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Commercial Fisheries News
Volume 36 Number 10
June 2009
2008 lobster settlement index down from ’07
WEST BOOTHBAY HARBOR, ME The latest installment of the lobster settlement index indicates that 2008 wasn’t the best year for very young lobsters in nearly all areas of New England and Atlantic Canada.
“It is interesting that the decline was pretty uniform throughout the region,” said Rick Wahle, senior research scientist at the Bigelow Laboratory for Ocean Sciences, who compiled the annual settlement index report. “We haven’t seen that very often.”
From Lobster Bay south of Yarmouth, Nova Scotia to Rhode Island, 2008 was a “poor” year relative to 2007. The number of young-of-the-year lobsters collected at sampling stations dropped by as much as 50% in some areas, according to the report, which was released early in May.
The one exception was Beaver Harbour, New Brunswick, just northeast of Eastport, where settlement, which is routinely huge in comparison to other areas, approached a five-year record high.
And, the survey identified the Gulf of Maine and the southwest Gulf of St. Lawrence as probable “hot spots” for young-of-year and older juvenile lobster settlement. Settlement occurs when larval lobsters move into the next stage of their lives, dropping out of the water column and seeking protection among rocks on the sea floor.
But, once again, there was no encouraging news for the beleaguered Southern New England region. Rhode Island reported the lowest settlement numbers in its 19-year history, and the already low densities in Buzzards Bay, MA fell “below detectable levels” for the first time in the 15 years that samples have been collected there.
While the results of any single year aren’t that telling, over time, the lobster settlement index can identify trends that hint at how abundant legal-size lobsters may be five-to-nine years in the future.
“In the late 1980s and early ’90s in Midcoast Maine, we saw a period of high settlement. From 1995 to 2000, it was poor. In 2001, it popped back up and stayed relatively high,” Wahle observed, adding that it’s hard to say at this point if 2008’s “poor” settlement is “an anomaly or the start of a trend.”
Wahle pointed out that there was an increase in settlement east of Penobscot Bay in Maine from the early 2000s onward, which he described as a gradual “ramping up” of juvenile densities in the Mount Desert/Jonesport/Cutler area.
“Things really changed in eastern Maine, and landings have reflected that,” he said.
Broader scope
The settlement index is based on samples of young-of-year and older juvenile lobsters collected at dozens of stations from Atlantic Canada and New England by a network of researchers who make up the American Lobster Settlement Collaborative.
All sampling sites are on the kind of prime cobble-boulder habitat lobsters use as nursery areas.
Participation in the settlement survey has grown over the last two decades, and Wahle was particularly pleased by the scope of the 2008 effort.
The state of New Hampshire, which has had only limited involvement in the past, resumed sampling after a 10-year break.
Suction method
The state fisheries agencies of Maine, New Hampshire, Massachusetts, and Rhode Island and, to a more limited extent, their counterparts in the provinces of New Brunswick and Nova Scotia, have adopted the suction sampling method. All now maintain their own monitoring programs, which helps enhance the credibility of the index.
These researchers primarily dive on specific sites each year at the end of the summer settlement season and use a suction sampler to collect the tiny lobsters that have drifted down to the sea floor, Wahle explained.
“A suction sampler is basically an underwater vacuum cleaner consisting of a 6’ PVC tube supplied with air for suction with a mesh bag at the end to retain the sample,” he said. “At each site, at least 12 samples, each from a half-square-meter of sea bed, are collected and then examined back at the lab.”
Passive collectors
One of the most exciting developments in the settlement index program, however, is the growing interest in participation by researchers in Canada.
“The real geographic expansion has been in the deployment of (passive) collectors in all the provinces of Atlantic Canada, including what is likely to be a one-time sampling effort in Newfoundland,” the report said. “This surpasses last year’s effort, which was already the largest (comprehensive) view of lobster settlement ever conducted.”
What appears to really have drawn in Canadian researchers is the demonstrated effectiveness of passive collectors, which Wahle, Boothbay harbor lobsterman Matt Parkhurst, and Maine Department of Marine Resources (DMR) lobster biologist Carl Wilson developed and tested over several years starting in 2005 with cooperative research funding from the Northeast Consortium.
The collectors basically are trap-wire trays with a footprint the size of a lobster trap but flatter. Each is filled with rocks that mimic juvenile lobster nursery habitat. The trays are lowered to the bottom and then hauled to allow researchers to count the young-of-year lobsters that have settled among the stones.
“Unlike suction sampling, collectors require the up-front effort of deployment,” Whale said. “Their great advantage is that they can be set in places that are too deep or too dangerous for divers.”
Depth patterns
In 2008, between the final year of the Northeast Consortium-funded project and the surge in Canadian participation, researchers set 1,127 passive collectors from Newfoundland to Rhode Island.
In New England during 2007 and 2008, the collectors were used to evaluate depth patterns in three regions of contrasting oceanography, according to the settlement index report.
“Depth-wise patterns of settlement have been consistent over the two years, mirroring the degree of water column thermal stratification,” the report said.
Researchers found that in Southern New England and Midcoast Maine during the summer, when water temperatures are higher closer to the surface than in deeper water, “most settlement occurred in the shallowest depths.”
In eastern Maine, where heavy tidal action keeps the water stirred up and prevents the development of layers of warmer and colder water, “settlement spread more evenly over all depths down to more than 80 meters,” the report said.
As the settlement index project enters its 20th year, participating researchers from New England and Canada are heading to Burnt Island in Boothbay harbor for a June 19-21 workshop hosted by the Bigelow Lab and the Maine DMR.
“We want to take a retrospective and critical look at our accomplishments and discuss the future of the collaboration,” said Wahle.
The workshop will address how to maintain sampling and data management standards across groups and will prioritize research questions. Researchers also will discuss sampling protocols and how to calibrate the results from the diver suction and passive collector sampling methods so that they both can contribute to the lobster settlement index in the future.
Lorelei Stevens
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