Salmonids in the Teign
Salmonids are a family of fish including the Atlantic salmon (Salmo salar) and brown trout (Salmo trutta). Salmon and trout have a fascinating life cycle which takes them on a journey between freshwater rivers and the open seas. Sadly, the number of salmon and trout have declined in rivers across the UK. Human changes to river habitats, such as the straightening of river channels, building dams and removal of bank-side trees, coupled with a warming climate and low river flows, place increasing pressure on these vulnerable fish species.
I investigated the populations of salmon and trout in the Teign catchment, Dartmoor, using Environment Agency data from 2002-2018. My mission was to understand how salmonids are coping with rising air and river water temperatures as a consequence of rapid climate change. In the 5 rivers in my study, air temperature and rainfall were important for controlling river water temperatures, but salmon and trout numbers were more affected by site-specific factors outside the scope of my study. This research highlighted the importance of consistent and local-scale monitoring of river habitat quality, water temperatures and species populations.
Conventional methods of monitoring fish populations include using an electrical current to attract fish towards a net where they can be safely collected, measured and returned to the water. This method relies on river water temperatures not exceeding 18°C, beyond which fish species are placed under high stress and sampling would pose too great a risk to their wellbeing. River temperatures are regularly exceeding 20°C. Not only are fish being exposed to dangerous living conditions for long periods of time, but we could lose the ability to monitor their populations and miss opportunities to implement restorative measures to save these species. New less-invasive monitoring technologies, such as eDNA, could be a solution to this, but this provides limited information on the age and sex of the fish which is important for predicting population trends into the future.
You can read more about salmonids in the UK here, or if you'd like to hear more about my research on this topic drop me a message!