Table 7.— Numbers removed (yields) for each did and exploitation rale; ex ptoilalion rates are indicated in parentheses 



' Removals omitted because of accidental mortalities in week 36. 



• Removals by error; added to week 43 removals in subsequent treatment. 



■^ Includes accidental mortality. 



' Omitted because of erroneous removals in week 43. 



' Accidental mortality considered to replace removals due in week 58. ' 



15 20 25 



BIOMASS (G) 



Frc.DRE 9. — Cun,es indic.iting relation of yield per 3-\vfck 

 1)1-00(1 interval to bioinass and exploitation rate (indi- 

 cated percentages) at each diet level. Points indicated 

 for percent exploitation rate arc average population 

 level.s for th<' 3 weeks immediately before exploitation. 



near the 0.33 exploitation rate (assuming that 

 the (different e.xploitation-jiehl rehuion at tlie 0.5 

 (diet was due to ran(iom variation rather than a 

 real difference in the relation). Tf the apparent 

 independence of the exploitation-Aaeld relation 

 from food level reflects what happens in commer- 

 cially fi.shed popidations, the findins: is si<];nificant 

 to fishery administration. Such independence 

 would mean that the same manapjement strategy 

 might be apj)lied when food organisms are scarce 

 as when they are abundant. 



From llic viewpiiinl of ihc rdiniiiercial (isher- 

 man, an exploited ixipulatioii is a nuKthinc for 

 converting aquatic food to niarke,lal)lc fish flesh. 

 It is of interest to see Imw ('ffi<'.iently our rniidcl of 

 tlie niacliino operateil at each food le\el. Maxima 

 of the yield curves (fig. 9) indicate yields ])er 3 

 weeks of abinil 2.4, 3.9, and 5.S g. at the O.r), 1.0, 



436 



U.S. FISH AND WILDLIFE SERVICE 



