Thursday, December 29, 2011

A Date with Medusa

Our morning today was a little different from most mornings at the office.  Kathlina and I decided to walk over to Ocean Journey, the marine-focused building at the Tennessee Aquarium.  We were going to help our aquarist friends feed Medusa, the Giant Pacific Octopus (Enteroctopus dofleini)
Medusa the Pacific Giant Octopus in the corner of her tank.
When we first arrived at her enclosure, she was curled up in the corner of the tank furthest from us, and was not being particularly social.  We decided to let her stay in her corner and threw a pan of shrimp toward her, which she quickly began to explore with on of her eight tentacles.
Medusa putting a tentacle into the pan of shrimp.
Once she was finished with her shrimp and playing with the pan, we served her the next course of breakfast.  Octopi are very intelligent, so staff at the Aquarium provide enrichment activities for Medusa to prevent her from getting bored.  One enrichment activity is making her work for her food.  Shrimp and squid are placed into a closed container that has a screw top, and the whole container thrown into the tank. It was entertaining to watch her try to open the container. 
Medusa curled up around the container full of shrimp and squid.

As she worked on getting to her breakfast, she slowly moved closer to Kathlina and me, providing a great photo opportunity that highlights some of the interesting traits octopi possess.

An underwater view.
Cephalopods are the class of invertebrates that include the octopus, squid, cuttlefish, and nautilus.  This is a very unique group of mollusks (yes, they are related to clams and oysters!).  Probably the most noticeable feature of cephalopods is their tentacles. They are lined with suction cups and assist with locomotion, eating, and anchoring the animal down.  To see a video of these amazing appendages in action, check out TNACI's Facebook page.

Close-up of Medusa's tentacle.
Some of the more remarkable traits about cephalopods is their developed senses, large brains and their ability to change color.  While other mollusks do not have eyes, cephalopod eyesight is very keen and is the main sense they use to hunt.  The intelligence of octopi is highly debated, but they do possess a brain larger than other invertebrates and experiments have shown an ability to solve mazes.

The group of cephalopods that includes squid, octopus, and cuttlefish (subclass Coleoidea) possess pigmented cells called chromatophores. Contracting and relaxing small mussels around the chromatophores causes the animal to change color, and they can do so very quickly.  Color change occurs during reproductive activities, times of stress, or in an attempts to camouflage with the surrounding environment.  Octopi can also change the texture of their skin.  We were lucky enough to catch Medusa in the middle of a color change.

Chromatophores allow octopi to change color.
Eventually, Medusa did get to the squid in the container we threw to her.  All-in-all it was a fun morning and a nice change in routine. 

Tuesday, December 20, 2011

I’m Dreaming of a Green Christmas

Can you believe that the holidays are right around the corner?  I know TNACI hasn’t accepted it mostly because of the weather.  Usually by now it is cold and crisp in eastern Tennessee.  Instead, it has been in the 50s and raining.  Despite the warm(ish) weather, we did have a wonderful holiday party last week, full of laughs and funny (some quite strange) White Elephant gifts.
Many of us have our own way of being green during the holidays, and we decided to share some of these ideas with you.  How are you eco-conscious during this time of year?  Please feel free to share in the comments section below.

Dr. Anna George, Director of TNACI
For a few years now, our family has been celebrating “Homemade Christmas.”  With so many talents among us—knitting, drawing, pottery, baking—it just made sense that we should celebrate with our time instead of our wallets.  One year, my husband drew a set of fish coloring books for all of our nieces and nephews, and last year I sewed nine pairs of flannel pajama pants for all of the family!  What’s really great is seeing what the kids are inspired to make for us—my niece has learned how to knit fabulous scarves, and the boys have made us flour dough sea creatures.  Though we still spend some money on our supplies, it’s wonderful not to have a pile of plastic packaging to throw away when Christmas is over.  And never underestimate the value of giving away experiences instead of things—taking my husband out for a nice dinner together is much more memorable—and greener—than buying him a new TV.
Kathlina Alford, Conservation Associate
I love to make things for people for Christmas so I try to use items that I find at yard sales, thrift stores or even the trash and turn them into something new. It’s a different kind of recycling! I also like to be creative with wrapping gifts. This year I bought re-usable grocery bags each time I found a cute one and used those in place of gift bags. I also like to wrap gifts in fabric for those of my friends and family who like to sew! For decorating I use clippings from fir trees and holly bushes in my neighborhood to make the house smell good and look festive. We don’t put up a big tree but instead decorate one of my indoor plants. This year we had a Christmas avocado tree!
Ashford Rosenberg, Sustainability Coordinator
The holidays are the most wonderful time of the year!  But they can also be the most wasteful.  In my family we try to decrease our footprint this time of year.  I keep gift bags from the year before and reuse them.  I also do a lot of holiday shopping at a used book store here in town.  Everyone in my family has strange enough tastes that I can always find a unique, gently used book that will interest them.  I have also moved more toward e-cards than paper cards.  We either re-use wrapping paper, try to find fun materials to wrap gifts in, or purchase paper made from recycled materials.  This year at a Christmas party, instead of buying disposable cups for everyone, we bought red and green plastic tumblers and sharpies so people could personalize their cup and take it home as a party favor.
Sarah Candler, Husbandry Intern
This holiday season, I have downsized the number of lights used in my decorating. Instead of buying all commercial gifts, I have made some of my own as well as purchased many locally made items. Most were wrapped using bows and bags from the previous year. Any bows and ribbons that can be salvaged after opening gifts this year, I will save for reuse next year. I also recycle my Christmas tree every year by mulching it.
Evan Collins, Research Intern
Christmas with my family is a pretty modest affair.  A small Christmas tree comprises the extent of our decorations.  This helps save time and energy.  The main course for the holiday dinner consists of local food, usually a chicken we raised and butchered at home, or locally caught fish for something a little different.  Gifts are packaged with boxes and wrapping paper from previous years and saved if possible.

Friday, December 9, 2011

TNACI Takes Serve & Protect to Chattanooga High Schools

TNACI's mission is to conserve native aquatic animals and their habitats through scientific research, ecosystem restoration, education programs, and public outreach. Historically, TNACI's focus has been on freshwater conservation. However, with the help of celebrity chef Alton Brown, TNACI and the Tennessee Aquarium are moving downstream into the realm of marine conservation through sustainable seafood education.
You may have heard all the buzz when Alton was in town during September. He delivered an engaging presentation to a sold out IMAX Theater, highlighting the importance of environmentally responsible, healthy seafood choices. He definitely brought down the house! But the journey for sustainable seafood education doesn't stop there. Our goal is for the message and actions to spread into the Chattanooga community and beyond.

To continue spreading the message, TNACI now offers a new outreach program called Serve & Protect: a new way to SEEfood. As our Sustainability Coordinator, I get to visit area high schools to educate students about the impacts commercial fishing can have on our ocean, the advantages and drawbacks of fish farming, and ways teenagers and their families can be active in ocean conservation through seafood choices.

Our first group of high schoolers to take part in this program was the students and Girls Preparatory School here in Chattanooga. I spoke to the marine science class at GPS at the start of this week, and had a blast. The students learned what characteristics make a certain species more vulnerable to overfishing, what popular seafood species are in trouble due to overexploitation, and sustainable alternatives. Check out our Facebook page , or GPS's website for more pictures from the program.

If you are interested in TNACI coming to your school to talk about sustainable seafood, contact Ashford Rosenberg.

Thursday, December 8, 2011

Logperch, Ashys, and Sunfish, Oh My!

The transition from our hatchery facility in Cohutta, GA, to our recirculating facility in Chattanooga, TN, has been quite the adjustment for TNACI this year. As the Lake Sturgeon project is winding down for the year, we are expanding the number of species we work with and taking on new projects. A greenhouse onsite has been converted into fish grow-out and propagation space. Currently there are three species living there with more to come soon.

The new TNACI fish propagation area, currently housing six separate recirculating systems making up 19 fish enclosures.
:Conasauga Logperch in the Conasauga River during the collection trip for the brood stock for the breeding project. (Photo courtesy of Kevin Calhoon)

In partnership with Conservation Fisheries Inc. (CFI), we are housing Conasauga Logperch and Ashy Darters! The Conasauga Logperch are part of a cooperative effort (also with US Fish and Wildlife Service and Georgia Department of Natural Resources) to assist the wild population of this species by developing techniques for a captive propagation and reintroduction program. In 2010, we helped CFI collect a group of broodstock. Amazingly, CFI produced a bumper crop (over 700!) of little guys in the first year of the program. So 120 of them are growing strong at TNACI until they can be released.

As for the Ashy Darters, they were part of a different program to learn to breed this species - which was obviously also successful! These darters will be held through the winter until they go to the Tennessee Aquarium for exhibit.

Two young Ashy Darters.
The three species in the genus Enneacanthus are another group we’re starting to work with in the new greenhouse facility. Blackbanded Sunfish are being held in a heavily planted system in hopes that the natural sunlight, temperature fluctuations and vegetation will optimize breeding for this species. There are many more plans for this space in the works. It is exciting to plan for the future and have the facilities to accomodate new conservation opportunities that will benefit freshwater species in the Southeast!

Blackbanded Sunfish in our breeding tank.

See a video of the Blackbanded Sunfish eating on our Facebook page!!/pages/Tennessee-Aquarium-Conservation-Institute/151884801512568

Monday, November 21, 2011

Lake Sturgeon Sampling

During the week of November 14-18, Kathlina and Sarah (husbandry intern) were privileged to join TWRA, USFWS, UT Knoxville, and TVA in a lake sturgeon sampling effort on the Ft. Loudoun Reservoir/Tennessee River in and near Knoxville. Two commercial fishermen from Alabama also helped with the effort by showing us their techniques. We set trot lines each evening (Monday through Thursday) and pulled them up every morning to see what we caught.
We baited the lines with chunks of common carp, buffalo, gizzard shad, and earthworms. The gizzard shad and earthworms were not popular with the lake sturgeon but seemed to be enjoyed by a whole lot of catfish! (Several hundred catfish were caught as by-catch during this effort.) We didn’t just see catfish, however, as this sampling effort yielded a record 27 lake sturgeon!!! These fish ranged in age from 1-11 years old and were up to 42 inches long! It was a wonderful experience and yielded much needed data about the size and survivability of the lake sturgeon that have been released over the past 11 years. We can tell how old the fish are by how we mark the fish before release.

Each year, a certain scute (bony plates on the side of the body) is removed from each individual. For example, 2003 year class fish are missing the 4th scute on the right side. Many of the sturgeon also have PIT tags, which are imbedded under the skin of the larger fish we release. We can scan fish with a PIT tag to give us a unique identification number. From these tag numbers, we are able to look up exactly when and where the fish was released.

Once all of this information is compiled, a map will be created to illustrate where and how much the fish are moving in the river. Any sturgeon that was not already PIT tagged was given a tag with a unique number in anticipation of future recaptures. What an exciting study to track the progress of this long-term project!

Thanks to everyone who was involved for all of their hard work in the rain and cold! For more pictures visit our Facebook page!!/pages/Tennessee-Aquarium-Conservation-Institute/151884801512568

Tuesday, November 15, 2011

Southeastern Fishes Council meets in Chattanooga again!

Last week TNACI hosted the annual meeting of the Southeastern Fishes Council, where scientists and students share their research on the conservation of southeastern fishes. It’s also an excuse for fish nerds to get together for a little bit of fun! The conference lasted for two days, and we were very happy with a turnout of over 190 people!

Thursday morning started with a great presentation from our keynote speaker Dr. Eve Brantley from Auburn University. She spoke about the importance of partnership for stream restoration, even severely degraded streams through agricultural areas (but don’t call them ditches in front of Eve!).

From left to right, Eric Spadgenske (U.S. Fish and Wildlife Service), Eve Brantley (Keynote Speaker, Auburn University), and Anna George (Director of TNACI).

Presentations began after the keynote speaker, with sessions lasting around 2 hours. During those sessions, scientists and students gave 15 minute presentations on their research. Between sessions there was much coffee drinking and socializing. Here’s a secret for those of you who don’t know…scientists need coffee to survive.

Coffee break after morning session.

On Thursday evening, after all the presentations, SFC and TNACI hosted a social and poster session at the Tennessee Aquarium.

Poster session and social at the Tennessee Aquarium

Like with the student talks, there was a competition between the students for who had the best poster.

John Johansen talks about his research.

There was also delicious food.

Casper Cox and Robert Hrabik

And a silent auction for original artwork of southeastern fishes drawn by Joe Tomelleri.

On Friday, the presentations continued. The winners of the student poster and presentation contests were also announced that afternoon.

Left to right: Loren Stearman, Brook Fluker, Mark Hoger (presentation winners), John Johansen, Laura Stewart, Matthew Wagner & Zach Martin (Chris Yates not pictured), poster winners

All in all it was a great weekend. We here at TNACI had a great time and we look forward to seeing everyone next year in New Orleans!

TNACI Staff left to right, Sarah Candler, Evan Collins, Ashford Rosenberg (Kathlina Alford not pictured because she’s behind the camera!)

Wednesday, October 19, 2011

New Addition to the TNACI team!

I have recently come on board the TNACI staff as the Conservation Associate and I am excited about all of the opportunities that this position comes with! Lee Friedlander formerly held this position and has moved on to teach at a local highschool. I am a native of middle Tennessee (Livingston) and graduated from Tennessee Tech in Cookeville with a bachelors in biology. For the past seven years I have been an Aquarist at the Tennessee Aquarium where my expertise has developed in Syngnathids (seahorses and their relatives), freshwater stingrays and also in native southeastern freshwater fishes, the latter being a reason this position was so attractive to me. I am also working on finishing my Masters degree at the University of Tennessee at Chattanooga where I am researching the population genetics of Hemitremia flammea (Flame Chubs) which are native to Tennessee, Georgia and Alabama. With this genetics experience I am excited to partner with Dr. Anna George on various conservation genetics projects and seek out new projects that will benefit southeastern fish populations as well as captive populations of rare fishes in zoos and aquariums. We live in such an amazing place, surrounded by beautiful scenery, flowing waters and immense aquatic biodiversity. I can't think of a better place to study freshwater fishes and, more than that, to be active in conservation efforts to protect those species and their habitats! Watch out for future postings about new adventures at TNACI as I get settled into this position and seek out conservation research opportunities.

Fall in the Spring

It's fall... which means time for a little spring work. This past week was our annual habitat and fish monitoring at Colvard Spring in north Georgia with our awesome friends at the Conasauga River Alliance, Georgia Department of Natural Resources, and the Nature Conservancy. And since the weather stayed warm, we also got to work on our underwater photography skills! Here are a few pictures from our trip:

Coldwater darters (Etheostoma ditrema) are shy, but seem be responding well to changes in vegetation type and abundance. 

In our fish sampling yesterday, we caught 464 darters--more than we've seen in Colvard Spring before!

Silt is still thick in some parts of the spring...

but is replaced by slightly coarser particles where spring upwellings blow the fine silt away...

 or around the bases of some of the clumps of vegetation (here, a Ludwigia sp.). A mix of stonerollers (Campostoma oligolepis), creek chubs (Semotilus atromaculatus), and orangeside dace (Rhinichthys obtusus) are milling about in the foreground.

One notable change this fall has been an increase in filamentous algae; here it's growing on muskgrass (Chara), sticks, and exposed rock. The floating clumps at the surface are algal mats that have floated free and are decaying.

The algae can look almost otherworldly... The small fish near the surface are western mosquitofish (Gambusia affinis), which are the most abundant fish species in the spring.

A happy TNACI team at the end of a long field day.  If you'd like to see more pictures from our field work at Colvard, check out our Facebook photo album!

Sunday, October 16, 2011

Snakehead Sampling

Wow, it's been a while since we've posted.  We've got a lot to catch up on, so we'll start with a post about our adventures with one of the more famous invasive species, the northern snakehead (Channa argus).  These fish are a popular food fish in their native range of eastern Asia.  Though we hate to villify a species, these fish can seem pretty nasty outside of their home range.  Snakeheads have plenty of teeth, can breathe air through an accessory lung and persist out of water for up to four days, and are very aggressive about guarding their nests from other predators.  So understandably, a lot of people are concerned about their introduction and the impacts they might have on native fishes.

At the end of September, we dashed over to Arkansas to collect snakeheads for a few exhibits.  They've been introduced into two counties in central Arkansas, and we spent a lot of time seining muddy-bottomed agricultural ditches like these:

While the collecting was hard work (and the mosquitoes ate well!), we did manage to find a nice scaly toothy critter for our new exhibit on invasive species for the Aquarium.
It wasn't all scales, though.  We found a nice little green tree frog (Hyla cinerea) at one of our collecting sites who wasn't too unhappy to pose for photos.
Stop by the Aquarium in December to check out our new invasive species exhibit!

Friday, August 26, 2011

Guest Post: Views from our High School Volunteer

The experience I had as a volunteer with the TNACI Sturgeon Husbandry Program was, in short, phenomenal. Throughout my six weeks with TNACI my eyes were opened to countless new perspectives and insights regarding conservation, ranging from sturgeon to silt, sustainable seafood to stunned sunfish, animal care to education. The Husbandry Program is undeniably ambitious, a quality emphasized more so when one considers the extreme frailty of the young sturgeon’s fettle. Nevertheless, what struck me the most about the project was the relentless torrent of enthusiastic energy that fueled it, particularly an eagerness to engage the external community. This desire to not only better the environment, but to also teach and encourage the participation of others was trademark of all of TNACI’s projects. Whether organizing an attention-grabbing production such as the highly publicized sustainable seafood event or contemplating smaller scale outreach to children with an iconic “Sammy the Sturgeon”—my personal favorite—the Conservation Institute dedicates itself to more than “giving fish” to the community. Rather than resuscitating the marine environment for a few more years, it strives ardently to but to “teach [us all] how to fish” on our own, ballooning effectiveness and longevity through mass participation. Examine my own experience. Hardly a high school senior, not to mention completely oblivious to the mechanics of sturgeon reintroduction and marine science, I was accepted into the TNACI scene with enthusiasm and welcome. Despite my initial ignorance, I was invited to partake in a slew of incredible experiences, not only watching the young sturgeon grow and fight off an Aeromonas attack, but even being invited outside of the husbandry facility, collecting sunfish for the aquarium via an electroshocking boat.

Caroline (l) and Sarah (r) snorkeling in the Hiwassee River
It was through TNACI’s willingness to educate and share its passion for conservation that I in turn was inspired. Thanks to my exploits this summer at the expense of TNACI’s generosity, I look forward to passing on the torch, to spreading the enthusiasm and commitment to educate within my own community.

--Caroline Wiernicki, Summer Volunteer

Tuesday, August 2, 2011

Snorkeling Day

Last Friday, we all headed out for some summer snorkeling in the Hiwassee River to celebrate the last day of our high school summer volunteer, Caroline. The access point was a bit remote (lots of time on gravel roads!), but it was a pleasant day and everyone saw many beautiful native fish species, including tangerine darters (Percina aurantiaca), mirror shiners (Notropis spectrunculus), whitetail shiners (Cyprinella galactura), and logperch (Percina caprodes). Despite the isolation of the area, it was still being impacted by aquatic nuisance species. We saw two invasive species, redbreast sunfish (Lepomis auritus, discussed here), and Asian clams (Corbicula fluminea).

Asian clams are native to Southeast Asia and parts of Russia. They were first seen in the United States in 1938 and have spread to almost 40 states since then. They were first brought into the country by immigrants using it for food, but now the main pathways of spread are bait buckets and intentional release.

Asian Clam (Corbicula fluminea). From

Once the clams are established in an area, they outcompete native invertebrates for habitat and food. They also spread very quickly, in part because they are hermaphroditic, possessing both male and female reproductive organs. Asian clams are capable of self fertilization, and a single clam can produce seventy thousand offspring per year. The larvae are free swimming, an advantage over the native mussels whose larvae must attach to fish to disperse. Asian clams also cause economic damage through biofouling. In a very short time, pipes can become clogged with these small clams, and they have cost the U.S. millions of dollars in pipe repair or replacement.

So we did our part for native species on Friday—we opened up a few Asian clams to feed to the tangerine darters and logperch swimming around us! It was quite the feeding frenzy.

Thursday, July 7, 2011

Red Alert

Redbreast sunfish (Lepomis auritus) and red shiners (Cyprinella lutrensis) are two common invasive species that inhabit Tennessee waters. However, they have native fishes on “red alert,” threatening them with extinction.

Redbreast sunfish are very common in Tennessee and popular with anglers. They inhabit a wide range of aquatic habitats including small creeks, large rivers, and reservoirs. They are in the same genus as other common sunfish species in the area, like the bluegill sunfish (Lepomis macrochirus), and longear sunfish (Lepomis megalotis). Despite their popularity, redbreast sunfish are are causing ecological damage.

Native to the Atlantic and Gulf slopes, they were introduced into Tennessee and other states in the 1920’s and 1930’s for sports fishing. Now they are established throughout the Tennessee River drainage. They occupy a similar ecological niche as native sunfish species, requiring the same resources and serving the same function in the ecosystem. Because of this, they compete with bluegill sunfish and longear sunfish for food and habitat. In some areas, redbreast sunfish have caused the extinction of longear sunfish becasue of resource competition.

Red ShinersRed Shiner (Cyprinella lutrensis) from

Red shiners are a small minnow species native to rivers and streams in the central United States. Introductions outside the native range occurred due to home aquarium and bait bucket releases. They are native to western portions of Tennessee, but not to central or eastern Tennessee. Currently, there are no established populations outside the native range in the state, but they are established in the Upper Coosa River System in Northern Georgia and are moving quickly. They pose a serious threat to native species in the Coosa River and to the Tennessee River should they establish.

Water quality in many streams of the southeastern U.S. is severely degraded due to urbanization. Red shiners are able to thrive under in these conditions, giving them an advantage over native fishes that cannot adapt to rapid environmental changes. Red shiners also reproduce with native minnow species, resulting in a variety of hybrids. So far, nine different red shiner hybrids have been documented. One of the common combinations is a red shiner-blacktail shiner (Cyprinella venusta) hybrid. Hybridization reduces genetic diversity and fitness of the native species. In some areas, hybridization happens so quickly, that the native parent species goes extinct.

Thursday, June 30, 2011

Water Weeds

Aquatic invasive animals are not the only species that cause problems in Tennessee and the southeastern United Sates. Invasive plants can cause just as many problems. Aquatic plants are introduced outside their native range by being transported on boat propellers and boat trailers or from home aquariums.

There are many ecological and economic problems associated with invasive plants. An overgrowth of an invasive plant can block the sun from native species, causing them to die and reducing plant biodiversity. The corresponding increase in dead plant material at the bottom of a lake or pond can result in the loss of all oxygen in the water as bacteria break down the dead plants. This process is called eutrophication. Invasive plant species can also crowd and degrade bottom habitat for fish and invertebrates.

Many invasive plants, like Hydrilla (Hydrilla verticillata), can form large mats. These mats often jam propellers and ruin boat engines. The mat may grow so thick that the water becomes inaccessible to boaters and swimmers. Plants can also foul anglers’ equipment. Some aquatic invasive plants are vectors for diseases that impact native wildlife.

To prevent the spread of invasive plants, check, clean, and dry. Check all parts of a boat and other equipment for plant fragments. Some of these species, like Eurasian watermilfoil (Myriophyllum spicatum) can reproduce by fragmentation. One small piece of the plant will grow into a full plant. Properly clean all gear before transporting either home or to another body of water. Let all equipment dry for 48 hours before using it another area.

Read the following stories from Chattanooga Times Free Press to learn about what is being done to control populations of invasive plants in local waters.

Monday, June 27, 2011

Guest Post: First Time River Snorkeling

As an intern at TNACI, I was recently given the opportunity to perform fieldwork with some of the aquarists from the Tennessee Aquarium. We traveled to the Tellico Plains area. Here, we focused on the Little Tennessee River and the Tellico River. Our goal was to collect fish for one of the River Journey exhibits.

The first place we stopped was the Little T River. Here, we used seine nets to catch shiners and darters. We mostly caught Saffron Shiners and Warpaint Shiners as well as some Rosyside Dace. There were also numerous sightings of Rainbow Trout of all sizes, suggesting they have moved into the area and are breeding.

Saffron Shiner.  Photo by Noel Burkhead
In order to catch other fish for the exhibit, we had to snorkel in the river with small hand nets. This seemed like a difficult and odd task at first, but snorkeling in shallow rivers is very exhilarating! Using this technique we were able to catch individuals from several darter species, including eight Tangerine Darters in the Tellico River

Tangerine Darter.  Photo by Conservation Fisheries, Inc.
My favorite part of the experience was discovering the diverse microhabitats of these river systems and which fish tend to be found where. I never knew there were so many colors to see! If given the chance, everybody should go snorkeling in a river, it is just as amazing as exploring a coral reef in the ocean.

--Sarah Candler, TNACI Intern

Thursday, June 23, 2011

When Bait Takes Over

The rivers of Tennessee and the southeastern United States are some of the most diverse ecosystems in the world, especially for invertebrates like mussels and crayfish. Crayfish are especially diverse in Tennessee, with at least 70 species inhabiting our waters. Many crayfish species are specially adapted to their environments, and many only inhabit one or two watersheds. The Nashville crayfish is found only in the Mills Creek basin in central Tennessee, while the Chickamauga crayfish is found only in the South Chickamauga Creek basin, which spans four counties in Georgia and Tennessee. These species are of greater conservation concern due to their small ranges or specialized habitat. Like many other native aquatic animals in the southeastern U.S., they are also under threat due to the introduction of invasive crayfish species.

Crayfish, also called crawdads, crawfish, or mudbugs, are commonly used as bait by commercial and recreational fishermen. They are either purchased from bait stores, or caught from the wild by anglers. Often at the end of the day, the bait is released where used, without regard to its original source. Virtually every invasive crayfish species in Tennessee has been introduced by bait bucket releases. Once introduced, non-native crayfish negatively impact ecosystems and can cause economic losses through damage to riverbanks, dams and dikes. Many invasive crayfish species directly prey on native snails, fish, and crayfish, while others eat or destroy aquatic vegetation that provides habitat and food for native fish. Many of the invasive species are very aggressive and outcompete native crayfish species for burrows or cover.

The Tennessee Wildlife Resources Agency lists six non-native crayfish species as warranting particular concern: bigclaw crayfish, Cumberland crayfish, red swamp crayfish, rusty crayfish, virile crayfish, and White River crayfish. Because these species are generalists compared to many of the native crayfish species, they can spread rapidly through a watershed if introduced. Rusty crayfish and virile crayfish have even been documented hybridizing with native species.

The biggest step you can take in preventing the introduction of invasive crayfish is to use them for bait only from the stream that you are fishing, to take only what you need, or to release bait crayfish from the same stream from which you caught them.

Thursday, June 16, 2011

River Invaders

The name Asian carp is used to describe four different species of carp: grass carp, bighead carp, silver carp, and black carp. These fish were introduced in the United States in the 1970s and since that time have spread rapidly. At least one species of Asian carp is found in every state except Alaska, Maine, Montana, Rhode Island, and Vermont. They pose a major ecological threat to native aquatic wildlife and river ecosystems, as well as a significant economic threat to commercial fisheries.

All Asian carp species are native to large rivers in eastern Asia and were introduced in the U.S. to “improve” water quality. Some species, such as the grass carp, were introduced to control nuisance plant species because they eat algae and other aquatic plants. Other species, such as the black carp, eat mussels and snails and were introduced to control disease carrying invertebrates in aquaculture ponds.

From aquaculture, Asian Carp were introduced into American rivers by illegal and intentional release, or by accidental escapes from river flood waters reaching aquaculture ponds. Once in the wild, they pose several threats to the ecosystem. Grass carp consume enormous amounts of plants. Their voracious appetite robs native fish and invertebrates of their food source. Large quantities of carp waste degrade water quality.

The two species threatening the Great Lakes are the silver and bighead carp. Millions of dollars have been spent on electric barriers, cameras, and other monitoring equipment attempting to protect the lakes. Asian carp have already caused extensive environmental and economic damage in the Mississippi and Missouri River basins. Many people have had to abandon their fishing grounds because of the presence of carp. This threatens a 7 billion dollar per year commercial and recreational fishery in the Great Lakes. Silver carp can also harm humans. When startled by boat motors, the fish (which can weigh up to 60 lbs!) leap out of the water, causing potential injury or fatality to people.

There is now concern that the extent of Asian carp’s range has increased. The flooding of the Mississippi and Missouri rivers this year may have transported some of these fish into lakes and tributaries where there are no established carp populations.

Thursday, June 9, 2011

Not-So-Effective Pest Control

There are two species of mosquitofish found in the United States, western mosquitofish (Gambusia affinis) and eastern mosquitofish (Gambusia holbrooki). They are very small fishes, with adults less than 3 inches in length. As the name suggests, mosquitofish eat mosquito larvae, along with plankton, small invertebrates, and larval fish. Because of their diet, they have been widely introduced around the world to control diseases like malaria that are associated with mosquitoes.

The native range of the mosquitofish is not well known because human introductions started in the early 1900s. The two species were likely restricted to Gulf and Atlantic coastal plains and the lower Mississippi River Valley. Due to the broad spectrum of their diet and water quality tolerance, mosquitofish are habitat “generalists” that are able to flourish in a wide range of conditions. These traits, combined with their high reproductive rate and frequent dispersal by humans, have resulted in two species that are very successful invaders.

Western Mosquitofish (Gambusia affinis). From

Despite their small size, invasive mosquitofish can have a big impact on their environment. Introductions of mosquitofish can lead to algal blooms if they have consumed the zooplankton that keeps algae under control. They can cause populations of native fishes to go extinct through competition for food and direct aggression. They also carry parasites that infect native fish. Worst of all, research has shown that mosquitofish are no more effective at controlling mosquito populations than native mosquito predators. They can even increase the size of mosquito populations by feeding on or outcompeting the mosquito’s native predators.

Mosquitofish can be a problem here in Tennessee because they threaten the Barrens topminnow (Fundulus julisia). This fish occurs in only in three counties in Tennessee and is part of our natural heritage. Unfortunately, the larvae of the Barrens topminnow are eaten by the mosquitofish, and larger juveniles have to compete with the invasive species for food. The Tennessee Aquarium Conservation Institute is currently reintroducing Barrens topminnows to springs with where mosquitofish have been excluded in order to prevent negative impacts from this invasive species.