Despite drought conditions at the start of the survey season, 2018 was the most successful season to date. In total 157 sites across the Derwent catchment were surveyed, including 27 main river sites. A whopping 2606 trout and 4257 salmon were recorded, and broken down into fry and parr; 2022 trout fry, 584 trout parr, 4025 salmon fry and 232 salmon parr. Of the total 157 sites surveyed, 127 sites (81%) had trout fry present and 84 (54%) had salmon fry present. 70 sites (45%) had adult European eels ( Anguilla anguilla) or elvers (young eels) present, 109 sites (69%) had minor fish species present such as lamprey, sticklebacks, minnows, stoneloach, and bullhead. When the total number of fry recorded was compared to the previous year (2017), there was a 564% increase in the number of salmon fry recorded, and a 7% increase in the number of trout fry recorded.
The main reason for the large increase in the number of salmon fry recorded between previous years and the 2018 survey season is down to these 27 main river sites. 49% of the salmon fry recorded were found at the 27 main river sites. Normally the main river sites can’t be surveyed due to high and fast flows, which would lead to poor catch efficiency and for the safety of the survey team. However due to the low river levels at the start of the season, the opportunity arose to survey these sites. The high number of salmon fry in the main rivers reflects that the habitat is more suited to them here and highlights why the main river Derwent is designated a SSSI and SAC for Atlantic Salmon. It is also possible that a high proportion of salmon fry were recorded at the main river sites because as water levels dropped and receded during the drought, the survival instinct kicked in and the fish swam downstream, out of the tributaries and into the main rivers, to where there was more water present.
The most number of salmonids ever recorded in a 5-minute survey by WCRT was recorded at Wanthwaite Bridge on St John’s Beck during the 2018 survey season. In total: 344 salmon (6 parr, 338 fry) and 1 trout fry, as well as 1 eel, 2 stoneloach, 2 minnows, 3 sticklebacks. We were measuring fish for ages!
© David Marshall (Natural Course team)
© Martin Pullan
Once again, a massive thank you to all the wonderful volunteers who helped conduct the surveys, and to the many landowners who gave us permission to access their land to get to the rivers.
|2018 Survey Report||20.22 MB|
|2018 Raw Fish Data||xlsx||108.45 KB|