196 



Fishery Bulletin 94(1). 1996 



May 



Apr 



Feb " 



1983 1984 1985 1987 



Figure 3 



Month of minimum sea-surface temperatures in Washington and Cali- 

 fornia from 1983-85. Source: Pacific Fisheries Environmental Group. 

 National Marine Fisheries Service, P.O. Box 831, Monterey, California 

 93942, unpubl. data, January 1984. 



Reproduction is unlikely to play a significant role 

 in the time of hyaline-zone formation. The only dif- 

 ference among the sexes in timing of hyaline-zone 

 formation occurred in March. In that month it ap- 

 peared that females were more likely to have either 

 wide or narrow opaque zones. It should be noted, 

 however, that 81% of the females had hyaline zones 

 (88% of males had hyaline zones). Males expend en- 

 ergy on spermatogenesis from October through Janu- 

 ary, whereas females expend most of their energy on 

 reproduction later, with parturition in February 

 (Wyllie Echeverria, 1987). 



In some studies, maturity has been shown to be 

 related to the time of annulus formation (Chugonova, 

 1931; Konstantinova, 1958). Although maturity was 

 not recorded, about half of the fish from both areas 

 in this study should have been sexually mature on 

 the basis of maturity-at-length relationships (Barss 

 and Wyllie Echeverria, 1987). If immature fish had 

 failed to lay down a hyaline zone, the differences 

 should have been evident in Figure 2; that is to say, 

 a large fraction of the fish would show no hyaline- 

 zone at any time of the year. If the timing of hyaline- 

 zone formation had been markedly different between 

 mature and immature fish, this would have been 

 reflected as a second mode in the month of hyaline- 

 zone formation. 



Several different methods of marginal increment 

 analysis have been used to validate ages. Beckman 

 et al. (1991) used four edge types in a classification 

 designed to characterize more precisely when the 

 hyaline zone is formed. Many researchers have mea- 

 sured the width of the edge (Nelson and Manooch, 

 1982; Barger, 1985; Maceina et al., 1987; Manooch 



and Drennon, 1987; Bullock et al., 1992; Hyndes et 

 al., 1992; Hostetter and Munroe, 1993). The mea- 

 surement approach has an advantage in that it 

 should be possible to plot growth of the edge over 

 time to verify that only a single hyaline mark is laid 

 down each year. However, in some species, it can be 

 difficult to determine a consistent location to mea- 

 sure on the otolith because of the inherent variabil- 

 ity of their otoliths. In addition, a great deal of time 

 is required to process the otoliths. The classification 

 of edge types into three or more categories is one way 

 to qualitatively judge the width of the edge (usually 

 relative to the preceding opaque zone). This approach 

 has an advantage over simply classifying the edges 

 as either hyaline or opaque in that it indicates 

 whether the opaque zone has just formed or whether 

 a new hyaline zone may be ready to form. 



Acknowledgments 



I express my sincere appreciation to Sandra 

 Rosenfield of the Washington Department of Fisher- 

 ies for providing the otoliths from Washington used 

 in this study. I also express my gratitude to Kenneth 

 Baltz, NOAA Corps officer (Southwest Fisheries Sci- 

 ence Center), who provided access to the sea-surface 

 temperature data from the Pacific Fisheries Envi- 

 ronmental Group, Monterey, California. Craig 

 Kastelle (Alaska Fisheries Science Center), Daniel 

 Kimura (Alaska Fisheries Science Center), Stephen 

 Ralston (Southwest Fisheries Science Center), and 

 Jean Rogers (Southwest Fisheries Science Center), 

 provided valuable help by reviewing early drafts of 



