592 



Fishery Bulletin 91(4). 1993 



canalized traits are unlikely to be sensitive indica- 

 tors of stress. High phenotypic variance can gen- 

 erally be considered an indication of low canaliza- 

 tion, and Zakharov ( 1989) has shown that, at least 

 for Lacerta lizards, FA rises with phenotypic vari- 

 ability (see also Soule, 1967). 



A related observation is that traits directly and 

 strongly affecting fitness, i.e., under intense stabi- 

 lizing selection and, therefore, with low heritabil- 

 ity, should be poor candidates for detecting stress 

 (Soule and Cuzin-Roudy, 1982). Similarly, struc- 

 tures whose development is affected by use may 

 not be appropriate for FA analysis. Locomotion, 

 for example, might discourage asymmetric growth 

 of limb size. Long-bone length in laboratory rats 

 shows no FA response to heat, cold, behavioral, or 

 audiogenic stress, while long-bone density, not a 

 size characteristic, does (Doyle et al., 1977). 



In choosing measures of developmental instabil- 

 ity, it may be useful to consider structural detail. 

 With respect to otoliths, weight, length, width, and 

 growth rate represent growth along a single di- 

 mension. These metrics, then, are a simple sum- 

 mation of one or more growth processes. Shape, on 

 the other hand, reflects growth processes whose 

 parts are separably measurable. Thus, shape does 

 not compound and thereby obscure information. 

 We might, accordingly, expect to find differences 

 in the shapes of corresponding right and left struc- 

 tures to be more sensitive indicators of stress than 

 simple metric differences, a prediction consistent 

 with the hake otolith results presented here. 



Do natural environmental stressors, as well as 

 man-caused disturbances, result in developmental 

 instability? The results reported here suggest an 

 affirmative answer, namely that while DI might 

 be usefully applied in management, it must be 

 used with caution. Use of fin asymmetries or scale 

 circulus aberrations in comparing hatchery stocks 

 for smolt quality, for example, should involve only 

 a single year class and should be given decreasing 

 consideration as stocks diverge genetically or geo- 



graphically. Suspected problems arising from water con- 

 tamination in Puget Sound might be investigated or moni- 

 tored by examining FA, but only so long as the control 

 population comes also from Puget Sound. 



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