Tasks in work package 4: Mapping of mesopelagic resources

Overview of tasks in work package 4

Using the methods and protocols developed in work package 2, this work package will carry out field campaigns in the North Atlantic Ocean, including the Nordic Seas and the Bay of Biscay to collect biological material and ancillary abiotic data (Task 4.1).

The processing and analysis will provide new knowledge on abundance, vital rates (Task 4.2), the relationships between distribution of mesopelagic biomass and the environment (Task 4.3) and its role in carbon sequestration (Task 4.4).

The activities and tasks proposed will vary according to the objectives pursued by each study area. The results will be used for further analyses and inputs for assessment and ecosystem modelling in work package 5 and for management tools and governance in work package 6 and work package 7.

Overview of work package 4
Flows of information and data to, from and within work package 4. Click to see larger version 

Task 4.1. Field campaigns and in-situ sampling

Lead: Marine and Freshwater Research Institute

This task will carry out a series of directed studies of the mesopelagic community on both dedicated surveys within the project and by applying for additional ship-time on existing nationally funded surveys. In sum the cruises cover major parts of the Northeast Atlantic.

A range of new methods and technologies (acoustical, optical, trawls/nets) demonstrated, tested, and described in work package 2 will be applied on these surveys for the quantification of abundance of the mesopelagic fauna at the finest taxonomic scale possible, ideally at species level. In addition, data on horizontal and vertical distribution of oceanographic parameters, such as temperature, salinity, light penetration, and chlorophyll-a will be collected.

Information on the distribution of higher trophic levels (e.g. cetaceans, seabirds) will be collated from historical databases. Further, distribution of megafauna apex predators will be collected during the cruise by IMAR – Instituto do Mar around the Azores to assess their spatial connectedness with mesopelagic resources. The MEESO project will also explore the possibilities of retrieving data on megafauna on other cruises by having experts on the observation and quantification of such data on board.

End-products will include regional maps of distribution and abundance of mesopelagic communities in the North Atlantic focusing on potential fishing areas and reported for the five study sites.

New trawl and acoustic technologies from work package 2 will be made available to all partners conducting surveys and deployed to the extent that research vessel capabilities allow.

The surveys include: 

  • The MEESO partners Institute of Marine Research, IMAR – Instituto do Mar and Fundacion AZTI – AZTI Fundazioa will carry out dedicated mesopelagic community surveys in 2019/2020 and in 2021 to the Azores, the Nordic Seas and Bay of Biscay. Some dedicated surveys were conducted in 2016- 2018 in the North-Atlantic by Institute of Marine Research, Lie Group and BIRKELAND (SINTEF) and data are made available to the MEESO project.

  • In addition, large-scale distributional data of mesopelagic fauna will be obtained by Institute of Marine Research performing along Atlantic transects, with acoustic mapping net and trawls samples surveying the eastern, central and western Atlantic from Norway to Brazil.

  • The partnership will also apply for additional time on existing nationally funded surveys in 2019/2020 and in 2021 in support of activities in MEESO. Study sites comprise the sea area west of Ireland and the Iceland Basin (mackerel, blue whiting surveys), Irminger Sea (redfish), Iceland Sea (capelin) and Norwegian Sea (Norwegian spring spawning herring).

Task 4.2. Processing of samples and data production to assess the standing stocks, ecological status and dynamics of mesopelagic fauna

Lead: Fundacion AZTI – AZTI Fundazioa

In conjunction with activities in Task 4.1, data from the five study sites will be assembled and processed to determine large-scale distribution of contaminants, nutrients, trophic status (lipids, stable isotopes), main diet and diel feeding patterns (stomach contents), vital rates, oceanographic parameters, light penetration and passive particle flux using optical methods and measured sinking rates in the North Atlantic. It should be noted that it will not be possible to analyse for all these parameters in all five areas, due to different vessel and analytical capabilities.

The analyses include: 

  • Water mass properties for the whole water column will be determined using standardized techniques for measuring temperature, salinity, oxygen, inorganic and organic carbon, and nutrients.

  • In-situ estimates of phytoplankton biomass (Chla) in the euphotic zone will be processed and evaluated against satellite derived values.

  • A conceptual model of trophic pathways will be assessed by employing stable isotope and fatty acid techniques complemented with gut content analyses for selected species.

  • Vital rates will be assessed by season (as far as possible): growth (length, weight, age), maturity (proportion maturity by length), fecundity (length), mortality (vertical life table analyses of field-based catch rates), consumption rates (stomach content by size).

  • Content of contaminants, nutrients and antinutrients will be compared and contrasted between regions.

  • Imaging technology (VPR) and "marine snow-catchers" will be used to quantify size, abundance and sinking rates of marine snow particles within the upper 1000 m of the water column. Samples will also be taken for POC analysis.

  • Existing survey data (acoustics from hull-mounted transducers and depth-stratified trawl data by pelagic fish trawls) will be compiled. They include time series for abundance quantification and species composition of the shallower (200-300m) mesopelagic assemblages in the Irminger Sea, Norwegian Sea, Bay of Biscay and west of Ireland.

Task 4.3. Spatial distribution of biomass

Lead: Marine Institute

Using data generated in Tasks 4.1 and 4.2, we will apply various statistically robust methods (e.g. GAMs, probabilistic modelling approach) to explore the effect of biological and ocean dynamic environment on the abundance of mesopelagic species and their spatial distribution. We will identify the most important explanatory variables explaining mesopelagic species abundance patterns, both in horizontal and vertical scale. Additionally, time series data will be reassessed to produce picture of changes over time of these species.

  • The large and small scale spatial distribution of the biomass of mesopelagic species will be explored in relation to key environmental variables (primary production, temperature, water masses, ocean circulation and bottom depths). Based on data collected and processed in Tasks 4.1 and 4.2 we will be able to disentangle the effect of 3D oceanographic variables at biologically meaningful vertical domains.

  • The standing stocks, size structure and vertical distributions of the mesopelagic communities will be assessed where survey information is available in the North Atlantic Ocean and the Nordic Seas using data from advanced acoustics, optics (e.g. VPR) and net/trawl samples generated in Tasks 4.1 and 4.2.

  • Size distributions and spatial distributions will be estimated using one or more methods, including advanced geostatistical models to estimate distribution patterns. These can include general linear mixed models (Thorson et al. 2015; see bottom of page) or, if supported by the data, a statistical model that combines spatio-temporal correlations with simple stock dynamics to estimate simultaneously how size distributions and spatial distributions develop in time (Kristensen et al. 2013; see bottom of page).

  • The diel vertical migration patterns of mesopelagic fauna (depth range and time) spent at shallowest and deepest depths will be described and quantified.

  • The spatial co-occurrence of the mesopelagic fishes and marine megafauna (e.g. cetaceans and seabirds) will be assessed to identify ecosystem structure and key interaction within the mesopelagic community. Data will be analysed using a probabilistic modelling approach developed by Veech (2013) and the cooccur package of the R environment.

  • Existing acoustic (vertical sounders) data from historic surveys in the study sites will be reanalysed to evaluate abundance indices, and variations of these, where possible by depth layers in the upper part of the Deep Scattering Layers. The following international surveys collect acoustic data:
    • International blue whiting spawning stock survey (IBWSS).
    • International Ecosystem Survey in Nordic Sea (IESNS).
    • The redfish surveys in the Norwegian and Irminger Seas.
    • The potential for including additional surveys in the analyses will be explored.
    All do 38 kHz acoustics, and some do multifrequency with 18, 38, 70, 120, 200 and 333 kHz transducers. All surveys now collect EK 80 data, but not on all ships. The surveys collect samples with pelagic trawls of different types that will be available to MEESO for analyses.

  • The spatial ranges will be determined across which species abundance remains consistent using project and historic, acoustic and sampling data to define the best spatial scales for routine monitoring and management.

Task 4.4. Role of the mesopelagic in carbon sequestration

Lead: Institute of Marine Research

The magnitude of the active carbon flux due to mesopelagic organisms relative to the gravitational flux will be quantified.

Active flux arises from processes such as ingestion, respiration and defecation taking place at different stages of the diel migration. The net downward flux will be estimated using data on vertical distribution (daily migration), abundance, and biomass derived from Task 4.3. Application of allometric formulae to estimates of size for major species will be used to quantify physiological rates such as respiration. Abundance data will allow these rates to be scaled up to the population. These data will be combined with data on timing and depth range of diel migration (Task 4.3) to estimate the active flux for each enumerated taxonomic group.

Passive flux will be estimated using data on abundance and sinking rates of marine snow particles from the "marine-snow-catcher" (Task 4.2).

Furthermore, data on abundance and size spectra of marine snow particles derived from the VPR will be combined with equations relating size of particles to sinking velocity to arrive at an independent estimate of flux of marine snow.


Kristensen, K., Thygesen, U. H., Andersen, K. H., & Beyer, J. E. (2013). Estimating spatio-temporal dynamics of size-structured populations. Canadian Journal of Fisheries and Aquatic Sciences, 71(2), 326-336.

Thorson, James T., Andrew O. Shelton, Eric J. Ward, Hans J. Skaug; Geostatistical delta-generalized linear mixed models improve precision for estimated abundance indices for West Coast groundfishes, ICES Journal of Marine Science, Volume 72, Issue 5, 1 June 2015, Pages 1297-1310.




Participants in work package 4: 

  • Marine and Freshwater Research Institute
  • IMAR – Instituto do Mar
  • Marine Institute
  • Institute of Marine Research
  • Fundacion AZTI – AZTI Fundazioa
  • Technical University of Denmark
  • National Oceanographic Center
  • Wageningen University
  • Liegruppen Fiskeri AS

Learn more about MEESO project partners


Work package 4 is lead by Marine and Freshwater Research Institute, Iceland. 

Astthor Gislason, astthor.gislason@hafogvatn.is 

Klara Jakobsdóttir, klara.jakobsdottir@hafogvatn.is

19 JULY 2024