8. OPERATIONAL ASPECTS OF OCEANOGRAPHIC 



INSTRUMENTATION 



PART III. FOR THE BUREAU OF COMMERCIAL FISHERIES 



(BIOLOGICAL) 



Vernon E. Brock 



Bureau of Commercial Fisheries 

 Washington, D. C. 



The instrumentation requirements for the investigation and 

 charting of the biological parameters are less easily defined than 

 the physical and chemical ones. The measurement of biological 

 parameters are of lower accuracy and the things measured are 

 frequently connplex, making measurements difficult to compare 

 and to define accurately. 



The measurements that physical and chemical oceanographer s 

 take have value for their own sake; these measurements can be em- 

 ployed very usefully without reference to the biological parameters. 

 Measurements of biological features are of less value and are more 

 difficult to interpret if taken alone; they are most useful when they 

 are taken in conjunction with physical measurements. 



Biological measurements should be quantitative and reproduce - 

 able. It should be possible to define precisely the quantity mea- 

 sured. This is easier said than done. In figure 8. 3 was a PLANK- 

 TON SAMPLER, a device to collect organisms from the sea. This 

 was a towed conical net. The catch of organisms can be estimated 

 in a variety of ways, such as by volume, weight, or species com- 

 position. However, the character and volume of catch may" be dif- 

 ferent in various places and it is often quite a problem to determine 

 what these differences reallv mean. The problem of the qualita- 

 tive differences may be attacked by considering perhaps the quan- 

 tity of bound nitrogen in the catch as a measure of protein, but 

 even here the differences in average sizes of the organisms in 

 various parts of the ocean may occasionally introduce an unknown 

 error in the results. In addition, even the simple matter of 

 estimating how big a change in the catch can be considered as 

 representing a significant change in the density of organisms in 



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