Indicator Species

The following was first posted on Working the Tweed as part of activities for Year of Natural Scotland 2013.

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.

Water crowfoot

Detail from Indicator Species series © Kate Foster 2013

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.

Details from Indicator Species series © Kate Foster 2013

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.

Photograph by Kate Foster 2013

Lamprey

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.

Photograph by Kate Foster 2013

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.

Detail from Indicator Species series © Kate Foster 2013

Each of the three species has its own characteristic mouthparts (diatoms slipped into the picture).

Detail from Indicator Species series © Kate Foster 2013

The drawing became about what lampreys eat, and what eats them.

Detail from Indicator Species series © Kate Foster 2013

Spawning time is when lamprey are most visible – look out for birds gathering to feast at the river’s edge in spring.

Salmon

Photograph by Kate Foster 2013 with acknowledgements to The Tweed Foundation

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.

Detail from Indicator Species series © Kate Foster 2013

Detail from Indicator Species series © Kate Foster 2013

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?

Detail from Indicator Species series © Kate Foster 2013

Researchers do not leap to conclusions: – they take a long view, and trust to salmon’s resilience.  I am chilled all the same.

Otter

Detail from Indicator Species series © Kate Foster 2013

Otter on the Tweed Catchment are becoming more common, but it takes skill to interpret the signs they leave.

Detail from Indicator Species series © Kate Foster 2013

What for example is the difference between otter or mink scat? or dog and otter footprints?

Detail from Indicator Species series © Kate Foster 2013

Detail from Indicator Species series © Kate Foster 2013

Detail from Indicator Species series © Kate Foster 2013

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.

Image © Findlay Ecology Services

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.