Dietary Polyunsaturated Fatty Acids and Disease Progression in Striped Bass, Morone saxatilis

The Chesapeake Bay has experienced significant declines in key species of forage fish. It has been suggested that these declines in prey availability have led to dietary shifts in apex predator species such as striped bass. Beginning in 1996 and continuing to date striped bass have been seen to exhibit signs of bacterial disease caused by Mycobacterium marinum, an acid fast positive bacteria common to marine systems. Since that time other species of mycobateria have been found. These two coinciding events have caused many scientists to believe that there is a connection between changing diet and mycobacterial disease in striped bass. Prey shifts can alter the nutritional content of the diet possibly leading to deficiencies in polyunsaturated fatty acids (PUFA), micronutrients that regulate vertebrate immunity. Predatory shifts to prey that contain relatively low PUFA may lead to an impaired immune response and increase the likelihood of succumbing to infection. The focus of this project is to determine if decreased consumption of PUFA can affect immune function and overall progression of disease in striped bass injected with M. marinum. In the current study, the immune response of striped bass fed a standard striped bass aquaculture feed (optimal PUFA content) was compared to fish that have been fed a low PUFA diet. Both diet groups were administered either an injection of M. marinum (1x10⁶ CFU) or phosphate buffer solution and sampled 2, 4, 8, and 17 weeks post injection. Measurements of phagocytosis, leukotriene B₄ production, bacterial counts, and histological evidence of inflammatory response were used to determine the immune response and progression of disease between fish fed the two diets.