Student Focus
Indoor Urchins
It's morning in Franklin, Maine, and the young ones
are already out for a swim. The temperature is perfect; the water is
clear, and just down the hall, refreshments are already percolating
away. This is the life — especially if you're a green sea urchin.
Tucked away in a quiet, temperature-controlled room
at the University of Maine's Center for Cooperative Aquaculture Research
(CCAR) in Franklin, dozens of bristly, thumbnail-size urchins vie for
position on the walls of specialized tanks, waiting to be released among
the rocky crags and crevasses of the Atlantic. Unlike their wild
counterparts, the verdant invertebrates lead a life of leisure, their
every need addressed by UMaine graduate student Nicole Kirchhoff.
Coddling baby urchins is part of Kirchhoff's
multifaceted investigation into green urchin aquaculture. Working with
CCAR Manager Nick Brown, she hopes to develop efficient and reliable
techniques for raising juvenile urchins. Hatchery-raised urchins could
one day be used to reseed the Maine coast, where overharvesting in the
late '80s and early '90s led to the collapse of the urchin fishery.
"No one had ever done this type of research before,"
says Kirchhoff as she harvested eggs from one of the large urchins
serving as brood stock for the program. "We have looked at everything:
brood stock management, how to grow juveniles economically. There is
still a lot we don't know."
The first stage of Kirchhoff's work focused on
urchins' reproductive biology. By manipulating the length of day and the
temperature in the lab, she was able to change urchins' seasonal
spawning cycle, causing them to produce viable eggs and sperm
year-round. Lab tests are under way to determine if the eggs and sperm
produced out of season are fully developed.
Since each female urchin is capable of releasing as
many as 3 million eggs per spawning, the few hundred or so hefty adults
that make up the program's parent stock provide more than enough
offspring to keep the trash can-size rearing tanks full of planktonic
urchin larvae. By precisely controlling environmental factors and diet,
Kirchhoff has been able to raise young urchins no larger than the period
at the end of this sentence to a respectable 10 millimeters or larger —
a critical size in the life of a young urchin.
"Once they get past 15 millimeters or so, they
become much less susceptible to predators," says Kirchhoff. "At that
size, they could be used to restock areas where the urchin population is
low."
Another part of Kirchhoff's master's work looked at
urchins' rate of growth under varied environmental conditions. Captured
and caged in mesh tubes beneath the waves of Penobscot Bay, a population
of more than 5,000 fingernail-size urchins was carefully measured and
monitored for six months. Data collected on the juveniles will help to
determine optimal bottom type, currents, temperatures and other factors
that could influence the success of green urchin aquaculture and
reseeding programs.
Kirchhoff is now applying what she learned from her
initial research to develop a better understanding of urchins' breeding
biology and to determine the optimal conditions for successful rearing
of juveniles. With every discovery, new questions arise that offer new
opportunities for research.
"The interest in green sea urchin aquaculture is
definitely growing," says Brown. "Nicole's research has been very
successful. We basically started with nothing and now we're at the
forefront of research in the U.S."
