444 



Fishery Bulletin 105<3) 



seasons and regions would be needed to precisely con- 

 vert the displacement volumes measured for the two 

 tow speeds. 



For projects focusing on zooplankton studies, there 

 may be a need to consider the higher tow speed as the 

 preferred sampling procedure. The escape reaction of 

 the dominant species to the approaching net or loss of 

 dominant species by extrusion through the net does 

 not appear to change substantially between 1.5 and 

 3.5 knots. At higher tow speeds cleaner samples are 

 collected — samples that are easier to process because 

 more phytoplankton and detritus are extruded from 

 the nets. Although the slower speed has been found to 

 be less damaging to ichthyoplankton specimens (Colton 

 et al., 1980), the condition of the zooplankton speci- 

 mens captured at the two tow speeds in this study was 

 similar. 



This study demonstrates that mean and median 

 counts of common zooplankton taxa collected during 

 3.5-knot bongo tows are not significantly different from 

 those collected during 1.5-knot tows. On the basis of 

 these findings, we feel that zooplankton data collected 

 at these two tow speeds can be used to compare or ex- 

 tend time series data at the regional level. 



Acknowledgments 



The authors are grateful to the Narragansett laboratory 

 facility support staff that restored the vfin depressor to 

 its original specifications. 



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