Fishing for Answers By Carl Glassman It’s hard to imagine that tons of the Hudson’s riverbed would be dredged without a single environmental study, hearing, or even a debate. But when the unimaginable happened on Sept. 11, the need to remove debris could not wait. Barges had to be brought in and the corner of the Hudson south of Tribeca’s Pier 25 was quickly deepened by 15 feet. Some 120,000 cubic yards of river bottom were taken away. Now researchers are asking: To what effect?   Last month, half a year after the last barge was towed away, a small trawler with a crew of four plied those same waters, scooping up fish and digging into the muck to find out. “Attention New York Waterway. Research vessel Acipenser from Cornell University. We’re under tow. Please steer clear. Thank you.” Through a haze of unremitting rain, Anne Gallagher steered the boat beyond the end of the pier and sent a second alert to a northbound ferry. Having completed another 1,000-foot-long trawl of riverbed—from seawall to pier head—she brought the Acipenser to a stop. As the boat bobbed in the wake-churned river, research volunteers Jeremy Dietrich and Ben Carr leaned over the stern, groaning as they pulled in the fish-laden net and its heavy lead weights. The job was made all the more difficult by the slippery mix of rain and hydraulic fluid on the floor that the crew had been trying hard to sweep dry. “If we were to slide off, we’d be inside the net. That’s why we all wear knives,” said project manager Geofrey Eckerlin, pointing to the sheath on his belt. “That hasn’t happened yet.” The catch was puny by a fisherman’s standards: some small striped bass, several types of herring, white perch and a few anchovies. But each was carefully weighed, measured and recorded—they are clues to the health of the underwater habitat and its ability to recover. Eckerlin and Gallagher are field researchers from Cornell University’s Department of Natural Resources. Under the direction of lead researcher Mark Bain, the two marine biologists and various volunteers have been spending one week each month along the waters of the Hudson River Park’s designated sanctuary, from Pier 25 to 59th Street, collecting and examining the underwater creatures. With a one-year, $190,000 grant from the Hudson River Park Trust that they expect to parlay into a second year of funding, the researchers are studying the effects of the dredging on the fish and invertebrates—clams, worms, snails, mollusks, etc.—and conducting a comprehensive inventory of fish and invertebrates throughout the park. Their findings will be compared to previous studies conducted by the Environmental Protection Agency. They will be looking at the types of fish they are catching, their abundance, diversity and health. In the dredged area especially, they will examine the changes over time, and how they differ from other park areas. “Fish have choices,” said Bain, “and dredging a section of the water there could have created an area that’s not nearly as desirable to them.” On the other hand, he added, deepening that corner of the river—and removing many of the pilings of defunct piers—may actually have made the area more attractive to fish. As for those tiny creatures that the team scoops from the mud, Bain said it will be important to see which species thrive there. If only the hardiest are found to recolonize the muck, it could mean that some unsettling changes—stirred up toxins or differences in the mud, perhaps—have made the riverbottom less habitable. It will be some time before there are any conclusive findings. Identifying the invertebrates under a microscope back in the lab is a painstakingly slow process that Gallagher has only just begun. And it will take a couple of cycles to draw conclusions about the fish. But early evidence, Bain said, looks encouraging. “So far we’re catching the normal fish you’d expect in a low salt environment on the coast and the fish seem normal in their appearance.” What still does not seem normal, said Bain, is the absence of the twin towers in the skyline—a thought that does not go away when he and his upstate colleagues are in the field. Still, trawling the city’s waters is unique. “Sampling fish with skyscrapers in the background,” he said, “that’s pretty tough to beat.”