Create a prey nutrient database and use it in a computer ration formulation program to evaluate factors influencing variation in nutrient composition among mixed prey pinniped diets

Pang, Janelle Ann Chiu Ghin
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[Honolulu] : [University of Hawaii at Manoa], [August 2013]
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Between the 1960s and 2000s, a substantial decline of Alaskan harbor seals (Phoca vitulina richardsi) and Steller sea lions (Eumetopias jubatus) prompted studies to enhance conservation and understanding of harbor seal and Steller sea lion population dynamics. The purpose of this study was to search the literature and establish a nutrient database that could be utilized in captive settings as well as a predictor for wild pinniped populations. With the aid of the MIXIT-WIN ration formulation program and the nutrient database of common northern Pacific and Alaskan marine mammal prey items, the nutrient composition of various mixed prey diets were assessed and the nutritional impact on the decline of Alaskan pinniped populations were evaluated. The nutrient variation within and between species of the various prey included in the nutrient database were evaluated, by comparing location, gender, age, season and size. Based on literature findings, different forage fish species had significantly different chemical compositions, in addition, to mineral and fatty acid concentration variability. The MIXIT-WIN ration formulation program, along with the nutrient database of selected prey, demonstrated how changes in both proportions and nutrient densities of each prey altered the nutrient content of the diet. Different mixed diet proportions of herring to pollock, suggested that low fat (LF) capelin could satisfy gross energy (GE) levels compared to high fat (HF) capelin. However, if a diet needs to contain more pollock at a 1:5.5 ratio, the ideal diet would need to contain HF Pacific herring and HF pollock. In addition, the impact of prey availability and quality in the wild population, by prey substitution, suggested that HF mackerel could serve as a substitute for capelin, HF smelt could serve as a substitute for Pacific herring and only HF Atlantic herring could serve as a substitute for Pacific herring, based on crude fat/lipid (CF) and GE levels. When looking for a diet to maximize ash and mineral intake, LF diets with greater proportions of pollock, offered the highest levels of macro-and micro-minerals. However, because ash was inversely related to CF content, LF diets offered the least amount of GE and CF. When substituting mackerel for capelin, a reduction in copper (Cu) and zinc (Zn) levels would result in LF mackerel diets. When substituting smelt for Pacific herring, LF smelt would increase both macro-and micro-minerals at the higher ratios. Low fat Atlantic herring could be substituted for Pacific herring, increasing both macro-and micro-mineral contents.
M.S. University of Hawaii at Manoa 2013.
Includes bibliographical references.
Steller Sea Lion
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Theses for the degree of Master of Science (University of Hawaii at Manoa). Animal Sciences.
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