ISOLATION OF OLIVE ROCKFISH, SEBASTES SERRANOIDES, 

 POPULATIONS OFF SOUTHERN CALIFORNIA 



Milton S. Love' 



ABSTRACT 



Movements of the olive rockiish. Sebastes serrancides, off Santa Barbara, California, were investi- 

 gated, using mechanical and parasite tags. The movements were restricted over shallow reefs though 

 somewhat less so around deeper oil platforms. Highly restricted movements may cause greater 

 vulnerability of populations to overfishing — comparisons of olive rockiish size fi'equencies between two 

 reefs indicated that fishing pressure had reduced olive rockiish populations to almost all prereproduc- 

 tive individuals on the more heavily fished site. 



Rockfishes, genus Sebastes (Family Scor- 

 paenidae), form a most diverse fish group along 

 the California coast. Some 57 species are found in 

 these waters (Miller and Lea 1972), inhabiting 

 virtually every marine habitat from estuarine (oc- 

 casionally) and intertidal waters to depths of more 

 than 610 m (Miller and Lea). Rockfish are very 

 important to both sport and commercial fishing 

 industries; in California waters in 1974, rockfish 

 ranked third in the commercial fishery (poundage 

 landed) and first in the sport fishery (numbers 

 landed) (McAllister 1976). 



California species can be roughly divided into 

 two bathymetric groups: shallow species that in- 

 habit subtidal areas of reef and kelp, and those 

 that live in relatively deep water (deeper than 

 about 70 m). All species are ovoviviparous, produc- 

 ing pelagic larvae. There is some evidence that the 

 shallow water species may remain within a rela- 

 tively small area of reef or kelp (Miller and Geibel 

 1973). 



A species that consists of relatively sedentary, 

 reef-oriented aggregations would present poten- 

 tial problems in management, as certain man- 

 agement strategies presuppose movements of this 

 fish (Harden Jones 1968; Gushing 1968). If the 

 exploited species inhabits reefs, for example, it 

 might soon be decimated at a heavily fished reef if 

 individuals were parochial and did not move from 

 an unexploited site to repopulate the depleted one. 

 Obviously, a management strategy to protect this 

 type of segregated reef species would differ from 

 that for a species whose individuals move between 



'Department of Biological Science, University of California, 

 Santa Barbara, Calif.; present address: Department of Biology, 

 Occidental College, 1600 Campus Road, Los Angeles, CA 9004 L 



sites. Many rockfish species grow very slowly 

 (Phillips 1964; Chen 1971: Westrheim and Har- 

 ling^). Thus, even if a depleted reef were densely 

 settled by a successful year class, it would not 

 harbor adults for a number of years. Before then, 

 the subadults would probably be caught before the 

 age of first maturity, so the reef would effectively 

 be lost as a site of propagation for the species. If 

 this process continued through all available reef 

 sites, the fisheries would be endangered. 



On the other hand, a rockfish species whose in- 

 dividuals move freely from reef to reef may be less 

 vulnerable to such perturbations. Even a locally 

 depleted reef could be sufficiently repopulated by 

 adults during breeding season because of the tjrpi- 

 cally high fecundity of females (Phillips 1964) and 

 great dispersability of pelagic larvae. Thus the 

 fishery might be effectively managed by conven- 

 tional procedures of establishing catch limits, etc. 



The olive rockfish, Sebastes serranoides, in- 

 habits reefs and kelp beds from San Benito Island, 

 Baja California, north to Redding Rock, Del Norte 

 County, northern California, and from intertidal 

 waters (juveniles) to 146 m (Miller and Lea 1972). 

 The species is most common in southern and cen- 

 tral California from surface waters to depths of 

 about 75 m. It is a major sport fish throughout 

 much of the state (Miller and Gotshall 1965), par- 

 ticularly in southern and central California. Ob- 

 jectives of the present study were to determine 

 whether individuals move from reef to reef and if 

 average size was smaller at heavily fished reefs. 



Manuscnpt accepted May 1979 



FISHERY BULLETIN VOL 77. NO 4, 1980 



^Westrheim, S. J., and W. R. Hading. 1975. Age-length 

 relationships for 26 scorpaenids in the northeast Pacific 

 Ocean. Fish. Mar. Serv. (Can.), Res. Dev. Dir. Tech. Rep. 565, 

 12 p. 



975 



