Longfin inshore squid ( loligo pealeii ) may not be on the menu, but it is an important local seafood that has grown scarce.

Recreational and commercial fishermen are perplexed, wondering how a once profitable and abundant bait seems to have disappeared. Tackle shop owners can’t find enough of it. The draggers working in Nantucket Sound have had slim pickings.

Down at Memorial Wharf, on a good night a small crew of squid fishermen have been trying all spring to fill their five-gallons buckets by jigging. But this spring, if they catch anything, they see themselves as lucky.

The migration of squid, used primarily as bait, is as much a part of the arrival of spring as the arrival of herring, or the arrival of striped bass.

Steve Purcell, owner of Larry’s Tackle Shop, is used to spending hours each spring filling plastic bags with freshly caught squid from Nantucket Sound. He usually freezes it in small bags and for the rest of the summer, he sells it to youngsters wishing to catch a scup or a sea robin with a small baited hook.

Everett (Porky) Francis, of Porky’s Bait and Tackle Shop on Dock street in Edgartown has memories from the 1970s of avid squid fishermen jigging at Memorial Dock every spring night. “I can remember in the 1970s, we would go down and have a ball. You could fill a five-gallon bucket in an hour, maybe quicker than that,” he said. In recent years it has taken a lot more time.

Now, Mr. Francis gets his frozen one-pound packets of squid from another source: “I get it from California. Some of it comes from Chile.”

Fishermen care about squid because the fish they love feed on squid. Striped bass, bluefish and flounders come to Martha’s Vineyard waters for a meal. The worry is that if the squid don’t show up, their predators won’t.

Squid are not considered overfished by state and federal fisheries managers, but they are watched.

Dan McKiernan, a deputy director of the state Division of Marine Fisheries, said the squid’s life span is partly to blame. “The animals live less than a year,” Mr. McKiernan said. “So it is hard to build up the biomass. The spawning success fluctuates from year to year.”

Squid swim into Nantucket Sound each spring to lay their egg masses. They spend most of their lives offshore, south of the Vineyard, Nantucket and out along Georges Bank.

It is nearly all about water temperature, according to Lisa Hendrickson, a research biologist with the National Marine Fisheries’ Northeast Science Center. She is an authority on squid.

“Everything is behind,” she said. Squid are driven by water temperature, and the water temperature in Nantucket Sound is behind schedule. “There is a correlation between water temperature and air temperature,” she said. Everyone has remarked how slow and cool this spring has been on the land. This has had an impact on the spawning of squid.

“It doesn’t mean this is a bad year. Every year the fishermen expect the squid to be there [in Nantucket Sound]. But they are really migratory. They don’t always go to the same place,” Ms. Hendrickson said.

There are studies that suggest that when the water temperature is cold in Nantucket Sound, the squid don’t show up there. Looking back to the months of April and May, Ms. Hendrickson said the region was getting a heavy dose of northeast breeze, overcast skies and a cool air flow.

Squid landings by fishing boats have declined every year for several years and for several reasons; Ms. Hendrickson is quick to point out that it is not due to a declining resource. The squid just aren’t where the fishermen expect.

It can be a matter of economics. Fishermen don’t make much money per pound on squid, compared to finfish, so when they motor around looking for them, the cost of fuel consumption can hurt a lot.

“When the fishermen can’t find them, they stop searching. They don’t want to spend on the fuel to look for them,” Ms. Hendrickson said. So stocks may be out there, just not being caught.

Scientists know the squid are sensitive to water temperature changes when it comes to where they reside, where they spawn. Changing water temperature in this region has caused a change in the behavior of other fish. Fisheries experts suspect that the decline of lobster south of Cape Cod down to Virginia is due to a stressed animal having a hard time with warmer water.

“In our spring and fall surveys, we’ve found tropical species off Narragansett Bay. Patterns are different now,” Ms. Hendrickson said, adding: “Squid is a data poor stock. We need to know more and we are trying to do some research.”

Owen Nichols, director of the marine fisheries research program with the Provincetown Coastal Studies, is finishing up his dissertation on the changes in squid distribution, for the University of Massachusetts. While he is just short of finalizing his years of work, he said that air temperature and subsequently water temperature play a part. He confirmed that the fishermen he talks to are reporting the same scarcity experienced here.

While it remains unclear why the squid are in decline on a large scale in this region, weather is playing a part in the more localized decline in Nantucket Sound.

“We have seen a combination of northerly winds and colder temperatures and it does often reduce the numbers,” he said.

There is also evidence that gray seals are having a larger part in influencing the data, Mr. Nichols said. It isn’t that the seals are eating huge amounts of squid, it is that their presence near fish weirs and fishing gear may be keeping the squid away.

Stephen F. Norberg fishes a 55-foot dragger out of Menemsha called Corrina. In April he worked as crew aboard the Menemsha dragger Unicorn, side by side with Capt. Gregory Mayhew, looking for squid in Nantucket Sound. It wasn’t a good trip, he said.

But Mr. Norberg plans to resume fishing for squid later this month. “I am waiting for the water to warm up,” he said. In late June and early July, he hopes to find squid on the backside of Nantucket and Martha’s Vineyard.