Fish community changes in an exploited marine ecosystem : Newfoundland Southern Grand Bank and St. Pierre Bank, 1951-1995

• Main Author: Casey, Jill M.
• Format: Thesis
• Language: English
• Published: Memorial University of Newfoundland 2000
• Subjects: Newfoundland; Northwest Atlantic
• Online Access: https://research.library.mun.ca/817/; https://research.library.mun.ca/817/1/Casey_JillM.pdf; https://research.library.mun.ca/817/3/Casey_JillM.pdf

Longterm fish community changes on southern Grand and St. Pierre Banks were examined from dedicated research survey trawls conducted by the Canadian Department of Fisheries and Oceans from 1951-1995. These time series pre-date the arrival of factory-freezer-trawlers in the 1960's and 1970's. and thus provide insight into changes in the biomass and diversity of an exploited system. The time series were standardized by applying conversion factors for changes in vessel, diel changes in catchability, and relative catchability of selected species. Total biomass in the 1990's was reduced to 11% and 9% of that observed in the 1950's on southern Grand Bank and St. Pierre Bank, respectively, and largely resulted from the decline of the haddock population. Compensatory responses to this decline were visible with the flatfish on southern Grand Bank and skate on St. Pierre Bank but continued fisheries for flatfish and bycatch of skate ensured that total species biomass would remain at low levels. This study shows the importance of examining data on as long a time-scale as possible. Failure to examine such historical data has resulted in the largest skate in the northwest Atlantic, the barndoor skate, being driven to near extinction without anyone noticing.