Huge squid are appearing off the Golden Gate Bridge. Striped bass have returned en masse to the Chesapeake, but some are mysteriously skinny. Around San Diego, the albacore tuna have gone AWOL.

Anyone who has ever dropped a line into the water knows that angling is a crapshoot. But in the waters off the continental U.S., anglers are finding the deep-sea fishing is getting weirder by the year. Stocks of some ocean fish are waning or losing weight. Others are booming. In Miami, charter operators are adding moonlight swordfish trips. And hard-fighting favorites like marlin are showing up hundreds of miles from home.

The causes are subtle and contentious, with scientists and fishermen citing everything from warmer water to regulations that have anglers catching too much -- or not enough. In one case, critics are pointing fingers at drug-store aisles: The harvest of millions of fish for Omega-3 dietary-supplement pills may be taking the food right out of the mouth of the Chesapeake's striped bass. The silver lining: There may never be a better time to catch six-foot squid.

While fish stocks naturally rise and fall over the years -- and fish naturally move around -- reports of odd catches have been increasingly coming in around the U.S. Last summer, charter boats operating from San Diego caught unprecedented numbers of 200-pound yellowfin tuna, which fishermen value for hourlong fights and sushi lovers know as ahi. But they also recorded a low catch of albacore, the tuna that normally drives the area's charter business. More than a thousand miles north, albacore have been caught in uncommonly large numbers off Washington for the last two years -- a good thing for local fishermen who've seen quotas slashed for salmon, their traditional catch.

The sea change has some fishermen feeling a bit seasick: John Kabay, a retired executive who lives in San Diego for part of the year, says he went on one five-day trip last season with about three dozen anglers that yielded 18 albacore total. "You just wanted to cut your throat," he says. "Usually one guy gets 18 albacore."

The state of marine life matters deeply to the estimated 44 million Americans who fish for sport. The sports-fishing business accounts for $42 billion in travel costs, lodging, equipment and fuel, according to research firm Southwick Associates. But the number of saltwater fishermen has dropped about 30 percent, to 13.5 million, since 1987, according to the Sporting Goods Manufacturers Association.

That may be because fishermen love surprises -- but not complete unpredictability. In the Pacific Northwest, where regulators have crimped salmon-fishing seasons, charter captains are trying to keep customers by offering trips for halibut or albacore that historically have been beyond the reach of day-trippers. In the Chesapeake Bay, charter fishermen are counting on striped bass to generate business, because captains say other traditional favorites -- trout, bluefish -- have been declining.

In San Diego, Captain Rick Craddick is outfitting his boat to follow the fish farther afield. On a rainy afternoon recently, Mr. Craddick sat under a blue tarp overseeing renovations that would add a larger fish hold -- five tons up from two -- and a new bathroom with showers to his boat, the Black Pearl. He's aiming to go for as long as five days, up from his usual two-day runs. "It's a pretty easy sell," he says.

But the recent shift in fishing is about more than whether you'll haul home a 200-pound yellowfin or a 30-pound albacore. The change in fishing also speaks to broader issues, feeding debates over the state of the environment, the effectiveness of fishing regulations and whether Americans are a doing a good job balancing the demands of a growing population who want to fish for food and sport, and also want waterways for power generation, irrigation and recreation.

The fish shift also speaks to one of the hottest issues of all, global warming. Global ocean-surface temperatures have increased at a rate of approximately 1.1 degree Fahrenheit per century since 1900, according to the National Climatic Data Center of the National Oceanic & Atmospheric Administration. According to temperature measurements provided by NOAA -- taken at spots including buoys and ships and by satellite -- the coastal temperature along the Pacific Coast has been above the long-term mean, an average calculated using measurements dating to 1880, for 14 of the last 20 years.

During Pacific Ocean El Nino events -- when the ocean becomes unusually warm and tropical trade winds weaken -- tropical fish are seen far from their usual haunts. "Where you never had a marlin north of (Santa Barbara), during an El Nino you catch them off of Washington State," says Tim Barnett, research marine physicist at Scripps Institute of Oceanography.

More broadly, the ocean's very contents have undergone dramatic changes over the past half century. The rise of commercial fishing has reduced the ocean supply of large fish, including many popular sport fish like marlin and swordfish, to about 10 percent of their 1950 levels, according to a study published in the journal Nature in 2003. This study came under fire by critics, but scientists generally agree the ocean's supply of large fish has seen a long-term decline.

And then there's the curious case of the enormous squid. For years, sports fisherman around San Francisco cooled their heels in the winter, waiting for the summer salmon season. But recently charter boats have been heading to sea in January and February to catch Humboldt squid, a species that reach 6 feet in length and attacks food and fellow squid with parrot-like beaks. They're typically found in waters off Baja California, but more recently the invertebrates have been spotted off the coast of San Francisco and as far north as Washington. Sportfishingreport.com, which tracks sport catches around California, began counting the local squid haul only in 2005 and reports anglers caught more than 12,000 this past winter, about six times more than the year before.

Stanford University biology professor William Gilly says the squid may have followed their food supply north. Or maybe, he says, the squid population is generally expanding thanks to an increase in food or a dearth of predators. "Something's going on. Exactly what that is, I'm not sure."

Regardless, it has introduced anglers like Brian Mathews to one of deep-sea fishing's most chaotic spectacles. This winter, the commercial real-estate broker in Oakley, Calif., took a squid expedition on the New Sea Angler, a charter boat out of Bodega Bay, Calif. About 20 miles from shore, he and his fellow passengers dropped spikey jigs (or "war clubs") hundreds of feet down. As fellow passengers pulled a few squid from the depths, a mass of the maroon-red creatures followed them to the surface and surrounded the boat.

With the captain screaming directions, Mr. Mathews and his fellow anglers threw lines into the frenzy of squid. Once hooked, fishermen say the squid surge away, peeling off about 10 yards of line at a tear. Mr. Mathews likened the sensation to hauling up a trash can full of water. At the end of the day, he had three sacks full of squid, good for months worth of fresh calamari steaks, and black stains from his shoes to pants to jacket. "As soon as they get onto the deck they blast this big old huge shot of water and ink all over you," he says.

To get a better handle on the factors reshaping deep-sea sport fishing, we surveyed the sport from Florida to the coast of Washington State. We consulted fisheries regulators, conservation groups, scientists and government researchers, as well as fishermen themselves. We also tested the waters ourselves on expeditions in the Atlantic, Pacific and Gulf of Mexico, hauling in a limit of striped bass in the Chesapeake, puny black-tipped sharks off Key West and a 40-pound amberjack off Louisiana. Here is our look at the state of fishing in selected areas:

Chesapeake Bay

THE OLD HAUL: Fishing boats hit the bay for bluefish and feisty striped bass.

THE NEW CATCH: More than half of the bass may have a "wasting disease."

The bass are back -- and many of them are sick. After overfishing in the 1970s, Maryland and Virginia have spent much of the past two decades coaxing back stocks of striped bass, a hard-fighting species that ranges along the Atlantic coast and returns to the Chesapeake to spawn. Now there's a new problem: Maryland's Department of Natural Resources says many of the bay's resurgent bass population have mycobacteriosis, an infectious disease some scientists say could be caused by malnutrition. The department estimates 60 percent of the bass are infected, more than double the rate since the department started tracking it in 1998. The agency says the bass are edible, but recommends avoiding those with visible sores.

Fishermen have various theories for the sickly bass. Some blame warmer water (it fosters algae blooms, the first step in a process that chokes oxygen from the water, restricting habitat) and overhandling (undersized fish that get caught again and again may become unhealthy).

Others say the bass's food supply is being overharvested. Menhaden -- the small fish better known as pogies -- are used by processors that grind them down for farm feed and Omega-3 fatty acid supplements. The menhaden population along the Atlantic has been below five billion fish since 2000, according to the National Marine Fisheries Service, compared with historical populations between 10 billion and 15 billion in previous decades. Fishermen and conservationists are currently lobbying the governor of Virginia, where the harvest is centered, for a cap on the menhaden catch.

One of the big menhaden processors, Omega Protein Corp., two years ago opened a $16 million fish-oil refinery in Reedville, Va., on the Chesapeake. The Menhaden Resource Council, a group funded mostly by Omega Protein, says the menhaden population isn't overfished.

On our own expedition, we didn't see skinny bass. On a late May trip out of Chesapeake Beach, Md., the eight anglers who set out at 6 a.m. on the charter boat Reel Attitude each caught their limit of fat and feisty bass -- two apiece -- in about 90 minutes, with boats nearby also filling up before 8 a.m. "I haven't seen a fish that looks sick or skinny," said our boat's mate, James Carrello. "Nothing wrong with these."

Miami

THE OLD HAUL: Days spent trying to catch sailfish or mahi mahi

THE NEW CATCH: A swordfish fight in the middle of the night

In Florida, recreational fishing is nearly as big a business as grapefruit and oranges. From the Panhandle to the Keys, in fresh and salt water, fishermen go after speckled trout and snook, bonefish and tarpon, cobia, red snapper and sailfish. The state has the largest recreational fishing industry in the U.S., which the American Sportfishing Association estimates at $7 billion.

Recently the focus has turned toward Atlantic swordfish. The storied fighting fish rose to popularity in the 1970s, but by the 1980s, its popularity at restaurants and the growth in the commercial fishing industry had caused numbers to dwindle. But in part thanks to new international regulations and quotas, swordfish stocks had rebounded markedly since 1999, according to NOAA.

The result has been a boom for charter boats moored just 15 minutes away from the area's swanky South Beach. Dean Panos, owner of Double D Charters in Miami, says evening swordfish trips now make up a quarter of his business, compared with nothing five years ago.

Paul Mucciolo has been fishing off the coast of Miami for decades, and he's gone after a number of billfish including marlin, the fish from Ernest Hemingway's "The Old Man and the Sea." But he'd never caught a swordfish. "When I started taking the boat out, in my late teens, you didn't consider going swordfishing," says the physician from Daytona Beach, Fla. "It was rare to even catch a small one."

Recently, though, he spent two nights reeling in five fish, including a 337-pounder that at one point attacked the charter boat with its bill. (The Florida record is a 612-pounder, caught in 1978.) "It was the hardest fighting and most aggressive thing I've ever fought," Dr. Mucciolo says.

Venice, La.

THE OLD HAUL: Heading to salt-water lakes, bays and bayous for redfish and speckled trout

THE NEW CATCH: Trying to find a working boat

Louisiana has one of the world's most diverse recreational fishing industries. In the span of a day, one can catch black bass in freshwater lakes and bayous, redfish (popularized by chef Paul Prudhomme's recipe for blackened redfish) in the brackish estuary, then head a few miles into the Gulf where oil rigs form de-facto reefs that attract snapper, grouper, cobia and king mackerel. But these days the problem isn't fish -- it's getting out on the water.

The state's estimated $1 billion sports fishing business is one of the many industries struggling to rebuild after Hurricane Katrina. According to the Louisiana Department of Wildlife and Fisheries, about 60 percent of the 156 recreational marinas in the state are "fully operational" -- which means boats can get in and out, but the sites may still lack services like lodging and restaurants. Meanwhile, roughly 300 charter boats are operating now, according to the Louisiana Charter Boat Association -- down from 600 before the storm.

But the fishing is great. "The same saltwater surge that destroyed homes and businesses brought in tons of fish," says Charlie Smith, executive director of the Louisiana Charter Boat Association. Adds Harry Blanchet, a fishery biologist with the Louisiana Department of Wildlife and Fisheries: "The fish, in many ways, took it better than the people."

On our drive from New Orleans to Venice, La., we passed homes flattened by Katrina and ruined boats deposited far from the water. At the Venice Marina, the launch point for our fishing trip, the docks were filled with dredged-up boats and stacks of lumber. The port building was being rebuilt and a new welcome sign -- "Fishing Capital of the World" -- was sitting to the side, unmounted.

Our fishing day started at about 5:30 a.m. when our captain, Devlin Roussel, pulled out of the marina and steered his 26-foot boat through duck-filled marshes to the Gulf of Mexico. After catching a snapper and releasing a redfish, our captain pulled next to an oil rig where larger, feistier amberjack were sheltering. There, 12-year-old Cameron Miller, with his father's arms clasped around him to keep him onboard, reeled in an amberjack weighing in at about 40 pounds, which he described as the biggest fish he'd ever caught. After the fight, Mr. Roussel doused his fingers in the fish's blood and wiped them across the young Mr. Miller's face -- a form of fishing initiation. Said Mr. Roussel, maneuvering back toward the oil rig for more: "Life is good."

Ilwaco, Wash.

THE OLD HAUL: Ocean fishing for salmon all summer long

THE NEW CATCH: Fewer days of salmon -- with more fishing for halibut and albacore

Ilwaco, Wash., on the mouth of the Columbia River, has seen the waning salmon fishery firsthand. In the 1970s, more than 150 charter boats in the port ran daily trips from May to September, with sports fishermen's three-a-day limits contributing to millions of fish harvested annually. This year's season starts in July, and Ilwaco's few dozen charters will operate Sunday through Thursday. Off that part of the Washington coast, fishermen will be allowed to land about 8,100 kings (or chinooks, the biggest salmon, which can reach 40 or more pounds) or 36,600 smaller cohos (or silver salmon), whichever comes first.

The clampdown comes as salmon become the focus of an increasingly divisive battle among fishermen, regulators, environmentalists, power companies and developers. Salmon traverse hundreds of miles through freshwater rivers to the ocean and then back to their native rivers, along the way touching the lives of virtually everyone in the state. Over the decades, native salmon runs have dwindled as dams, logging and development interfered with their ability to spawn in streams up the Columbia. Hatcheries took up the slack, rearing tiny salmon that swam downstream and mingled with native fish in the ocean from California to Alaska. For decades, commercial and sport fishermen have harvested one type alongside the other.

But recently, in a move to save wild salmon runs, regulators have asked sport fishermen to keep only hatchery fish. How to tell the difference between those and the native ones? Hatchery workers remove a small rear fin before releasing the fish, and sports fishermen can keep only fish missing this adipose fin.

Fishermen say the solution is far from perfect. Dan Schenk, a third-generation charter-boat captain in Ilwaco, says wild and hatchery fish have intermingled for so many years that there's little difference between the two. Regulation, he says, is aimed at cutting down on the harvest, instead of addressing the issues that impact the size of the runs -- how many fish make it through dams or whether development is allowed on streams. And, he says, there are plenty of fish in the sea. He figures that for every fish he caught with a missing adipose fin last year, he'd release two or three others -- and he had a hard time explaining to his customers that they're doing it because fish are scarce. "We're all frustrated," he says. "But it's fantastic for our customers. I tell them, 'You're going to catch a lot of fish. But I can't promise you'll be coming home with them.'"

Meanwhile, Mr. Schenk says, he's been taking his boat, the Nauti-Lady, out for halibut and albacore more often, and he's seen fish he hadn't seen in the past -- including a marlin and Humboldt squid. Says Mr. Schenk, who is also a middle-school science teacher: "I'm seeing things now I haven't seen in nearly 40 years of doing this."

Advantage: Fishermen

Another big change in fishing: Thanks to technology updates, anglers have even more of an edge. Here's a sampling of products:

GEAR/WHERE TO FIND IT: Raymarine E120 w/fish finder $5,198.98 WestMarine.com
THE EDGE: Digital fish finder replaces analog model, shows fish depth on higher-resolution screen
COMMENTS: This navigation system, released last year, uses sonar at 220 pings per second (compared with 60 pings for some earlier models). The fish finder shows the depth and relative size of the fish (an experienced captain can sometimes tell the species by the mark on the screen).

GEAR/WHERE TO FIND IT: Shimano Calcutta TE DC Casting Reel $499.99, Basspro.com
THE EDGE: Cast faster and farther -- with less backlash -- to get at more fish
COMMENTS: This reel generates spool speeds up to 30,000 revolutions per minute, or about double the company's standard reels. That makes for casts as much as 20 percent longer. A computer chip inside the reel regulates spool speed to keep the line on the reel and cuts down on snarls. The spool's rotational energy powers the circuit board.

GEAR/WHERE TO FIND IT: Garmin GPSMAP 76CSx $474.89 Amazon.com
THE EDGE: GPS unit marks locations so you can get back to where they're biting.
COMMENTS: Handheld GPS device runs the company's "BlueChart" system, which can be downloaded for about $150 extra and provides maps, tide data and contours of underwater surfaces.The GPS unit floats -- just in case.

GEAR/WHERE TO FIND IT: REC Recoil Nickel Titanium Guide up to $25, AnglersWorkshop.com
THE EDGE: Lighter-weight material promises longer casting, and doesn't rust.
COMMENTS: Rod guides are made from a metal alloy and are available on some G. Loomis and Cabela's rods. Manufacturer REC Components says lighter weight makes for longer, faster casts -- and says they won't break if you slam them in the car trunk.

GEAR/WHERE TO FIND IT: Stimulate Attractant with Ultrabite (3-ounce aerosol spray) $9.95, Jannsnetcraft.com
THE EDGE: Supposed to make fish come to your bait
COMMENTS: Newest incarnation of Ultrabite Stimulate, in the U.S. for about a year, is said to work by triggering a feeding mechanism in fish's brain. Available for bass, trout, salmon, catfish and a generic saltwater version for fish like tuna and mahi mahi. Warning: It smells like fish.

GEAR/WHERE TO FIND IT: Cabela's AquaGlow Hoochie Koochie Swim Shad/$2.99 (for 10), Cabelas.com
THE EDGE: Bait glows underwater, and curious fish have a look-see.
COMMENTS: This bait, shaped like a small shad, comes stuffed with salt and garlic to attract fish and cover up "fish-spooking odors" such as the smell of a human hand.