it was the maximum distance that could be covered at N2 and JC. Addi- 

 tionally, this was approximately the distance covered in 15 minutes when 

 the boat was hauling a trawl net with the engine at idle speed and no 

 influence of tidal current. These changes in methodology have been 

 summarized in Table 1. 



Fish in each haul were identified to lowest practical taxon, counted, 

 and measured (total length) to the nearest mm. 



Analytical Methods 



Several methods were used to analyse the demersal data. Preliminary 

 data reduction provided such summary statistics as the percent species 

 composition, and total and species catch per unit effort. These statistics 

 were scrutinized and those data collected since October 1977 were used 

 to characterize the trawl data. Subsequently, various methodologies 

 were used to determine if any changes had occurred in these descriptive 

 statistics. Included were tests for determining the underlying probability 

 distribution of the data, analyses of variance, time-series analyses, 

 and the Krumbein and Tukey (1956) method of analyzing proportions. 



Historically, the trawl data were used to estimate catch per unit 

 effort (CPUE) based on a 15min tow. So that the longest possible series 

 of data could be established, catches in a region and sampling period 

 were summed and divided by the sum of the total time spent trawling. 

 This number was then multiplied by 15 to give CPUE (NUSCo 1982). However, 

 for the data collected since October 1977 (when the actual unit-effort 

 was changed from a time basis to a distance basis) these data manipulations 

 may have contributed undesirable variance to the catch statistics. Thus 

 the first aspect to be investigated was the effect of changing from time 



