Category Archives: Research

From glass eels to silver eels and everything in between The life stages of the American Eel

Imagine yourself hiking next to a babbling creek.  You come to a small waterfall surrounded by rocks.  The rocks glisten from the spray of the falls.  You walk closer and see dozens of small snake like creatures slithering over the wet rocks.  You watch them move from the top of the rock pile to the bottom.  Then they slide back into the creek.

You saw the American eel utilizing one of its unique adaptations.  Their bodies are coated in a mucus layer, providing protection and a way to absorb oxygen through their skin.  This mucus, in combination with their muscular bodies, allows them to move out of water and across land to avoid barriers.  This, and other adaptations, makes the American eel able to live in more diverse habitats compared to most other fish species.

American eels are fish, despite their snake like appearance, and the only species of eel that live in North America.  They are catadromous, migrating from the saltwater of the Sargasso Sea to the freshwater of streams and lakes.  The Sargasso Sea spans a part of the Atlantic Ocean between Bermuda and Puerto Rico.  Once they reach maturity, they journey back there to spawn.

The vastness of the Sargasso Sea makes it tough for researchers to locate and observe eels spawning in the wild.  At this point, observations of spawning eels remain to be made, although one silver eel was tracked to the Sargasso Sea. Researchers believe the eels die right after spawning.  Some mystery surrounds the final life stages of the American eel.

What happens as they grow?

Let us review the known information about the life stages of the eel.  The eel’s life begins in the Sargasso Sea.  First, they resemble a willow leaf.   These small, oblong, transparent fish, called leptocephali, lack the snake like form of adult eels.  They are about one inch long and rely on the ocean currents to bring them to the east coast.  This journey takes about one year.

Lept
The beginning life stage of the American Eel is called a leptocephalus and these leptocephali use the current to travel to the East Coast. Kils at the English language Wikipedia [GFDL (http://www.gnu.org/copyleft/fdl.html) or CC-BY-SA-3.0 (http://creativecommons.org/licenses/by-sa/3.0/)%5D, via Wikimedia Commons
Now they resemble vermicelli or rice noodles.  At two inches long and still transparent, they are called glass eels.  They make their way into estuaries which connect saltwater to freshwater.  Many of them find themselves in water bodies of local New York State parks along the Hudson River.  Once in freshwater, they develop a brown coloration.  This signifies the shift to their next life stage as elvers.

Glass
The American eel in their glass eel life stage as they arrive to the coast. Chris Bowser

As the elvers grow longer over the next few years, they enter their yellow eel stage.  They live in this stage right before they reach full maturity.  Their size varies based on sex.  Males can grow to two feet long whereas females can reach sizes of four feet.  Their size in each life stage is based on their surrounding environment.  They become silver eels when they reach full maturity to start their migration.

This silver eel stage happens to be the most understudied of all the life stages.  There is no set age that eels are known to reach full maturity and age cannot be determined from external characteristics. Researchers look to study silver eels right before they begin their migration.

What kind of research?

Sarah’s motivation to study silver eels stemmed from her previous experiences working with them in their other life stages.  Her work with eels started with a summer project at Bard College, eight years ago.  After graduation she continued to work with glass eels, elvers, and yellow eels as a Student Conservation Association (SCA) intern at the Hudson River National Estuarine Research Reserve and Estuary Program.  Studying silver eels seemed like the next logical and exciting step for her. Sarah Mount at the SUNY College of Environmental Science and Forestry conducted research on yellow and silver eels.  Her research led to a model that sorts yellow and silver eels into different maturity classes.  The model relies on external characteristics such as the length, weight, eye diameter, pectoral fin length, head length, head width, and body depth of the eels to differentiate maturity classes. This means that future researchers can utilize this model to study the relative age of eels with a capture and release method that does not harm the fish.

With the guidance of Karin Limburg at SUNY College of Environmental Science and Forestry, she developed her research ideas into a master’s level study.  With the help of colleagues at the Hudson River Research Reserve, she spent two summers and two autumns collecting yellow and silver eels from the streams of the Hudson River estuary.

Interns
SCA interns at the Hudson River Research Reserve help Sarah set up a silver eel fyke net. Chris Bowser

Silver eels migrate at night during rain events in the autumn.  To catch them, Sarah set up a fyke net the day before a predicted rain storm.  This v-shaped net spanned the width of the stream and was removed the next morning.

The final life stages of the American eel still remain a mystery.  Sarah Mount’s research begins to solve it both for future research and for herself.  Her model will help future researchers understand when eels reach their full maturity to begin their migration.  When asked about her next steps she said, “Now the only missing piece left is the ocean, I’ve got to get out to the Sargasso Sea sometime.”

Post by Brianna Rosamilia,  Master of Science candidate in Environmental Interpretation at SUNY College of Environmental Science and Forestry

 

Tracking The Elusive New England Cottontail

New England Cottontail
New York’s rarest native rabbit, the New England Cottontail, photo by Amanda Cheeseman

 

It is a typical morning at the Taconic Outdoor Education Center (TOEC) in Fahnestock State Park. The sunshine beams through the forest, a chorus of song birds are greeting the day, and 60 elementary school students are making their way to breakfast to fuel up for an active day of learning in the outdoors. Meanwhile, a familiar truck and crew rolls in to begin their workday visiting several small animal traps set in specific locations in hopes that at least one will contain a rabbit, particularly a New England Cottontail.

The State University of New York College of Environmental Science and Forestry (SUNY ESF) is collaborating with State Parks, and the Department of Environmental Conservation to conduct important research about the population decline of native New England Cottontail. Over the past decade, studies have indicated that their numbers have decreased about 50%. The two major factors contributing to the population decrease are loss of suitable habitat, and the expanding range of the Eastern Cottontail. The only native rabbit species east of the Hudson River is the New England Cottontail; however the range of the Eastern Cottontail has been expanding and now overlaps this territory which causes competition for resources. Predation is also playing a role in the decreasing population; part of this research project is keeping an eye on who’s eating New England Cottontails by using trail cameras. These cameras placed in baited locations and use a motion sensor to take pictures when an animal walks by. Different predators are “captured” in a photo as they come to investigate the bait, which shows the species that a present in the rabbit survey area.

Back at the TOEC, the students are gathering to meet with their instructors for their morning lesson, the phone suddenly rings. “We have a rabbit” says the voice on the other end. Flexibility is part of the job description of an outdoor educator, and no one passes up an opportunity to enjoy a teachable moment, especially when it involves a live animal. All plans are dropped for the moment and after a short walk the students quietly approach the researchers who are preparing to identify, collect data, and radio tag the small mammal.

Juvenile
Measuring a juvenile New England Cottontail, photo by Amanda Cheeseman

Many of students who visit the TOEC are from the New York City area and rarely get to experience being this close to a truly wild animal, and they have a lot of questions such as: “Why is it in a pillowcase?”, “How long are its feet?”, “Is that a baby?” and “What’s That!?”. Their sense of wonder is contagious and the SUNY ESF researchers return the enthusiasm by answering the barrage of questions being hurled at them, while also safely collecting data on their captive rabbit. Measurements are taken, and the data is recorded onto forms and will go into a large database to allow for comparison across the entire northeast. The final step is to attach a small antenna to the rabbit’s back so that the researchers will be able to locate the individual rabbit again through radio telemetry. Now comes the exciting part! The rabbit is released, and in a flash it darts away, immediately out-of-sight, camouflaged amongst the underbrush.

Camouflage
A well camouflaged New England Cottontail. Can you see the antennae? photo by Amanda Cheeseman

Upon reflection, many students will say seeing the rabbit was their favorite part of the week, and they walk away with the feeling of being included in something important. Nothing teaches better than experience; giving students the chance to interact with a living, breathing part of the ecosystem around them. It sure makes for a pretty great day.

Post by Dana Mark, environmental educator at TOEC

Painted Turtles of Point Au Roche State Park in Clinton County, New York

Lower pond site at Point au Roche Park where all 4 turtle hoop traps are set. (Danielle Garneau)
Lower pond site at Point au Roche Park where all 4 turtle hoop traps are set. (Danielle Garneau)

Point Au Roche State Park is a beautiful and diverse park with a lot to offer visitors. By visitors we’re talking both the reptile and human kinds.  Not only does the park offer spectacular views of Lake Champlain for park visitors, it also provides great habitat for painted turtles!

Beginning in September 2012, two SUNY Plattsburgh students and Professor Danielle Garneau began their first field experience handling painted turtles. The goal of the project was to compare sex ratio and age structure of turtle populations in both urban, as well as rural ponds in Clinton County, New York. This research is part of the Ecological Research as Education Network’s (EREN) on-going TurtlePop project that is a collaboration among numerous colleges across the country.

Participants perform the same experimental protocol to determine if a greater number of adult males exist within urban turtle populations, and if this is a nationwide trend. The decline in young females is thought to result from their high rate of road kill when laying eggs at roadsides. An additional cause of death for urban painted turtles is an increase in the abundance of mesopredators (e.g., skunks, raccoons, opossum, foxes) who raid nests for eggs. Since starting, the TurtlePop project has offered field research experiences to many SUNY Plattsburgh students.

Painted turtle basking on a log with VHF transmitter glued to carapace (top of shell) at the golf course site (urban). Transmitters are used to track animal locations and note movement behavior, nest site selection, and overwintering spots. Note the shedding of scutes (keratin layers) on the top of the turtle shell, which occurs in the middle of summer as turtles grow. Days later this transmitter device fell off the turtle and was relocated along the pond shore. (Danielle Garneau)
Painted turtle basking on a log with VHF transmitter glued to carapace (top of shell) at the golf course site (urban). Transmitters are used to track animal locations and note movement behavior, nest site selection, and overwintering spots. Note the shedding of scutes (keratin layers) on the top of the turtle shell, which occurs in the middle of summer as turtles grow. Days later this transmitter device fell off the turtle and was relocated along the pond shore. (Danielle Garneau)

About a year into the project, as participants grew ever more curious, a radio-telemetry dimension was added by placing a VHF transmitter on the top of turtle’s shells in order to monitor their movement around a gold course pond complex (urban site) in the city of Plattsburgh. Findings suggest that city turtles do not tend to wander far from the shores of their pond and commonly used basking sites (e.g., downed trees, rocks).

In the summer of 2015, with the help of Point Au Roche State Park Naturalist and SUNY Plattsburgh Ecology alumnus Gillian Dreier-Lawrence, park visitors and college students had the opportunity to participate in and contribute to this growing collaborative research effort at Point Au Roche State Park. We are learning that Point Au Roche State Park has high turtle abundance; approximately 33 individuals were caught over three months of trapping in the lower ponds. Plans to further investigate the turtle population at Point Au Roche are in the works, as the  large number of turtles found indicate that  the population size at the park is likely quite large, only 11 marked turtles have been recaptured so far!

Post by Danielle Garneau, Associate Professor at SUNY Plattsburgh

Useful websites:

http://www.nysparks.com/parks/30/details.aspx

https://www.facebook.com/Friends-of-Point-au-Roche-State-Park-116729181851239/timeline/

http://erenweb.org/new-page/turtle-pop-project/

https://www.facebook.com/#!/ErenTurtlePop?fref=ts

Note: All photos were taken by Danielle Garneau and permissions are granted to use in press.