Lobsters from Long Island Sound, a fishery in dramatic decline, will be tested for overall health and the presence of pesticides in a new study announced Tuesday by the state Department of Energy and Environmental Protection.

This summer, DEEP staff will begin collecting lobsters for the study from throughout the Sound from lobstermen and local buyers, said Dave Simpson, DEEP's director of marine fisheries. The samples will be sent to labs at the University of Connecticut for analysis.

The purpose of the study, DEEP Commissioner Daniel Esty said, is "to obtain a better understanding of why this species - and an industry it has historically supported - is now in danger of collapse in Long Island Sound."

Funding for the study will come from $200,000 allocated by the state legislature for lobster restoration, Simpson said. The study will examine the impact of warming water temperatures and chemical contaminants on the lobster population, which has been declining in the Sound since 1998 to record low levels, and the lobster fishery along with it, DEEP said in a news release.

The decline has been most dramatic in the central and western Sound, where landings have fallen 99 percent since 1998. Landings from the Sound overall have declined from 3.7 million pounds in 1998 to 142,000 pounds in 2011.

Last fall, DEEP staff conducted tests of nine dead and weak lobsters and one healthy one in response to reports from fishermen about seeing many sick and dead lobsters in the western Sound, DEEP said. The 10 lobsters came from an area near Norwalk.

Initial tests of whether the stress of warm water temperatures or bacterial or parasitic infections were responsible for the dead and ill lobsters were inconclusive, DEEP said. Tissue samples from the lobsters were then tested for three pesticides used to control mosquitoes: malathion, methoprene and resmethrin.

The tests showed some of the samples were exposed to resmethrin and one was exposed to methoprene. No malathion was found.

"This was a very surprising result, finding it at all in the lobsters," Simpson said. "We're trying to find out what the likely sources are, and how it found its way into Long Island Sound."

Resmethrin and malathion are used to control mosquitoes through fogging, but small amounts were used in Connecticut in 2011, Simpson said. Both pesticides are also used for general applications such as tick control on land. They decay rapidly and are not expected to accumulate in the environment, DEEP said.

Because of the small number of lobsters tested, researchers could not determine whether the pesticides were responsible for the mortalities. The new study is intended to answer that question, as well as to develop criteria for an overall lobster health assessment based on bloodwork and other indicators, Simpson said.

The study will also consider whether pesticides accumulate in lobsters' internal organs or are flushed out of their systems, and how much of each pesticide is harmful, he added.

"Hopefully, we will get a much better understanding on what these compounds do to lobsters," Simpson said.

Esty said the study will help provide a complete explanation for the decline of the lobster population. The fundamental cause had been attributed to stress from warming fall water temperatures in the Sound, but there may be other contributing factors.

"There has not been a thorough study conducted with the type of sophisticated laboratory tools now available to us," Esty said. "We look forward to launching this study and sharing the results with everyone who has an interest in this critical issue, so we can consider any steps that might reasonably help rejuvenate our lobster population."

j.benson@theday.com