Graph of the Day: Length of Four Fish Species on the Scotian Shelf, 1970-2002

There has been a decline in the size and condition in a number of groundfish species. There has been a reduction in the size of some groundfish species (e.g., haddock, cod, pollock, and silver hake) since the start of the time series in 1970. This decrease in size has been observed both on the Eastern Scotian Shelf, where decreasing water temperature may have had an influence on growth in the late 1980s through early 1990s, but also on the Western Scotian Shelf, where temperatures remained relatively stable over this same period. A change in the average size of exploited species can be related to long-term fishing pressure if larger individuals are removed selectively from the population. The trend of reduced size on the Scotian Shelf has persisted despite the current low population levels of groundfish and low exploitation rates, suggesting that the population dynamics (or genetics) of these species has been altered.

Canadian Science Advisory Secretariat Science Advisory Report 2010/030, 2010 Canadian Marine Ecosystem Status and Trends Report [pdf], July 2010