138 sites were surveyed during the summer of 2016 using a semi quantitative method. 26 of these sites were also calibrated with the EA by completing fully quantitative, area based surveys. A total of 614 trout and 551 salmon were recorded at the 138 sites, of which 451 were trout fry and 461 were salmon fry. All fish numbers in 2016 were lower than in the summer of 2015, likely due to the effects of Storm Desmond which hit during spawning season and may have washed many eggs away. Notwithstanding the storm many sites still had salmonids present; 61 sites or 44% of those surveyed had salmon fry present, whilst 92 sites or 67% of those surveyed had Trout present.
Again corresponding habitat data was collected alongside the fish data and then each site was assigned a habitat condition or category of either Maintain, Repair or Restore. Out of the 138 sites, 52 were classed as Maintain, 65 as Repair, and 21 as Restore. This is then up scaled to a tributary classification of which, of the 45 tributaries surveyed 9 were classed as Maintain (21%), 32 as Repair (71%), and 4 as Restore (8%).
Whilst the overall fish numbers were lower in 2016 than the 2015 surveys, most likely as a result of the severe floods in December 2015, a remarkable number of salmonid fry have survived. A lot of the sites with low fry numbers in the 2016 surveys, still had parr present, which suggests that the floods in 2015 had greatest effect on redds (where eggs are laid by adult fish), whilst some fish were able to find shelter from the flood waters. This is the second year of surveying juvenile salmonids in the River Derwent catchment so whilst the results cannot yet be used to detect trends, a database is being built using the results. With more sites surveyed in 2016 a greater database of habitat conditions has been built. This database will then be used to inform areas where habitat work would provide the greatest benefit for fish populations. It was noted that sites with greater fish densities reflect the sections of river with good habitat and with room for flood waters to spread out across the flood plain and therefore reduce redd washout. In areas where the river has been modified, with built embankments and a straight channel, the effects of fast flood flows appears to have reduced the survival of juvenile salmonids.
A huge thank you to everyone involved including funders, landowners who gave access permissions and especially all the wonderful volunteers who came along to give us a hand surveying.
|Survey Report 2016||5.59 MB|
|2016 Raw Fish Data||xlsx||86.85 KB|