Biological data from 1125 female Atlantic wolf-fish Anarhichas lupus were collected during 2002–2006 at their main spawning and fishing grounds in Iceland. The results demonstrated substantial annual variation in growth and maturity of female A. lupus. The fast growing females mature earlier than the slow growing ones. In addition, females mature at a larger size and greater age in warmer temperatures than colder ones. There was a strong negative relationship between temperature and growth, which may indicate that the sea temperature west of Iceland has risen above the optimum for growth of female A. lupus and thereby reduced the reproductive potential of the species.