One of the main objectives of fisheries management is to ensure the sustainability of fished stocks. To reach this objective scientists have to adequately assess the status of fished populations with quantitative models of the fishery systems. Most of these models require estimates of population parameters such as growth rates, mortality rates and catchability (the proportion of the population caught by a single vessel each day). Most of these parameters are unique for each stock; unfortunately they are not easily estimated because marine organisms are inherently difficult to observe and study. Estimation is generally done through statistical analysis of catch data, either from the fishery or from research surveys.