The objective of this study is to develop a set of web services to support the organization and data analysis of calibration workshops, both for age and maturity information (WebGR). The most common exercises carried out during these workshops are counting otolith growth rings or classifying gonads, with subsequent analysis of the results in order to build age-length keys or maturity ogives and it must be possible to do this on line using WebGR services. WebGR must also implement procedures for training purposes, like browsing images, reading experts' annotations or simulating a calibration exercise. The services must be implemented in a coherent tool installable as a website. The website should consist of a repository of images grouped or classified by workshop (species, date, area, etc) and accessible to all workshop participants. Each image must be annotated by several scientists. The annotations must include fields for the classification (age x or maturity stage y, etc), observations, scientist, etc. This information must be stored on a database so that the statistical analysis of the results can be automated as far as possible and made public as on line reports. The software developed must be licensed by an Open Source license to promote transparency, technology transfer and peer review; and allow the scientific community to get involved in further developments, like linkage to statistical analysis engines, or any other specific features.