Effect of proteins, lipids, minerals, and pigment in prepared diets on the somatic growth of juvenile green sea urchins, Strongylocentrotus droebachiensis

Kennedy, Edward J. (2002) Effect of proteins, lipids, minerals, and pigment in prepared diets on the somatic growth of juvenile green sea urchins, Strongylocentrotus droebachiensis. Masters thesis, Memorial University of Newfoundland.

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Abstract

This study investigated the effects of proteins (fishmeal and soybean), lipids (corn, linseed, and menhaden oils), minerals (modified Bernhart-Tomerelli and Shur-Gain salt mixes), and pigment (beta-carotene) over a range of concentrations in moist-extruded prepared diets on the somatic growth performance of juvenile green sea urchins, Strongylocentrotus droebachiensis, in five feeding experiments (ranging in length from 159 to 300 days). The growth of juveniles (ranging in size from 1 mm to 20 mm initial test diameter (TD)) fed prepared diets was compared to the growth of similar sized juveniles fed kelp, Laminaria longicruris. Juveniles fed the diets with the different sources and concentrations of proteins and lipids had smaller, poorly pigmented tests with short, stubby spines compared to the juveniles fed kelp after each experiment. Those fed kelp allocated more energy towards test production, whereas those fed the prepared diets allocated more energy to gonad production. The dietary protein treatments used in this study had no effect on growth and survival of the juvenile sea urchins. The lipid source treatments, which differed in the major essential fatty acids (i.e., n-3 and/or n-6), also had no effect on juvenile growth and survival in this study, but juveniles fed diets with lower lipid concentrations (i.e., 1% and 3%) had larger test sizes, but similar survival, than those fed diets with a high lipid concentration (i.e., 10%). The poor growth and physical appearance of the juveniles fed the protein and lipid diets were attributed to nutrient deficiencies in the prepared diets and the associated stress in the juveniles. Juveniles fed pigmented diets grew to a larger size than those fed non-pigmented diets. Similarly, dietary mineral concentration had a positive effect on juvenile test growth. Juveniles (1-2 mm initial TD) fed a pigmented diet with high mineral concentration (15%) grew to a larger size than kelp-fed juveniles. The data indicate there were no differences in the nutritional needs of the various sizes of juvenile green sea urchins used in this study. Hence, nutritionally balanced prepared diets can be used for a wide size range of green sea urchins to increase juvenile test growth while maintaining health and survival.

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