areas shown on charts as having soft mud 

 bottom. When the echo sounder indicated that 

 the bottom was level enough to permit trawl- 

 ing, the net was fished. Considerable gear 

 damage often resulted, for the echo sounder 

 recording did not always enable us to interpret 

 the bottom type correctly. During more recent 

 cruises the use of a high-resolution, low- 

 frequency echo sounder provided better defi- 

 nition of bottom configuration and type, thus 

 reducing gear damage and destruction (Hitz, 

 Johnson, and Pruter, 1961). In most instances 

 exploratory drags were 30 minutes long. 



Known commercial shrimp grounds were 

 not fished except when it was necessary to 

 establish that the gear was functioning prop- 

 erly. 



ANALYSIS OF DATA 



To facilitate discussion, the region investi- 

 gated has been divided into four areas as 

 follows: Oregon and Washington, Southeastern 

 Alaska, central Alaska, and the Alaskan 

 Peninsula. The data were analyzed to deter- 

 mine the average catch per unit of effort by 

 areas and by 10-fathom depth intervals within 

 the areas. The depth of each haul was resolved 

 as the median between the deepest and shal- 

 lowest depths recorded for the particular 

 fishing effort. Although in a few hauls the 

 depth range varied considerably, the average 

 depth variability per drag was approximately 

 6 fathoms. Yield rates reported here are 

 based on 30-minute drags. All drags of more 

 or less than 30 minutes have been equated to 

 30 minutes. As data are not available to 

 calculate the difference in catch efficiency 

 between the beam trawl and Gulf shrimp 

 trawl, results obtained with each type of 

 trawl are discussed separately. 



Since the exploratory fishing surveys were 

 not conducted with the objective of assessing 

 total population sizes, and the explorations 

 extended over 10 years, general conclusions 

 on interarea abundance must be considered 

 relative and perhaps more indicative of avail- 

 ability than of true abundance. Interarea com- 

 parisons were based on average catches after 



those hauls containing less than 1 pound of 

 shrimp had been removed. The data have 

 been examined to determine the species com- 

 plexes present and other pertinent information 

 on the resources within the areas. 



Changes in environmental factors affecting 

 shrimp survival may have influenced interyear 

 or interarea abundance of the species investi- 

 gated through the decade during which explora- 

 tions were conducted. As no measures of .the 

 factors are available, it is impossible to 

 estimate what effect they may have had on 

 the shrimp populations. The relative abundance 

 is discussed only as it was found during the 

 explorations. 



It is necessary to assume that the fishing 

 gear gave an accurate estimate of the avail- 

 ability of the species present. As large pro- 

 duction is not the purpose of exploratory 

 fishing, no efforts were made to restrict 

 fishing only to areas where higher catches 

 occurred. The primary purpose was to sample 

 all grounds on which shrimp gear could be 

 operated. 



To avoid confusion of names, the common 

 and scientific names of the species discussed 

 and the geographic range over which they 

 were collected are given (table 2). 



The average number and range in number 

 of whole shrimp per pound per area are given 

 in table 3. 



INTRA-AREA DISTRIBUTION AND 

 RELATIVE ABUNDANCE 



Washington-Oregon 



In 1955-60, seven exploratory cruises were 

 made in waters adjacent to Oregon and Wash- 

 ington. These explorations covered the general 

 area offshore from the Coquille River in 

 Oregon to Cape Beale, Vancouver Island, and 

 the Strait of Juan de Fuca. Sampling was 

 conducted at depths ranging from 20 to 275 

 fathoms. 



