RESEARCH SUMMARY 



This report describes a new multiprobe freeze method for 

 determining salmonid redd sediment particle size distribution. 

 This method will collect salmonid eggs and alevins in the redd at 

 any stage of development, any air or water temperature, any stream 

 depth, and determine their horizontal and vertical location. This 

 method allows larger size samples to be collected which can help 

 improve our understanding of embryo and alevin survival rates and 

 causes of their mortality. 



This substrate freeze method differs from the past freeze 

 methods that expanded CO2 liquid to atmospheric pressure. This 

 method expands CO2 to a pressure of 78 psia (a boiling liquid - gas 

 medium) which provides a higher heat transfer because of the better 

 control of gas use, higher cooling efficiency, and fewer clogging 

 problems. A field test is described where the ratio of CO2 consumed 

 to redd materials lifted was 0.34 lb CO2 per 1 lb of redd material. 

 A complete step-by-step description of the methodology is given 

 with a listing of parts, materials, and suppliers. 



The use of trade, firm, or corporation names in this publication is 

 for the information and convenience of the reader. Such use does not 

 constitute an official endorsement or approval by the U.S. Depart- 

 ment of Agriculture of any product or service to the exclusion of 

 others which may be suitable. 



