STEVE INSKEEP, Host:
As NPR's Christopher Joyce reports, some biologists say the problem is not overfishing this time. It's the weather.
CHRISTOPHER JOYCE: Brad Burns started fishing for striped bass in 1960. Last week, I caught him by phone as he was running a booth for his group, Stripers Forever, at a fly-fishing show in New Jersey. He says his members have been singing the blues about stripers.
BRAD BURNS: What we hear from people that go striped bass fishing, the general trend very decidedly is down.
JOYCE: Stripers live in the ocean, as well as in estuaries and some rivers. Burns says members have been reporting fewer fish for the past five years. As for the cause...
BURNS: Well, I don't know, and I don't know that anybody does.
JOYCE: But Bob Wood thinks he might. Wood's a biologist at the National Oceanic and Atmospheric Administration. He studies his fish in a boxy little building on the Maryland shore of the Chesapeake Bay.
BOB WOOD: Come on in. And what we have here is a way to run controlled experiments on nutrition and disease.
JOYCE: Here, scientists keep vats full of striped bass and white perch, two species that spawn in the Bay. This is where Wood's team tries to figure out why striper numbers go up and go down. They thought they had the 1980s crash figured out.
WOOD: The striped bass crashed because of overfishing, and then it recovered because we closed the fishery.
JOYCE: But now Wood has new idea that's just taking shape.
WOOD: This research, at first glance, seems to call that into question. But it's not that easy.
JOYCE: This novel idea focuses not so much on fish, but on the weather, and especially the Atlantic Multidecadal Oscillation, or the AMO. The AMO is a mash-up of wind and ocean currents, a flip-flop that happens every 35 years or so in the North Atlantic.
WOOD: Circulation changes in a way that warms the entire basin. And you can imagine if you warm the entire North Atlantic basin, you're changing the weather because the air and circulation patterns above the ocean are then affected.
JOYCE: Ed Martino is a fisheries scientist who works with Wood at NOAA. He says when that AMO shift happens, it affects the local weather along the Atlantic Coast.
ED MARTINO: You're talking about differences in temperature and precipitation, and therefore river flow or salinity, ultimately all affecting the base of the food chain. It's the way that the climate affects the microscopic plankton.
JOYCE: Then the AMO flips - drier springs, less rain, less food. After a lag, it looks like striper numbers start to decline. Wood says the past 100 years of fishing records show that very trend, which brings us to the present crash in stripers.
WOOD: It hasn't been so good in the last, say, five years. And it just so happens, this is also the time when the Atlantic Multidecadal Oscillation seems to be switching phase.
JOYCE: Janet Nye studies fish stocks for the federal Environmental Protection Agency. She thinks this research could help fisheries managers.
JANET NYE: We would be able to say, OK, for the next 35 years or so, we're pretty certain that the AMO is going to be more positive or warm. And we'd be able to say, these are the fish that respond favorably to that. You might be able to fish those more.
JOYCE: Or in a down cycle, says Bob Wood, fish less.
WOOD: If we know that there is this cycle coming up, a trend that we are beginning to enter, we can keep that in our heads as we set limits.
JOYCE: Christopher Joyce, NPR News.