Trawling for good news
Photo Credit: Alan Searle
There are plenty of statistics available in research papers which provide evidence that the seas are warming, both globally and around the UK coasts. Undoubtedly, this rise in water temperatures will have implications for marine wildlife. However, impacts below the water surface may well go largely unnoticed at first, emerging only when fishing industries find their traditional fishing grounds becoming less productive.
Sea surface temperatures in waters around the UK have risen by an average of 0.8⁰C since 1870 and the trend since the 1970s has been unremittingly upwards. Indeed, parts of the North Sea have seen temperatures rise by 1.5 – 2⁰C in the last 40 years.
Warmer water contains less dissolved oxygen than cold water. This means that marine life will find it more difficult to thrive or even survive in such seas. In addition, extra carbon dioxide absorption caused by increasing atmospheric concentrations of the greenhouse gas, is leading to enhanced acidification of the seas; something which has particular relevance for shellfish growth and food chains. Since the 1980s, it is estimated that the oceans have absorbed about 20-30% of man-made carbon dioxide emissions.
Effects on Fishing
- There has been an overall poleward shift in the distribution of species of fish
- Some species are spawning earlier than previously
- Warm water species, such as Red Mullet, are becoming more common around the UK
- Cold water species, such as Atlantic Cod, are becoming less common and there is some evidence to suggest that they may ultimately be unable to persist in UK waters
- Aquaculture, mainly the farming of Atlantic Cod and Blue Mussel, is at risk since it is already taking place near the southern limit of these species’ European ranges
- The East coast port of Whitby has suffered with the northward migration of fishing grounds because this has meant it is becoming more economic to land catch further North at places such as Aberdeen
- Some species are now much more prevalent than before. For example, in the North Sea, squid are now found in large numbers and anchovies, which were rare until the 1990s, have increased dramatically in recent years
- Seabass is another species which had been expected to thrive in warmer waters, but although this happened at first, the rapid increase in catch over recent years has since slowed or even reversed its initial gains
- Another possible consequence of a warming climate might be that storms increase in frequency and severity, although models differ on such regional detail. However, if worsening weather keeps the fishing fleet tied up in port for longer, the effect on fishing could be serious
Possible mitigations and adaptations
The overall impact of our changing climate is clearly going to vary across and between geographical regions. It seems clear that solutions are going to have to be sought through a variety of approaches
- Fishing methods may need to adapt
- New gear may be needed on vessels
- As species move to new waters, fishers may have to follow them
- Regulatory changes involving things like net mesh sizes and new catch quotas may be needed. These are kept under review by governments, but all actions will need to be sustainable and mutually agreed
- The consumer too may have a part to play. If people can be persuaded to try something new on their plates and take advantage of the arrival of different species at traditional fishing grounds, then that may open up hitherto unexpected opportunities for the fishing industry.
- The industry itself could also take steps to reduce greenhouse gas emissions from its own activities. Fuel efficiency could be improved by switching to more efficient equipment or changing fishing practices, as well as reducing the travel distance of products and increasing consumption near the source.
Sources: Pinegar, J.K. et al. (2017) Fisheries. MCCIP Science Review 2017, 73-89. doi:10.14465/2017.arc10.007-fis
UK Government Report: Future of the Sea: Biological Responses to Ocean Warming 2017
UK Marine Monitoring and Assessment Strategy. https://moat.cefas.co.uk/ocean-processes-and-climate/sea-temperature