Indicator Species

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Tweed Creatures © Kate Foster 2013

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

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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.

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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.

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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.

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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.

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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.

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Detail from Indicator Species series © Kate Foster 2013

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

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Detail from Indicator Species series © Kate Foster 2013

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

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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

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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.

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Detail from Indicator Species series © Kate Foster 2013

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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.

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As the Arctic opens up to ships, what paths will these cold-water migrants take? Can they adapt?

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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

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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.

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Detail from Indicator Species series © Kate Foster 2013

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

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Detail from Indicator Species series © Kate Foster 2013

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Detail from Indicator Species series © Kate Foster 2013

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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.

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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.

listening upriver, downriver

Yesterday’s mission was to walk to my nearest tributary junction, and join World Listening Day by paying attention to sounds. I had an equidistant choice of going upriver and downriver. I walked upstream late morning, and downstream in the early evening.

Going along the riverside road became part of the listening. There were signs of heat – grasshoppers, flies buzzing, swallows chattering.

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Cattle are noisy eaters I learn –  a bullock catches my ears, grazing and wading in the burn (appreciating the coolness I assume).

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My attention brings quiet, as the herd pauses to look at me.

Through the gate to the next holding, I am wished Good Listening by the neighbour who farms there. She tells me of a band of thirsty scouts, concerned for them in this heat as they walk down this reiver’s valley to the Borders Abbey Way.

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I meet the Scouts and we look at the map of their walk. I suggest which houses they can get water from. A mix of adolescent voices drift away: tired, broken and half-broken tones.

Now close to the burn, a skin-slap against a horsefly, the dog slumping in the river.  I stop in tree-shade and listen to water flowing: noticing that a fish-ripple is soundless but that a crow caw has two-beats.  I learn that few of the things I look at yield sound, and I see little of what I hear.

The particular chink of a gate; the stridulation of a cricket; a ewe moving through a wire fence (metallic string tone), cool wind in my ears – all can be heard.

The open thistle, bone dry grass, distant forming clouds – all quiet.

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At the farm-bridge at the river intersection, I remember falling off, into the river, last summer. With children’s laughs ringing alongside my shock as the plank broke.

I realise my intersection map should have been of sounds not sight, but the allocated hour is up.

The evening mission starts with a swim in the loch and from there to the road-bridge, where the burn meets the river. The moon is visible – is it always silent?
Shoes giving a rubbery flap on dry grass. There is a nettle wall between the road and my chosen point. I manage through to see, on the opposite bank, a woman watering her garden in a bikini. She might take my watchful presence amiss.  My mistake: to consider visual rather than aural access. Hidden in bracken, I start to listen and things rapidly become more abstract.

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I find I can’t listen well with my eyes open

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I draw birdsong from above, mistakenly using pink (not exactly a flutey hue)

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Drawing sounds becomes a movement. I compromise with half-closed eyes, but the midges have found me.

 

This post is part of the project Working the Tweed (Year of Natural Scotland 2013).

Click here for a thought-provoking TED talk by Bernie Krause on ‘The Voice of the Natural World’ that motivates me to keep listening.

scaling the Tweed

In the burn, salmon eggs could be hatching just now. I learn that pimples on the fish’s skin become scales with marks that register their growth pattern, like tree rings. In actuality, these are in life tiny and transparent, but to understand them I draw them large and salmon coloured.

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The Tweed Foundation collects scales from anglers, and accumulates data that helps interpret seasonal changes in the fishing catch. With a microscope, an expert eye might see that a salmon lived for two winters in the river, with a further winter at sea before returning to the Tweed to spawn. The wider separated bands in the blue drawing (a detail) suggest that this fish made a rapid transition to sea and began to feed well.

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Sometime, there are checks in the usual pattern of faster summer growth, where the circuli stay tight and close.

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Very rarely, a female salmon manages to return to sea after spawning, and runs upriver a second time. The Tweed is a long river, and perhaps only one in a hundred manage this. These fish have scales with spawning marks developing from interrupted growth where scales were consumed, reabsorbed for energy to swim upstream.

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Typically a spawned salmon, a kelt, will die in the river and the eroded scales will document the exhaustion of the fish’s reserves.

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Having learnt something of what can be seen close-up, I needed to take a step back to take this in. A textbook informs me how they deserve their name, ‘Atlantic Salmon’: they are a species who use ocean currents to drift to cold subarctic waters. Rich feeding to the west of Greenland allows them to mature before returning to their home river in mating mood.

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Towards the end of this first lesson in scale-reading, our careful tutors say that there is currently speculation about future patterns that will be read in salmon scales. Within ten years perhaps, the north pole will be a navigable ocean, allowing passage to the Pacific.

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To reflect on this, I look at recently published papers. With anxiety, I start to draw icebergs on perspex – dotting out the zone that was navigable to ice-hardy ships in 1970. In my drawing the icebergs lessen over time, and tail off at 2100. I wish it was the other way up, and I could draw them more concentrated at the pole, like this:

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Scaling the Tweed started with a close-up view, but also is making me look further away.

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Acknowledgements and thanks to Tweed Foundation. The text and drawings, and any errors, are my responsibility. This research drawing was undertaken as collaborative work with tabula rasa, in a project Working the Tweed, part of Year of Natural Scotland 2013.