Establishing the photo-thermal conditioning regime
From March 1st to 15th 2006, each conditioning system was
stocked with reproductively ripe wild adult (N40 mm test diameter)
S. droebachiensis. Two hundred and seventy four urchins with a mean
test diameter of 66.4±1.0 mm were stocked into the Constant Spring
system (Constant Spring group 1) and 251 urchins with a mean test
diameter of 64.4±1.1 mm were stocked into the Advanced system
(Advanced System Group). The urchins were obtained by divers from
three locations in Penobscot Bay, Maine, during a typical commercial
harvest. Urchins were collected from a variety of bottom types, kelp,
cobble or ledge, at depths between 5 and 15 m. They were transported
moist to the Center for Cooperative Aquaculture Research (CCAR)
within 2 h from landing at the dock and were randomly distributed
among the two conditioning systems. After a one month acclimation
period, the Constant Spring system was held at a constant photoperiod
of 12 L:12 D and a temperature of 6 °C ±0.3 °C. The Advanced
system received an advanced photoperiod and temperature regime
adjusted so that by the 19th of November 2006, the apparent ambient
temperature and photoperiod would be similar to that of the 10th of
April in the northeastern Gulf of Maine, i.e. an advancement of
6 months (Fig. 1). An additional 50 urchins were stocked into the
Constant Spring system in March 2007 and conditioned in the same
method (Constant Spring group 2). The urchins were fed to satiation
weekly with fresh, locally harvested kelp (75% Laminaria saccharina,
15% Laminaria digitata, and 10% Ulva lactuca; approximately 10% dry
matter), about 4.5 kg wet weight per system per week. Fecal pellets
were siphoned biweekly and tank sides scoured twice per month in
each conditioning system.