Fifteen years ago, a lobsterman who agreed with a government
scientist was a rare if not impossible find. Number crunching by
regulatory agencies showed that lobsters were overfished, while the men
and women hauling traps in the Gulf of Maine were harvesting record
numbers of crustaceans. Everyone was using a different source of
information and nothing made sense. Disagreement led to mistrust, some
bitter words and overall discontent in the world of lobsters.
Was the lobster population healthy or not?
For answers, the University of Maine and Maine Department of Marine
Resources (DMR) turned to Yong Chen.
"My work is like being an ecological detective," says Chen, a fisheries
population dynamics researcher who came to UMaine in 2000 from Memorial
University of Newfoundland. "You collect data from wherever you can and
try to create a story about why species numbers are changing. From
there, you can estimate what kind of impact fishing would have on a
Chen has analyzed fish populations in Canada, Australia and China, but
the stock assessment needs in the northeastern U.S. are different, he
"In many ways, they were behind the times," he says. "On the West Coast,
in Australia, they were using newer technology and methods. And there
was this history of problems because the assessment of lobster kept
predicting overfishing. So I came at the right time, because people were
ready for something new."
Counting lobsters is no trivial matter. Lobster is one of the most
valuable fisheries in the U.S., generating $350 million each year, and
Maine's 7,000 license holders bring in about 75 percent of all the
lobsters landed in this country.
Chen's first task was to identify potential problems with the existing
stock assessment. One concern was that the model used only one source of
survey data, which didn't include the range of lobster sizes and ages.
Many marine stock assessments are age-based, taking into account the
proportion of older and younger fish in a given population. But
lobsters, like most invertebrates, do not have the ear bones and scales
that record growth over the years.
Chen developed a new computer model based on lobster size that accounted
for many factors, including seasonal patterns and lobster
biology. Different management scenarios can be plugged into the model to
predict results of different fishing activities, such as v-notching.
Before, v-notching (the practice of fishermen marking reproductive
female lobsters with a v-shaped notch in their tails and not keeping any
such marked lobsters in their catch) was undocumented and unsupported by
the government and fisheries scientists. Chen's models have helped
confirm that v-notching has made a difference in the lobster fishery by
protecting reproductive stocks, says Carl Wilson, a DMR lobster
Fisheries population dynamics is a complex and sophisticated
the Northeast, only two or three people are familiar with these models
and use them on a routine basis, says Larry Jacobson, a biologist with
the National Marine Fisheries Service.
Whether modeling population dynamics of lobsters, Jonah crabs,
seaurchins, sea cucumbers, groundfish or marine worms, Chen must work
with limited surveys conducted by the state and federal governments, and
the catch reported by harvesters. The more information Chen has about a
species and its environment, the better he can build his computer model,
but there is always some negative space. To fill in the gaps, he uses
various statistics that let him assume certain situations.
The lobster stock assessment model developed by Chen, Wilson, Jacobson
and postdoctoral researcher Minoru Kanaiwa endured rigorous review for
years before the Atlantic States Marine Fisheries Commission adopted it
for the 2008 lobster assessment. Chen's tool will be used to assess all
the lobster stocks in the United States.
Because the model is so complicated, Chen is developing a user-friendly
version for biologists and fishermen. Ph.D. student Michael Errigo is
doing further testing, funded by a three-year fellowship from the
National Marine Fisheries Service, the National Sea Grant College
Program and UMaine.
The rigors of Chen's field and his work require that people trust him.
"What Yong and his lab have been able to do, in a remarkably
unconfrontational way, is to introduce new methods and ways to evaluate
how we assess lobster stocks. He is cutting edge in his field," says
For Chen, the key is in working closely with managers and biologists,
and attending government meetings to get input. He also maintains a
global perspective as an adjunct professor at both Central China
Agricultural University and Shanghai Fisheries University, and a
visiting professor at National Taiwan University. He served as a
consultant to the United Nations, studying the impacts of the Gulf War
on the fisheries of the Middle East.
"Trust-building is a long process, but it works," he says.
More models are needed for more fisheries, which will require more
experts like Chen. But with a shortage of well-trained people with
technical fisheries expertise, one of Chen's critical responsibilities
is in preparing the next generation of marine scientists in fisheries
dynamics, says Jacobson.
Students tend to prefer marine biology or even economics to population
dynamics, which requires knowledge of biology (How long do lobsters
live? How often do they mate?), ecology (How do lobsters interact with
other species? What are the migration patterns?), statistics (What is
the probability of a given population in a given time frame?), math
(What is the formula for exponential population increases?), computer
science (Can I write a computer program that will calculate all of the
above?), and policy (What do the outcomes need to look like so the
government can decide on their regulations and fishermen can keep their
Today, Chen has nine graduate students in his lab, many who are working
with DMR and fishermen while pursuing their research. Chen also
regularly meets with DMR staff and many DMR employees take his course in
fisheries population dynamics.
In turn, DMR provides Chen with data collected in its trawl surveys and
landings reports from fishermen, which he uses to develop models and
assessments that he hands back to the agency.
"He's really interested in the nuts and bolts of fisheries science, and
he understands that fishermen need good models and assessments," says
Linda Mercer, resource management director with DMR. "He's enthusiastic
about new methods. He seems pretty undaunted by the needs we've thrown
his way, species after species."
Chen designed the first-ever stock assessment for Maine's sea urchins,
and he was the first to study the population of sea cucumbers - a
species that has the potential to become a new fishery without much
knowledge of the animal's biology. A sea cucumber model to estimate
population and biomass will allow DMR to determine if the fishery can be
expanded, and get more people fishing, says Mercer.
Sheril Kirshenbaum worked on the sea cucumber project as a graduate
student pursuing dual degrees in marine policy and marine
"The emerging fishery provided invaluable experience," says Kirshenbaum,
who graduated in 2005 and is now an ocean and coastal policy research
associate at the Nicholas Institute for Environmental Policy Solutions
at Duke University.
"I was involved in understanding the population dynamics of a
fascinating species, while exploring real-world socio-economic and
political implications. Science informs policy, and this was the ideal
setting to learn to communicate between worlds."
by Catherine Schmitt
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