The Hard Decision Not to Rescue an Ailing Dolphin Could the dolphin have been saved? As a seven-foot dolphin struggled in the filthy waters of Brooklyn's Gowanus Canal on Friday, onlookers -- both on the canal's freezing banks and on the Internet, where the animal's throes were widely broadcast -- questioned the decision by the Riverhead Foundation, the region's officially anointed marine-mammal rescue group, to wait for high tide and see if the dolphin made it out to New York Harbor under its own power. And when the dolphin died around 6 p.m., an hour or so before high tide, about eight hours after it was first spotted and perhaps four hours after Riverhead arrived on the scene, the second-guessing grew louder. Images of the day -- the dolphin surfacing for air with its snout, or rostrum, covered in black muck, a man going over a railing to reach down into the water to stroke the dolphin ("if this man could do that, rescuers could have saved this dolphin," posted one Twitter user, Raelene C.) -- seemed to illustrate both the pressing need for and the possibility of some sort of intervention. The foundation's director and senior biologist, Robert DiGiovanni, was quoted in The Daily News saying: "Unfortunately, all we can do is watch and wait for the tide to rise, so the animal can get out on its own. It's not safe for us to get people in the water. This led to headlines like "Injured dolphin trapped in New York canal dies after rescuers refused to help because water is 'too polluted' to go in" (in London's Daily Mail) and further recriminations on Twitter. But Mr. DiGiovanni said in an extensive interview on Saturday that far from "letting" the animal die, he and his staff determined that the dolphin's best chance for survival lay in not intervening. The foundation weighed many factors, Mr. DiGiovanni said, among them the risk of the animal injuring itself in the process of being captured; the daunting logistics (including federal permission) and lead time required for safely removing a dolphin from water; the very low survival rate, under 10 percent, of dolphins that are taken in for rehabilitation; and, yes, the possible danger to staff members of exposure to the canal's toxic goo, the subject of a $500 million Superfund cleanup. The waterway is polluted with more than a dozen contaminants, including PCBs and heavy metals like mercury, lead and copper. Further, Mr. DiGiovanni said, if the dolphin was not strong enough to survive in the canal for more than a few hours, there was little chance its life could be saved anywhere. "If it's not going to make it through the next tide cycle, it's an animal that's completely compromised," he said. The fact is, Mr. DiGiovanni said, that a solitary dolphin that found itself more than a mile up the canal -- farther than Mr. DiGiovanni had ever seen one -- was overwhelmingly likely to be mortally ill and in the process of dying. The dolphin, an older male who weighed 345 pounds, was taken to the Riverhead Foundation's headquarters on Long Island, about 75 miles east of Brooklyn, on Saturday, and a necropsy is to be performed tomorrow, with final results expected in several weeks. Here are some excerpts from Mr. DiGiovanni's interview: On the risk to the dolphin of injury during capture: The capture process is very stressful to the animal, Mr. DiGiovanni said, and even seriously injured marine mammals will naturally try to escape. In the confines of the narrow canal, he said, "everything that it was going to hit was going to be concrete, and it's not favorable." He added, "In many cases where there is a compromised animal and we intervene, they die as soon as we get them on the stretcher." On the dangers to the rescuers: Not only is the canal indisputably toxic, Mr. DiGiovanni said, but it was not clear to his staff members exactly what kind of dangers they would face in its waters. Is the water dangerous to get on your skin? If someone falls in the water and accidentally swallows some, are they in danger? If we were going to intervene and jump in, we would want to make sure that we had the protective equipment to deal with that scenario -- all that takes time as well, which puts us back to our original plan. On the possibility of herding the dolphin out to the relatively clean water of New York Harbor: He said that even that minimal intervention would require drawing up a plan and getting clearance from the National Marine Fisheries Service, which again takes time. All too often, Mr. DiGiovanni said, sick animals brought out to sea simply beach somewhere else the next day. The bottom line was that "the tide-cycle plan doesn't do harm to the animal or to the people inadvertently at all," Mr. DiGiovanni said. That gives us the largest chance of success. Here are more videos of the dolphin: Correction: January 26, 2013 A previous version of this article gave an incorrect length of the dolphin. The dolphin was seven feet long, not six feet.