HOW WILL CLIMATE CHANGE AFFECT OUR FISHERIES?
The only certainty is that long-term global warming, climate change and disruptive weather will have consequences both good and bad
“Warmer summers and mild winters are good news for many UK coarse fish species...”
AS WINTER bites it can be difficult to believe that global warming is a real phenomenon. Yet whether or not you believe it’s caused by human activity, the climate is changing and this will affect our fisheries for centuries to come.
The Earth’s climate has always been in a state of flux, with periods when the planet was hotter than it is now and other times when it was significantly cooler. The last Ice Age, for example, which covered most of the UK in an ice sheet hundreds of metres thick, ended just 12,000 years ago – a mere blink in geological terms. Whatever the reasons, we’re now seeing the planet warm up and, with the complex weather patterns we see in the UK, this is already having an effect on our climate. The weather affecting the UK is becoming more extreme and less consistent.
Which species will thrive?
Warmer summers and mild winters are good news for many UK species of coarse fish, many of which are close to the northern limit of their range. Species such as carp, tench and bream aren’t native to Scotland and the Borders, but are increasingly stocked in fisheries here and do well. Successful recruitment of small fish into the next generation is likely to be limited, though, particularly because of lowerthan-required sustained temperatures in summer.
Higher summer temperatures and longer summers could well see recruitment improving for these species, particularly further north.
It’s not all good news, though, especially for some of our rare native species that require much cooler conditions. The once abundant burbot disappeared from our rivers after the last Ice Age, because it requires low temperatures to survive. Powan, a rare whitefish found in just a few glacial lakes in the UK, are also under increasing threat from rising temperatures and pollution. Grayling are perhaps another species that could see their range diminished as some rivers become too warm for them to tolerate.
Records may be broken
Will rising temperatures see our coarse fish records broken as fish will be able to grow faster? Once
again, what benefits one species may limit another. Longer summers and mild winters can, other factors being equal, mean that fish can grow faster and for longer. Food must be plentiful, though, and oxygen levels must remain high for fish to feed.
Over the last few decades we’ve seen tench, carp and barbel records shoot up to weights previously thought unobtainable in the UK. Interestingly, the sizes reached by these species are now approaching those seen some years ago in mainland Europe.
The average size of specimens of all three species has also increased massively and across the whole country, which suggests that this is not just a localised phenomenon. While the carp record could be expected to increase as more fish of better strains have been stocked, the other two species are perhaps more intriguing. While many different reasons for this size increase have been postulated, only changes to the climate can explain why this has happened in so many, such diverse, venues.
Other species have seen no increase in their maximum size and specimens have, if anything, become more rare.
Pike and roach are good examples of species that appear to have been ‘left behind’. Both species are not close to their northern extremity in the UK, and so the climate here is probably already close to the optimum.
The records for these species are also similar to ours in many other European countries, suggesting that they derive no benefit from climate change.