Sardines and anchovies are small pelagic fishes that support important commercial fisheries around the world. This project reviews the inverse cyclic behavior in the abundance of these two stocks, which is a striking feature in many regions. In addition, the project used qualitative loop analysis techniques to analyze the feasible sardine-anchovy model configurations that result in the inverse relationship between sardines and anchovies. A simple community model was examined that considers fishing, sardine and anchovy biomass, and food resources for the sardines and anchovies. First, the stability of these model configurations was investigated to determine the conditions that should be met to stabilize the unstable configurations. Second, the behavior of the feasible sardine-anchovy model configurations was examined when fishing was removed from the models. Finally, model configurations were identified that best represent the sardine-anchovy system in terms of predicting qualitative changes in the system variables. These best models define the crucial interactions between sardines and anchovies that require further studies. Based on the results of the literature review and the loop analysis a set of questions was developed and used in interviews with fishers in Oman to investigate whether the sardines and anchovies in Oman are inversely related. Based on the survey results and lessons learned from the literature review and loop analysis, recommendations were developed for further research and management of the fisheries in Oman for sardines and anchovies. In systems where the sardines and anchovies vary inversely in abundance refuge areas for the sardines and anchovies are very important for maintaining the two fish stocks and their cyclic behavior. The results from the loop analysis suggested that interactions between sardines and anchovies (e.g., competition and amensalism) are not important provided the two fish populations can regulate themselves by means of their refuge areas. The expansion and contraction of sardines and anchovies is a function of environment suitability and long-term shifts in the environmental regime. The study found no evidence that sardines and anchovies in Oman are inversely related. / Graduation date: 2003