University of Houston-Clear Lake | Grad student collaborating with UHCL institute to study American eels

“Slippery as an eel” is a 600-year-old English language simile that describes a character as being elusive, evasive, crafty and cunning. Eels are at least all that, besides having smooth, sleek scales and a natural slime. Just ask University of Houston-Clear Lake graduate student Justin Hansen, who will spend the rest of 2018 and the better part of 2019 searching for them in the estuaries of rivers, streams and bayous along the Texas Gulf Coast.

Specifically, Hansen is searching for glass elvers (young eels) of the species Anguilla rostrata, or American eel. These eels are catadromous, which means they live their lives in fresh water but are born and will die in the ocean.

Hansen – working with UHCL’s Environmental Institute of Houston on a grant from Texas Parks and Wildlife – hopes to learn about their migration through Texas.

During one of July’s muggy weekends, he sloshed through Boggy Bayou, off old Highway 146 in La Porte, to set fyke nets –large, funnel-like mesh contraptions that exclude larger fish while trapping smaller ones.

“The nets have wings. When a fish approaches the wings, the hope is they follow them into the mouth of the net,” he said. “In the back of the net, there’s an excluder. It reduces the mesh down to about a quarter-inch size so that only small individual fish can fit in to the net in hopes that we catch just eels.”

Hansen left the nets out overnight in order to catch the incoming tide. “Eels are nocturnal and there’s some evidence suggesting that they avoid the light.”

He did trap a 6-inch eel that weekend. But it was the wrong species. “The eel we caught was a Speckled Worm eel. It’s a saltwater eel, but it’s known to come into estuaries and bays.”

Far from home

Hansen, who is pursuing a master’s degree in environmental science at UHCL, will spend much of his time traveling the coast between Corpus Christi and Sabine Pass. From Albany, Ore., he received his bachelor’s degree in Fisheries and Wildlife Sciences at Oregon State University in nearby Corvallis. “I can go 60 miles east to the east to the mountains, 60 miles west of the coast, 60 miles south I’m in higher elevation near Eugene, and then 60 miles north I’m in Portland and basically on the Columbia River. It’s a pretty good location,” he said.

“I was encouraged to get away from my comfort zone. But I was really interested in this program because of its collaborative effort. At the Environmental Institute of Houston, we get to work on a multitude of projects, not just our thesis work. I want to do spatial and temporal ecology (understanding how changes in climate, ocean and land systems affect habitat). That’s what I’m really interested in. And I’m interested in studying fish. So this is right up my scientific nerd alley.”

At the mercy of ocean currents

American eels spawn in the Sargasso Sea, a slow-moving ellipsis in the North Atlantic. It’s about 2 million square miles and at its deepest, 4.3 miles. It’s the only sea surrounded on all sides by ocean: bounded by the currents that circle the North Atlantic. Bermuda lies on its western fringe. It’s called the Sargasso for the rust-colored Sargassum seaweed that dots its glassy surface, like sagebrush in a desert.

From an American eel’s eggs, larvae-like leptocephali are hatched – transparent ribbons with gelatinous organs and tiny fins, useless at this stage. “They are subjected to ocean currents. They end up where the currents put them, making it extra difficult to figure out where they go,” Hansen said.

When they eventually reach the continental shelf, they begin their metamorphosis into so-called glass eels: translucent, except for their black eyes and silvery spines.

In fresh water, their pigmentation darkens, Hansen said. As elvers, they are about 4 inches long. They’ve been known to portage over natural and man-made barriers, working cooperatively to scale vertical climbs over rapids, locks and other obstructions. They are able to live out of water for several hours. As adults, they grow to 3-4 feet long. By then they are silver, slivering along riverbeds and lake bottoms. While they shy away from light, they are fierce predators known for their aggressiveness. American eels can have a lifespan of more than 40 years, he said.

As they mature, they develop into either male or female, depending on their population. After mating, the females migrate thousands of miles back to the Sargasso Sea, where each lays 4-8 million eggs and dies, becoming a nutrient-rich haven for their offspring in a nutrient-poor sea.

A question of abundance

American eels are fairly common but not commonly fished, Hansen said. They live all along the Eastern Seaboard – from Maine to Florida – and in the waterways that drain into the Atlantic. They inhabit Mississippi River and the tributaries both east and west of Mississippi.

In Texas, American eels have been spotted in the Brazos, Sabine, Colorado, Pecos and Rio Grande rivers and elsewhere. While Texas anglers have recorded the occasional catch of adult or juvenile eels, Texas has no records of glass eels or elvers, Hansen said. There are no records of adults’ migration back to sea, either. “How many of these eels entered Texas before impoundments were put in place? Because if they’ve been here for 40 years, some of our waterways may not have had obstructions in them to block their out-migration,” he said.

“There’s an interest in the commercial harvest of the species. But the state doesn’t have sufficient data to be able to develop a fisheries management plan,” Hansen said. “We really don’t know much about how and when they migrate into Texas waters, where they are or how many. We want to know abundance. That’s our goal.”

Supply and demand

Unagi. Eel roll sushi is so popular in Japan, that the country’s native freshwater eel is an endangered species. Japan turned to the European Union for harvests of European eel – genetically similar to its American cousin and also a native of the Sargasso Sea – until sources there were depleted. The European eel is now on the International Union for Conservation of Nature “Red List” as a critically endangered species. About six years ago, Japan began looking to the U.S. as a source, National Geographic reported.

Of the states that have conservation or fisheries plans for the American eel, harvesting glass eels is only legal in Maine and South Carolina. Even so, strict quotas are in place. Trappers fill buckets and coolers with live, writhing glass eels and sell them to commercial fisheries. This spring’s 10-week harvest season, prices started at about $1,900 a pound and spiked to $2,800 a pound, the Bangor (Maine) Daily News reported. The fisheries resell to Japan’s fish farms at three-to-four times the price. At the fish farms, the elvers are raised to juveniles or adults, processed and commercially sold worldwide.

Glass eel harvesting is so lucrative, that some fishermen and fisheries have colluded to catch eels in states where it’s illegal and transport black-market catches to Maine or South Carolina – running afoul of federal wildlife trafficking laws. In June, 19 East Coast eel smugglers received either prison sentences and/or fines in a multistate investigation named “Operation Broken Glass,” National Geographic reported.

Why the concern?

It takes 2,000-3,000 of these tiny glass eels to tip the scale at a single pound. Some conservationists don’t want to see the eel population decimated by commercial interests. Currently, the American eel is not on the U.S. Fish and Wildlife’s endangered list, although it came up for review in 2015, the agency noted on its website. Others argue that not all glass eels would live to adulthood, anyway – it’s a fish-eat-fish world. Nothing is known about how they factor into the freshwater food chain.

Catch and release

“Oh, man. It’s going to be a celebration,” he quipped. “We want to try to take data on each individual eel, if we catch them. But if we catch thousands or hundreds in one net, it would take take a long time to process all those fish.”

He said EIH would keep about 10 of them to send to the University of Texas to record their genetic information. “I want to take length and weight data in the field on every individual. We’re going to release as many as we can when we find them,” he said, and acknowledged, “That’s optimistic.”

Grad student collaborating with UHCL institute to study American eels