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4. Acoustic Surveys 



Surveys conducted with sophisticated electronic fish-finding and 

 sonar equipment hold great potential value for the future. Existing 

 sounding techniques can spot and track schools of pelagic fish, determine 

 the bottom type and configuration, and frequently can spot groundfish in 

 the waters close to the bottom. 



Advantage : Such surveys, charted continuously, deliver a continual 

 visual record of the survey vessel^ passage, are relatively cheap (once 

 the equipment is purchased), and in some cases, particularly for schooling 

 species, provide rough estimates of the size of the observed school. 



Disadvantage : Acoustics are difficult to interpret, require fine 

 tuning, do not appear suitable for biomass or stock abundance* estimates, 

 are not species selective, and are only useful, in any case, for the 

 area immediately beneath the transducer--i .e. , results will depend upon 

 the course of the research vessel. 



5. Oceanoqraphic Conditions 



Various methods have been developed to provide data on ocean tempera- 

 ture, salinity, currents, dissolved materials, and the geological charac- 

 teristics of the bottom. 



Advantage : The gathering of this data is relatively precise. 



Disadvantage : Like all surveys, but particularly for this one, the 

 data is often based on a single observation taken at several areas or 

 several observations taken over time at the same area. Neither case 

 gives a consistent record of oceanographic conditions, which are in 



