Spatial and temporal changes in the groundfish assemblages on the north‐east Newfoundland/Labrador Shelf, north‐west Atlantic, 1978–1991

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Abstract
From 1978 to 1991, biomass and abundance have declined in members of the marine fish community on the Newfoundland‐Labrador Shelf. This decline was common to all commercial groundfish and to many noncommercial ones as well. Since about 1985, the biomass decline has been accompanied by major shifts in the geographic distribution of almost every species. Some species disappeared from inshore, others disappeared from the north, and others did both. Some species appear to have had major shifts in abundance (north to south or inshore to offshore) whereas other species exhibited a biomass decline in one area but maintained a rather uniform level in others. Multivariate analysis of groundfish survey data identified four groundfish assemblage areas on the shelf, i.e. areas characterized by a homogeneous faunal composition. Distribution patterns of the assemblages remained relatively stable from 1978 until 1987, but have entered a period of dramatic change since then. Changes in the distribution patterns of individual species anticipated changes at the community level. Intense exploitation of groundfish is the most likely explanation for the decline of fish biomass on the Newfoundland‐Labrador Shelf. The shifts in distribution observed, however, suggest that broad‐scale environmental effects may also be at work.