Somatic Growth of Juvenile Strongylocentrotus droebachiensis Fed Artificial Feeds of Varying Nutritional Composition INTRODUCTION Background Three decades ago, the increased demand for sea urchin roe stimulated large scale harvesting of the green sea urchin Strongylocentrotus droebachiensis from the Gulf of Maine. Beginning in 1987, the rapid rise in harvests off the coasts of Maine and New Hampshire made urchin recruitment the second largest wild fishery operation behind lobsters with a peak of 39 million pounds in 1993 (1). Since then, the subsequent decline in harvests paralleled the reduction in urchin populations especially in locations where natural recruitment occurred at high densities. This drastic shift in ecology can be observed in the southwestern portion of Maine, where extensive areas of urchin-dominated communities have become algae-dominated and completely devoid of urchins (1, 2). The overfishing of sea urchins led to increased interest in a hatchery system for stock enhancement and replenishment of natural populations. The goal of the hatchery system is to produce commercial quantities of sea urchins for out planting into the wild as quickly and economically as possible. Currently, it appears out planting is most successful in the winter. Since spawning begins by January or February, this design allows the urchins one year from spawning to out planting at the preferred test diameter of 15 mm (1). From newly settled (0.5 mm) to out planting (15 mm), the goal of the hatchery system is to rapidly while efficiently increase the somatic growth rate of the animals. Problem The goal of the hatchery is to produce commercial quantities of the animals in the least amount of time and with the most economical method. However, urchin feed is not well studied for its nutrient composition in relationship with somatic growth especially during the juvenile stage of the animal as it reaches the out planting test diameter of 15 mm. Therefore, current feed could be inept in providing the greatest rate of growth possible for the urchin hatchery. The nutrient composition of urchin feed is a key factor in the efficiency of the hatchery process. Sau Wai Hung Department of Biological Sciences (Zoology) University of New Hampshire, Durham, NH OBJECTIVE To determine the relationship between the nutrient levels of protein and carbohydrate and sea urchin somatic growth HYPOTHESIS Higher levels of protein will stimulate the greatest rate of somatic growth EXPERIMENTAL DESIGN Methodology Measure Urchin Weight and Size Place 10 Urchins into Individual Compartments of Each Box Feed Urchins a Particular Type of Feed Orient Box Vertically in Tank to Maximize Water Flow Feed Protein (%) : Carbohydrate (%) : 21 = : 21 = : 39 = : 21 = : 30 = : 30 = : 30 = : 21 = : 39 = 0.31 Conditions  Urchins were kept in the cold room under a constant water temperature of 14 o C.  Each tank contained a filter and an air stone for increased water movement.  Salinity of the water was 32 ppt. 1 Week Works Cited 1. Harris LG, Madigan P, Waters K (n.d.) A hatchery system for green sea urchin aquaculture in the Gulf of Maine. In press. 2. Harris LG, Tyrrell M (2001) Changing community states in the Gulf of Maine: synergism between invaders, overfishing and climate change. Biological Invasions. 3: Acknowledgements I would like to thank Dr. Larry Harris for his continual support and assistance of my senior honors thesis, the UNH Hamel Center for Undergraduate Research for funding my work, and Dr. Jim Haney for the frequent use of his laboratory. In addition, I would like to thank Dr. Stephen A. Watts from the University of Alabama at Birmingham for generously providing the urchin feed. RESULTS Average Urchin Growth Over 12 Weeks Average Initial Sizes of Urchins Survivorship of Urchins Over 12 Weeks  For each type of feed, all of the urchins’ overall growth percentages were averaged.  In both the case of test diameter and wet weight, feed produced the greatest percentage of urchin growth.  Feed generated the second highest percentage of growth, with having similar results. CONCLUSIONS  Feed was not the feed highest in protein. In fact, it had the most intermediate ratio of protein to carbohydrates. Even though protein is a critical nutrient for somatic development, the relationship between protein and carbohydrate may be an even more vital factor to consider.  Feed contained the most protein and had the highest protein-to-carbohydrate ratio. With enough protein, the same growth results may be obtained as with the balanced diet. CONCLUSIONS  It is known that smaller urchins grow at a faster rate than larger urchins.  Since all urchins began the experiment at approximately the same size (no significant difference), the rate of somatic growth between the urchins should be equal. CONCLUSIONS  Feeds and were the most effective for the somatic growth of juvenile sea urchins.  Due to low survivorship, the diet may in fact be the least effective of all the feed options. It contained the least amount of protein and had the lowest protein-to-carbohydrate ratio.  The initial sizes of all urchins were measured by test diameter and wet weight, and then averaged by feed type.  The standard errors of the mean were calculated for the two methods of measurement.  In both cases, all standard error bars overlap. Therefore, there is no significant difference between the starting sizes of the urchins of the various feed types.  Throughout the experiment, a few individual urchins died. For each feed type, the survivorship percentage of the urchins was calculated.  In addition to producing much growth, feeds and both had 100% survivorship.  Although feed was initially concluded to be highly effective, it only yielded 50% survivorship.