NARRAGANSETT, R.I. — March 11, 2013 — Twenty one years after the first suction survey sampling in Rhode Island’s Narragansett Bay of post-larval lobster settlers, known as young-of- year (YOY), Rick Wahle returned in 2011 and 2012 to resample the bay’s Southern New England nursery grounds.
Despite including additional sites recommended by industry, the results were disappointing.
“It was rather disturbing. Itwas especially shocking that, in 2011, juveniles had fallen below detectable levels at the six sites that are sampled annually,” said Wahle, a marine biologist at the University of Maine’s Darling Marine Center.
Suction sampling measures the number of YOY and juveniles per square meter at each site, which, when combined with data collected at other sites from Canada to Rhode Island, is used to create the settlement index (see CFN June 2012). YOY and settlers measure 5 millimeters (mm) to 13 mm carapace length. Juveniles measure up to 60 mm carapace length.
In 2011 and 2012, the researchers found less than one settler per 10 square meters. That compared to 1990, the first year of the index, when there were closer to 10 or more settlers in those same 10 square meters, according to Wahle.
To get the same number of YOY now as 22 years ago, Wahle and his team would have to put in 10 times the effort and cover 10 times the area to find them, he said.
Wahle noted that there was a slight uptick in 2012 compared to 2011, but the increase was not enough to change estimates of abundance for the Southern New England lobster population.
“This doesn’t mean that the YOY are completely gone,” Wahle said. “It is more like having a signal that is too faint for radar to pick up.”
Still, some lobstermen firmly believe that the young-of-year are settling out in the region, but at different locations and different times.
Dellinger said commercial fishermen are pulling up settlers and juveniles in their gear at odd times.
“Fishermen are finding them in places where there’s not a lot of information,” he said.
Dellinger said there are concerns that the data cover too short a time span to determine that Southern New England lobsters are in a state of permanent decline. A number of environmental factors can change from year to year and affect settler abundance, he suggested.
Among them are predation by black sea bass. Another is the timing of state trawl surveys, particularly if the weather gets too cold or too hot. In both cases, settlers and juveniles may go into the mud for protection, he said.
This story orignally appeared in Commercial Fisheries News. It is reprinted with permission. Read a PDF of the full article here.