SMALL STREAMS: Contribution to populations of trout and sea trout.
Report of a workshop held at Carlingford, Co. Louth, Ireland on 27 and 28 November 2012 |
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- 15/ In discussion it was noted that small streams were particularly vulnerable to the impacts of climate change. Increased water temperatures are likely to pose particular problems. There is evidence that these are affecting egg growth, with reduced times to hatching (although this could be being offset by later spawning). Relatively limited increases in temperature have been shown to affect juvenile growth and survival, and there is also evidence that higher temperatures reduce survival rates among ranched salmon. There is a need for data on the effect of higher temperatures on energetics and on marine survival. Overall, trout have a narrower range of optimal temperatures than salmon, and it is possible that increased in-stream temperatures will serve as a driver for increases in levels of anadromy.
- 16/ Climate change is also likely to lead to more extreme conditions, with more floods and droughts; the impact of these will be accentuated by the limited resilience of small streams .It was noted that work was needed on how algae, plants, invertebrates and fish would survive and on their ability to adapt; interfaces between small and larger streams and small streams and loughs would be critical as refuge areas. Climate change would also increase the risks posed by invasive species, disease and parasites.
- 17/ The workshop concluded that it was important to record and map the impact of climate change on small streams, including cumulative impacts, using appropriate indicators, and that there was a clear need for national repositories of climate change information. It was pointed out that in Ireland a great deal of relevant information was held in the National Biodiversity Data Centre (www.biodiversityireland.ie/). It was also necessary to bear in mind that there is evidence for the existence of microclimates within catchments, so extrapolation of data from particular sites needed to be done with caution.