4-91 



mates of density would be higher for the 1/2 m net during spring peaks 

 and somewhat lower than CB-estimated densities when less than 1355/m 

 occurred according to both methods. The scatter plot showed that the 

 regression line was based on few erratically distributed points. 



Acartia tonsa was detected in lower densities by the 1/2 m net 

 than by the CB and had an equivalence point just less than midsxmimer 

 peak densities. Presence/absence differences between the methods were 

 peculiar, in that, when CB samples indicated densities greater than 

 5000/m , 1/2 m net samples generally indicated absence. The reverse 

 occurred at 1/2 m net densities below 400/m . Thus, CB samples produced 

 high estimates of peak abundance and low estimates at other times. This 

 scatter plot showed that a small number of poorly related points con- 

 tributed to the regression. 



Temora longicornis was captured twice as frequently by the 

 1/2 m net and was only caught by both methods on 15 occasions, clearly 

 showing that the CB net was relatively ineffective for this species. 

 The equivalence point was above most peaks of abundance, so that, when 

 captured by the CB net, this method gave the higher density estimate. 

 However, because of the paucity and scatter of points, there is little 

 reason to have faith in the regression equation. 



Copepod copepodites were more effectively sampled by the 1/2 m 

 net, as shown by capture frequency and detection threshold. Also, at 

 densities below 2251/m the CB net gave higher density estimates than 

 the 1/2 m net; such densities were exceeded only during major spring or 

 fall abundance peaks as measured by the CB net . Although some evidence 

 of linearity was apparent in the scatter-plot, many of the points 

 plotted were nearly an order of magnitude removed from the regression line. 



Copepod nauplii were sampled similarly by the two methods in 

 terms of detection thresholds; presence/absence disagreements were few 

 The equivalence point was exceptionally high, near the absolute peak of 

 abundance, and was rarely exceeded by the CB net and never by the 1/2 m net. 

 Scatter was substantial and the plot showed no real linear tendency. 



Cirripedia nauplii were more frequently captured by the 1/2 m 

 net than by the CB net (Table 4-4) ; this was attributable to the numerous 

 catches by the 1/2 m net at densities below the threshold of detection 

 for the CB net. As with copepod nauplii, the equivalence point was 

 high (11,427/m ) and corresponded to sporadic and infrequent abundance 

 peaks. While scatter was great, a distinct linear tendency was apparent. 



Gastropod veligers were captured far more frequently and 

 effectively by the 1/2 m net; on 26 occasions low densities were indicated 

 by the 1/2 m net which were undetected by the high- threshold CB method. 

 Gastropod larvae were rarely more dense than the equivalence value of 

 2023/m , and were thus estiamted as more abundant (when captured) by 

 the CB net. Linearity was not apparent in the scatter-plot. 



Polychaete larvae were fairly effectively sampled by both 

 methods, although both indicated absence a nimber of times when contradicted 



