By Syma A. Ebbin
First published on March 31 in GOSA News, Spring 2014 edition
Have you been to the Sheep Farm? It is one of GOSA’s recent open space acquisitions. It boasts the highest set of waterfalls in the town of Groton along with remnants of a historic grist mill dating back to the 1700s. It is a lovely place to hike any time of year.
On a warm Sunday over three years ago, June 6, 2010, to be precise, I hiked the Sheep Farm with my family. We enjoyed a picnic on a rocky outcrop in the middle of one of the fields and then hiked down along Fort Hill Brook until we reached the falls. My husband and children clambered up and over the rocks while I explored the pools at the bottom of the falls. My husband yelled down to me that he had found a fish in one of the pools atop the falls. I climbed up the rocks and, although I had never seen one before in fresh water, I easily identified it as an American Eel (Anguilla rostrata). The eel was dead, about 14 inches in length and in fairly good condition. I thought that a raptor might have dropped it into the pool, which is about 10 feet above the stream, but there were no talon marks or tears. No, this fish had probably migrated up this stream several years before as a tiny elver, working its way up the moist and fairly vertical walls of the falls, living its life in the fresh waters of Fort Hill Brook. Or perhaps, our eel took a detour on land, relying on the ability of its skin to absorb oxygen, and slithered over the damp ground to make its way around the obstacles in its path.
If all had gone well, our little eel would have matured into a silver eel with a blackish back, silver underside, large eyes and a host of other physiological changes, and eventually migrated back downstream to Mumford Cove, out through Fishers Island Sound and headed south, swimming in deep waters to the Sargasso Sea. Here, in the North Atlantic Subtropical Gyre, a shifting area of two million square miles delineated by the clockwise movement of ocean currents, our eel would join with other members of its species in a mass spawning event along with European eels (Anguilla anguilla), which spawn in the same area. After spawning, our eel would have died. This spatially unified approach to reproduction with spawning occurring in the same location results in what is termed a panmictic species – that is one that shares a common gene pool, with no genetically distinguishable populations or stock structure. All North American eels basically belong to the same and only population within the species A. rostrata.
If our eel spawned successfully, the fertilized eggs would have hatched in the salty waters of the Sargasso as transparent, somewhat flattened eel larvae called leptocephali. These would have transformed into glass eels and migrated to estuarine or freshwater environments in North America over the course of a year or so. They would migrate upstream, becoming elvers, rounder in shape and darker in color, ranging from three to six inches in length. Not all eels ascend freshwater tributaries; some remain in brackish coastal waters. Elvers are nocturnal and live in and around bottom sediments, growing over the course of several years into yellow eels, which is the stage of eel that we found at the Sheep Farm. During this period of their life, which may extend from three to 40 years, they are green or yellow in color, attain lengths of one to several feet; females usually growing larger than males. In Connecticut, the largest eel on record weighed in at 10.2 pounds and measured 52 inches in length, but in other areas, larger eels have been reported to reach five feet in length. After they mature sexually, they head downstream. Once they return to the ocean, they stop eating and undergo a series of physiological changes to allow them to navigate deep marine waters on their way to the Sargasso.
This life history strategy is called catadromy, similar but opposite to the approach taken by anadromous fish species such as salmon, which spawn in freshwater, mature in marine waters, and then return to fresh waters to complete their life cycle. Over 700 species of eel within the order Anguilliformes have been identified, most are marine, and only one family, Anguillidae, contains freshwater species.
The mysteries of the eel’s life history are numerous, our understanding is full of “data gaps,” and our assessments are considered “data-poor.” No one has ever found or captured an adult eel in the Sargasso Sea or open ocean, eels have never been observed mating, nor have the carcasses of eel been retrieved after spawning. What has been found are the newly hatched planktonic eel larvae, leading scientists to believe that adults have spawned nearby. It’s not certain that eels die after mating, but there is no evidence that eels are repeat spawners or that they ascend freshwater tributaries after spawning. No one knows how the newly hatched eels distribute themselves among the thousands of different freshwater tributaries along the Gulf and Atlantic coast of North America nor how they navigate to places to which they have never been. The list of unknowns is long, as is the list of research priorities as evidenced by the Atlantic States Marine Fisheries Commission’s 2013 Review of the American Eel which lists 21 multifaceted eel-related research questions in need of answers.
Unfortunately, despite the lack of data, one thing is becoming clear: the depleted status of American eels throughout their range, including localized extirpations. In the last decade, the U.S. Fish and Wildlife Service (USFWS) has been petitioned twice to list the American eel under the Endangered Species Act (ESA). In response to the first petition, the USFWS concluded in 2007 that a listing was not warranted. The second petition, however, made in 2010 by the Center for Environmental Science, Accuracy, and Reliability (CESAR) was found to contain substantive evidence that might warrant a listing as threatened. USFWS decided the petition required more review; however, CESAR filed suit against USFWS in 2012 for failing to complete its review within the one year stipulated under the ESA. A Settlement Agreement was issued last April by the Court, which extended the USFWS’s deadline for issuing a finding to September 30, 2015. So we’ll have to stay tuned to see how the eel fares in its migration through that regulatory thicket.
Astutely, you might ask why are eels faring so poorly? As an animal which migrates both up and down rivers and streams, eels are subject to the same threats that have led to the depletion and extinction of salmon, namely dams. Dams not only block the passage of eels in both migratory directions, but the turbines associated with hydropower production puree the eels as they head out to the ocean on their way to spawn. Add to this threat the many other ways that humans have obstructed, impaired, and even destroyed freshwater habitats, the pollutants which find their way into these waters, and the existence of a recently introduced swim bladder nematode, Anguillacolla crassus, a non-native Asian parasite likely brought in through aquacultural operations that are now infecting American eels and impacting their growth and reproduction. Overarching these threats is the growing impact of climate change which is causing waters to warm, flows to diminish, and droughts to persist, leading ultimately to the reconfiguration of the eel’s essential fresh and marine habitats to the detriment of its survival.
In addition, American eel fisheries feed into a multibillion-dollar international eel industry fueled primarily by Asian consumption patterns. As a child, I caught eels as bycatch while targeting winter flounder in Baker Cove, Groton. They put up a great fight, but once caught, they were so difficult to free from the gear due to their notorious slime production that there was high release mortality. The only eels that are legal to harvest in Connecticut are the yellow eel, which is primarily used for bait or sold and consumed in some ethnic markets. According to the Connecticut Department of Energy and Environmental Protection, which is responsible for managing the eel in Connecticut waters, there are two commercial eel fishermen in Connecticut, who in 2012 harvested a total of 3,560 pounds of eel at or over six inches in length, as well as a small targeted recreational fishery. With the depletion of Asian stocks of Anguilla japonica, Asian producers have turned to hatchery production; however, eels have proven to be difficult to breed and grow in captivity, and Asian hatchery production relies on wild-caught juveniles, now imported from the U.S. and Europe. This demand has spiked the market price for glass eels and elvers to rise to over $2000 a pound. Maine and South Carolina are the only Atlantic states that permit a commercial glass eel or elver fishery. Although they are not legally harvested in Connecticut at this time, a bill proposing the legalization of a glass eel fishery was introduced to the Connecticut legislature earlier this year.Illegal harvests are common in all states along the Atlantic coast given the lucrative nature of the fishery and difficulty in monitoring and enforcing regulations. There is a company in Connecticut that buys glass eels and elvers from fishermen in other states and sells them to Japan for grow-out in hatchery facilities.
Taken together, this is a recipe for extinction. Let’s hope that eel researchers are able to uncover some of the mysteries of the eel’s life history soon and that fishery regulators get their act together and can devise a rational plan to ensure the American eel’s continued existence as a species. Let’s hope that my children’s children will be able to scramble over the rocks by Fort Hill Brook and discover their own yellow eel hiding in a gravelly nook at the bottom of the brook. Steps in this process certainly involve the continued preservation of both our freshwater tributaries and the lands which surround these arteries, like the Sheep Farm and The Merritt Family Forest, along with continued efforts to ensure that our rivers and streams are unblocked and waters run pure. That’s the eel’s deal after all and not so bad for us either.
About the Author: Syma A. Ebbin, Ph.D. is research coordinator for Connecticut Sea Grant, faculty member of the UConn Department of Agricultural and Resource Economics, and a member of the GOSA Board of Directors.