San Marcos Mussel Biologists Sciencing the Way to Healthy River Systems and Clean Water


hey listeners this is Al Barrus with the
US Fish and Wildlife Service and today we’re talking about a freshwater mussel
conservation freshwater mussels are easy to miss they’re nondescript they’re
often mistaken for rocks and they sometimes spend decades underwater surrounded by mud and gravel and while they stay out of sight their vital to
ecosystems they remove silt and bacteria from our water which improves the
quality and clarity they’re often compared to Canaries in the coal mine of
our rivers if water quality is low they will close their shells and stop
filtering with over 70 percent of North American mussels listed for
protection or concern this is troubling news. Biologists speculate that a century
of habitat alteration in the forms of dams and industrial water diversion and
chemical runoff from agriculture brought these freshwater bivalve
molluscs to the brink the Texas horned shell for example was recently listed
for protection under the Endangered Species Act it’s native to the Rio
Grande watershed it’s the last remaining native mussel species in New Mexico
Texas is other watersheds are also seeing steep declines in native mussel
populations the state is home to over a dozen protected mussel species whose
numbers have dwindled in recent decades but there’s hope coming in the form of
research from scientists at the US Fish and Wildlife Service San Marcos National
Fish Hatchery located between San Antonio and Austin they’re optimistic
and hard at work on the cutting edge mussel science they’re developing
conservation techniques to help strengthen the wild populations of these
subtle but ever so vital shellfish my name is Josh Abel and I’m a biological
science technician with US Fish & Wildlife Service in San Marcos Texas I
work at the San Marcos aquatic Resources Center and I’m part of the invertebrate
and amphibian ecology and conservation research program there so right now
we’re currently working with five species
native to Central Texas Texas pimple bag Texas fat market Texas fawns foot smooth
pimple back and false spike four of those species are currently candidates for
federal protection and one more is proposed for listing we’re also
currently working with the newly endangered a Texas horned shell which is
found in the Rio Grande drainage part of what makes freshwater mussels unique is
their means of reproduction since it all mussels can’t move they send their
offspring away to begin their lives as travelers stowing away aboard a
unwitting vessel mussels start out their life basically as parasites so they’re
they’re parasitic to fish in their earliest life stage the larval mussels
they’re known as glochidia and they they lack most of the anatomical
features of an adult muscle so when the female is gravid she basically will
release the glochidia and they attach the fish gills and and while they’re
attached to the fish house they’re obtaining nutrients from the fish’s
tissue and blood plasma from while they’re undergoing metamorphosis to
become an actual muscle many mussel species’ pregnant female will entice a
host by mimicking other organisms luring them close enough for her to spray glochidia and the fishes face other species will produce a glob of goo called
conglutinate which the fish will ingest I mean from a life history standpoint it’s
it’s pretty pretty fascinating adaptation so these are animals that are
that are basically sessile meaning they don’t move around much throughout their
life and they developed this way to have their young transported distances but
you know just wouldn’t be possible if they didn’t have a host fish also the
ways in which they attract their specific hosts are absolutely awesome
some mussels use lures which are actually part of their manual tissue
that mimic minnows crayfish etc just whatever their host fish would like to
eat and others produce can gluten a switch our mimic all sorts of food
sources for their specific hosts so the host fish attractants are really where
these animals would spend their life in donating a rock let their charisma
really show through a major theme of the hatcheries and research is developing
science so the other hatcheries can breed the muscles
this is called propagation and to do this they need to learn to maintain a
kind of Noah’s Ark for the muscles by keeping a genetically diverse
representation in captivity which is called refugia they have a fail-safe in
case a wild population or two disappear and while the San Marcos hatchery isn’t
specifically meant as a refugee site they’re developing breeding and Refugee
techniques that will be free to any hatchery interested in making a mussel
refugia and from the refugia the mussels can eventually be transplanted to
restored river sections any of these filter feeding water Canaries the tricky
part is getting the habitat back to how it was
mussels are indiscriminate filter feeders they ingest anything that’s in
the water and so they’re very sensitive to river bottom conditions since they
can’t move they’re really at the mercy of their neighbors habits each mussel
species needs a specific habitat if conditions change too much they can
survive survival factors for mussels including how fast the water flows the
waters chemistry different contaminations water temperature and the
amount of silt if there’s too much silt then they’ll suffocate
is there enough water flowing year-round many southwestern rivers dry up because
of drought and industrial diversion these conditions that can kill them are
called limitations learning limitation is a major part of research for San
Marcos biologists knowledge of these conditions is necessary before they can
restore each species back to their original range most extra patients that
have happened and are continuing to happen with fault active animals are
mostly because of habitat loss so that’s not obvious correction that needs to be
made before any restocking efforts going to be successful water quality and water
quantity are also concerns that need to be addressed the limitations of life
history studies can really help elucidate if parameters are suitable for
restoration in that area mussel conservation
hope to restore muscles to their old habitats from hatchery to refugia
however they must first assess what caused the mussels to disappear in the
first place this is called extirpation yeah so it’s really just gonna be
correcting those problems there should be a smoking gun of what caused
extirpation of that population to begin with a lot of these rivers are highly
urbanized so you’re also talking there about water quality so whatever the
issue may be whether it be a historic sewage treatment plant before standards
or as high as they are today is a likely culprit so it’s making sure that those
issues are corrected mussels live in decades long lives and it takes years
for them to breed in the wild the soul their conservation and re-introduction
takes a really long time basically you put a mussel back in the river in a cage
system where you can go back and tie them and you just monitor their survival
growth and health over time and some of these species it takes several years for
them to reach sexual maturity so you might not know that your efforts have
paid off for several years you know close to a decade the roots of muscle
recovery isn’t gonna be overnight and the words isn’t easy but the outcome is
well worth the effort anytime you’re restoring a population in
my opinion that’s the victory in it of itself you’re returning things to the
way they’re supposed to be but in addition to that mussels are also
important in further restoration so not only are they the goal of restoration
but they’re a tool that can be utilized for restoration the effect of
reintroducing native mussels into any ecosystem will have a positive effects
radiates into those surroundings and they encourage the recovery of the rest
of the system their presence you know improves water quality they can
filter the tremendous amount of water adults of larger species can filter in
excess of 30 gallons a day per muscle they also help stabilize Bank substrate
as well as transfer nutrients from the water column to the river bottoms the
set of challenges presented in some muscle biologists in the America
and Southwest are especially unique here in the southwest we have a really unique
group of ecosystems you know if you look from basically east to west you’re
talking Eastern Texas to western Arizona those are a starkly different as you
could possibly get in this country scientists at San Marcos are very much
on the frontiers of fish biology so much is still unknown for freshwater
shellfish in this region so it’s still like the Wild West
for them we’re really at the cutting edge for what’s known at a lot of those
habitats so mussel work here is probably equivalent to where fish research was
you know 100 years ago which that’s incredibly exciting as a scientist it’s
also great to introduce people to this entire tax of animal that they know
little about and kind of show them the importance of them in our region so I
guess my point is that hopefully mussel restoration area will be a success and
that folks can witness and be a part of it in the coming decades that was Josh
Abel and San Marcos Texas talking about mussel conservation for the US Fish and
Wildlife Service my name’s Al Barrus and that’s what’s up you

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