Case Study: State of the Atlantic cod | Kustportaal

Case Study: State of the Atlantic cod

It seems that the future of the Atlantic cod in the North Sea is not looking very bright, or so states the article that was published on the Canvas website (https://www.canvas.be/maatschappij/jan-seys-over-de-kabeljauw). In the article, Jan Seys, marine biologist and head of science communications at Flanders Marine Institute (VLIZ) discusses the species' future for the Belgian part of the North Sea. A plea that is meaningfully named "an ode to what is disappearing", as the conclusion of the article is that the cod is steadily disappearing from the Belgian part of the North Sea. Scientists predict that in case of a raise in sea water temperature of four degrees, the cod will be gone completely from North Sea waters. Quite striking, considering that the Atlantic cod is sometimes referred to as the "King of all North Sea fish".

This negative conclusion is backed up by other sources such as the chart next to this article. It shows the state of the Atlantic cod in 2018 for the different habitats in the North Sea, with almost all habitats graded as "not OK" for both biomass and mortality rates. Only the Irish Sea seems to be an exception. The chart is part of an infograph made up by the Research Institute for Agriculture, Fisheries and Food (ILVO) and VLIZ. There are infographs on 11 other species as well, all published together in december 2018. The Coastal Portal already discussed these infographics in an earlier article, which you can find using this link.

The reasons behind the cod's decline seem twofold. First, the past rise in sea water temperatures has made living conditions too warm for the species. Secondly, also the cod's food sources are migrating north because of the heated sea waters. This makes it difficult for premature cods to find enough food in our region to survive the important first weeks in their life cycle. 

Yet, the cod is not the only species having to deal with these issues. The northward shift is also visible for the haddock, sole, whiting and herring. This produces newly available niches for other species that are ordinarily not occurring in our region. Such opportunists are the sea bass, squid, sting-fish and sardine. 

More information on al these species can be found on the Fish themepage within the Coastal Portal. Below is an example of the dynamic maps linked to this theme, showing the number of occurrences counted for different species within a certain period of monitoring. Additionally, the trajectory followed by two cods between the North Sea and the Western Scheldt in 2015 can be visualized as wel. 

The data displayed above is collected using the acoustic telemetry network of the LifeWatch-Project. This network consists of 160 permanent receivers that register the movements and occurrences of fish that are fitted with an acoustic transmitter. The unique ID of each transmitter allows the identification of the species that is registered as well. The network comprises the Belgian part of the North Sea, the Scheldt estuary, and several rivers and channels, as well as being part of the larger European Tracking Netwerk (ETN). All data gathered by the network can be accessed through the LifeWatch data explorer.