NSWC/WOL TR 76-155 



4.3 TOTAL FISH-KILL AND ITS SPATIAL DISTRIBUTION 



In this section we calculate the total fish-kill from an 

 underwater explosion and its distribution as a function of horizontal 

 range and depth, assuming a uniform spatial distribution of a single 

 size class of one species of fish. 



Table 4.3.1 (top) lists the bladder oscillation parameter Z 

 for 21.5 cm White Perch calculated over a cylindrical grid surround- 

 ing a 32 kilogram charge fired at 9 meter depth. Table 4.3.1 

 (bottom) lists the corresponding kill probabilities from Equation 

 3.2.1. 



To calculate the fish-kill we must know which fish are 

 where; and, in general, this is impossible. Nevertheless, to gain 

 insight as to the potential of a given explosion geometry for killing 

 fish it is useful to assume a fictitious fish density distribution. 

 For this purpose we will assume a nominal uniform density distribution 

 of 1 fish per thousand cubic meters of water. 



To calculate the fish-kill we must integrate the product, 

 fish density x kill probability, over the region surrounding the 

 explosion. Thus, for this example we compute the products of "fish 

 present" and "kill probability" (Tables 4.3.2 and 4.3.1) to get the 

 "fish killed" in each mesh volume, Table 4.3.2 (bottom) — each mesh 

 consisting of a cylindrical annulus 10 feet thick and 5 feet in depth. 

 Summing the distribution of "fish killed" shown at the bottom of 

 Table 4.3.2 results in a total kill of 1245 fish out of 6228 fish 

 present. Note that we have neglected 200 fish present in the 150-ft 

 radius cylinder of water containing the charge as well as all fish 

 present beyond a horizontal range of 850 feet. Nevertheless, we 

 have described the most significant portion of the distribution of 

 fish killed by this underwater explosion. 



It is apparent, for example that if fish were present only 

 at depths greater than 70 or 80 feet relatively few fish would be 

 killed. Likewise, if fish (of this particular size) were present 

 only within some 10 feet of the surface the kill would be relatively 



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