LOVE and WESTPHAL: GROWTH AND FOOD HABITS OF OLIVE ROCKFISH 



Figure 5. — Length- weight relation- 

 ship based on 312 male olive rockfish 

 sampled off Diablo Cove. 1972-77. 



15.0 



are very rare in California waters (the "hybrids" 

 mentioned by Phillips (1964) are now recognized 

 as distinct species), indicating that other anti- 

 hybridization mechanisms are involved. 



Though it is possible that extensive cross- 

 specific mating occurs, and gametic or zygotic 

 mortality prevents hybridization, it seems more 

 likely that internal fertilization, necessitating 

 close coordinated contact, has lent itself as a mech- 

 anism of mechanical and/or behavioral isolation. 

 The copulatory organs of male S. serranoides 

 are relatively small, thus a degree of closely 

 coordinated movements is probably necessary to 

 effect mating. Auditory, visual, and chemical cues 

 may all play a part. It is known, for instance, that 

 some rockfish species produce sounds (Hallacher 

 1974) and these may be used in species recogni- 

 tion. Deeper water species, living in relative 

 darkness, may depend primarily on nonvisual 

 recognition during mating season. 



Size and Age at Maturity 



It was often difficult to distinguish prereproduc- 

 tive female olive rockfish from mature late resting 



20.0 



25.0 



30.0 35.0 



TOTAL LENGTH ICMI 



400 



45X) 



SOO 



stage females (as noted by Westrheim 1975 and 

 Gunderson 1977 in S. alutus). Females develop 

 small orange ovaries 1 or 2 yr before they repro- 

 duce. During much of the year these "maturing" 

 fish were easily distinguished from reproduc- 

 tive individuals by their consistently small, pale 

 orange ovaries. However, during late spring and 

 early summer, the ovaries of both reproductive 

 and maturing fish are small and orange. Because 

 mature and maturing females were not readily 

 differentiated during late spring and early sum- 

 mer, females captured during this period were 

 not included in this analysis. 



There was considerable variation in size and 

 age at first maturity (Figures 8, 9). A few fish were 

 mature at 3 yr old (males 28.1-32.5 cm TL, females 

 31.1-33.6 cm TL). Yet not all males were mature 

 before 7 yr and 39.0 cm TL, nor females before 8 yr 

 and 37.0 cm TL. Over SO'^c of the females had 

 spawned by 4 yr and 34.0 cm TL, while males were 

 age 5 and 32.0 cm TL before reaching the 50% 

 mark. In general, males first matured at a some- 

 what smaller size and somewhat later age than 

 females. 



Limbaugh (1955) reported that, off southern 



539 



