Wednesday, 15 September 2021
RiverBum Fly Fishing Gear

Appalachian Highlands Network Freshwater Mussel & Cobble Bar Monitoring

(wilderness sounds) (lighthearted instrumental music) – [Voiceover] Big South Fork National River and Recreation Area and Obed Wild and Scenic River are two of the very few remaining rivers in the region that are protected – [Voiceover] The Big South Fork is one of the crown jewels in the Cumberland River System

It is one of the last places in which you can still find some of our most rare species – There are over 50 mussel species and probably 25% of them are federally endangered – This is Epioblasma brevidens, the Cumberland combshell, a federally endangered species Big South Fork is one of the last great places this animal occurs – [Voiceover] Mussels are considered important because they are, if you will, the canaries in the coal mine

They are filter feeders, they don't move, so whatever comes down the river, in terms of contamination, they're subjected to, they cannot avoid it So what's being done here is long-term quantitative monitoring to figure out what species of mussels are here and how many – The actual process is to establish a grid in these locations within those grids we monitor square meter units and within a sampling frame we'll count the mussels, identify the species and measure the mussels so over time we have a good idea of how the mussel populations are doing, how many young ones, middle aged ones, and old ones are there, what the structure of the population is – These are two individuals, same species, the individual in my left hand is perhaps three, four years old The individual on my right, guessed on the number of growth lines, this thing is quite old

– It can be very difficult to find mussels – especially in a cobble gravel environment They range in size from the size of your little fingernail to the size of a small dinner plate They blend in, they are partially buried or completely buried, and so it takes a trained eye to find them sometimes – Mussel monitoring involves taking the mussels out of their habitat in the substrate and handling them briefly because there are endangered species involved we have to have people that have been permitted by the US

Fish and Wildlife Service We place them back in the substrate as close to the original orientation as we can Out of an abundance of caution, we don't do this monitoring often We only do it infrequently, every three years – Of the 300 species of freshwater mussels in North America, about 70 percent of them are imperiled, they're declining, or they have disappeared altogether

It's important to monitor what we have left because that way we know what's happening in our rivers (wilderness sounds) – [Voiceover] Cobble bars are a unique vegetation community in the bottom of these steep-walled river gorges – and they resemble the Western tall grass prairies – They have a lot of the same species – but they have a lot of their own endemic species, species that don't occur anywhere else in the world Unlike the tall grass prairies of the West that are maintained by wildfire, these are maintained by the roaring floods that come down these rivers and scour everything that's not flood-adapted away The plants that are native to the cobble bars have really deep strong roots, most of their mass, most of the plants are actually underground, so if their top parts are scoured away by the floods they can easily re-grow the top parts

They include the two main species of tall grass that are the keystone species in the Western prairies, big bluestem and Indian grass The roots go 15 feet into the ground, winding their way between the rocks and holding them solidly there And they hold everything in place against the force of the floods It's hard to believe, but sometimes, on this very plot, right where we're standing, there is a house-sized pile of woody debris, of logs, giant logs, trees this big around, that have just been washed in by the river and all piled up here I've seen that pile here 15 to 20 feet high, right where we're standing

And then you come back a week later and another flood has come through and washed it away The point of the long-term monitoring of the cobble bars that we're doing is to see if the community is changing Most of these species cannot survive in shade, so if anything happens to cause trees to advance out over these habitats that species would completely disappear, they'd be gone This is Cumberland rosemary, it's a federally-listed, threatened plant and the vast majority of all that remains in the world is inside the boundaries of Big South Fork National River and Recreation Area and Obed Wild and Scenic River (lighthearted instrumental music) Some of these cobble bars are pretty challenging, most of them involve a lot of off-trail work, a lot of bushwhacking down extremely steep places

Sometimes it's crawling on hands and knees hauling a heavy pack, and then, either swimming or wading the river to get to where you need to be The monitoring that we do has to be something that can be objectively quantified and then repeated several years later and then repeated the same way You can walk out on to a cobble bar and say, “well, it kind of looks different to me”, but that doesn't count, you have to have something that you can measure And so the way we do that is to pull transect tapes out across the cobble bar at intervals Transects have to be straight, and so if you're pulling the transect tape and you see a wall of greenbriar in front of you and black locust, you can't go around it

You have to go straight through it, that tape has to be straight, and then we use a laser device every half-meter along that transect to count what we're hitting in terms of the stony substrate, the grass that's supposed to be there, the other herbs that are supposed to be there, or the woody things that are not supposed to be there And we measure the extent of canopy over the line, over those transect tapes, by species so that we know whether they are being invaded by species that are not flood-adapted, which is a very bad sign, or whether they are being encroached upon by species like sycamores and river birches that are supposed to be there (lighthearted instrumental music) This river system, not just the river itself and the aquatic creatures, the fish and the fresh water mussels that live in it, but everything adjacent to it, even the forests that come down to the edge of the river, definitely the cobble bars, all of it is connected The other things that we monitor, the freshwater mussels, the water quality are very important – As a manager of the park, you can't manage resources without having scientific data

So the scientific data associated with the monitoring program, gives us the ability to understand the natural environment, the health of the river and its organisms – The value of long-term monitoring is so that we can know what's happening to the plants and animals and their habitats, in the time that we can do something about it – One never knows what all the connections are, what it would cost if those species were lost, if this habitat type were lost These things might not still be here if it weren't for the protection of the National Park Service (lighthearted instrumental music)

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