Impact of climate change on Greenland ecosystems and fish resources, first report on decadal scale changes in fish community structure along the West Greenland coast

Based on summer trawls surveys along the West Greenland coast and shelf, the spatiotemporal
variation in the demersal fish community was quantified between 1993 and 2016. A
substantial change was observed with 4 to 10-fold increase in total biomass, increase in the
average size of specimens and an increase in the average trophic level in net hauls. Findings
suggest a substantial quantitative and qualitative change in the importance of demersal fish for
the coastal food web with likely cascading effect to trophic levels below and above. Based on
near-bottom temperature measured on the trawl gear we identify slight warming trends in the
northern region and in the two deepest depth strata (200-600 m).

When compared to decadal variability based on CTD data from available data bases we find that the recent warming trend is not outside the range of a previous “warm period” in the 1930s underlining the importance of identifying decadal variability in climate. Decreasing fish mortality from shrimp by-catch
contributed to improved mitigation practice combined with decreased fishing effort is
identified as a major driving factor. However, it coincides with atmospheric warming and
consequently reduction in sea ice concentration and increased summer run-off from the
Greenland Ice Sheet, which improve light and nutrient for primary production. Thus, it is an
important example of how recovery from over-exploitation may be shaped by climate change.