0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0 16.0 18.0 20.0 22.0 



0^1 iih Length - mm 



Figure l. — Scatter diagram and regression lines and equations 

 of otolith length against fish fork length for Theragra 

 chalcogramma . 



mixed collections of otoliths, the cumulative im- 

 portance of these differences should be minimal. 

 The relationships between fish lengths and 

 weights of the three species were best fit by expo- 

 nential equations of the form: weight = a (length)" 

 (Table 3). These relationships may vary somewhat 

 with time of year, geographic location, sex, repro- 

 ductive status, or fullness of stomach. Variation is 

 probably most pronounced in sexually mature in- 

 dividuals with mature reproductive products, a 

 condition which persists for only a few months of 

 the year. Since small (juvenile) fishes are eaten by 

 most marine mammals (Frost and Lowry 1980), 

 birds (Hunt et al. in press), and other fishes 



IS 



m 





f>CD 



Otoliths > 8. 5 mm 



Y = 2.323X-4.839 

 N = 110 

 R = 0. 963 



Otoliths 5. 8. 5 mm 



Y = 1.740X-0.090 

 N = 36 

 R = 0.932 



2.0 4.0 6.0 8.0 10.0 



Otolith Length - i 



12.0 



14.0 



16.0 



Figure 2. — Scatter diagram and regression lines and equations 

 of otolith length against fish fork length (or Eleginus gracilis. 



(Frost and Lowry unpubl. data), this is probably a 

 small source of error. Significant differences in 

 weight-at-length by sex and geographic area were 

 found for Arctic and saffron cods by Wolotira et al.^ 

 but they justified use of a single regression equa- 

 tion since the differences were small (3-7%). Simi- 

 lar differences have been noted for walleye pollock 

 (BakkalaandSmith^). 



Otoliths are valuable indicators of the diet of 

 piscivorous marine consumers. Published keys 

 such as Morrow (1979) allow determination of the 

 species and numbers of fishes represented by 

 otoliths in stomachs, intestines, or scats. By using 

 the relationships between otolith size and body 



Table 3. — Length-weight relationships observed for walleye 

 pollock, saffron cod, smd Arctic cod in the Bering, Chukchi, and 



^Wolotira, R. J., Jr. 1977. Demersal fish and shellfish re- 

 sources of Norton Sound, the southeastern Chukchi Sea and 

 adjacent waters in the baseline year 1976. Processed rep., 292 

 p. Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Boulevard E., Seattle, 

 WA 98112. 



^Bakkala, R. G., and G. B. Smith. 1978. Demersal fish re- 

 sources of the eastern Bering Sea: Spring 1976. Processed rep., 

 233 p. Northwest and Alaska Fisheries Center, National Marine 

 Fisheries Service, NOAA, 2725 Montlake Boulevard E., Seattle, 

 WA 98112. 



190 



