A system has been developed for computer-assisted photographic identification of marine animals. The system creates and maintains a database of images of dorsal fins or flukes, and the user queries it by entering a new image acquired in the field. The system searches the database for similar images based on the notching pattern of the dorsal fin or fluke, and offers a list of database members ordered by similarity to the query image. A syntactic/semantic string representation method is used for matching and is compared with matching by direct alignment of edge patterns. The system has been tested with data sets of images of several biological species.