Currently under intense fishing is important to keep the population of commercial fish within safe biological limits. To check the status of the stock dynamics, scientists estimate its size. Assessment of fish stocks is an essential tool in the study of marine ecosystems. However, the observations always contain errors and uncertainty in the measurements. The book is an attempt to investigate part of the uncertainty in stock assessment and prediction of target species. The research results can be used as additional information for the main stock assessment. This uncertainty analysis, using bootstrap, is only the first step in the construction of full analysis of uncertainty in stock assessment. Additional work to more fully characterize all important sources of uncertainty in the assessment process, including modeling errors, should be used to estimate the applicability of the current biological reference points as well as any harvest control rules.