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UMaine Today Magazine

Student Focus

Nicole Kirchhoff
Nicole Kirchhoff

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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."

UMaine Today Magazine
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