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Research Document 1998/130

State of Zooplankton on the Scotian Shelf, 1997

By D. Sameoto, N. Cochrane, A. Herman, E. Head, and M.K. Kennedy

Abstract

There were no significant differences in the mesozooplankton biomass levels between the Louisbourg and Halifax lines in either April or October, 1997. This result was different from that reported for 1996 when there were higher levels of zooplankton biomass on the Halifax Line. The krill index showed a significant increase in Emerald Basin over the values of 1996. Highest estimated concentrations of krill were found on the western half of the Shelf in the region of Roseway Basin. During April, 1997, the C. finmarchicus biomass in the top 100m was higher on the western half of the Shelf than on the eastern half, C. hyperboreus biomass was higher on the eastern half and C. Glacialis showed a relative uniform biomass distribution. In October higher concentrations of young copepodite stages of C. finmarchicus were found on the Louisbourg Line than on Western Bank or the Halifax Line, suggesting that reproduction of C. finmarchicus extended longer into the fall on the eastern Shelf region than the central region represented by the Halifax Line. An intrusion of very cold fresh water on the slope at the shelf break was observed in October extending from the Louisbourg Line to midway between the Halifax Line and the Browns Bank Line. This cold water had flooded Emerald Basin by April, 1998.

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