Ecologists have taken four species to act as indicators of the ecological health of the Tweed catchment: Salmon, Lamprey, Water Crowfoot and Otter. Conversations with specialists at Riverside Meetings prompted me to make a series of drawings. These were ink on perspex, and were shown in the project space at Harestanes last October. Combined with field visits, making these drawings let me develop knowledge and become more observant. I now also understand these species better within my own life – as indications of time of year, of place, of change.
In summer Water Crowfoot (various species of Ranunculus – the buttercup family) can grow into great mats that include other plants. I learnt these are called ranunculion – assemblages that can alter river flow and sedimentation pattern, sheltering the locality downstream. How had I never noticed them up till now?
I learnt the five species found in the Tweed Catchment have underwater leaves with varied branching patterns, examples below.
These species show great plasticity – their form is very variable according to environmental conditions. Water Crowfoot readily hybridises, so its precise identification is complicated. I need to look closer to see patterns in ranunculion.
Three types of Lamprey spawn in the rivers of the Tweed Catchment: Brook, River and Sea. The photo below shows electrofishing at a fish rescue by The Tweed Foundation and Tweed Forum at Eddleston Water in July 2013, where mature lamprey were found.
Primitive jawless fish, that I had never before seen. Through google I learnt they sift microscopic organisms from silt in the riverbed in the larval form.
The larger two species (River and Sea Lamprey) mature and migrate to the estuary. They are parasitic and attach to fish to suck their flesh.
Each of the three species has its own characteristic mouthparts (diatoms slipped into the picture).
The drawing became about what lampreys eat, and what eats them.
Spawning time is when lamprey are most visible – look out for birds gathering to feast at the river’s edge in spring.
Scientists at The Tweed Foundation explained to us what a fish-scale can reveal – you can see more here about how the scales of Atlantic Salmon show how they move to cold northern waters to feed and grow.
The drawing above is taken from a prediction of expanding scope for navigability, opening the arctic up for human commerce. I have learnt that the Tweed is one of the best salmon rivers anywhere – and also that researchers are speculating about future patterns of Salmon migration in a warming Arctic.
As the Arctic opens up to ships, what paths will these cold-water migrants take? Can they adapt?
Researchers do not leap to conclusions: – they take a long view, and trust to salmon’s resilience. I am chilled all the same.
Otter on the Tweed Catchment are becoming more common, but it takes skill to interpret the signs they leave.
What for example is the difference between otter or mink scat? or dog and otter footprints?
Infra-red videos used in camera traps give more information into how otters behave.
Findlay Ecology have made a long-term study of a natal holt, where otter cubs are nursed. It was found that that the male otter regularly stayed in the same holt as the breeding female and her cubs.
Now in my mind, being an otter becomes a sociable kind of thing. I imagine the parents underground with their cubs, and traversing long sections of river to maintain territory and fishing rights.