Fisherman Richard Sawyer Jr. came back disappointed yet again after carrying armloads of empty lobster traps onto shore in Groton, Conn.

Sawyer is just one of hundreds of fishermen in the Connecticut and New York area calling it quits after another underwhelming lobster season, which is forcing a nearly three-month closure of the Long Island Sound fishery.

"What we catch now in a week I used to catch in a day," Sawyer, 71, who's been a lobsterman since the 1960s, told The Day. "The last really big year was 1999, and since 2005 it's really been going down."

American lobster (Homarus americanus) is a bottom-dwelling crustacean that is found all over North American waters, according to the Atlantic State Marine Fisheries Commission. In inshore waters of the United States, these lobsters are most abundant from Maine through New Jersey, while offshore they extend as far down as North Carolina.

Lobster landings in Long Island Sound in particular are of growing concern, as they have declined from 3.7 million pounds in 1998 to just 142,000 pounds in 2011, according to the state Department of Energy and Environmental Protection (DEEP). The central and western Sound - where landings have fallen by 99 percent since 1998 - saw the greatest evidence of decline, the DEEP said.

State officials estimate that 11 million lobsters or 90 percent of the entire population died in the Sound last fall, ABC News reported. This summer, the main money-making season for most lobstermen, the crustaceans are again a no-show.

These losses are devastating considering that the Sound usually generates about $45 million in annual sales and is the nation's third-largest lobster source, behind Maine and Massachusetts.

"It's way worse," Jeff Carbone, a lobster distributor based in Huntington, N.Y., who says he's taking in 80 percent fewer lobsters than last summer, told ABC News. "I had 25 lobstermen supplying me, now I've got eight. These guys just don't want to take any chances."

The Problem: Pesticides or Parasites?

Amid continuing evidence and concern of the declining lobster population in the Long Island Sound, the DEEP announced plans in 2012 to launch a study to get to the bottom of it.

Among the factors the DEEP is taking under consideration is the potential impact of pesticides, which many of Connecticut's lobsterman have blamed for the crustacean's diminishing numbers, said DEEP Commissioner Daniel C. Esty.

"The study ... will fill in major gaps in our understanding of the decline of the lobster population in Long Island Sound," Esty said in a statement. "There has not been a thorough study conducted with the type of sophisticated laboratory tools now available to us."

Testing will seek to learn more about the presence of pesticides in lobster tissue and the possible impact it might have.

In a separate study conducted last September, Robert Bayer, director of the Lobster Institute at the University of Maine, examined sickly lobsters from the Sound. Though he did not find traces of any of the bacteria or viruses he was looking for, Bayer did find hints of the pesticide malathion, which was sprayed in New York last summer in an effort to keep mosquitoes carrying the West Nile virus at bay. However, those results proved inconclusive.

While pesticides seem like one probable cause for the recent die-off, another finding so far is that of a protozoan parasite.

University of Connecticut veterinary pathologist Richard French conducted research last fall and found the same parasite in all 150-200 lobsters he sampled from the Sound.

"It would be unusual to see such a massive mortality associated with a single parasite," French told ABC News. "But it's not out of the question."

So it is pesticides or parasites that's the problem?

Well, Bayer believes that it is a combination of the two. According to the researcher, pesticides may be a cause of the lobster die-off and the parasite might be a secondary problem for already stressed lobsters.

"We didn't find any malathion in the lobsters we had, but that doesn't mean it wasn't there," Bayer said.

Bayer also points out that New York and Connecticut have used at least two other kinds of pesticides besides malathion. The states have sprayed low concentrations of resmethrin and sumethrin, types of synthetic pesticides similar to a natural pesticide produced by chrysanthemum flowers that kill insects by attacking their nervous systems.

Simply a Turn of the Tide?

Despite these findings, some fishermen believe their bad luck in recent years is simply do to a turn of the tide. In 2012, Stonington lobsterman Richie Maderia, who says he catches about 20,000 pounds of lobster each year, actually had a fairly good year.

"It's really important that we're having a good year, because it takes all their science out the window," he told the New Haven Register during a time when DEEP was considering imposing a two- to three-month closed season on lobstering.

Although Maderia thinks the phenonmenon is all part of a cycle, the DEEP's director of marine fisheries, Dave Simpson, believes otherwise.

It "is part of a much larger drop in abundance that we have seen throughout southern New England," he told the Resigster.

"The decline in the western end of the Sound - let's say west of the Connecticut River and especially west of the Housatonic River - has been especially dramatic," Simpson said.

According to ABC News, scientists point out that there are several other environmental factors that could be weakening the Sound's lobsters. For example, dredging materials, which are routinely dumped near the waters of Long Island Sound, carry oils and fertilizers. These can feed bacteria, which then consume oxygen and release toxic by-products that lobsters are vulnerable to.

Climate change may also be a factor. Things are heating up for Maine's lobster fisheries, too, Nature World News recently reported. Lobsters in the region are seeking cooler habitat in the face of warming waters in the Gulf of Maine.

The brief three-month enforced break for the Long Island Sound industry may be able to give the lobsters some reprieve, but when it ends, what will the lobstermen do?

"I don't know whether we'll fish again next year," Sawyer told The Day.