FISHERY BULLETIN: VOL. 77. NO 4 



rates between host groups within a species can 

 indicate reduced movement offish between popu- 

 lations (Kabata 1963). Twenty olive rockfish from 

 each of six sites ( Naples Reef, Ellwood Pier, Horse- 

 shoe Reef, 4 Mile Reef, and oil platforms Houchin 

 and Hillhouse — Figure 1) were sampled quarterly 

 by hook and line or spear, between June 1976 and 

 March 1977, placed on ice and frozen for later 

 dissection. After thawing, fish were measured and 

 were examined for parasites on the external sur- 

 faces as well as the gills, gill cavities, mouth, 

 mesentery, heart, gallbladder, stomach, intestine, 

 and muscle. Initially, copepods and monogenetic 

 and digenetic trematodes were fixed in an 

 alcohol-formaldehyde-acetic acid (AFA) solution 

 and the trematodes were stained with Harris' 

 hematoxylin, cleared with xylene, and mounted. 

 Protozoans were studied unpreserved after thaw- 

 ing. Because most of the parasites recurred fre- 



0% 25% 50% 



LU 

 < 



(/) 

 U.' 

 Li. 

 O 



cc 



LU 



10 



a 24 



26 28 3d 



:5% 50% 



HASKELS 



TTT1 



NAPLES 

 REEF 



^ 



34 36 3e 40 42 



TOTAL LENGTH (CM) 



Figure 2. — Size frequencies of olive rockfish taken by partyboat 

 at a heavily fished (Naples Reef) and lightly fished (Haskels) site 

 (Naples Reef— W = 121, x = 27.3, SD = 2.5; Haskels— N = 76, 

 X = 32.8, SD = 4.4). Dashed lines indicate size at which 0%, 

 25%, and 50% of the fish were mature. 



quently, only those not readily indentifiable were 

 preserved in the latter parts of the study. 



After a year of sampling, it was apparent that 

 the Ellwood Pier population was the only one not 

 infected with the gill monogenean, Microcotyle 

 sebastis. To test whether environmental condi- 

 tions precluded M. sebastis from the site, 21 

 tagged, infected fish from the Horseshoe Reef were 

 introduced into the Ellwood site. Specimens were 

 collected after 1 and 6 mo. 



Size Variation 



To test whether heavy fishing pressure altered 

 the size composition of olive rockfish on reefs, I 

 compsired size frequencies offish taken by a sport 

 fishing partyboat at Naples Reef ( 13 trips) and at a 

 portion of the mainland bed called "Haskels" (four 

 trips), which lies inshore and east of Naples Reef 

 A 4-yr study of partyboat operations indicated 

 that Haskels had been fished by partyboats no 

 more than four times in 5 yr. 



Data on size and maturity of olive rockfish ( Fig- 

 ure 2) was taken from Love ( 1978), who examined 

 365 individuals from off Santa Barbara. The 

 gonads of mature olive rockfish undergo marked 

 annual changes, similar to those in the Pacific 

 ocean perch, Sebastes alutus, (Westrheim 1975) 

 and mature individuals are readily distinguished 

 from immature specimens, based on gonad size 

 and color. 



RESULTS 



Of the 1,847 fish artificially tagged, 216 were 

 recovered, an 11.2% return (Table 2), and 9 were 

 recaptured twice. Recaptured fish were at large 

 1-514 days. Highest return rates were from Horse- 

 shoe Reef (34.6%^), Naples Reef (23.7%), and the 



Table 2. — Percentage recapture of tagged olive rockfish at the 

 study sites off Santa Barbara, Calif. 



'Platform Hilda, Platlorm Holly, Anacapa Island. Smugglers Cove 



978 



