Carl Safina, in Montauk, says he wants to develop a “sea ethic.” The best place to observe this fusion is aboard his 24-foot powerboat First Light at the time of day for which it is named, when Dr. Safina is scanning flocks of terns hovering over the tide-roiled waters between Montauk, the tip of Long Island, and the slate-dark hump of Block Island to the east.

Dr. Safina s doctoral thesis was on the interrelated behaviors and annual rhythms of the common tern and bluefish, which feast on the same bay anchovies and other small prey.

On many days, though, he is carefully tracking the birds not in pursuit of new knowledge, but in hope they will point him to dinner.

On a recent three-hour fishing trip, in snippets of windblown conversation while steering his boat, jigging or casting, then fighting, landing and cleaning fish, Dr. Safina reflected on two decades of work revealing the enormous disruption of ocean ecosystems by industrial-scale fishing and other human activities.

Now 51, he has written three books on the rising human impact on seas once presumed boundless. The first was on fishing, the next on the travels and travails of albatrosses. His latest, “Voyage of the Turtle: In Pursuit of the Earth s Last Dinosaur” (Henry Holt, 2006), follows the struggles of the ocean s ancient leatherbacks and other sea turtles.

His prime goal, he has said, is to develop a “sea ethic” similar to the land ethic of Aldo Leopold, and a scattering of success stories has convinced him that a balance is still possible between exploitation and conservation of marine resources.

On this day, several bluefish were hooked and two were landed as he zigzagged over the North Rips, a series of shallow ridges that, like Long Island and Block Island, are deposits of sand and gravel left behind after the great ice sheets of the last ice age stopped their southward advance.

The next stop was Treasure Holes, dimples in the sea floor favored by fluke, a hefty, toothsome flatfish prized for both its fight and its flavor. He hooked a heavy fluke and reeled it toward the surface.

Question - O.K. if I net him?
(The large brown, speckled fish flopped onto the deck, and Dr. Safina grabbed a yardstick to see if it topped the 18-inch limit.)
Answer - For this one I would say you don t really need the ruler. He s about 21 inches. These fish were very depleted about 10 years ago, and they ve been recovering. The minimum size has been raised several times, so I kind of feel O.K. about taking a couple of these for the table. In general, I m O.K. with using what s in the oceans. I just don t think we should be using it up. So the point to me is not necessarily to put things off limits, although some places probably should be off limits where fish spawn and places like that. But the main thing is to restore the abundance of what s in the ocean so that we can have a viable system where all these animals can live and eat each other, and then we can take a little bit.

Q. There are all these sexy critters in the ocean — sharks, whales — and then along come these things called sea turtles. Why did you choose to focus a couple of years of your life and a book on sea turtles?
A. Well, actually, I was writing my book on albatrosses, and I saw sea turtles laying eggs for the first time. I had seen them in the ocean a number of times, and they always struck me as extremely graceful and just really lovely. There is something about the magisterial slowness of their movements, and many of them get to be rather old, so they seem like venerable citizens of the deep. But seeing the turtle lay eggs was also a very moving experience, and I thought that it would be nice to follow them around, write a book about how the oceans are changing sort of through the eyes of sea turtles.

Q. What most discourages you related to the trends you see in the oceans?
A. That it s so easy to see what we need to do, it s so easy to see how things can be so much better and yet it s taking so much time to come around to it.

Q. What are some of those improvements?
A. We need to just set fishing quotas and adhere to them, and make them realistic, and listen to what the scientists say about how many fish can come out of the ocean. And if we do that, we will get more of what we want.

Q. Why do you think scientists don t tend to be listened to very much?
A. Because usually people are very greedy and try to cheat. Everybody tries to get the most of what they can before everybody else gets to it.

Q. And what s one of the most encouraging things you ve seen?
A. That fish are recoverable. Many of the fish that we have here were much less abundant 15 years ago than they are now. We did get some good regulations passed, and the fish began recovering right away. They know what to do. If you just don t kill them as fast, they start coming back. So the most encouraging thing is that it works, but a lot of that could be much more widespread throughout the country and the rest of the world.

Q. One thing that seems to be encouraging about the way the oceans behave is you tend to fish something to commercial extinction long before it s actually gone forever. Do you think that s true, and is that why there is this sense of always being able to go back to the well?
A. I saw a photograph the other night in a book on extinction of the last bear in Switzerland. There were about 50 people surrounding this thing, and you know they had been trying very hard to kill the last bear. It was about 100 years ago. But in the ocean, things get very rare and then it becomes in most cases not economically profitable to keep after them, so the fishery tends to go out of business before they completely extinguish the last fish. There are exceptions to that. There are some populations of cod that seem to have been fished out of existence. They no longer spawn in those areas. Those individual populations seem gone. But for the most part, because we re not so much building structures in the ocean, the habitat is still there. When we leave before the last fish is caught because we are not making money, there is usually this little reservoir of recovery potential. And also fish tend to have a very high rate of fecundity; they lay millions of eggs. If the bulk of the habitat is there and the pressure comes off a little bit, they usually can rebuild much faster than some other kinds of animals. We ve seen that with a lot of these species here, including these fluke that we re fishing for at the moment. Striped bass is a fantastic recovery, another fish that we love to catch locally. In the mid-1980 s we were talking about putting them on the endangered species list. Black sea bass are recovering. That makes me very hopeful that we can actually solve a lot of these problems on a bigger scale and for the long term.

Q. What s the farthest afield from here you ve ever fished, the most exotic, unusual, different place?
A. I did a little bit of fishing in Palau, a little in Alaska. But you know when I m in really exotic places far from home I tend not to really want to go fishing. I like seeing wildlife and things like that. But I really don t like fishing so much if I don t understand the area or why we’re in a certain spot. What I like is really understanding where to look for the fish, what to do to try to catch them, a sense of the season, what it was like last week, what it was like at this time last year or 10 years ago. The context really means a lot to me. So a lot of what I like about fishing goes away if I m far from home.

Q. What s the best thing about fishing?
A. Well, it s called recreation, and I think of that as re-creation. It does get you back in touch with a lot of the things that have to do with who we are, and my love of being outdoors, my love of nature, all those things. Sometimes I have other things to do that are a lot more important, and I put this off and I just sort of downgrade the importance of coming out here. Then, when I get out here, it s like, “Oh, that s right,” how nice this is, how relaxing, how rejuvenating, how original it seems to feel.
(Por Andrew C. Revkin, The N.Y. Times, 25/10/2006)