WARNER: REPRODUCTIVE BIOLOGY OF PIMELOMETOPON PULCHRUM 



ing yolky oocytes. A thick cross-section of the 

 ovary was cut from near the middle of the lobe, 

 weighed, and then agitated to dislodge as many 

 oocytes as possible from the ovarian lamellae. 

 Oocytes remaining in the lamellae were teased out 

 so that a complete count could be made. An es- 

 timate of the number of yolky oocytes per gram of 

 ovary could then be made directly from the 

 sample. The total number of eggs in the ovary was 

 then approximated by multiplying by the total 

 weight of the ovary. 



Relative abundance of coloration types was es- 

 timated directly from field observations. To 

 eliminate the effects of any differential depth 

 distribution, visual transects were either run per- 

 pendicular to depth contours or were compiled 

 from a series of equal length runs parallel to suc- 

 cessive contours. Transects were approximately 50 

 m in length. The number of California sheephead 

 in each color phase was recorded. It was assumed 

 that both coloration types are equally visible, and 

 this is probably valid. California sheephead are not 

 secretive when adults; only juveniles tend to 

 remain close to cover. Larger males appear warier 

 than other individuals, but still remain in sight. 

 The problem in observing California sheephead is 

 not in avoidance, but inquisitiveness. Occasionally 

 transects had to be aborted because of the ten- 

 dency of Pimelometopon to follow the diver. 



RESULTS 

 Age and Growth 



Van Oosten (1929) set forth criteria for the ac- 

 ceptance of annuli on scales or bones as yearly 

 marks. These criteria apply equally well to spines, 

 and are as follows: (1) The spine must remain con- 

 stant in identity and grow proportionally with the 

 fish. (2) Only one mark must be formed each year. 

 (3) The body lengths calculated by using prior an- 

 nuli on the spine (back-calculated lengths) should 

 agree with the actual lengths of younger age 

 groups. 



The criteria will be discussed in order. 



(1) Dorsal spines were certainly constantly 

 identifiable in all individuals of P. pulchrum 

 examined. The relationship of spine radius to 

 standard length (Figure 1) is satisfactorily 

 expressed in a linear fashion (r = 0.787) and there 

 is no apparent indication of allometric growth of 

 the spine, at least for fishes of lengths greater 

 than 130 mm. Much of the scatter in the data is due 



to variability in the location of the cut made across 

 the tapering spine. 



(2) The increment of distance from the last an- 

 nulus to the outer edge of the spine should increase 

 with the time since the formation of that mark. If 

 one mark is formed each year at a particular time, 

 the average marginal increment should drop to 

 near zero at the time of annulus formation, then 

 steadily increase for the rest of the year. This 

 pattern is shown (Figure 2) for 77 California 

 sheephead from Catalina taken throughout the 

 year. Successive age groups did not differ in time 

 of annulus formation, so the data are combined for 

 all aged fish. The distinct hyaline bands appeared 

 to be formed in June and July, at the beginning of 

 the period of warming water in the Catalina area 

 (Quast 1968). Formation of growth marks has been 

 found to occur in other inshore California fishes 

 at a similar time (Joseph 1962; Norris 1963; Clarke 

 1970). Ring formation also overlaps with the ini- 

 tiation of reproductive activity, although egg 

 production and spawning continue well into Sep- 

 tember (see below). 



(3) Lengths of P. pulchrum at previous ages 

 were calculated by a modified direct-propor- 



O 6 12 18 24 30 36 



SPINE RADIUS (ocular micrometer units) 



Figure 1.— The relationship of dorsal spine radius to standard 

 length for 117 specimens of Pimelometopon pulchrum from Cat- 

 alina Island. One ocular micrometer unit equals 0.033 mm at 30 X . 



265 



