Opakapaka (Pristipomoides filamentosus) is a snapper (family Lutjanidae) native to the waters around Hawaii. Recent population declines of this commercially important species have increased interest in the culture of this fish. Survival of this fish through the larval period in culture has been consistently low, usually not exceeding 2%. The aim of this thesis was to provide an extensive diagnostic report of diseases affecting opakapaka larvae in culture. Opakapaka larvae mortality was found to be the result of a synergy of factors including larvae development stage, larvae nutrition, environmental conditions, and the presence of infectious agents. During culture, high larval mortalities occur around first feeding and around a period of rapid development. Crucial periods of development in both the digestive system and the respiratory system coincided with these catastrophic mortality events. It is therefore suspected that failure to complete the progression of development from one stage to the next is partially responsible for low larvae survival. A large proportion of opakapaka surviving to the juvenile stage had deformed jaws and/or vertebral columns. Therefore, the development of the jaw and other skeletal elements was investigated. Lower jaw deformities were found to occur as early as 2 days post hatch and larvae with some deformity represented roughly 30% of the population. Given the severity of these deformities, it is likely that this results in increased larvae mortality. Due to the identified risk of ammonia toxicity, experiments were designed to determine the concentration of ammonia lethal to opakapaka larvae. The 50% lethal dose for post-hatch opakapaka larvae was found to be 1.4 mg/L total nitrogen. Ammonia toxicity could have been a factor in opakapaka larvae mortality, because this concentration was lower than that observed in larvae rearing tanks. The evaluation of the role of infectious disease in opakapaka culture showed that current infections are primarily opportunistic. Observed infections included bacterial gill disease and external lungal infection. Although infectious disease is not currently a significant cause of mortality, continued surveillance for infectious disease introduction is recommended. The success of intensive opakapaka culture hinges on the ability to culture a large number of opakapaka to the juvenile stage. As a result of this study, major issues of concern in opakapaka culture were identified. This information could provide direction for culturists in the refinement of opakapaka culture and subsequent improvement of larvae survival. / Graduation date: 2005