Research Document 1997/127

Overview of 1997 hydrographic sampling effort and near-50 meter water temperature and salinity conditions during the Canadian research vessel groundfish surveys conducted during the Spring on the Eastern Scotian Shelf (4VsW) and Georges Bank (5Z)

By F.H. Page, R. Losier and J. McRuer

Abstract

Hydrographic sampling effort and near-bottom water temperatures and salinities from the 1987-97 Canadian research vessel spring groundfish, stratified random, bottom-trawl surveys are summarised. The surveys cover NAFO divisions 4VsW and 5Z. The timing of the surveys continues to be variable between years. Therefore, caution must be exercised in interpreting the hydrographic trends as climatic variability in the hydrography. Never-the-less, the conditions are representative of the conditions in which the fish were caught. In both, the 4VsW and 5Z surveys the temperatures have increased marginally over the past few years. In 1997, the surveys were conducted near the mid-date of the previous surveys in the series and samples were obtained from all strata. The temperatures and salinities sampled in 1997 were near or above those observed in previous surveys. In 4VsW sampling effort was extended further north in strata 401, 402 and 406 than in most previous surveys. This resulted, in part, in the temperatures in several strata being near or above historical maxima. In 5Z the amount of relatively low salinity water was the greatest in the survey series.

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