JOHNSON and HORTON: RATFISH, ASPECTS OF BIOLOGY 



D 



Figure 4. — Regions of mature ratfish showing (A) the frontal tenaculum, (B) the prepelvic te- 

 nacula, and (C) the claspers, of the male; and (D) the absence of a frontal tenaculum, and (E) 

 the presence of well-developed openings to the oviducts of the female. 



In general, there was an increase in the size 

 of other body parts (teeth, vertebrae, base of left 

 pectoral fin, and base of dorsal spine) with in- 

 creasing body length. We did not find any lay- 

 ering or structures in these body parts which 

 were sufficiently correlated with body length to 

 provide a possible means of age determination. 



The number of tritors (horizontal ridges) on 

 the posterior side of the left vomerine dental 

 plate was compared to the respective body length 

 of male and female ratfish in the Cape Blanco 

 and Newport collections. In general, the num- 

 ber of tritors increased with increasing body 

 length (Figure 6) . Two problems arose in using 

 this structure as a basis for age determination: 

 (1) No comparison to known-aged fish was pos- 



sible. (2) The amount of wear on these ridges 

 per unit of time was not known. 



ACKNOWLEDGMENTS 



Drs. C. E. Bond, R. E. Millemann, R. C. Simon, 

 and J. D. Hall, Department of Fisheries and 

 Wildlife, Oregon State University, provided 

 counsel and reviewed the manuscript. Dr. W. S. 

 Overton, Department of Statistics, Oregon State 

 University, provided direction in the statistical 

 analyses. Special thanks are due personnel of 

 the Fish Commission of Oregon for assistance 

 in obtaining ratfish for this study. James Mee- 

 han and Gary Milburn were particularly helpful. 



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