Fish make up a substantial percentage of our protein intake and provide 1.7 million jobs which are tied in with a fishing industry which brings in $199 million dollars per year (NOAA.gov). It’s therefore easy to see why the well-being of our wild and farmed fish is a top priority.
Climate change is no doubt a term we’ve all heard before, but what is climate change? Climate change is first and foremost a natural phenomenon driven primarily by Milankovic Cycles. These cycles dictate the shape of the earth’s orbit around its own axis and around the sun; and therefore, are responsible for giving us seasons and climate. Although Milankovic Cycles dictate long term climate (glacial and interglacial periods), climate can also be changed over a short term period, this can be driven by multiple factors but one of the most important is ocean currents, these short-term cooling events are called Dansgaard-Oeschger Events (Skinner and Murck, 2011).
So, that is an explanation to what natural climate change is. Unfortunately, the large input of carbon dioxide that has been occurring since the industrial revolution has been accelerating this process of climate change. Most of the solar radiation which warms our planet usually rebounds back into space, but this excess of carbon dioxide and other pollutants means that more of this solar radiation is trapped within the atmosphere. This is called the greenhouse effect.
Effects on North Sea Fish
The North Sea is just one area where the marine ecosystem has been effected by climate change. Research conducted in 2005 by Allison Perry suggests that warmer temperatures are driving North Sea fish towards colder waters. This is a problem since these cooler waters may not have the suitable habitats required for these fish to survive, causing the fish to become weaker and less likely to reproduce; this would have a very negative effect on commercial fishing and the economy. Research shows that certain species such as Atlantic Cod (Gadus Morhua) and the common sole (Solea solea) had their centres of distribution shift northwards buy at least 48 kilometres and as much as 403 kilometres (Perry et. al, 2005). Certain species such as plaice (Pleuronectes platessa) and cuckoo ray (Leucora janaevus) may have shifted depths instead of latitudes in order to reach cooler waters (Perry et. al, 2005). Overall, nearly two thirds of North Sea species show distribution changes in response to climate change. It was also found that the boundaries of 10 species of fish shifted northwards towards more intensely fished waters; these shifts range from 119 kilometres to 816 kilometres. These findings are supported by reports that bib (Trisopterus luscus), a specie that has shifted northwards, is more intensely fished than it was in the past (Perry et. al, 2005).
The Blue Planet: An Introduction to Earth System Science (Skinner and Murck, 2011)
Climate Change and Distribution Shifts in Marine Fishes (Perry, 2005)