Structure and distribution of demersal fish assemblages on the northeast Newfoundland and Labrador Shelf

Villagarcia, Maria Guadalupe Del Mar (1995) Structure and distribution of demersal fish assemblages on the northeast Newfoundland and Labrador Shelf. Masters thesis, Memorial University of Newfoundland.

[English] PDF (Migrated (PDF/A Conversion) from original format: (application/pdf)) - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. Download (14MB) [English] PDF - Accepted Version Available under License - The author retains copyright ownership and moral rights in this thesis. Neither the thesis nor substantial extracts from it may be printed or otherwise reproduced without the author's permission. (Original Version)

Abstract

Multivariate analysis of 14 years of scientific survey data has distinguished four groundfish assemblage areas on the Northeast Newfoundland and Labrador Shelf. The assemblages were characterized by an homogeneous faunal composition, and relative abundance and persistence over time. From 1978 to 1986, their spatial distribution was maintained within certain geographical boundaries which followed bottom topography and exhibit characteristic bottom temperature ranges. Starting in 1987 and coincident with a decline in the commercial fisheries, there was a shift of three of the assemblages towards the east. Further analysis revealed a decrease in biomass in all of the more abundant species as well as in some of the less abundant. Rare species were found to decrease earlier than dominant ones, perhaps acting as indicators of major changes taking place across the continental shelf. Increasing density of certain species near the shelf/slope break has produced groupings of fish offshore of the main banks which has made them more vulnerable to the fishery. Possible causes for this behaviour, e.g. varying bottom temperature and lost of stability in the main species, are investigated. Intense exploitation of groundfish is the most likely explanation for the decline of fish biomass on the Northeast Newfoundland and Labrador Shelf. Less abundant species distribution may also be affected by discard or as by-catch of the commercial species. The homogeneous fish assemblages found could be used as the basic units to manage the shelf in a smaller scale basis from a biological perspective and to define highly sensitive areas where fish tend to aggregate that might need to be protected.

Actions (login required)

View Item