Date of Award

12-2007

Level of Access

Campus-Only Thesis

Degree Name

Master of Science (MS)

Department

Marine Biology

Advisor

Nick Brown

Second Committee Member

Linda Kling

Third Committee Member

Mary Tyler

Abstract

The collapse and slow recovery of the green sea urchin, Strongylocentrotus droebachiensis, fishery in the Gulf of Maine has caused concern within the industry and among researchers that wild stocks will not recover without assistance from aquaculture for all or part of the life cycle. Prior research has pinpointed the optimal timing and seed size for reseeding to be November using 15 to 20mm test diameter juveniles. Using traditional sea urchin hatchery technology this would require considerable landbased culture. Methods used in this report attempt to reduce the amount of landbased culture necessary in sea urchin aquaculture, thereby increasing the economic viability of the industry. This report represents one of the longest duration cage culture experiments with green sea urchins to date. A uniquely designed culture tube was used to evaluate the success of on-bottom nursery culture of juveniles. Juveniles, 7.93 ± 0.65mm, were grown to 11.08 ± 1.488mm with a 69% survival after six months of on-bottom cage culture. Significant effects were found between bottom type and culture success, with mussel and ledge bottom type resulting in increased growth yet reduced survival over cobble bottom. Bottom type may therefore be a good site selection criterion for green sea urchin nursery cage culture. These results suggest on-bottom culture is technically feasible and may represent the most economical way to rear hatchery produced green sea urchin seed to the 'planting out' size. This study also reported the first out-of-season spawning induction of the green sea urchin. Two different photo-temperature manipulations were used; the first used constant spring conditions to maintain maturation over the entire year, while the second advanced the urchins through the yearly cycle in six months, reducing the total length of reproductive cycling. The number of eggs per ml, percent fertilization, and percent hatch from conditioned urchins out-of-season did not vary significantly from that of wild urchins in-season. Increased specific fecundity was found for both sets of conditioned broodstock compared to the wild out-of-season. Using either broodstock conditioning method or a combination of the two may significantly increase the efficiency of a sea urchin hatchery, reducing the cost per individual produced.

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