THE RELATIONSHIP BETWEEN GULF-STREAM POSITION AND COPEPOD ABUNDANCE DERIVED FROM THE CONTINUOUS PLANKTON RECORDER SURVEY - SEPARATING BIOLOGICAL SIGNAL FROM SAMPLING NOISE

The mean annual abundance of copepods was calculated from Continuous P lankton Recorder records for the period 1966-1992, and for an area to the north of the UK bounded by latitudes 58-64-degrees-N and longitude s 3-degrees-E and 21-degrees-W. Spatial heterogeneity of copepod abund ance, when combined with changing tow routes, introduced considerable noise as well as an artifactual increasing trend in copepod abundunce into the time series. We therefore defined a more homogeneous subarea spanning approximately 270 km either side of the shelf edge between la titudes 59 and 61-degrees-N, within which the noise introduced by chan ging tow routes was considerably less. There was a significant (P < 0. 01) positive linear relationship between the annual copepod abundance for this small homogeneous subarea and the annual Gulf Stream position between longitudes 79 and 65-degrees-W. The copepod abundances for th e last 4 years of the time series (1989-1992) were, however, significa ntly (P < 0.01) lower than those predicted from the Gulf Stream positi on in these years. Evidence suggests that the anomaly of these years w as not an artifact caused by poor sampling or changing tow speeds.