Shifting Latitudes - North Sea Fishes

Globally, spatial distributions of fish stock are increasingly shifting in latitude as well as depth. Although arguably intensive fishing pressures plays a role, however, patterns observed recently are most likely attributed to recent climate change and increases in seawater temperature. It is widely known that changes in sea temperatures may influence fishes through their growth, reproduction and their food web from changes at other trophic levels. Species having limited dispersal capability of responding to the changes or have troubles finding a suitable habitat may potentially face widespread extinction. Research has shown species that recently responded to the changing conditions tend to have faster life cycles and smaller body size than non-shifting species – meaning that some species are currently losing or might lose out in the future!

                                                               Shoal of Fish Migrating!

Allison Perry and her colleagues noted that temperatures of the North Sea water have increased by an average of 0.6 degrees between 1962-2001. Their research showed that Atlantic cod (Gadus morhua), scaldfish (Arnoglossus laterna), snakeblenny (Lumpenus lampretaeformis) and common sole (Solea solea) have all shifted northwards with a distance ranging from 48 – 403 kilometers (WOW!). 403 kilometers seems as though a huge but unsurprising number, as the rates of migration are likely much higher than other wildlife (such as butterflies) since they are less likely to face barriers and constraints during the process.

   Snakeblenny 

Similarly, Engelhard and his team examined historical and contemporary fisheries data and revealed that current distribution of North Sea cod – located mainly in northeastern parts of the North Sea is entirely opposite to the distribution in 20^th century, where they were mainly found in the west, just off the coast of England and Scotland. They suggested that the northward shift is likely due to warming, however, intensive fishing pressures have likely caused the eastward shift shown.  

     North Sea Cod

Future estimation by UK Climate Impacts Programme suggested that North Sea water temperatures are predicted to increase by 1 to 2.5 degrees by 2050. And it has been suggested that blue whiting, redfishes and many more species may completely retract from the North Sea by 2050!  Sad :/