The striped bass is fun to catch and good to eat. It’s also enigmatic, historically prone to wild fluctuations in numbers and to inexplicable disappearances from area waters. And with the annual Island fishing derby opening Sunday, the old question is being asked again: where are all the fish?

Cooper Gilkes 3rd, an Island fisherman for more than 50 years and the owner of Coop’s Bait and Tackle in Edgartown, is concerned, for catch numbers seem to be in sharp decline.

“I believe the derby is headed on a downward spiral this year, from all the evidence,” he said this week. “I think the bass is getting hit again. I think we’re heading for problems.”

His gloomy assessment is based on anecdotal evidence, coming from his personal experience and the many bass fishermen he knows and deals with through his business.

Four or five years ago, he said, the spring catch-and-release tournament would see 1,200 fish caught in a night.

“This year it was down to 200-some, a considerable drop,” Mr. Gilkes said, adding: “I think we’re over-fishing them, all the way from down south to up north. If it is the case, then I’m very concerned.

“The fishery managers are saying everything’s okay. Now, I’m only a fisherman, but I want to know why it is that when they re-opened the fishery, we were catching 80 a night on fly rods. Lobsterville was absolutely phenomenal. Now I’m lucky if I catch six.

“Maybe it’s just a pulse, but if it is, we’ve got to get on top of it, or things can go downhill very quickly.”

His remarks speak to the history of the fishery.

When Europeans first came to these parts, stripers apparently existed in enormous numbers as did cod.

Captain John Smith wrote in 1614: “I myself at the turning of the tyde have seen such multitudes pass out of a pounce [fish trap] that it seemed to me that one might go over their backs dry-shod.”

Striped bass quickly became one of the most important commercial fisheries on East Coast. Indeed, along with cod, they were one of the first stocks which were managed. In 1639, the Massachusetts Bay colony passed a law that neither bass nor cod could be used as fertilizer.

By 1776, concerns about stocks of the fish saw all sales prohibited in the winter months.

After the Civil War, said another veteran Island striped bass fisherman, Kib Bramhall, bass fishing became so fashionable that famous fishing clubs were set up at various points along the coast, among them, Squibnocket, Noman’s Land, Cuttyhunk and Pasque Island, and fishing piers built out over the water.

They were elite places, attended by the wealthy, with fine dining facilities.

“According to rumor,” Mr. Bramhall said, “buy and sell orders were sent from Squibnocket to Wall Street by carrier pigeon.”

But then the fish disappeared, and with them most of the clubs.

The Division of Marine Fisheries Web site notes that striped bass have a long history of fluctuating abundance and scarcity. None at all were caught north of Boston for 30 years after 1897, for example. But between 1934 to 1940, they were present again in vast numbers. And so it has continued to modern time. In 1970, 6.6 million pounds of fish were caught; in 1979, the catch had fallen to 1.7 million.

The rapid deterioration of the fishery in the 1970s and ’80s led to both state and federal legislation and since 1981, the striped bass fishery has been controlled by the Atlantic States Marine Fisheries Commission (ASMFC) through a management plan for states along the eastern seaboard. Fishing activity was all but ended for several years in the late 1980s, so stocks might recover.

They were deemed to have fully recovered by 1995. Indeed, the striped bass serves as the poster child for the success of fish stock management.

Since 1982, according to commission figures, the fish population has increased from some seven million fish to an average of 58 million over the past five years.

“Recreational harvest has grown steadily since the reopening of many state fisheries in 1990, approaching 30 million pounds in recent years,” says the commission Web site.

“Under the most recent management program, commercial harvest has averaged nearly seven million pounds annually.”

Still, much mystery surrounds the population fluctuations of striped bass. The collapse in the 1970s and 1980s was apparently due in large part to over-fishing, but there were many other possible causes too, including pollution (particularly in the case of the fish caught here, in Chesapeake Bay and the Hudson River), disease, declines in food stock and the damming of rivers. Stripers are anadromous fish — that is, they move from salt to fresh water to breed.

Apart from catch limits, other measures which probably helped were pollution control, fish farming and fishways to allow them to bypass dams on breeding rivers.

Nonetheless, as Paul Diodati, director of the Massachusetts Division of Marine Fisheries, acknowledges there are wide variations in the breeding success of the fish from year to year.

“There are large year class effects,” he said. “That is, there are years where the numbers born are significantly higher than in the year before or after. It seems to happen every three or four years.”

Why? No one really knows, although unusually heavy rains at hatching time can cause flushing of the rivers which washes the eggs out. Acid rain, Mr. Diodati said, also is suspected to have a negative effect on hatchings.

“And the Chesapeake in particular continues to have troubles with agricultural runoff, carrying chemicals into the water,” he said.

Whatever the causes of these fluctuations in hatching numbers, the result is that while the total fish numbers have remained fairly constant in recent years, the age range of the fish which comprise that stock can fluctuate a lot.

And this, Mr. Diodati suggested, might be part of the reason fishermen — particularly recreational fishermen — see big differences in their catches.

“Some years, because of these class effects, fish reach our shores 14-16 inches long and two to three years old. In those years they seem very abundant because they are caught close to shore. Then as those fish grow they tend to move further from shore,” he said.

Also, he suggests the apparent decline of striped bass might be attributable to an actual decline in other fish on which they feed, in particular herring.

“They go where there is food available. For the past three years there has been a moratorium on river herring because their stocks are so low. Without river herring, there is nothing to attract them so close to shore,” Mr. Diodati said.

This year, he noted, there appear to be unusually large numbers of striped bass on Stellwagen Bank, north of Cape Cod, where there also were large numbers of sand eels.

“So populations move around, but I can assure you overall the stock continues to look good,” he said.

The evidence is in the catch statewide. The commercial season closed this week, with just over one million pounds of fish caught, about 75,000 pounds below the state quota, but still very healthy.

There remains, of course, the question of how that stock is apportioned — who gets to catch how many and by what means.

But while some level of disagreement is inevitable, Mr. Diodati said it is not a source of significant tension. Partly, he suggests, this is because in Massachusetts recreational and commercial fishermen are all limited to the use of rod and reel.

“It’s not unusual for an avid recreational fisherman to become a commercial fisherman or a charter operator,” he said. “So they are culturally the same people.”

This is less true in other states, which allow netting — beach, seine, fish traps, trawling gill netting. The greater the technological difference between amateur and commercial, the greater the resentment.

“Here, you can’t possess striped bass if your boat is rigged with any type of netting,” he said.

Mr. Bramhall likewise thinks the long debate over how to manage the striped bass fishery is not particularly hot right now.

“When the fishing isn’t very good in a certain area, fishermen in that area tend to think the sky is falling. And it has been the case in this area this year, because the fishing has not been very good,” he said, adding:

“The managers say stocks are in good shape and sustainable at present levels of harvesting, and I believe them. I hear the fishing has been very good in New Jersey and New York; it just seems a lot decided not to come as far up the coast as usual, or went offshore, probably because they found food out there more to their liking.”

Mr. Bramhall is critical of some of the more aggressive recreational fishermen, who would like to catch more.

“There are some Web sites always bitching and moaning about commercial fishermen, like Stripers Forever, which would have no commercial fishery whatsoever,” he said.

For his part, he thinks the current bag limit of two fish per person per day for recreational fishermen is too generous.

“I think that’s one more than we need,” he said.

And really, how big would your family have to be, to eat more than one 28-inch long fish per day, no matter how delicious?