Research Document - 2010/132

Variations on spatial distribution on fish abundance in eastern Scotian shelf over the past four decades

By V. Harvey and M.O. Hammill

Abstract

Over the last four decades there have been major changes in demersal fish abundance. During the same period grey seal abundance has increased dramatically to the highest levels seen in the last 5 decades. Synoptic bottom trawl surveys conducted on the Scotian shelf (NAFO fishing zone 4VsW), were examined to determine if there have been changes in the abundance of fish with respect to distance from Sable Island. Survey data were combined into 10 years blocks (1970-1979, 1980-1980, 1990-1999, 2000-2009) which corresponded to periods of low, high, declining and low cod abundance for each decadal period respectively. Fish abundance was examined  in relation to distance classes of 0-50 km, 50-100 km, 100-150 km and 150-200km from Sable Island. A significant shift in distances of high abundance away from the Island was observed for cod, hake, herring and haddock when the 2000s were compared with the 1970s as would be expected as a response to minimize predation mortality from grey seals. 

View complete PDF document
(16 pages; 142K)