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Commercial Fisheries News
Volume 35 Number 2
October 2007
Urchin hatchery goal to supply sustainable fishery
LUBEC, ME – On Water Street in Lubec, just north of the bridge to Campobello Island, sits the R.J. Peacock Canning Company. On the back side of this historic building, past piles of processing equipment, old line, chain, and other waterfront clutter, emerge two small, black polyethylene pipes. The pipes run into the nearby channel, and they don’t begin to tell the story of the facility that sits just inside – the region’s most productive hatchery for the green sea urchin, Strongylocentrotus droebachiensis.
The hatchery sits in part of the building’s bottom floor and is filled with a series of concrete and plastic tanks, pumps, piping, and filters. Most of it is cobbled together, and sometimes it’s a little finicky to keep things running.
On the other hand, significant developments in the hatchery production of urchins have happened here, developments that have the potential for a big impact on wild urchin populations, the fishery, and aquaculture.
The eventual goal is to supply enough urchins to help support a sustainable fishery in Cobscook Bay, which could then be used as a model elsewhere in the state.
It’s an interesting mix of an aquaculture technique in support of a wild fishery, much the same as spat collection and re-seeding of scallops.
“Since it’s expensive to think about growing urchins to market size in Maine” said Michael “Mick” Devin, “why not produce the small ones and let Mother Nature do the rest of the work. It’s a way for aquaculture and fishing to work together.”
Unlikely team
Devin and Hank Stence are the two principal operators of the hatchery. Stence began in 1988 as part of the “Special Projects” department of the Peacock business, and Devin joined the group in 2000.
Capt. Robert Peacock is the facility owner. He runs his seafood business upstairs from the room that he grew up in, and his children are the sixth generation of Peacocks in Lubec.
They make, perhaps, an unlikely team, but with complimentary expertise.
Peacock was in the Merchant Marines for 20-plus years, skippering big offshore tankers, and came back to run the family business. Devin is a former Navy engineer with an advanced degree in marine biology and a penchant for sea urchins and larval ecology. Stence has a long history in aquaculture in the Lubec area, including as a quality control officer for a former salmon farming operation, and as one of the first to obtain an aquaculture lease from the state.
Together, they produce urchins as a way to augment depleted populations and to work toward a sustainable fishing industry.
Breeding
All activities common to any other shellfish hatchery happen here– broodstock holding and conditioning, spawning, larval rearing, algal culture for food, and care of juveniles.
Broodstock are collected locally from the wild and fed liberally to allow them to come up to spawning condition. Eggs and sperm, which collectively are known as gametes, are collected through one of several methods: natural spawning; stressing the ripe urchins by means stuch as lifting them out of the tanks; injection with potassium chloride; or dissection.
Once the gametes are collected, they are combined to fertilize the eggs. Immediately afterwards, they require a lot of care, including a gentle rinsing every eight hours or so.
As Stence says, “The developing egg has a sticky protective covering. If you don’t rinse the eggs to keep them clean, that sticky shell picks up all kinds of debris and can cause the whole batch to crash.”
As the eggs divide and grow, they go through several early larval stages until they begin to swim around, thanks to two bands of cilia, which are microscopic hair-like structures that whip back and forth.
At this point, the larvae are about 90-100 microns in size or roughly one-tenth of a millimeter (mm). They are held as close to 45°F as possible and, for about the next three days, will not feed.
Once they do begin feeding, they act as small predators, moving about to gather cells of microalgae. Tetraselmis and Isochrysis are common feeds at this point.
Critical steps
The next couple of weeks – about 30 days post-fertilization if all goes well – involve frequent drain-downs and tank cleaning, feeding, and close attention to the developing larvae.
Care is warranted. Not too long ago, when a larval tank was filled too far in advance and in the time before urchin larvae were put in, a copepod bloom occurred. These tiny crustaceans wiped out the urchin larvae as soon as they were put into the tank.
The next big hurdle that Devin and Stence face is the transition from a swimming larva to a bottom-living urchin. This step is called settlement.
“It’s a pretty spectacular change from an eight-armed stage to a stage where the arms are re-absorbed, and they grow five tube feet and five spines,” Devin explained. “They also create the test, which is the shell of the urchin. It takes another week or so for the young urchin to develop mouth parts so it can start feeding again.”
Diets
The time they begin to feed as juveniles is another critical point, and Devin and Stence are currently experimenting with diets. The approach they’ve used is extremely low-tech, though based on biological principles.
They allow one-gallon plastic jars to sit in seawater for up to several weeks, so that the jugs develop a layer of algae. The algae layer contains benthic diatoms and bacterial mats, and they feel that this is a good start at healthy urchin feed.
Once the jars are suitably fouled, they put the post-set urchins into the tank with the jars, and let them graze normally. Nothing changes for a few days, but pretty soon the color on the jars lightens up as the fouling is removed, which is evidence that the urchins are doing their job.
Calcium need
Settlement and post-set care remain the big sticking points for the operation. Recently, Devin and Stence have been pondering the young urchins’ need for calcium and how they obtain this element. They have concluded it’s another line to put under the heading “More Research Needed.”
Urchins apparently don’t get calcium from their feed and may only be able to take it up via seawater. This has implications for the development of hard parts such as teeth and other feeding apparatus, as well as for the conditions that the urchins should be kept under as they go through this change.
At a later point, the urchins begin to feed on wild-harvested macroalgae such as kelp pieces collected right off a dock adjacent to the hatchery. As they grow, the urchins are placed into floating plastic colanders, together with feed.
Right size
Oddly, a group of urchins from the same spawn and held in identical conditions will have drastically different growth rates. When the larger urchins in a group are removed, the growth rate increases for those left behind. While the cause for this is unknown, it is an area of interest.
The goal of the operation is to produce urchins about 10-15 mm (about 1/2") across for reseeding. At this size, Devin noted that the urchins are pretty well protected from predators.
“A lot of the predation by fish is limited by mouth size,” he said, ”and when the urchins are 10-15 mm, they’re larger than what a lot of fish can eat.”
This critical size also seems to be right for hiding. The urchins can fit into nooks and crannies to get away from other predators like crabs.
Persistence
In coming months, the team will be working on setting out urchins at the Federal Harbor Farm lease site located between Hog and Long Islands in South Bay in Lubec.
Devin and Stence have been working with the husband-and-wife team of Olaf Ellers and Amy Johnson of Bowdoin College, who have developed a unique system of tagging urchins with fluorescent dyes.
The dyes form a “bar code” on the mouth parts, visible under certain wavelengths of light, which can be used to track groups of urchins over time. Devin and Stence will release urchins on the lease site and track their progress.
The way it looks now, this small group of dedicated people will continue to make advances. Their connections to both the local community and scientific world help them along and keep them grounded. The rest is observation, creativity, persistence, and a commitment to give back to a community and to a resource that has benefited them in the past.
Dana Morse
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