Jointly, the Expert Centre for Taxonomic Identification (ETI, Amsterdam; linked with UNESCO), the Netherlands Institute for Research of the Sea (NIOZ, Texel) and Alterra (Wageningen University) have just put a new CD rom on the market, discussing and illustrating otoliths of fishes of the North Sea. The authors are all involved in the study of fish predators. There are six main ‘chapters’, namely Introduction, Species, Glossary, Index, Identifylt and Literature, as well as a word of welcome to this ETI production, a list of contributors (other than the authors) and additional information on ETI, NIOZ and Alterra. The ‘Introduction’ comprises the sections Preface, Introduction, Sampling, Measurements and Regression. In the ‘Preface’, the preservation potential of otoliths, their use in the identification of fossil and extant fishes, daily/annual growth increments and age determination are discussed. The next section, the ‘Introduction’ proper, outlines which fish have (good) otoliths, presents data on fish hearing and balance and, mainly, on otolith degradation in predator stomachs. For some groups, other identifiable hard structures are treated, such as pharyngeal bones and chewing pads of cyprinids, dermal denticles and vertebrae of pipefish and lumpsucker, and stickleback spines, all of which are well illustrated (Species, Multimedia). Here there are two errors: to describe cyprinid sagittae as potato-shaped is wrong (in fact, they are arrowhead-shaped), and in many cases fossil otoliths are certainly not more brittle than extant ones.