The northern shrimp fishery’s top scientist, Department of Marine Resources (DMR) biologist Maggie Hunter, works in Lincoln County, in an office overlooking Boothbay Harbor.
The Atlantic States Marine Fisheries Commission (ASMFC) Northern Shrimp Section regulates the fishery. Hunter serves as the chairwoman of the Section’s Technical Committee, a position she has held since 2002.
A graduate of the University of Maine at Orono, Hunter performs multiple functions at the DMR facility on scenic McKown Point. She studies sea urchins and shrimp and maintains the DMR website.
She became a member of the Technical Committee in 2001, accepting the gavel the following year. Hunter and the four other members of the committee – biologists from Massachusetts, New Hampshire, ASFMC and the National Marine Fisheries Service, respectively – are responsible for making recommendations to the Section.
She’s “not one of the decision makers,” as she puts it, but the decision makers rely heavily on the information she collects and compiles about the shrimp stock.
Hunter, in turn, relies on the committee’s “most important tool,” a survey conducted every summer in The Gulf of Maine.
Hunter and a team of scientists trawl for shrimp using gear similar to what shrimpers use, except the scientists’ finer mesh captures small shrimp, too. The scientists catalog their catch and organize the data by size and weight.
Hunter also looks at the results of other surveys, the work of experimental fisheries and industry numbers, including landings and a statistic known as catch per unit effort or, more simply, catch rate.
The statistic measures the amount of shrimp a boat is able to catch in a certain amount of time, Hunter explained. “The concept is, if the fish are abundant, you’ll catch a lot,” she said.
The statistic is far from foolproof, however, as fishermen often record high catch rates as the stock continues to decline. Like many other fish, shrimp congregate in large, dense groups.
“As long as the fishermen can find the schools it can look like the fish is still abundant,” Hunter said.
Other important statistics include biomass, counts per pound (the number of shrimp in a pound, which helps the scientists figure average size) and instantaneous fishing mortality (F), a complex mathematical logarithm.
Based on these statistics, between 1985 and 1994, the fishery enjoyed what scientists refer to as a stable period. The average F during the stable period was 0.32. Hunter and her colleagues use this number as a target. “Anything above that is risky,” she said.
Following the stable period, the F skyrocketed, reaching nearly four times the target in the late 1990s before plummeting in the early 2000s, a meager time for the industry.
The F in 2011, when total landings exceeded the quota by about 4.4 million pounds, was 0.68, more than double the stable period figure.
The total landings in 2010 and 2011 were in the vicinity of 6000 metric tons (13.2 million pounds), exceeding what the data signifies as a threshold for trouble. “It’s happened twice in the history of this fishery and twice the stock has crashed right afterwards,” Hunter said.
From 1969-1972, landings averaged 11,400 metric tons per year. The bottom fell out in 1977, resulting in a closure the following year.
The fishery recovered and, after the stable period, landings shot up dramatically, reaching 9500 metric tons in 1996, declining in subsequent years, all the way to 450 metric tons in the 25-day 2002 season.
This year, the Technical Committee gathered and weighed a great deal of unusual data in preparing its recommendation for the 2012 season.
Shrimp are protandric hermaphrodites, meaning the miniature crustaceans mature as males and transition to females around the age of 3.
Females mate at about 3.5 (with 2.5-year-old males) and migrate inshore to hatch their eggs in the winter. These 4 and 5-year-old females, for the most part, are what Maine shrimpers harvest.
The majority of the 2010-2011 catch, according to a Technical Committee report, was four-year-old shrimp. The 2011 summer survey results show a scarcity of older females, while first-year (four-year-old) females and three-year-old males are unusually small. The youngest shrimp are of equal concern to Hunter for another reason – they’re missing.
“We’ve never seen anything quite like this,” Hunter said. “The whole distribution is odd.”
Hunter suspects high water temperatures in The Gulf of Maine as the culprit. The Gulf of Maine is the southernmost part of the northern shrimp’s range and warm water, especially in spring, appears to negatively impact the stock.
The higher temperatures might be a temporary phenomenon, as they proved to be in the 1950s, when shrimp were very scarce, Hunter said. There’s another, more troubling, possibility.
“If climate change is happening in The Gulf of Maine, this species is going to be in trouble,” Hunter said. “If we’re returning to that temperature regime [of the 1950s], and it looks like we might be, we may not have a shrimp fishery in the future.”
It’s too early for predictions of doom, however. “I don’t think we know enough about climate change in the Gulf of Maine,” Hunter said. “Next year, [temperatures] may just go back down again.”
Ultimately, the Technical Committee recommended that 2012 landings not exceed 1834 metric tons, or slightly more than four million pounds.
The Section didn’t stray far from the Technical Committee’s recommendations, rounding up the quota to 2000 metric tons. The Section’s announcement of a shorter season with three-day weeks for trawlers and daily limits for trappers shows the influence of the Technical Committee, citing its findings at length.
Some in the industry – from fishermen to seafood corporations – disagree with the Technical Committee’s science and support other means of data collection that point to a more optimistic conclusion about the strength of this season’s fishery.
Hunter is aware of the criticism and admits the survey is imperfect, but it’s more specific than other models and carries the all-important endorsement of peer review panels.
The occasional difference of opinion belies a common goal: the health, stability and sustainability of the fishery. “The goal is to try to have stable landings and a stable stock,” Hunter said.