Ichthyoplankton and pelagic fish assemblages in the Greenland Sea in 2017. Technical Report No. 110

Following a Strategic Environmental Study Plan for Northeast Greenland commissioned by 
the Danish Centre for Environment and Energy (DCE), the Greenland Institute of Natural 
Resources (GINR) and The Bureau of Minerals and Petroleum Greenland (BMP), a scientific 
cruise was conducted onboard the R/V Dana from 23 august to 11 September 2017. The main 
objective of the cruise was to provide environmental information for the planning and the 
regulating of oil exploration activities in the Greenland Sea. The specific objective of the 
present report is to provide information on ichthyoplankton and pelagic fish in the region. The 
methods used include ichthyoplankton nets, pelagic trawl and hydroacoustics. The
ichthyoplankton collected belong to a very low number of species, predominantly polar cod
(Boreogadus saida), a key species in arctic marine ecosystems. Spatially, polar cod dominated 
the assemblage on the continental slope and offshore while the other species dominated the 
shelf assemblage. Preliminary investigations suggested an apparent shift towards earlier 
hatching for polar cod, which could be associated with a relaxation in the extreme 
environmental conditions typical of the region (long sea-ice season and freezing sea surface 
temperature) over the past 25 years. This shift, if confirmed, could represent an increase in the 
recruitment of polar cod populations in the Greenland Sea. To investigate further this issue, a 
study based on otolithometric measurements of the polar cod larvae collected will be initiated 
in the coming months, and the results will be published in a peer-reviewed scientific journal 
such as Polar Biology. Combining the data from the echosounder with those of the trawl 
allowed to associate different echo patterns to specific organisms in the water column.
Spatially, the acoustic data showed that the northeastern part of the study area appeared as a 
region of high biomass for the entire water column. The area encompassed the shelf break, an 
habitat polar cod is known to occupy in large biomass in other Arctic regions. Further analyses 
linking the acoustic data will with environmental parameters such as salinity, temperature and 
sea-ice dynamics will be done, compared with similar studies from other arctic seas, and 
synthesized in a publication to be submitted in a peer-reviewed scientific journal such as 
Progress in Oceanography.