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Fishery Bulletin 91(4). 1993 



(Dobzhansky and Wallace, 1953; Lerner, 1954; 

 Lewontin, 1956; Bader, 1965; Bruckner, 1976; Soule, 

 1979; Vrijenhoek and Lerman, 1982; Leary et al, 1983, 

 1984; Mitton and Grant, 1984). Increased homozygos- 

 ity is one consequence of inbreeding (one form of ge- 

 nomic disruption). Within populations of outcrossing 

 species, inbreeding is associated with lowered fitness 

 (Lewontin, 1956; Charlesworth and Charlesworth, 

 1987). Bader (1965), Bailit et al. (1970), and Clarke 

 ( 1992 ) have all found positive correlations among popu- 

 lations between inbreeding and FA. 



The converse of inbreeding depression is outbreed- 

 ing depression. Hybridization and subsequent intro- 

 gression of sufficiently different populations can lead 

 to the disruption of coadapted gene complexes and thus, 

 in theory, promote both decreased fitness and develop- 

 mental instability (Vrijenhoek and Lerman, 1982). 

 Zakharov and Bakulina (1984) found that when indi- 

 viduals of similar populations ofDrosophila virilis were 

 crossed, no increases in FA over the parental types 

 were observed. When more divergent strains were 

 crossbred, FA was pronounced in the offspring. Out- 

 breeding depression should be most apparent in inter- 

 specific hybrids. Leary et al. (1985) have found FA to 

 be higher in laboratory hybrids of rainbow (On- 

 corhynchus my kiss) and cutthroat (0. elarki) trout than 

 in either parental type. 



Environmental disturbance, or deviation from the 

 conditions to which organisms are adapted, leads to 

 lowered fitness and developmental instability. Tempera- 

 ture stress causes increased FA in laboratory mice and 

 rats (Beardmore, 1960; Siegel and Doyle, 1975, a and 

 b; Siegel et al., 1977), in lizards (genus Lacerta, 

 Zakharov 1982), and in chum salmon (O. keta, Beacham 

 1990). Audiogenic stress has the same effect on labora- 

 tory rats (Siegel and Smookler, 1973; Siegel and Doyle, 

 1975c). Valentine and Soule (1973) demonstrated that 

 FA of laboratory grunion {Leuresthes tenuis) popula- 

 tions rose with concentrations of DDT. Clarke (1992) 

 showed increased FA in pesticide-treated bush flies 

 iMusca vetustissima) even at concentrations too low to 

 produce statistically detectable changes in mortality. 

 Zakharov and Rubin (1985) demonstrated the effects 

 of contamination on FA in animals in the Baltic Sea. 

 Thus FA may be an extremely sensitive indicator of 

 stress. 



Chronic stress indicators may be sensitive to natu- 

 rally occurring events as well as anthropogenic distur- 

 bances. Zakharov et al. ( 1991 ), for example, found that 

 intensified population density feedback led to increased 

 FA during the decline phase of shrew population cycles. 

 Data exist (Emlen, unpubl.) suggesting increased asym- 

 metry occurs in the canine teeth of population-stressed 

 northern fur seals. Clearly, if natural stressors are 

 important contributors to developmental instability. 



then their effects must be considered when using DI 

 as a tool for identifying or monitoring anthropogenic 

 disturbances. In this paper we provide an example of 

 FA responses to another natural stressor, the El Nino 

 event of 1982-1983. 



The Pacific hake (Merluceius produetus) ranges along 

 the Pacific coast of North America from Mexico to 

 Alaska. Several genetic stocks can be distinguished. 

 These include two spawning in Puget Sound, one from 

 the Georges Straits, several from the fjords of Van- 

 couver Island, and a so-called coastal population that 

 ranges from San Francisco Bay to southern Baja Cali- 

 fornia. Reproduction occurs from January to April, and 

 young fish enter the fishery at about age three. In- 

 dividual growth occurs largely between May and 

 September. 



Environmental conditions associated with the 1982- 

 1983 El Nino may have caused significant dislocations 

 of the coastal hake stock on the summer fishing 

 grounds, since the entire population apparently moved 

 northward (Francis and Hollowed, 1985). Length and 

 weight information from the data set used by Francis 

 and Hollowed and gathered by the National Marine 

 Fisheries Service showed no significant differences be- 

 tween the 1980 and 1984 year classes for either sex. 

 However, the 1980 El Nino year-class fish were slightly 

 longer and lower in weight, and a Mann-Whitney test 

 showed them to have significantly lower condition fac- 

 tor (weight/length 1 ) than the 1984 control year-class 

 (respective means=0. 06709, 0.07208; rc=85, 63; 

 P=0.0001). Both the dislocation in position and the 

 diminished condition factor of population members sug- 

 gest a drop in population viability and, thereby, impli- 

 cate stress. Might this stress also have provoked de- 

 velopmental instability? 



Methods 



The development of otoliths, small calcareous struc- 

 tures used in maintaining balance in some fishes, is 

 known to reflect growth rate and transition points in 

 life histories (Wilson and Larkin, 1982; Volk et al., 

 1984; Alhossaini and Pitcher, 1988; Sogard, 1991). As 

 such, they may be useful indicators of developmental 

 instability. We do not suggest that otoliths fit the cri- 

 teria given above for cost effectiveness and harmless- 

 ness to the organisms monitored. We use them here 

 simply as a convenience (they were readily available 

 and came with appropriate, attendant data on fish age, 

 length, weight, and date of collection). The National 

 Marine Fisheries Service, at its Alaska center in Se- 

 attle, maintains a collection of otoliths taken by scien- 

 tific observers aboard commercial hake fishery boats. 

 From this collection we obtained paired right and left 



