitive interactions between the epipelagic and mesopelagic, but we're currently unable to explain the estimated ~1 order of magnitude difference in micronekton standing stock. The resu, We greatly appreciate the Captain and crew of the R.V. G.O. Sars for their dedication and help during the BASIN survey. We also thank the technical support from the Institute of Marine Research that helped during the cruise and those that contributed to the processing and analysis of the data on land. The sampling, data analysis and reporting have been supported by IMR and University of Bergen through funding of ship time, laboratory costs and salaries of researchers through internally funded projects. We would also like to acknowledge the funding from Euro-BASIN, EU FP7, Grant agreement No 264933, HARMES, Research Council of Norway project number 280546 and MEESO, EU H2020 research and innovation programme, Grant Agreement No 817669. KD undertook this study as part of the Ecosystem Studies of Subarctic and Arctic Seas (ESSAS) programme.

© The Author(s), 2020. This article is distributed under the terms of the Creative Commons Attribution License. The definitive version was published in Klevjer, T., Melle, W., Knutsen, T., Strand, E., Korneliussen, R., Dupont, N., Salvanes, A. G. V., & Wiebe, P. H. Micronekton biomass distribution, improved estimates across four north Atlantic basins. Deep-Sea Research Part II: Topical Studies in Oceanography, 180, (2020): 104691, doi:10.1016/j.dsr2.2019.104691., Distribution of micronekton was investigated during early summer of 2013, using data from a cruise covering the central parts of four north Atlantic basins, the Norwegian Sea (NS), Iceland Sea (ICS), Irminger Sea (IRS), and Labrador Sea (LS). Continuous underway acoustics mapped vertical and horizontal distributions, and trawl sampling provided data on biomass and taxonomic composition. The hull mounted acoustics and trawl catches suggested that, among the four basins, biomass of epipelagic, larger nektonic species (>20 cm length) during the cruise was highest in the NS and ICS basins, while mesopelagic non-gelatinous micronekton biomass peaked in the IRS and LS basins. Biomass of Scyphozoa was also about 1 order of magnitude higher in IRS and LS compared to ICS and NS. In ICS and NS, crustaceans made up about 50% of total non-gelatinous micronekton biomass, with fish making up less than 20% of total biomass. In contrast, fish constituted more than 60% of non-gelatinous biomass of catches in IRS and LS. In catches from ICS and NS the myctophid Benthosema glaciale dominated the catches, whereas bathylagids, gonostomatids, barracudinas and stomiids contributed to the high biomass densities of fish in IRS and LS. In addition to the differences in biomass between the basins, the acoustic measurements suggested gradients within the north-eastern basins, and large differences in vertical distribution of biomass between the basins during the cruise., The detailed comments of two anonymous reviewers improved this paper. We gratefully acknowledge the cooperative effort and support provided by the Captains and Crew of the RV G.O. Sars during the six-week trans-Atlantic expedition. We are sincerely thankful for the financial support of the Institute of Marine Research that made the mission with G.O. Sars possible. The EU is thanked for support through EuroBasin (Integrated Project on Basin Scale Analysis, Synthesis and Integration), funded by Framework Programme 7, Contract 264933. The Research Council of Norway is thanked for the financial support through “Harvesting marine cold-water plankton species - abundance estimation and stock assessment” - (Harvest II, RCN 203871). The work is also a contribution to the Norwegian Sea Ecosystem Programme at IMR.

Data are collected from a variety of acoustic systems in many countries to address a range of ecosystem monitoring and stock management objectives. A key step in the analysis of fisheries acoustics data is target classification, i.e. categorizing the backscatter data, ultimately by target species, so that it can be converted into estimates of abundance or biomass. The information needed to classify acoustic targets may be contained within the acoustic measurements, particularly if they are made over a range of frequencies. The SIMFAMI project, financed by the European Union, presented some multifrequency methods for species identification (Fernandes et al., 2006). Readers should also note that there are two other ICES reports on related topics: CRR No. 238 Report on Echo Trace Classification (Reid, 2000) and Acoustic seabed classification of marine physical and biological landscapes (ICES, 2007). However, as these reports were written when multifrequency and wideband methods were less mature, they mostly focus on single-frequency methods. Acoustic classification of biological targets is a fast-moving field. While most of the theoretical principles in the earlier reports are still relevant, there is a need to evaluate recent developments, expand their applications to contemporary technologies, and recommend target-classification protocols for use in fisheries research and ecosystem surveys. Several ICES Member Countries and observer countries have identified these needs and conveyed them to ICES Working Group on Fisheries Acoustics, Science, and Technology (WGFAST) and Science Committee (SCICOM). This is the first ICES CRR to detail the latest multifrequency and wideband methods for acoustic target classification.

Data are collected from a variety of acoustic systems in many countries to address a range of ecosystem monitoring and stock management objectives. A key step in the analysis of fisheries acoustics data is target classification, i.e. categorizing the backscatter data, ultimately by target species, so that it can be converted into estimates of abundance or biomass. The information needed to classify acoustic targets may be contained within the acoustic measurements, particularly if they are made over a range of frequencies. The SIMFAMI project, financed by the European Union, presented some multifrequency methods for species identification (Fernandes et al., 2006). Readers should also note that there are two other ICES reports on related topics: CRR No. 238 Report on Echo Trace Classification (Reid, 2000) and Acoustic seabed classification of marine physical and biological landscapes (ICES, 2007). However, as these reports were written when multifrequency and wideband methods were less mature, they mostly focus on single-frequency methods. Acoustic classification of biological targets is a fast-moving field. While most of the theoretical principles in the earlier reports are still relevant, there is a need to evaluate recent developments, expand their applications to contemporary technologies, and recommend target-classification protocols for use in fisheries research and ecosystem surveys. Several ICES Member Countries and observer countries have identified these needs and conveyed them to ICES Working Group on Fisheries Acoustics, Science, and Technology (WGFAST) and Science Committee (SCICOM). This is the first ICES CRR to detail the latest multifrequency and wideband methods for acoustic target classification.

Data are collected from a variety of acoustic systems in many countries to address a range of ecosystem monitoring and stock management objectives. A key step in the analysis of fisheries acoustics data is target classification, i.e. categorizing the backscatter data, ultimately by target species, so that it can be converted into estimates of abundance or biomass. The information needed to classify acoustic targets may be contained within the acoustic measurements, particularly if they are made over a range of frequencies. The SIMFAMI project, financed by the European Union, presented some multifrequency methods for species identification (Fernandes et al., 2006). Readers should also note that there are two other ICES reports on related topics: CRR No. 238 Report on Echo Trace Classification (Reid, 2000) and Acoustic seabed classification of marine physical and biological landscapes (ICES, 2007). However, as these reports were written when multifrequency and wideband methods were less mature, they mostly focus on single-frequency methods. Acoustic classification of biological targets is a fast-moving field. While most of the theoretical principles in the earlier reports are still relevant, there is a need to evaluate recent developments, expand their applications to contemporary technologies, and recommend target-classification protocols for use in fisheries research and ecosystem surveys. Several ICES Member Countries and observer countries have identified these needs and conveyed them to ICES Working Group on Fisheries Acoustics, Science, and Technology (WGFAST) and Science Committee (SCICOM). This is the first ICES CRR to detail the latest multifrequency and wideband methods for acoustic target classification.

Author Posting. © Acoustical Society of America, 1991. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 90 (1991): 37-47, doi:10.1121/1.401261., Echo sounding is a powerful and widely used technique for remote sensing of the marine environment. In order to enhance the power of the echo sounder, a postprocessing system has been designed and realized in standard software that is essentially machine independent. This has been done by adhering to the following international standards: UNIX operating system, C programming language, X Window Systems, Structured‐Query Language (SQL) for communication with a relational database, and Transport Control Protocol/Internet Protocol (TCP/IP). Preprocessed data are transferred from the echo sounder to the postprocessing system by means of a local‐area network (LAN), namely Ethernet. Development of the postprocessing system, for analysis of such diverse scatterers as plankton, pelagic, and bottom fish, and the bottom itself, is documented in the following way. The history of echo integration is summarized. User requirements for the new system are listed. Reasons are given for the choice of the particular computing environment, including both hardware, software, and external communications. The system design, consisting of data flow and graphical user interfaces, is described. Implementation of the system is defined through integration techniques and a discussion of performance issues. Operating procedures and the first field trials of the system are described. Several features characteristic of and perhaps unique to the postprocessing system are, for example: (1) user definition of arbitrarily shaped integration regions, including non‐constant‐depth intervals, by means of interactive graphics; (2) preprocessor error correction, e.g., adjustment of the noise threshold or redefinition of the detected bottom; (3) use of several color map techniques in order to extract such information as signal strength and shape; and (4) the scheme of interconnections of graphical user interfaces, database, and data files. This work does not introduce a set of computer instructions. It does d

Author Posting. © Acoustical Society of America, 1991. This article is posted here by permission of Acoustical Society of America for personal use, not for redistribution. The definitive version was published in Journal of the Acoustical Society of America 90 (1991): 37-47, doi:10.1121/1.401261., Echo sounding is a powerful and widely used technique for remote sensing of the marine environment. In order to enhance the power of the echo sounder, a postprocessing system has been designed and realized in standard software that is essentially machine independent. This has been done by adhering to the following international standards: UNIX operating system, C programming language, X Window Systems, Structured‐Query Language (SQL) for communication with a relational database, and Transport Control Protocol/Internet Protocol (TCP/IP). Preprocessed data are transferred from the echo sounder to the postprocessing system by means of a local‐area network (LAN), namely Ethernet. Development of the postprocessing system, for analysis of such diverse scatterers as plankton, pelagic, and bottom fish, and the bottom itself, is documented in the following way. The history of echo integration is summarized. User requirements for the new system are listed. Reasons are given for the choice of the particular computing environment, including both hardware, software, and external communications. The system design, consisting of data flow and graphical user interfaces, is described. Implementation of the system is defined through integration techniques and a discussion of performance issues. Operating procedures and the first field trials of the system are described. Several features characteristic of and perhaps unique to the postprocessing system are, for example: (1) user definition of arbitrarily shaped integration regions, including non‐constant‐depth intervals, by means of interactive graphics; (2) preprocessor error correction, e.g., adjustment of the noise threshold or redefinition of the detected bottom; (3) use of several color map techniques in order to extract such information as signal strength and shape; and (4) the scheme of interconnections of graphical user interfaces, database, and data files. This work does not introduce a set of computer instructions. It does d

Current acoustic survey protocols for Atlantic herring (Clupea harengus) abundance estimation are principally dependent upon 38-kHz backscatter data. This can constitute a substantial problem for robust stock assessment when 38-kHz data are compromised. Research vessels now typically collect multifrequency data during acoustic surveys, which could be used to remediate such situations. Here, we investigate the utility of using 18- and 120-kHz data for herring abundance estimation when the standard 38-kHz approach is not possible. Estimates of herring abundance/biomass in the Celtic Sea (2007–2010) were calculated at 18, 38, and 120 kHz using the standard 38-kHz target-strength (TS) model and geometrically equivalent TS models at 18 and 120 kHz. These estimates were compared to assess the level of coherence between the three frequencies, and 18-kHz-derived estimates were subsequently input into standard 38-kHz-based population models to evaluate the impact on the assessment. Results showed that estimates of herring abundance/ biomass from 18 and 38 kHz acoustic integration varied by only 0.3–5.4%, and acoustically derived numbers-at-age estimates were not significantly (p . 0.05) different from 1:1. Estimates at 120 kHz were also robust. Furthermore, 18-kHz-derived estimates did not significantly change the assessment model output, indicating that 18-kHz data can be used for herring stock assessment purposes.

Current acoustic survey protocols for Atlantic herring (Clupea harengus) abundance estimation are principally dependent upon 38-kHz backscatter data. This can constitute a substantial problem for robust stock assessment when 38-kHz data are compromised. Research vessels now typically collect multifrequency data during acoustic surveys, which could be used to remediate such situations. Here, we investigate the utility of using 18- and 120-kHz data for herring abundance estimation when the standard 38-kHz approach is not possible. Estimates of herring abundance/biomass in the Celtic Sea (2007–2010) were calculated at 18, 38, and 120 kHz using the standard 38-kHz target-strength (TS) model and geometrically equivalent TS models at 18 and 120 kHz. These estimates were compared to assess the level of coherence between the three frequencies, and 18-kHz-derived estimates were subsequently input into standard 38-kHz-based population models to evaluate the impact on the assessment. Results showed that estimates of herring abundance/ biomass from 18 and 38 kHz acoustic integration varied by only 0.3–5.4%, and acoustically derived numbers-at-age estimates were not significantly (p . 0.05) different from 1:1. Estimates at 120 kHz were also robust. Furthermore, 18-kHz-derived estimates did not significantly change the assessment model output, indicating that 18-kHz data can be used for herring stock assessment purposes.