NOTE Laidig and Ralston: Use of otolith characters in identifying larval Sebastes spp. 



169 



goodei and S. paucispinis were correctly clas- 

 sified, whereas the remaining species showed 

 lower accuracy varying from 56 to 68%. 



Discussion 



Otolith characteristics have been shown 

 to vary among species and among stocks. 

 Rybock et al. (1975) and Postuma (1974) 

 used nuclear dimensions to identify differ- 

 ent fish stocks. McKern et al. (1974) used 

 otolith dimensions to separate seasonal 

 stocks of steelhead trout, and Victor ( 1987) 

 used otolith dimensions to separate differ- 

 ent species of pomacentrids and labrids. 

 Postuma (1974) related otolith opacity to 

 nuclear size and compared this relationship between 

 stocks. Messieh (1972) used otolith shape to distin- 

 guish among stocks of herring. Hecht and Appelbaum 

 (1982) and Gago (1993) also used otolith shape to 

 distinguish between species. 



We have found that otolith characteristics can effec- 

 tively distinguish certain species of Sebastes. Four of 

 the species examined, S. jordani, S. goodei, S. auri- 



Figure 2 



Annual variation in average nuclear radius and first 

 increment width for the six species of Sebastes that 

 had multiple year observations, ent = S. entomelas. 

 fla = S. flavidus, goo = S. goodei, jor = S. jordani. 

 mys = S. mystinus, and pau = S. paucispinis. 



culatus, and S. mystinus, had significantly different 

 nuclear radii from each other and from the other spe- 

 cies examined. Sebastes jordani, S. goodei, S. pauci- 

 spinis, and S. flavidus each had unique shading pat- 

 terns that may help in species identifications. Sebastes 

 jordani and S. paucispinis were correctly classified over 

 90% of the time in the blind test, displaying the useful- 

 ness of otolith characteristics for identification. 



The specificity of otolith characters gives research- 

 ers an opportunity to separate larvae using these 

 characters alone. Without otolith data, the separa- 

 tion of S. mystinus larvae from other rockfish larvae 

 is difficult. Although larval S. jordani are relatively 

 easy to identify on the basis of pigmentation (Moser 

 et al., 1977), identifications can be confirmed with a 

 few additional otolith measurements. 



We suggest from these findings that the difficult 

 task of identifying rockfish larvae can be facilitated 

 in some cases by employing otolith characters in com- 

 bination with more traditional traits like pigmenta- 

 tion. Of the eight species examined, six species (S. 

 auriculatus, S. flavidus, S. goodei, S. jordani, S. 

 mystinus, and S. paucispinis) had distinctive otolith 

 characters that allowed separation from other spe- 

 cies. Many of the larval stages of the more than 60 

 species of rockfish found in the northeast Pacific Ocean 

 are very similar, and pigmentation alone cannot always 

 reliably separate species. Otolith character examina- 

 tion may be one further method that can aid research- 

 ers in accurately identifying species in this group. 



Acknowledgments 



We would like to thank the crew of the RV David 

 Starr Jordon and all the scientists who participated 

 in the collection of samples. We also thank all of the 

 reviewers for their informative comments. 



