Changes in the temperature/depth niche occupied by demersal fishes in the Northwest Atlantic between 1978 and 1993

Realised temperature/depth niches of 16 demersal fish species of the Newfou ndland continental shelf are visualised graphically with a novel method, an d annual patterns from 1978 to 1993 are described. Together, the graphical visualisation of realised temperature/depth niche space and the associated niche width (Ht) can be used to differentiate a species' niche from that of co-existing species; they can also be used to assess changes over time in a single species or a whole community of species. The study period was one during which disturbances, from declining sea temperature and heavy fishing effort, increased across the Newfoundland shelf ecosystem and many fish sp ecies declined in abundance and/or average size of individuals. The analyse s showed trends towards occupation of deeper water over time in most fish s pecies studied. These were mostly accompanied by a significant reduction in the size of realised niche space.