Climate change survival
QWhat effect is global warming likely to have on fish spawning?
Eileen Brooke, via email.
AClimate change is a huge and complex global problem, which has wide-ranging social and economic implications, as well as those relating to the natural environment, and whatever climate change deniers say, it’s here, it’s happening, and it won’t go away.
Average temperatures in the UK have risen by a degree since the 1970s, and ocean temperatures by 1.5 degrees since the 1980s, and even if emissions are cut dramatically with immediate effect, the level of greenhouse gases already in the atmosphere means that further warming is inevitable.
Computer modelling based on current data suggests that winters in the UK will become wetter and summers will become warmer. Wetter winters will increase the likelihood of flooding, which brings with it the potential to reshape riverine habitat, and threaten the survival of overwintering fry.
Higher summer temperatures will result in greatly reduced river flows, poor groundwater replenishment, increased evaporation, increased siltation, greater water enrichment, reduced dilution of pollutants, and reduced oxygen saturation. Overall, it’s not a pretty picture for the aquatic environment, with finely balanced ecosystems likely to be adversely impacted by a huge range of environmental variables.
As far as fisheries are concerned, the current, bigger picture is focussed more on the impact upon the commercially important marine and migratory species than on our coarse species, but the implications are clear.
Coldwater marine species, such as cod and haddock, are already moving further northwards, to stay within their ecological temperature range, and southern ‘invaders’ are beginning to push into UK waters, including sardines, red mullet and John Dory.
There are, however, a few potential benefits for anglers, including the possible reestablishment of a UK tuna fishery, but this has to be balanced by the potential failure of our Atlantic salmon fishery, due to disruption of temperature-related migration and spawning, and the loss of vulnerable and endangered species, such as the European whitefish (powan/pollan).
As with all environmental change, there will be some species that win and some that lose. With global warming, all predictions suggest that there will be far more losers than winners, and that works in all habitats right across the globe, not just in the aquatic environment.
Spawning is just a small part of the overall climate change picture, albeit an important one. As far as spawning is concerned, the main short-term impact, as with marine and migratory species, will be upon those species at the extremes of