What Alternative Energy Taught Us About the Fish that Live in the East River

I've got a guest post up at the Public Library of Science blogs today!

Lesson 1: There are fish that live in the East River

Sure, New York City's East River has long been a punchline for jokes about industrial pollution and mafia homicide, but it's far from being a dead zone. That stereotype is one of Jonathan Colby's biggest pet peeves. There are many species of fish living below the water, he says, and diving birds, such as cormorants, that live above. You can even watch the cormorants–big, jet-black creatures with yellow beaks–doing their thing from the promenade along the Eastern edge of Roosevelt Island.

The River really was once in trouble, but it's rebounded in a big way since the 1980s. It's just that, until recently, Colby says, nobody had documented the results that successful clean up had on fish populations.

The impetus behind the East River's first wildlife study in decades: Hydroelectricity. Colby is a hydrodynamic engineer with Verdant Power, a company that's working on installing 1 megawatt of electric generation in the East River, using a system of spinning blades on posts–similar to wind turbines. To make sure the fish don't hit the fan, Colby had to document a baseline population and then monitor fish numbers and behavior over two years, while Verdant ran a 185-kilowatt demonstration project.

Monitoring happened round-the-clock, 24-7, using both traditional sonar and a new system called Dual Frequency Identification Sonar, or DIDSON. While basic sonar tells you that an object is in the water, DIDSON can show you what the object is–whether fish or plastic bag. The images produced by DIDSON look a lot like fetal ultrasound pictures. Suffice to say, the results might look a little abstract to you or me, but experienced analysts can get at least an Impressionist level of information out of it, including the direction the fish are traveling and, in some cases, what kind of fish are out there.

"There are like 1000 fish, per month, that just kind of live here [in the area surrounding Verdant's turbines] during the non-migratory period," Colby said. "During migratory periods, you can see upwards of 10,000 fish per month traveling through these waters."